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Messages - A-Team

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1
Arctic sea ice / Re: The 2017/2018 freezing season
« on: Today at 03:07:49 AM »
Very elastic pack. lot of shatter lines
The irregular shear lines are not elastic deformations as those terms are defined at english language wiki or used say in classical 19th century continuum mechanics. This ice is brittle. What we are seeing is more like a crystal dislocation or earthquake strike-slip faulting than a Glen's law deformation of ice 1000 m under the surface of Jakobshavn Glacier. Elastic too is used very differently in physics; here kinetic energy was not conserved but went off entirely into frictional heat.

Thanks for the animation rate suggestion. I've added some additional frame rates to the 200ms one above, having no idea whether various web browser actually switch between the two frames at the advertised rate. These are 600ms, 1000ms and 2000ms.

Myself, I've come to the opinion that mousing ImageJ stacks offline is by far the best viewing option for climate science time series. (That would involve a download of the forum gif and opening in ImageJ freeware for your platform.) Mousing can be varied from fast to slow, notably for some interior subset of interest. Elsewhere on the screen, several Gimp playback windows could be looping more conventionally through the animation at various fixed speeds.

The other thing ImageJ does very well is montage all the frames at any combination of rows x columns (eg 360 frames as 24x15 30x12). This makes optimal use of rectangular monitor displays: you can see all the animation frames at once. Further, contrast improvements consistently affect all the frames in the montage. The result can be sliced and diced back into the animation stack.

ImageJ will also subset an animation or concatenate or combine several. Somehow someone got all this to happen in milliseconds whereas Gimp can take several minutes on high frame count products.

2
Arctic sea ice / Re: The 2017/2018 freezing season
« on: Today at 12:51:04 AM »
Climate Reanalyzer is now also offering Forum-supported mp4 videos of their forecasts...
It just keeps getting better!

Here is a pair of high resolution Sentinel-1B separated in time by only 12 hours. It shows the lower tongue of that Kara ice intrusion. Note the ice rearranging itself like a jigsaw puzzle. There was an additional translational component, towards the Fram, which was removed by shifting the second image back up to the sub-central fixed point to which the residual motion is relative to.

3
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 19, 2018, 01:49:10 PM »
Kara ice intrusion volume being exported over the last 50 days?
The intrusion is not picked up by SMOS ice thinness or AMSR2 concentration but it's seen clearly (at much improved detail) in Sentinel-1AB. Overlaying a rescaled lat lon grid from Panoply and using an online grid cell calculator, the intrusion area works out to about 40,000 km^2. UH SMOS has a fairly large pole hole here but is showing the ice being displaced averaging maybe 1.4 m in thickness. So that would be roughly 56 cubic km of export. That would be 3.8% of wipneus' 2017-12-31 PIOMAS volume of 14,418. The event isn't over (see one day change of 8 km below) so it might worth doing this more carefully when it is.

4
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 18, 2018, 04:04:42 PM »
not light and fluffy. It’s hard and compacted
Meaning little trapped air to provide insulation. It sounds like the corners of hexagonal plate snowflakes have broken off, leaving rounded cores that pack much tighter.

may see exceptionally early opening of Bering strait and Chukchi as early as late March with knock-on consequences for ESS and Beaufort.
Quite plausible. For mid-January, the peripheral freeze season seems weak (except for the central Laptev-ESS). The Beaufort still shows extensive regions of thin ice, though by tracking individual CAA floes frozen into its matrix, we know cold air at a fixed position there sees a rapidly moving target to thicken.

Very little can be learned about this region from FDD80º as parts of these seas are in a different weather regime 1400 km to the south of that parallel. Indeed even the reanalysis wind seems to have a so-so correlation with ice velocity, suggesting it is mostly guesswork or that Beaufort currents dominate because floes have been consistently moving westward for 117 days (since day 266 of 2017).

The velocity accelerates markedly up a swath from Banks Island to eastern Chukchi, reminiscent of ice getting caught up in the Fram. Indeed, export there resumed around the same date following a massive intrusive squeeze from the Kara. A slug of ice almost 600 km long has been exported, mostly off the Laptev/SZ but with some north of Morris Jesup streaming in. A streak develops leeward of the small island, Ostrov Ushakova. [Note FJL is mislabelled as SZ on the final frame.]

One has to wonder how the volume being exported over the last 50 days compares to that newly created (and retained) by ice thickening.

5
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 18, 2018, 02:29:40 AM »
Thanks, I had not come across this article! M Böttinger https://www.dkrz.de) can be credited for the remarkable animation -- we rarely see hillshading to represent a variable (here thickness) on these forums other than NASA SVS productions.

Although these are effective as scientific visualizations (especially the mp4 linked below), they lose frame by frame data. I myself don't plan to "Download dataset as tab-delimited text" because this is better distributed (like RASM-ESRL forecasts) as two Geo2D time series within a single netCDF that can be operationally combined within Panoply (for alternatives to hillshading).

The AWI announcement does not point to a follow-up animation -- four years have gone by -- nor to an actively maintained near-real time archive that covers the current freeze season. The UH sea ice concentration netCDF archives are up to date but not properly geo-tagged (in contrast to the SMOS archive).

While we can agree that 'improving previous resolution from 111 km to some 4 km' is an important advance, it is no longer state of the art, given 200x better resolution from the ~.020 km daily resolution of Sentinel-1AB composited by R Saldo at DTU.

However the question is, does this improved resolution already pick the low hanging fruit in terms of capturing significant heat loss and new ice formation, or do we need to include the many narrow width but very long extent leads? That issue is discussed in the 7 subsequent papers citing this 2016 publication, notably the 2018 paper at 1 km.

For a valid article link, Wiley wants 'abstract' or 'full' on the end of links, here since it open source:
http://onlinelibrary.wiley.com/doi/10.1002/2016GL068696/full

Sea ice leads in the Arctic Ocean: Model assessment, interannual variability and trends
Q. Wang, S. Danilov, T. Jung, L. Kaleschke, A. Wernecke 13 July 2016

https://tinyurl.com/ydh9nzsr AWI press release links to HD versions of youtube

1995-2004 MP4 29.8 MB   https://tinyurl.com/yd7rd9nb too big for forum
2005-2014 MP4 27.9 MB   https://tinyurl.com/yd4k9u4n too big for forum

Q. Wang et al: FESOM Arctic Ocean sea ice concentration and thickness 1995-2014, links to movies in mp4 format. PANGAEA, https://doi.org/10.1594/PANGAEA.860354
 
"Sea ice leads in the Arctic are important features that give rise to strong localized atmospheric heating; they provide the opportunity for vigorous biological primary production, and predicting leads may be of relevance for Arctic shipping. It is commonly believed that traditional sea ice models that employ elastic-viscous-plastic (EVP) rheologies are not capable of properly simulating sea ice deformation, including lead formation, and thus, new formulations for sea ice rheologies have been suggested.

Here we show that classical sea ice models have skill in simulating the spatial and temporal variation of lead area fraction in the Arctic when horizontal resolution is increased (here 4.5 km in the Arctic) and when numerical convergence in sea ice solvers is considered, which is frequently neglected.

...The scientists used a widely known theory, which describes the material qualities of the sea ice as an elastic-viscous-plastic medium. This was often criticised in recent years. But 'the new results show that the old theory for sea-ice physics still remains valid, if the calculation is performed with high accuracy'.

The model results are consistent with satellite remote sensing data and discussed in terms of variability and trends of Arctic sea ice leads. It is found, for example, that wintertime lead area fraction during the last three decades has not undergone significant trends.

Supplement: Northern Hemisphere sea ice from a Finite-Element Sea-Ice Ocean Model (FESOM) 4.5 km resolution simulation. Concentration is shown with color; thickness is shown with shading. A global 1 degree mesh is used, with the "Arctic Ocean" locally refined to 4.5 km. South of CAA and Fram Strait the resolution is not refined in this simulation. The animation indicates that the 4.5 km model resolution helps to represent the small scale sea ice features, although much higher resolution is required to fully resolve the ice leads.

Even in cold winters, more and more leads are forming due to wind and currents, which only adds up to a small amount of the total area, but is responsible for a large part of the growth in ice.'

A 4.5 km resolution Arctic Ocean simulation with the globalmulti-resolution model FESOM1.4
Q Wang et al  24 July 2017
https://www.geosci-model-dev-discuss.net/gmd-2017-136/gmd-2017-136.pdf

Scaling Properties of Arctic Sea Ice Deformation in a High-Resolution Viscous-Plastic Sea Ice Model and in Satellite Observations
N Hutter et al 8 January 2018

Sea ice models with the traditional viscous-plastic (VP) rheology and very small horizontal grid spacing can resolve leads and deformation rates localized along Linear Kinematic Features (LKF). In a 1-km pan-Arctic sea ice-ocean simulation, the small scale sea-ice deformations are evaluated with a scaling analysis in relation to satellite observations in the Central Arctic.... The agreement of the spatial scaling with satellite observations challenges previous results with VP models at coarser resolution, which did not reproduce the observed scaling. The temporal scaling analysis shows that the VP model, as configured in this 1-km simulation, does not fully resolve the intermittency of sea ice deformation that is observed in satellite data.

To summarize, our understanding of various Arctic Ocean ice physical processes is demonstrably improving, as is near-real time tracking of the current season, but the ability to make end-of-season or multi-year predictions is not advancing. We understand better what is happening (and why) but not what will happen in the future, other than trend lines.

The problem with unpredictability, given the phenomenon of Arctic amplification, is Arctic sea ice is a leading indicator -- indeed driver -- of global climate change. Lacking a solid foundation here, ambitious 'coupled' climate models are not in a position to reliably predict the future, notably because the onset and consequences of positive feedbacks from Arctic sea ice loss can't be anticipated.

6
Developers Corner / Re: Creating Animated GIFs
« on: January 17, 2018, 06:58:17 PM »
User's Guide to a new Panoply Time Series Scripting Tool

Introduction Climate science data is mostly stored and distributed as netCDF (.nc) files. Those bundles multiple data files that need to stay together. These are almost always geolocated, each data point being tied to its latitude and longitude (and ocean depth or atmospheric height if applicable).

The geolocated files within a netCDF bundle are called Geo2D files; they are the only ones that can display data over a base map of the earth. Typically a new netCDF file is created each day as conditions change. 

It is quite difficult to un-bundle netCDF bundles and re-assemble a particular Geo2D file set as a new netCDF. The tool described here provides virtual un-bundling, all that is need in most situations.

Panoply is easy-to-use free software used to make maps that display climate data. A large number of parameters (~70) can be set to control the map's appearance, notably the map projection, its center and horizon, data range displayed, and color palette.

The choices can be saved out as text file (type .pcl) which can serve as a script to regenerate the map using PanoplyCL (command line). Given such a script, it can be modified by 'mail merging' in a list that increments parameter placeholder settings in some useful way, for example over a date range.

The tool described here concatenates all the variant scripts into a single text file that, when run as a PanoplyCL script, will generate a separate output map (a .png image) for each element in the list, each according to its parameter settings.

In the example, if the list pointed to 365 netCDF files, a year's worth of daily images would be created. These images, loaded into ImageJ free software, can be saved out as a .gif animation or .mp4 video.

Example 1 The case studies here all refer to Arctic Ocean ice data via Uni Hamburg's correctly constructed, illustrative netCDF bundle, updated daily and archived online without registration barriers. If you acquire some of those files along with Panoply, PanoplyCL and ImageJ, you can follow along as examples are developed.

The settings below fix the map projection to stereographic centered on North Pole in standard 'Greenland down' position with the Arctic Circle as horizon. (This allows your map to be rescaled to match maps you might find online for which no netCDF file is provided.)

// Open a dataset.
var ncdata1 = panoply.openDataset ( "Downloads/SMOS Hamburg nc/SMOS_Icethickness_v3.1_north_20180103.nc" );

myplot.set ( "proj-name", "Stereographic" );
myplot.set ( "proj-lat0", 90.0 );
myplot.set ( "proj-lon0", -45.0 );
myplot.set ( "proj-xparam-1", 23.6 );

You can adjust these numbers in the friendly Panoply interface; the four lines below show up in the exported CL script. Two other common settings emphasize the Bering Straits (to show conditions in the Chukchi, Beaufort, and East Siberian Sea) or the Fram Strait/Svalbard/Severnaya Zemlya area.

Suppose now you viewed the -45.0 as a placeholder. Making a list that increments this by one degree 360 times, the new mail merge tool will output a concatentated script with the effect of displaying ice data on a rotating globe (restricted to the Arctic).

If the path to the file on your hard drive and the date associated with the netCDFs are also varied, the display will increment the data by a day for each increment of rotation. In other words, construct a 3 row, 365 column table in a spreadsheet, save as comma separated variables (.csv format), and paste into the tool.

var ncdata1 = panoply.openDataset ( "[PlaceholderPath] [PlaceholderDate]" );

myplot.set ( "proj-name", "Stereographic" );
myplot.set ( "proj-lat0", 90.0 );
myplot.set ( "proj-lon0", [PlaceholderLong] );
myplot.set ( "proj-xparam-1", 23.6 );

... to be continued.

7
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 17, 2018, 04:30:52 PM »
Dawn at Little Diomede yesterday (arrow). WorldView will be showing some of the Chukchi soon in its visible and IR channels. That may be soot in the lower left and center, third image.

The eastern Lincoln Sea area is being pulled apart by conflicting motions: rotation westward but eastward Fram export, animation. We've seen that many times before.

Two views of the Beaufort (thermal and radar brightness) emphasize different features, second image.

Technical note: NOAA AVHRR at DMI shows ice fractures better than higher resolution DTU Sentinel-1AB images, probably because open ice leads reveal water (or new ice) at a different temperature. The flip side is that heat escaping from opening ice can condense to 'black smoke' (fog) that obscures ice details. It then becomes difficult to disentangle the actual width of newly opening leads from the width of lead + black.

Arctic ice is sometimes treated as a viscous plastic which works well enough in describing ice pack motion at very low resolution but underlying this at higher resolution are rips in the fabric that are important heat vents but more difficult to model.

8
Consequences / Re: Global Surface Air Temperatures
« on: January 17, 2018, 03:11:54 PM »
Whoa. That #1673 twitter geoengineering quote is not even approximately a fair summary of doi 10.1002/2017GL076079; it is actually about how to best reduce GHGs and aerosols without a NH overshoot from the latter.

"Limiting global warming to 1.5 or 2.0 °C requires strong mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline, due to co-emission with GHG, and measures to improve air quality. However, the combined climate effect of GHG and aerosol emissions over the industrial era is poorly constrained. Here we show the climate impacts from removing present day anthropogenic aerosol emissions, and compare them to the impacts from moderate GHG dominated global warming.

Removing aerosols induces a global mean surface heating of 0.5-1.1 °C, and precipitation increase of 2.0-4.6 %. Extreme weather indices also increase. We find a higher sensitivity of extreme events to aerosol reductions, per degree of surface warming, in particular over the major aerosol emission regions. Under near term warming, we find that regional climate change will depend strongly on the balance between aerosol and GHG forcing.

Plain Language Summary:
To keep within 1.5 or 2 degrees of global warming, we need massive reductions of greenhouse gas emissions. At the same time, aerosol emissions will be strongly reduced. We show how cleaning up aerosols, predominantly sulfate, may add an additional half a degree of global warming, with impacts that strengthen those from greenhouse gas warming. The northern hemisphere is found to be more sensitive to aerosol removal than greenhouse gas warming, because of where the aerosols are emitted today. This means that it doesn't only matter whether or not we reach international climate targets. It also matters how we get there."

free text working at sci-hub
Right, my impression is that all effort at blocking working urls for that site, such as https://sci-hub.la/, have been abandoned.

9
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 16, 2018, 03:41:05 PM »
equivalent to a 10CM thick wall filled with fiberglass insulation, more or less.
If dry fluffy powder. But how does that stay in place given month after month of strong surface winds? More likely it will drift onto irregularities, leaving bare ice in some places and meter-thick snowdrifts on the lee of pressure ridges. There's only an even blanket of snow when viewed with 50 km x 50 km grid cell averaging. No one goes out there to measure snow transects Oct through May.

If rain on snow -- which we are seeing this week off Svalbard and likely off Alaska -- that will melt the snow entirely or form layers of weak ice within the 'snowpack'. The only recent extended winter in situ monitoring of the Arctic Ocean snow is N-ICE 2015. They documented warm moist air driven melt events as well as the effects of waves washing over the meagre freeboard of FYI-SYI.

For better or worse, comprehensive physical modeling programs like RASM-ESRL bake all this in to their near real-time daily state descriptions: snow, rain, water-ice-air heat equation transfer, wind, mid-latitude advection, high vs low clouds and up-and-down radiative energy transfers. Those netCDFs will resume 14 Feb 18.

Can we do better intuiting quantification?

Then there is bottom-line ice thickness observation by combined satellite altimetry and salinity. These have error issues in processing steps but are far better anchored in reality than pure models. (A snow-driven correction factor for Cryosat from upwardly extruded brine mentioned up-forum has not yet made papers like Stroeve 2018.)

Following the thinner ice on the periphery plus FDDAO for thermal thickening may be the best current guides to how the freeze season is going, as compared to recent years past. The peripheral seas are the last to freeze and the first to melt and so affect the core via ice mobility, long-fetch waves, and air moisture.

The second image below restricts the UH snow thinness product for 14 Jan 18 to ice between 0.25 and 1.25 m thick, which could be the Goldilocks range for tracking (in terms of intrinsic accuracy) in the post freeze-over winter. Open water in September can freeze to ~2m thickness by the end of winter so the deficit is of interest. (SMOS alone does not go out to that thickness.)

The third image shows the same date after the big melt summer of 2012 (which was followed by an unremarkable 2013 extent). The time series available is too short, relative to variation, for statistical trending. Further, later years might have used improved algorithms.

It's feasible also to use weekly or monthly averaging out of Panoply but ice acceleration this year in the western Beaufort means individual floes have moved on and their thickening isn't being followed. The bottom animation shows the last 30 days of motion, including a couple of feature trackers over a blowup of export to the Fram.

This is a very unfavorable pattern for retention of thicker remnant CAA ice which is getting stretched in two directions: into the warmer Chukchi and towards export.

These maps are only feasible to produce when a Geo2D thickness file within a netCDF bundle is provided to Panoply for range-picking (eg UH, not UB). Here ice <0.25 m is re-colored light blue (distinguishing it from open water) and ice >1.25m off-white in Gimp.

Technical note: it is feasible to replace the two bounding colors in Panoply continuum palettes with distinct colors from the ambient gradient. This would directly resolve situations where 0 and NaN conflict. The question really is whether long time series can be automated in Panoply (yes, see DevCorn) and wrapped in ImageJ to movies without invoking manual curation in Gimp (probably).

http://www.npolar.no/en/projects/n-ice2015.html
http://www.npolar.no/en/projects/n-ice2015.html
https://seaice.uni-bremen.de/data/smos/png/
https://icdc.cen.uni-hamburg.de/thredds/catalog/ftpthredds/smos_sea_ice_thickness/v3/catalog.html

10
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 15, 2018, 05:05:16 PM »
Here are a couple of movies that seem to be working for Mac/Window users over at DevCorner. The first is a synchronized display of the last four freeze seasons, from the Sept minimum up to 13 Jan 18. It looks like it can be bumped to 9 years of ASCAT data without the file size getting out of bounds (as it does with our more familiar gif animations). Note occasional satellite glitches (missing days) have been replaced by duplications of flanking dates.

The second shows UB SMOS thin ice development just for this season. That could also easily be bumped to 2x2=4 years, which allows comparison of freezing stages. Note a few of the frames have substantial radio frequency interference (gray flashes).

Note the forum mp4 controller offers a full screen mode that may or may not be beneficial. Some people will do better downloading the file and viewing on their own player.

Thanks to member Dryland, we now have automated plucking of netCDF files from daily packages, imaging them as specified with PanoplyCL scripts, animating in ImageJ, and saving out as mov --> mp4 videos.

We are thus in position, between ImageJ's montage compositing tricks and PanoplyCL, to provide some unprecedented internet offerings of historic and current cryosphere conditions at very reasonable file size with relatively little future effort.

11
Developers Corner / Re: Creating Animated GIFs
« on: January 15, 2018, 03:48:44 PM »
Yes, very helpful. Between windows and mac, it should work for most people here. The key seems to be at my end, processing the .mov saved out from ImageJ to .mp4 using a modern free online converter like https://movtomp4.online/

Now I'm wishing there was some way to specify a delay before it begins another loop. One could not have it loop at all but press again on the start controller each time. I don't think it would work to add repeats of the final frame of the parent 65 MB gif animation because the codecs would probably see nothing changing and suppress them I suppose credits or ads or annotations or voice-over or music could be added but I'm not going there at this point.

More experimentation on the early stages first. The new attached has been downscaled to 650x650. that seems to max out the room available in forum width. The second version, ICA indexed color, does well on thicker ice but the green needs to be replaced. The process has also wiped out the day numbers.

12
Developers Corner / Re: Creating Animated GIFs
« on: January 15, 2018, 12:25:34 PM »
Just testing a preliminary four year array of ASCAT. 121 days from Sept minimum until 13 Jan. Forum software is accepting the .mov uploads but not displaying them. Believe further admin enabling is needed as was done for mp4 and youtube.

Back to converting mov to mp4 (which displays for some but not many people). It sometimes takes a reload to get the actual image going; on the first go-round it only shows the controller. But it is going nicely now. It cannot remember my preferences (loop, play, controller off) and always goes back to default (controller on).

It is fairly wide though at 750x750 which is the natural scale for ASCAT's Arctic Ocean images. The dates need to be offset a bit to the right so that they are more readable over the snowy white background of Greenland. Four years takes about 3 MB so the full eight year record is manageable saving at 'normal' quality. Probably best as 2x4 array. It looks like 8 years at 365 days is too large but 8 years at 182 or 121 would both come in under 10 MB which the forum has accepted in the past. NSIDC uses 52 days per year or 1 date out of 7 for sea ice age animations.

13
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 14, 2018, 07:21:02 PM »
it's possible for any year from now on to become nominally ice-free
It reminds me of the critters around here getting extirpated, like the elf owl, deer and jackrabbits. There's a long-term declining trend as the habitat deteriorates, upon which the usual wild swings of natural variation are superimposed.

The upswings don't much affect the trend nor lead to recovery but the downswings can be enough, when the trend has brought things low enough, for numbers to hit zero from which no recovery is possible. (There'll be an open wind fetch of 3395 km from Little Diomede to Longyearbyen.)

So while we're already getting significant regional effects from our current position on the trend line, I wouldn't be surprised to see an effectively complete blowout over the Sept 2018-2020 time frame.

However the loss of multi-year ice is preceding more rapidly than anyone envisioned (by export and translocation to kill zones), moving us on a parallel track, distinct from bad weather blow-ins and blow-outs, to essentially all FYI which already has consequences fairly similar to no ice.

So more thought from the scientific community should be probably allocated to what comes after that, though I expect mostly wait-n-see as previous modeling didn't worked out and it won't be any better in fast-moving uncharted territory (eg permafrost emissions).

Note nothing we post here affects the ice outcomes one way or another ... previous words of wisdom from Oren.

14
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 14, 2018, 06:26:37 PM »
Allowed file types: gif, jpg, mpg, pdf, png, txt, jpeg, mp4, m4v, mov, avi
Build it and they will come!

Just some cross-posted images from a longer more technical post on issues in making a  simultaneous titanic 9-year daily ASCAT movie coming to a forum near you soon(?)

https://forum.arctic-sea-ice.net/index.php/topic,1259.msg138784.html#msg138784




15
Developers Corner / Re: Creating Animated GIFs
« on: January 14, 2018, 06:10:50 PM »
A larger improved version of that last multi-year Beaufort-Chukchi comparison file, needs a click.

16
Developers Corner / Re: Creating Animated GIFs
« on: January 14, 2018, 05:26:30 PM »
It's been claimed that no one ever looks at 99.999% of all archived satellite scenes, even the cloud-free ones. It's also true that 99% of the web sites archiving single daily satellite records never put together a simple time series movie that could give visitors a quick preview of what was in the collection.

For example, NOAA's ASCAT archive of 9,040 gifs in a single directory does see too many visitors who want to 'download them all' with wget or plugin. However only 1820 of these show the Arctic. Still, at 547 KB each, that is 995 MB. A movie size would be much much smaller, depending on quality retained, rescaling, restricting to even-numbered or just weeks, and codecs used.

It's very much worth doing but would it be distributable?

The ASCAT time series for 2012-18 provide an excellent direct record of ice pack motion, though weather artifacts in individual images can be quite distracting. The gif below looks at using UH AMSR2 double-masking of land and water, leaving only ASCAT ice (which benefits greatly from normalizing and adaptive contrast enhancements).

The land mask is a one-time stationary product, made here from the 6.25 km AMSR2. That does not have a Geo2D file in its netCDF so it cannot be redisplayed in Panoply without its lat-lon lines. Here the Gimp color picker was used, along with single pixel 'grow selection' to replace the distracting red with a bland land mask color. Open water varies day to day but can be color-picked once for the whole time series when the AMSR2 are tiled. This has to be done at the original resolution (ie prior to rescaling to fit ASCAt's scale).

It is easy to escalate the double mask to a tiled layer floating above the ASCAT tile and apply after the latter is enhanced in ImageJ (which mostly lacks alpha channel masking). Gimp cannot de-tile beyond 100 frames due to a limitation in a plugin nor save out as a video so those operations have to be finalized in ImageJ.

Having done each year from 2010 to 2018 separately (which works better seasonally rather than per calendar years) to keep intermediate files small, it is easy to combine these within ImageJ either end to end as a continuous six year roll, or gridded into say a 2x3 rectangle which affords simultaneous display of the same date of each year.

This would make a gif gigantic file because of 365 frames x 6 years x 700 pxl x 650 pxl is a lot to display, even if reduced from RGB to grayscale and gif-differenced to compress. Using movie codecs, file size would become manageable, though display on say QuickTime would need prior testing. It's not clear if or what the forum would show.

Movies can also be extended by adding clips but that would only benefit making a long-term roll; there is no juxtapositioning option. Quicktime Pro 7.6.6 can do a lot more but while AAPL still distributes the Pro software(http://support.apple.com/kb/dl923), it no longer sells the enabling key though these are sometimes offered free online or sold on ebay.
 
.. edit, layer, change all kinds of metadata, add and delete tracks, QT 10 can do less.
.. has the controls outside the movie, 10 has it covering a part of the movie.
.. can add effects
.. can open a wider range of codecs,  QT 10 has to convert a lot of formats
.. has excellent A/V tools to adjust the video brightness, color, contrast, tint, playback speed, audio volume, audio balance, bass, treble, pitch shift, and playback.

2010 vs 10/11
2011 vs 11/12
2012 vs 12/13
2013 vs 13/14
2014 vs 14/15
2015 vs 15/16
2016 vs 16/17
2017 vs 17/18 Jan
2018 Jan only

To crop image batches identically (to the Arctic Ocean plus a bit of the Fram), use 320x350 as the lower crop on ASCAT and 375x375 as upper crop. After reducing to 8-bit grayscale, 365 images of that size require 48.7 MB or 170 MB if rescaled to 700x700. Since ASCAT is available in the same format back to 2010, those numbers have to multiplied by 8 to reach 31 Dec 2017. That is well within the RAM memory limits of ImageJ (and my Mac) but some menu operations might be 'challenged' allowing no room for error. Hence rescaling is best deferred to the very end of the process.

The 9-year gif for today below is 3.7 MB; movies don't work well when so few frames are available. The still png showing all 9 years has 2010 in upper left and ends in 2018 in the lower right. The goal here is to animate this still image into a good quality movie, preferable at native ASCAT resolution (375x3 --> 1125x1125 (or even better to 2250x2250) to allow all years to play simultaneously in contrast-enhanced mode, possibly with masked and false color versions.

Note 2018 is not unusual in having thick CAA floes having rounded the Beaufort bend and stringing out up into the Chukchi (where they will melt out next summer): six of the 9 years show this same pattern for this Jan date.

Note the widespread confusion between NSIDC's averaged monthly motion at each point (vector sum of daily motion) and actual monthly floe trajectories which are line integrals of the daily displacement of the floe from its current position. It's not possible to get at the latter using the former.

17
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 14, 2018, 02:32:09 PM »
Last year saw all these Atlantic clones bring warm wet weather up into the Arctic, accompanied by presumptions that this might be the new normal for the New Arctic. However 2017/18 so far is not going along with this idea.

The significance of these storms for the 2016/17 winter are reviewed in Stroeve 2018 using CryoSat2 and the above-mentioned ice thickness distribution fields.

Thorndike's influential work on this dates back to 1975 per gScholar search:

The thickness distribution of sea ice
AS Thorndike, DA Rothrock…
https://tinyurl.com/ydb2z3l3

The polar oceans contain sea ice of many thicknesses ranging from open water to
thick pressure ridges. Since many of the physical properties of the ice depend upon its
thickness, it is natural to expect its large-scale geophysical properties to depend on the
  Cited by 682

Simulating the ice‐thickness distribution in a coupled climate model
CM Bitz, MM Holland, AJ Weaver… - Journal of Geophysical …, 2001 - Wiley Online Library
… [1975] suggested a plausible b(h) might decrease linearly with the cumulative thickness
distribution up to some value G*. We adopt Thorndike et al.'s … 7(h•,h2)dh2, which describes the
increase in the concentration of ice in the interval (h2, h• + dh•) when a unit of ice of thick …
  Cited by 300

Estimates of sea ice thickness distribution using observations and theory
AS Thorndike - Journal of Geophysical Research: Oceans, 1992 - Wiley Online Library
Abstract The thickness distribution of sea ice is maintained by a balance of thermal and
mechanical processes. Observations now exist that make it possible to quantify this balance
and to test models of the individual physical processes. In particular, the observed
  Cited by 23


Influence of the sea ice thickness distribution on polar climate in CCSM3
MM Holland, CM Bitz, EC Hunke… - Journal of …, 2006 - journals.ametsoc.org
… Mechanical redistribution is parameterized following Rothrock (1975), Thorndike et al. (1975),
and Hibler (1980) … Figure 4 shows the simulated seasonal climatological Southern Hemisphere
ice thickness. The thick solid line shows the 10% concentration from SSM/I data …
  Cited by 206

Measuring the sea ice floe size distribution
DA Rothrock, AS Thorndike - Journal of Geophysical Research …, 1984 - Wiley Online Library
Abstract Sea ice is broken into floes whose diameters range from meters to a hundred
kilometers. This fragmentation affects the resistance of the ice cover to deformation and the
melting at floe sidewalls in summer. Floes are broken by waves and swell near the ice edge
  Cited by 142

Ridging and strength in modeling the thickness distribution of Arctic sea ice
GM Flato, WD Hibler - Journal of Geophysical Research …, 1995 - Wiley Online Library
… The transfer function, 13(hl, h2), defines the distribution of ridged ice thicknesses produced by
deformation of an area of thin ice. Thorndike et al. [ 1975] proposed that ice is ridged into a fixed
multiple C2 of its original thickness, namely, 1 [•(hl, h2) = •5(h 2-C2hl)•2 (16) …
  Cited by 214

Sea ice thickness distribution in Fram Strait
P Wadhams - Nature, 1983 - Springer
… Thorndike et at. 15 estimated that ice growing thermody- namically will reach a draft of 1m
(thickness 1.11 m) in late April after a growth period of 76 days … during the observation period,
ice within 100 km of the ice margin in the Pram Strait was mainly first-year ice, while ice in the …
  Cited by 86

The under‐ice thickness distribution of the Arctic Basin as recorded in 1958 and 1970
AS McLaren - Journal of Geophysical Research: Oceans, 1989 - Wiley Online Library
… open water [Thorndike et al. 1975]. Thickness distribution is basically the frequency of different
ice thicknesses arising from the spatial coverage of open water, thin ice, and thick ice. A particular
combination generally determines its degree of roughness (ie, the thicker and more …
  Cited by 92

Theory of the sea ice thickness distribution
https://arxiv.org/abs/1507.05198
S Toppaladoddi, JS Wettlaufer 22 Aug 2015

We use concepts from statistical physics to transform the original evolution equation for the sea ice thickness distribution g(h) due to Thorndike et al., (1975) into a Fokker-Planck like conservation law. The steady solution is g(h)=(q)hqe− h/H, where q and H are expressible in terms of moments over the transition probabilities between thickness categories. The solution exhibits the functional form used in observational fits and shows that for h≪1, g(h) is controlled by both thermodynamics and mechanics, whereas for h≫1 only mechanics controls g(h). Finally, we derive the underlying Langevin equation governing the dynamics of the ice thickness h, from which we predict the observed g(h). The genericity of our approach provides a framework for studying the geophysical scale structure of the ice pack using methods of broad relevance in statistical mechanics.

18
Policy and solutions / Re: Batteries: Today's Energy Solution
« on: January 13, 2018, 05:49:34 PM »
It's air pollution from abusive smelting, not so much the mining.

Actually a great many stories in newspapers are plants. Papers today are looking for free content. Someone is kiting a stock option, sends out a press release. Front-running the gullible.

Until someone repeals the laws of supply and demand elasticities, there will never be a cobalt shortage. It will never contribute meaningfully to the price of an auto. If it did, it would be replaced, just like png replaced gif when the patent trolls came around to collect royalties.

Remember the phony chromium shortage? The Ruskies were buying up the world's supplies (in the Congo, circa 1965). We would no longer be able to plate shiny chrome on our steel car bumpers leading to societal collapse.

Remember the phony silicon shortage? It had to come from this special beach in Coos Bay, Oregon. We're gonna run out of sand.

Remember the phony lithium shortage? The millions of hectares of open-air playas and millions of cubic km of salt beds in the western US vanished overnight. Along with all the salt in the sea.

Remember the phony rare earth element shortage? We're gonna have to go back to rotary dial phones unless the wilderness protection act is repealed.

Remember those viseroij tulips? Now there was a commodity that actually couldn't keep up with demand (because it was a fungus rather than a genetic variant):

Tulip mania (Dutch: tulpenmanie) was a period in the Dutch Golden Age during which contract prices for some bulbs of the recently introduced and fashionable tulip reached extraordinarily high levels and then dramatically collapsed in February 1637.

It is generally considered the first recorded speculative bubble... In many ways, the tulip mania was more of a hitherto unknown socio-economic phenomenon than a significant economic crisis. And historically, it had no critical influence on the prosperity of the Dutch Republic, the world's leading economic and financial power in the 17th century. wiki

19
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 13, 2018, 04:21:11 PM »
actual temp. With heavy rainfall. Surreal
The freezing season is not going so well off Alaska either, 1st image and animation.

Rebecca Woodgate from the PSC would have info on this
Actually that paper, to the extent it deals with summers 2014-16, is somewhat passé given the rate of change in the Arctic.

More to the point is Woodgate's summer 2017 rent-a-cruise mooring retrievals. This is actually a detailed fascinating trip log that shows the dicey nature of oceanographic research. An entire year can be wasted because of biofouling of a seabed cable release mechanism, snagging of lines by passing trawlers, high seas during narrow operating windows, and malfunctions in data recorders.

Even though 3 Chukchi moorings make for a very sparse sample for 9 million sq km, they still represents a huge expensive effort. Actual daily data at depth is imperative though as only the ocean surface can be directly accessible to satellite. Profiling buoys don't hold their position nor operate for long. Beyond that, you are looking at long long runs of ungrounded model theories.

A big breakthrough though has come with new autonomous buoyancy gliders that can operate up and down a sawtooth depth range over a huge distances for six months or more untended, then surface and beam up their data like a satellite swath only with an extra dimension. (There's one down in the AO now but it hasn't yet reported.)

http://psc.apl.washington.edu/HLD/Bstrait/BeringStrait2017CruiseReport_Norseman2_22ndJuly2017witheventlog.pdf

"Key Preliminary results. As discussed below (p.67), the mooring data show some remarkable changes this year:

(i) a remarkably warm June 2017 (~ 3°C warmer than climatology);

(ii) remarkably early arrival of warm water in the strait in spring/summer 2017 (in hourly data, ~ 15 days earlier than in any prior recorded year and ~ 1 month earlier than the average)

(iii) very late departure of warm waters from the strait in late 2016 (in hourly data, more than 20 days later than any prior recorded year)

(iv) anomalously fresh waters in winter (~1 psu lower in winter, ~0.5 psu lower in the annual mean)

(v) a record maximum freshwater flux in 2016, of ~ 3500km3/yr (relative to 34.8 psu)

(vi) record high northward flows in fall 2016 (in 30-day smoothed data).

Key Statistics: 3 moorings recovered, 3 moorings deployed, 342 CTD casts on 19 CTD lines"

Meanwhile, on the thin ice front:

Warm Winter, Thin Ice?
Julienne Stroeve et al  review: 04 Jan 2018
https://www.the-cryosphere-discuss.net/tc-2017-287/tc-2017-287.pdf free fulll

Winter 2016/2017 saw record warmth over the Arctic Ocean, leading to the least amount of freezing degree days north of 70° N since at least 1979. The impact of this warmth was evaluated using model simulations from the Los Alamos sea-ice model (CICE) and CryoSat-2 thickness estimates from three different data providers.

While CICE simulations show a broad region of anomalously thin ice in April 2017 relative to the 2011–2017 mean, analysis of three CryoSat-2 products show more limited regions with thin ice and do not always agree with each other, both in magnitude and direction of thickness anomalies.

CICE is further used to diagnose feedback processes driving the observed anomalies, showing 11–13 cm reduced thermodynamic ice growth over the Arctic domain used in this study compared to the 2011–2017 mean, and dynamical contributions of +1 to +4 cm.

Finally, CICE model simulations from 1985–2017 indicate the negative feedback relationship between ice growth and winter air temperatures may be starting to weaken, showing decreased winter ice growth since 2012 as winter air temperatures have increased and the freeze-up has been further delayed.

20
Policy and solutions / Re: Batteries: Today's Energy Solution
« on: January 13, 2018, 04:13:48 PM »
Cobalt can be mined in many other places.  even a town Cobalt, Ontario
Byproduct of nickel mining. Every day a new scam and faux facts to fleece investors. There is nothing sillier than 'peak cobalt' unless it be 'peak lithium' or 'peak silicon' or 'peak oil' or 'solar roadways' or 'boring tunnel systems' or 'methane collecting tarps' covering the ESAS seabed. When 'peak peaks' hits, good time to dump hoarded stockpiles.

The magical hand of the marketplace: when the price of something goes up, so does the supply:

Price elasticity of supply is a measure used in economics to show the responsiveness, or elasticity, of the quantity supplied of a good or service to a change in its price.

21
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 12, 2018, 07:48:13 PM »
It's like fragments of older rock in a breccia.
Nice summary and an important distinction. Oren also made this point over at the Lincoln Sea collapse video. There's still ice forming in narrow leads and cold polynyas even in summer. So some of this ice is neither fish nor fowl in terms of FY, SYI or MYI. Overall, the latter two are more of a melange every year.

That has to be having some effect on thickness variation over short scales, shear strength, deformation, rafting, ridging, keeling, landfast dislodgement, and ice pack mobility. I don't immediately see how to put a trend number on it though.

Maybe turn our backyard wildlife cam on a screen animation? It has motion detection capability and only takes a shot when change exceeds a tunable threshold. Probably could emulate that by Gimp differencing histograms on an Ascat series though weather makes them noisy.

22
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 12, 2018, 04:44:20 PM »
one last try with the mp4 format, this time converting it using HandBrake
Loads and plays for me on Opera and Chrome but oddly not Safari mac. Handbrake is at https://handbrake.fr/

Below, H.264 codec wants to put out a .mov but if I change that manually to .mp4 it seems to play ok but only loads as an attachment, does not play here. So I ran it by an online converter to get a legitimate mp4 that is playing for me at least. It has a modified controller that allows full screen display (which doesn't work for this postage stamp size image.) https://movtomp4.online/

Technical note: Something else that folks might find useful: if you can get the object into ImageJ, it has a very nice feature called montage that will make a single image of whatever rectangular dimensions you provide, for example 248 = 31 rows x 8 columns which takes better advantage of screen ratio. This is also the place to apply global contrast operations because you can test the effect on all the frames. It then offers un-montage which along with concatenate and combine, allows multi-years to be shown side-by-side.

The simple gif animation below shows ice thinness the other day, whole ocean and Fram/Nares views. The Beaufort, Chukchi and Svalbard areas still have significant areas of thin ice.(Unusual, not unusual, temporary, or not long even a time series to say -- a lot of known unknowns there.

23
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 12, 2018, 04:10:37 PM »
Yuha's doesn't work for me directly or via download!
Double ditto. Not compatible with Mac QuickTime Player.
HELP Ice looks sicker in 2017! What does the colour coding mean?
Nothing was intended other than binning the 256 grayscale colors into 16 arbitrary distinct colors (ie 8-bit to 4-bit) for purposes of possibly illustrating floe motion better. This was the most effective of the canned palettes in ImageJ. However now I see that it actually is a 'spectral' lookup table and so the colors do correspond to snow/ice surface dielectric ~ ice surface salinity ~ extent of brine exclusion ~ sea ice age ~ sea ice thickness. More or less, the more less the farther down the chain towards thickness.

In other words, the whiter grays tend to be older and thicker and so are shown more as reds and magenta. However to compare volume export, wipneus estimates that on Piomas forum; to compare years for the whole Arctic Ocean in January, SMOS is probably best.

Technical note: any 256-color palette -- and there are thousands of these used in climate science -- can be imported into ImageJ or Gimp. However, many dozens of palette formats are in use. Patent trolls don't sit on these but it is still a major nuisance to move color tables around because most software wants to be in RGB full color which is 24-bit rather than 8-bit. ImageJ is currently in ruins because of a bad update so an older version has to be used (which has no movie export of any kind!).

Of the five options for saving out video on my computer, only three of them would open on my computer. ImageJ itself cannot open mp4's it just saved! However it can open the file back up when the raw avi codec is used yielding, weirdly, a gif.

So it looks like .mov, .avi, and .mp4 are the most promising. Neven would have to enable attachment uploads and media playing for .avi and .mov to pursue this further.

I emailed some of these mp4's to myself as attachments and they ran fine. But that's not a good test because I use aapl Mail rather than the more common google gMail.

fram.mov
fram.wmv
Fram.flv
fram raw.avi
fram mpeg.mp4

24
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 12, 2018, 12:49:52 PM »
cyclone looks like it's still going to be very deep and cause extreme issues for Fram ice due to wave action
Here are Fram and Nares export the last two years, from the mid-September minimum until January 11th. Again, way too large as gifs. To best view, turn controller off, loop to on, hit play.

25
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 12, 2018, 11:03:37 AM »
I cannot watch mp4s due to lack of software.
No computer, no web browser other than the phone's?
upload the video to a youtube account and then paste the youtube video's 'share link' (not the embed link) straight into your forum message.
Are not youtubes restricted to fixed length x width proportions? That would not work too well given Arctic Ocean shape. Then there is Twitter but their software has major weirdness issues.

It seems like movie formats are still a total tower of babel, dozesn of them. I think the problem is the codecs and patent troll law firms.

Be great if everyone could see the movies. They are about the only way that year-long ice time series can be shown as the file sizes get out of hand with gifs. For example, downsizing the 361 year of ASCAT to a 150 pixel postage stamp still requires 8 MB as a gif, close to forum limits but with horrific loss of quality.

The left half of the png shows the save options I have within ImageJ. There are none within Gimp. The right half shows some online file format conversion options. These often fail to work as advertised.

The mp4's may upload ok to youtube though there's been complaints online about that not working. Can someone with an account give the full year Ascat a try here?

26
Policy and solutions / Re: Renewable Energy
« on: January 12, 2018, 03:06:21 AM »
solar system eliminates as much carbon pollution as 5.6 acres of mature trees.
We have 7 kw net-zero system but today I had to seriously top the mesquite tree southeast of the roof because it was shading some of the panels. However new branches will grow like crazy and the slash will not compost here for decades. So go figure.

27
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 12, 2018, 02:50:11 AM »
Here's a full year of ASCAT ice pack motion. Summer is a bit hard to follow because of atmospheric interference. Other than that, fascinating. It makes more sense to just compare fall to spring for various years so watch for that tomorrow. (And thx to a NOAA team for some timely help on file accessing side!)

Technical note: this is technically difficult to make because of the immense initial file size  prior to cropping down to the Arctic Ocean. Yet at the end, it is not a large file though not all web browsers seem able to display forum mp4. However download seems to work ok and can be viewed on your local movie player. Even Opera is showing an artifactual green stripe down the Fram that is not in the original file or its QuickTime representation. However a crop at the level of the original gif seems to cure this problem. Note the day-number is initially hidden under the inept controller.

28
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 11, 2018, 05:02:35 PM »
Ice pack motion -- and Fram export -- really picked up this fall and has continued into January 2018. It's easy to see but difficult to describe ice pack motion.

The pack has gotten much more fluid as first and second year ice has come to predominate. Wind circulation drives ice motion but the coupling depends on roughness and ridges and is resisted by ice keels. Ice motion in turn controls surface oceanic currents (though not those at depth such was western bathymetric boundary currents).

Watching the 2007 ice age video, another two weeks of that weather around the minimal extent would have resulted in a total ice blowout. That failure mode, which is a major alternative to the drip drip drip of the trend line, would have been 'premature' in the sense that Arctic Amplification of the air and Atlantification and Beringification of the portal seas had not progressed to the extent seen today and so would not have been able to sustain fall open water. (The Arctic Ocean is far too warm to seriously freeze once its stratification is stirred up.)

The ice is currently being exported as two merged streams of the last thicker ice. However it's not easy to draw an ice envelope over a 10 Sept 17 satellite image that shows which ice will be exported (or be in export position) by 11 Jan 18.

The problem here from the AI perspective is that feature-tracking tools like SIFT work best on consecutive days. However they aren't able to follow an initial tracking point over a season because point features don't have stable signatures. Small regional features do, and at least to the eye, remain recognizable even as they rotate and deform.

However the eye of even the dumbest person is a whole lot better at seeing this than the smartest AI.

Thus the issue of 'virtual buoys' is unresolved. With the advent of all-season Sentinel-1AB and its daily tiling up at DTU, the data is there to track ice motion at high resolution (if you like large files). However the 'line integral' problem of upgrading daily movements to buoy-like drift tracks has not been resolved on a seasonal or multi-year time scales.

Technical note: I've belatedly noticed that ImageJ has far better features for processing huge series of daily satellite images than Gimp. These are buried in sub-sub-sub menus of the Image menu and have to do with tiling (called montage), re-layering, adding date labels in clean text from constituent file names, allowing very fast simultaneous processing steps on all layers such as adding arrows, adjusting global contrast, enhancing local contrast, and ability to save out in greatly reduced file size as forum-shareable mp4.

Indeed the single best way of scanning an animation is simply mousing the slider back and forth just in the stack window. Here you can see immediately whether a project has an prospects of going anywhere, prior to doing the many subsequent steps.

The old-fashioned scatterometer images of ASCAT works quite well for ice pack movement. Here we could care less about its careful instrumental calibration of σ0. A lot of researchers don't get this: when trying to draw out feature recognizability, the information is in there, but the originals are highly sub-optimal for that purpose, whether following on with eye or AI. Below, adaptive contrast enhancement is piled on top of a conventional histogram stretch. ASCAT comes as rgb but is actually grayscale; were it in color like Sentinel-2AB white-on-white, decorrelated channel stretching would apply.

The mp4 below runs from the Sept minimum up to yesterday ... the caption shows day-number rather than calendar date. The epoch converter site tabulates these. The default forum mp4 setting is no-loop but that can be changed under the stop-start arrow. However there is no way to add a final frame delay other than high multiplicity in the original gif stack. The controller can be hidden and mouse-down will play or pause. 'Open video in new tab' results in an obligatory download at least in Opera. Copy-overs of mp4 posted elsewhere does not work in the manner of pngs or gifs.

Here parent gif was 695 pixels wide but for some reason the mp4 is going slightly out of bounds. (But at least it is playing and scrollable!) The 121 day file is just 3 MB at 150% resizing and high quality mp4 export so 2-3 years of continouse ASCAT could be displayed here, more by cutting to every 2nd or 3rd day. Note the quality of single day frames remains better in gifs.

Enhancements have been very successful here in suppressing some of the weather noise and promoting longer term recognizability of features. There's no Beaufort Gyre nor Transarctic Drift in sight though some days the wind pattern needed for the BG will set up on nullschool for a few hours.

See also the blow-up of the rotating block of ice along the CAA over at
https://forum.arctic-sea-ice.net/index.php/topic,416.msg138526.html#msg138526

29
Arctic sea ice / Re: Arctic Image of the Day
« on: January 11, 2018, 03:26:50 PM »
Here is an odd bit of floe motion that occurred this fall during the big ice pack lurch to the west and CW rotation, Nov  27 - Dec  17 . The circled block of ice is pinned between the immovable islands of the CAA and the main westward moving ice pack. It responds by rotating in position.

We see this same effect happening to tributary ice streams over a 15 year time scale on the east side of Petermann glacier, see gif animations on that forum.

It is also very similar to what happened over 20 myr to the Transverse Range off Santa Barbara, Ca (the same area in the news because of the Thomas Fire and subsequent landslides). The plate tectonics there was animated years ago by Tanya Atwater of UCSB.

http://emvc.geol.ucsb.edu/2_infopgs/IP4WNACal/dSoCalifTect.html

30
Developers Corner / Re: Creating Animated GIFs
« on: January 10, 2018, 11:45:46 AM »
Panoply provides 9 main plot sizes that are described in rather odd units. These can be further interpolated in 10 'size' increments. The table below looks at pixel dimensions of the resulting saved-out stereographic circle png images.

Those are computed by opening each size graphic in Gimp, adding an alpha channel, whiting out text and color key, selecting the contiguous white boundary, deleting the selection, followed by "autocrop image" to cleanly delete transparent rows and columns to obtain the minimal square containing the image.

In terms of 700 x 700 pixel limits, the best fit is Panoply size 190 which will give a circle of 686 x 686 pixels. Each 10 units of Panoply 'size' adds 36 pixels to width and height.

There is an issue here with interpolation. The data comes on a grid of a certain resolution (shown in the netCDF header). That resolution might be fairly meagre. Panoply strictly uses linear interpolation, never bicubic, to get up to the requested map size on the requested map projection. There's an option to shut off Panoply interpolation, use a smaller Plot size comparable to data resolution, and then bump up to final map size later with Gimp bicubic or sinc. However that will wreck the correspondence between palette colors and map colors and not allow pixel counting of bins. Consequently it's probably better to precede as described here.

At this width, the maximal size of the palette key with no-gap triangular wings ('Bar Width' parameter) is 50%. This will have a height of 46 pixels (including scale numbers) regardless of its width setting. The width changes as shown in the second table. A wider key allows for more internal subdivisions. That can create conflicts when say a discrete palette with 9 colors is chosen, those can sometimes be resolved by adjusting the range min/max settings.

Since only 14 pixels of height are left from the 700 available, the scale key needs to be lifted into the circle, leaving 686 x 640 of data. This is seldom a problem for the Arctic Ocean centering on the north pole since it is asymmetric, meaning only lower Greenland is covered up by the scale.

Technical notes: the image below shows the circle and key only. The image is really rectangular with transparencies filled by the forum color. The trick here is to take a small screenshot of the two alternating forum colors, fill an extra layer with the appropriate one, and then blend it into the image and rendered text with the 'darken only' layer command in gimp.

In computer graphic manipulations, it is highly desirable to avoid  'micro-management' of image elements, ie squinting at the screen and nudging elements into place. Here the key can be cleanly excised as described above, then added as a floating layer. Here gimp will center the layer but only put it at the top. However by using a vertical flip, it can be put cleanly on the bottom and merged down into the receiving circle image.

1082 x 1082      max.png  size 300
 866 x 866      king.png  size 240
 722 x 722    sjumbo.png  size 200
 686 x 686   sjumbo-.png  size 190
 650 x 650     jumbo.png  size 180
 578 x 578    xlarge.png  size 160
 506 x 506     large.png  size 140
 434 x 434  standard.png  size 120
 362 x 362     small.png  size 100
 290 x 290    xsmall.png  size  80


25%  344 pixels
30%  412 pixels
35%  482 pixels
40%  550  pixels
45%  619 pixels
50%  686 pixels

31
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: January 10, 2018, 11:18:08 AM »
Jim Petit wrote back in #637 of 2017:  I spend a few daysof the new year tweaking all my graphs and charts. I've read the suggestions for changing the baselines and so on; any changes incorporating those suggestions will be made public in early January.
@zlabe linked to the definitive meteorological article used to justify climate baseline definitions, anomaly charts, and what to do during periods of rapidly changing baselines, first article below. It has been cited 131 times; I chased through those to find the best five, all free full text.

The Definition of the Standard MO Climate Normal
The Key to Deriving Alternative Climate Normals
by A Arguez and RS Vose
http://journals.ametsoc.org/doi/pdf/10.1175/2010BAMS2955.1
131 cites since 2011

NOAA's 1981–2010 US Climate normals: an overview
A Arguez et al
http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-11-00197.1

Projecting “Normals” in a Nonstationary Climate
DS Wilks
http://journals.ametsoc.org/doi/pdf/10.1175/JAMC-D-11-0267.1
Discussion of "hinge" functions to represent changing normals

Performance of Alternative Normals for Tracking Climate Changes, Using
Homogenized and Nonhomogenized Seasonal U.S. Surface Temperatures
DS Wilk RE Livezey
Considers eleven alternatives to the annually updated 30-yr average for specifying climate normals

How well must climate models agree with observations?
D. Notz 2015
http://rsta.royalsocietypublishing.org/content/373/2052/20140164
Arctic sea ice-free timing used to illustrate ideas

Public Perception of Climate Change and the New Climate Dice
J Hansen M Sato R Ruedy
https://arxiv.org/pdf/1204.1286.pdf

32
Developers Corner / Re: Creating Animated GIFs
« on: January 09, 2018, 10:36:58 PM »
Below I look at whether RASM ice thinness ten-day forecasts can, after some adjustment, serve as UH SMOS forecasts (or provide it with pole hole infills). The animation compares 26 Dec 17 for the two ice thinness products. These are carefully adjusted to the same upper and lower range of ice thinnesses.

It can be seen immediately that the agreement between the two is quite poor and varies regionally. Thus it isn't possible even in the grayscale domain to adjust endpoints, stretch contrast, and adjust midpoint gamma to bring the RASM into a good match with SMOS.

This is probably because SMOS is 'directly' observable and optimized for thin ice measurement whereas RASM is largely just driven from one day to the next by a physical model off a questionable initial calibration, though both are constrained by AMSR2 to the same ice pack edges.

33
Science / Re: 2018 Mauna Loa CO2 levels
« on: January 09, 2018, 05:16:57 PM »
So this is a ratio of Mauna Loa observed vs honor system claims of progress and/or bottom-up model guesswork on emission sources and sinks? Many countries seemed incentivized to show progress when in fact they are stationary or regressing.

Mauna Loa is worsening faster and faster each year, but that's not quite the bottom line because rising methane, NOx and other greenhouse gases have pushed the real number today close to 500. That is the number that Arctic permafrost and other runaway feedbacks are seeing.

Where are livestock? They are huge sources when the whole ag production chain is figured in.

Where are non-revegatable forest wildfires (permanent loss of sinks), under land use change like conversion of rainforest to cow pasture and palm oil plantations?

34
Arctic sea ice / Re: Latest PIOMAS update (January update)
« on: January 09, 2018, 05:09:18 PM »
wip: thickness animation for the last month. It seems you need to click, even with size less than 700x700, for the animation to start.
I tested sizes on a tiny 3-frame animation over at DevCorner. It seems 601 width and above will not animate properly any more. 600 animates irregularly. 599 and below animate as before.

Note these slightly larger animation still load fully and take up exactly the same amount of server storage space, they just need a click-tab to get going. They do not record visitor view counts otherwise.

There was an admin setting shown once upon a time where the 700x700 was displayed as the choice. Maybe Neven changed that? Or it got defaulted down to 600x600 in the course of other admin changes?

https://forum.arctic-sea-ice.net/index.php/topic,1259.msg138340.html#msg138340

35
Developers Corner / Re: Creating Animated GIFs
« on: January 09, 2018, 04:34:56 PM »
Here I am just exploring why the forum software is not running animations any more. It seems to be size dependent as you can see 100, 300, 500, and 599 pixel widths are working but not the usual 600 or 700. These load fully and display in a new tab but that is a big step backwards from previous forum settings. However a new version 600b is now playing so perhaps it is a fault in loading. However 601, 650 and 699 are loading but not playing.

These are tiny 250 k files of just 3 frames so it is not a size issue.

So what got changed at the admin level??? Actually for purposes of the Arctic 750 x 700 would be a significant improvement over the older 700 x 700 because of the intrinsic proportions of the Arctic Ocean in 'Greenland down' NSIDC position and the native resolutions of major data sources. (However other areas like Antarctica might not especially benefit.)

36
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: January 09, 2018, 04:27:00 PM »
10 days of no data is too much!
RASM_ESRL to resume its forecasts on 14 Feb 18. After a 50 day hiatus! No word on whether they will infill missing data days nor if algorithm is changing (and backwards-comparable). Possibly a good window to get in comments, feature requests and bug reports. Email contacts on web page.

https://www.esrl.noaa.gov/psd/forecasts/seaice/

37
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 09, 2018, 12:38:09 PM »
Ice thinness on 08 Jan compared for the last 8 years; bulk ice salinity changes 01-07 Jan 2018. Both need a click-tab to display properly.

The available date range for UH SMOS is too short to speak about trends and anomalies but the last two years are showing considerably more thin ice for this late date in January than previous years, including the blow-out year 2012 (which is 2013 in January terms).

The issue of departure from climate normals is discussed in depth here:

https://forum.arctic-sea-ice.net/index.php/topic,2223.msg138433.html#msg138433

38
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 08, 2018, 07:29:42 PM »
Nice. SMOS is probably the best single tool for monitoring progression of the freeze season. They don't provide any forecasts at this time though perhaps it could be integrated with NOAA's RASM-ESRL forty-frame ten days out when that resumes.

Just cross-posting to our automated script animation effort which is using PanoplyCL on daily UH SMOS netCDF files as its instance for range optimized display. The first post explains how to compare the same dates in various years via differencing map animations in Panoply, ImageJ or Gimp; the second how to optimize data to palette for visualizations.

https://tinyurl.com/yadgrfsq file repository
https://forum.arctic-sea-ice.net/index.php/topic,1259.msg138130.html#msg138130
https://forum.arctic-sea-ice.net/index.php/topic,1259.msg138256.html#msg138256

39
Developers Corner / Re: Creating Animated GIFs
« on: January 08, 2018, 06:02:43 PM »
The main mistake seen in Panoply-type map products has to do with setting the range. The impulse is to have the palette represent the full data range (the 'fit to data' button in Panoply scale tab).

However the full range often has noise, outliers and/or long thin tails, for example Arctic ice thickness today is overwhelmingly in the 0-2 m thickness range but a few 5-6 m thick floes still hang in there.

In this case 'fit to data' will make poor use of the color palette. Too many palette colors are wasted on thickness bins that are scarcely used and so barely visible in the product; not enough palette colors are left to resolve thinner ice classes.

The first approach to rectify the display is a 'histogram equalization' command that non-linearly stretches the image (and embedded palette) to create an optimal match between value frequencies and the number of colors available to represent them.

Panoply does not offer this, just a monotonic log10 virtual adjustment of data which helps in the ice thickness instance but not very broadly.

Panoply does not require that 'fit to data' be used. Instead the lower and upper ranges can be set manually. This has two effects: linear stretching of the palette to just the new range and lumping of outliers to the single colors of the left and right scale triangles.

These values cannot be saved as Plot Preferences. That wouldn't make sense because the next map made might be salinity or surface temperature so thickness ranges would be generate nonsense.

However, exporting as PanoplyCL script will save those settings. Thus in the common situation making say a 100-day animation of a single Geo2D file within a set of 100 daily netCDF packages.

The script can be revised so that it scrolls through the list of local file paths saving out each png as an animation frame. Indeed it could scroll through a choice of range settings too.

//how lower and upper scale settings appear in a saved PanoplyCL script
myplot.set ( "scale-min", 0.5 );
myplot.set ( "scale-max", 1.5);

The animation below scrolls around various range settings of the same UH SMOS sea ice thickness file for 03 Jan 2018. Watch how the ice display changes as the min and max range numbers are varied.

Depending on what the range of most interest is, the appropriate setting will effectively highlight the chosen ice classes (while suppressing less interesting ones as single colors that can be picked and replaced later in Gimp).

The gif version has been reduced to forum constraints and so is slightly dithered by sinc rescaling; it is now running with a click but without a new tab. Exporting this gif as Movie mp4 reduces file size by 4:1

40
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: January 08, 2018, 10:40:19 AM »
JAXA 2018 data and extent graphs still not available
Ditto NOAA's RASM-ESRL: it is still frozen on 26 Dec 17 with no advisory 13 days later about when or if it will resume. [[Update: forecasts to resume 14 Feb 18]]

The attached image, adapted form @zlabe, wraps up 2017 extent for the Chukchi. The definition of that sea is elusive, with boundary definitions varying widely by source. The inset shows a common choice that may be what NSIDC used for the data.

Researchers at NSIDC often do not use this boundary in their journal articles, more often taking a contour line such as -150 m as the northern extent, which makes more oceanographic sense than a latitude line oblivious to bathymetric shelves and basins. It is also common to see no definition, simply Chukchi text floating conceptually north of the Bering Strait.

The scale has been changed to percent of maximal possible extent as this is more to the point of seasonally ice-free. By pixel counts, 63% of maximal extent was realized over the year but only 44% over May-Dec and similarly over the insolation season. So we are about halfway there to 'seasonally ice extent-free' for the Chukchi and many of the consequences will have set in already.

On the admin oddities front, it appears that "viewed n times" is not working today.

41
Walking the walk / Re: Managing PV + battery system
« on: January 07, 2018, 04:22:09 PM »
Excellent posts, Etienne.

Today I climb the mesquite tree to prune off the top and one side as it is shading our rooftop panels with the low winter sun angle. It will grow back worse than ever though. Tomorrow the guys come out to change the bracket legs a little because the first row of panels is shading the second from 2:00 pm on, again a winter problem. We are at 32.2° N.

It doesn't matter really because as just a residence, we are close to net-zero and would be paid little by the utility for giving them excess energy because of how they lobbied bribed the state rate commission.

Clothes dryer? I just sling the wet laundry over the back of the patio furniture. It is bone dry in an hour. Like Southern California, we have been 3-4ºC over climate for months now. It has not rained since late July. Biggest issue is the cute little squirrels (Ammospermophilus harrisii). They come on the deck and chew up socks, cotton clothing and even shoe laces to line their nests.

42
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: January 07, 2018, 03:55:30 PM »
Now the question is, what got changed to cause our usual gif animations not to play? Below is a tiny 3-frame animation intended show what ice ages are being exported out the Nares. This is animating normally so let's try a larger one but still well within the 700x700 pixel and file size constraints. It is not animating without a click which somewhat localizes the admin settings problem. A half-size also does not animate but a quarter size does. Weird!

43
Older ice age classes -- which are strongly correlated with ice thickness and so volume -- have been pinching out for decades. A vastly improved new algorithm for that shows the situation is worse than thought, ie almost all the ice is now first and second year. (The 'graduation' date is usually taken as mid-September.) The 01 Oct 17 concentrations are shown below. This affects Piomas because the level of its algorithmic error increases with ice thinness. That's better captured by UB and UH SMOS (or snow-salinity corrected CryoSat) for sub-meter.

Gifs are still not animating because of admin changes (?) so the animation below needs a click. Note some of the very oldest remaining ice was poised for Fram export on this date; very active export did resume later so that ice is gone.

A new tracking algorithm for sea ice age distribution estimation
AA Korosov et al
https://www.the-cryosphere-discuss.net/tc-2017-250/tc-2017-250.pdf

Effect of Snow Salinity on CryoSat-2 Arctic First-Year Sea Ice Freeboard Measurements
V Nandan et al 17 October 2017 DOI: 10.1002/2017GL074506

44
Developers Corner / Re: Creating Animated GIFs
« on: January 07, 2018, 09:24:35 AM »
I've noticed some confusion concerning how to combine data series according to arithmetic, statistical or logical rules.

This can be done in Panoply provided two maps have been made and are open by clicking on the 'Combine Plot' icon. The options are then given as shown below in left column. (Here 'merge' refers to over-writing NaN with data when available.)

It is not possible to then combine a third map with the result of combining of the first two. That would require exporting the first product and then re-importing it as a new netCDF file. However Panoply only emulates 'ncdump', not 'ncgen' so the latter would have to be done in a command line tool.

It is also fairly tedious to combine say a month of two series of daily maps as 'Combine Plot' would have to be repeated 30 times. It may be possible though to script this in PanoplyCL version of Panoply.

A better option in some ways is to select the grayscale palette for both maps, save them out, and combine in ImageJ or Gimp. All Panoply palettes are 8-bit [0,255], in effect color lookup tables or CLUTs so map color can be added back later.

Note too that Panoply uses bilinear for interpolation to make larger size plots, ie not bicubic or sinc. So if you are exceeding the intrinsic scale of the data, your maps sizes will be be rescaled in this way (unless interpolation has been shut off in Preferences).

The number of colors never exceeds 256 however. Panoply does not produce a dithered product: the colors in the associated map palette are exactly those of the map.

Once the two maps have been exported as grayscales, they can be combined in ImageJ (middle column) and/or Gimp (right column). This makes sense if the grayscale value represents a simple numerical data parameter. Data cannot be represented at higher precision than 8 binary 'decimal points'; there is no 16, 24 or 32-bit precision available within Panoply; only ImageJ supports this.

For example, Gimp will conveniently averages a whole month or year of data when given 30 or 365 layers of grayscales. The product is a new grayscale where each pixel represents the numerical average of the stack of pixels above it. That can be re-colored using any of the thousands of climate science palettes online using its CLUT in 'indexed color' (gimp) or lookup table (ImageJ).

It is easy to pass Panoply images back and forth between Gimp and ImageJ. The key trick for combining more than one pair of maps, ie combining time series (animations) is to horizontally tile up all the layers into a single image in gimp. After completing the math or logic operation as one step on a pair of tiles and applying the CLUT, the tiles are sliced back into single frames and reloaded as layers for saving out as animation.

Most of the operations work pointwise, at the level of a single pixel. They do not consider the values of neighboring pixels (2D local information). However some of the ImageJ commands will consider a 3x3 or larger neighborhood, eg a median filter.

The most important of these is the adaptive contrast tool (menu item CLAHE). For satellite imagery
the actual observed corrected value is critical for the original quantitative design purpose, say radar return brightness for salinity. However ice and snow scenes tend to have very little contrast. So if your interest is primarily in visual effective display, it may be better to use non-linear contrast stretching (some form of grayscale histogram equalization). Example: ASCAT imagery can be enhance to show ice pack motion far better than the original.

A second topic in combining Panoply maps is illustrated below. This involves mask replacement. The main application is to pairs of maps which show ice and open water properties, respectively. If the first netCDF file shows a property only defined over the icepack, uses a second color for open water, and a third color for land, it can be combined with a second netCDF file showing a different property (usually for the same date) only defined over open water.

This only works because Panoply does not dither its output maps. The 'select by color' global tool in Gimp can then select each of the complementary sets in the 3+way partition. By 'deleting' ice to transparency in the upper open water layer, water and ice layers can be combined into a new layer using 'new from visible'. I sometimes replace land with the background blue-gray of the forum which gives a further effect of transparency, only showing data.

The only issue arises if a gif animation is being made. The number of colors there is limited to 256. So if two complex palettes are used initially, this limit will be exceeded and the animation ruined. However it is easy to cut the initial palettes down to 128 colors each and import them into Panoply.

The example shows sea water and snow/ice surface temperature from two ESRL netCDFs using a single palette. This works ok visually even though the temperature ranges are different and the ice has a natural reddish boundary demarcating the two. It would have been possible to do additional like snow depth on land but visual complexity may begin to outweigh the benefits (of being easier to understand data presented together rather than in a pair of images or pair of unsynchable animations).

45
Arctic sea ice / Re: Arctic Image of the Day
« on: January 06, 2018, 08:23:09 PM »
Nice photo (click to view properly) below of walrus hauling out on some Arctic sea ice, where and when not provided.

Despite it all being in plain view, I am totally baffled (as usual) as to how it should be scored for area, extent, concentration, thickness and volume. For example, what is the freeboard on that slanted floe behind the walrus? How should that jumble of snow, ice and air be treated? What do the various satellites see looking down?

Life is so much easier when some algorithm with 25 km x 25 km does the scoring and gives us a single number for the whole Northern Hemisphere.

46
Science / Re: Importance of pollution and clouds in the Arctic
« on: January 06, 2018, 03:38:54 PM »
Some interesting remarks in the article, notably about the irrelevance of biomass burning to radiative properties of Arctic clouds. (Note algal surface growth, not so much soot, seems behind Greenland darkening). It's all about plume tracks and their dilution with distance: hypothetical reductions in Asian pollutants may well be offset by increased Arctic shipping emissions.

The article addresses 2005-10 and does not provide any products relevant to predicting cloud contribution to the current freeze or melt seasons.

High Sensitivity of Arctic Liquid Clouds to Long-Range Anthropogenic Aerosol Transport
Q. Coopman, TJ Garrett et al
3 Jan 2018 DOI: 10.1002/2017GL075795

The rate of warming in the Arctic depends upon the response of low-level microphysical and radiative cloud properties to aerosols advected from distant anthropogenic and biomass-burning sources. Cloud droplet cross-section density increases with higher concentrations of cloud condensation nuclei, leading to an increase of cloud droplet absorption and scattering radiative cross sections. The challenge of assessing the magnitude of the effect has been decoupling the aerosol impacts on clouds from how clouds change solely due to natural meteorological variability.

Here we address this issue with large, multi-year satellite, meteorological, and tracer transport model data sets to show that the response of low-level clouds in the Arctic to anthropogenic aerosols lies close to a theoretical maximum and is between 2 and 8 times higher than has been observed elsewhere. However, a previously described response of arctic clouds to biomass-burning plumes appears to be overstated because the interactions are rare and modification of cloud radiative properties appears better explained by coincident changes in temperature, humidity, and atmospheric stability.

Increased concentrations of cloud condensation nuclei (CCN) cause cloud droplets to become more numerous and, for constant liquid water content, this leads to smaller droplets and higher radiative cross-section densities.

The radiative impacts of CCN are important enough to potentially lead to a warmer surface and accelerated melting of arctic sea ice, particularly in winter and spring when the longwave response dominates and pollution levels are high.

The last decade has seen a lengthening and intensification of boreal forest fires that has led to increased biomass-burning (BB) aerosol concentrations in the Arctic, a trend that is expected to continue.

On the other hand, a downward trend in mid-latitude anthropogenic (ANT) emissions has lowered concentrations of arctic sulphur although this may be offset by future Arctic industrialization and shipping.

Assessment of the impact of these aerosol changes on arctic clouds has been a challenge because surface and airborne observations in the Arctic are sparse, aerosol compositions are regionally varied and complex, and both aerosol transport and cloud formation are determined by meteorological conditions, in particular by the humidity, temperature, and lower tropospheric stability (LTS).

Our study aims to robustly isolate how lower-latitude ANT and BB aerosols affect clouds over the Arctic, independent of local meteorological changes. For maximum coverage, we use space-based data sets for the retrieval of low-level liquid cloud properties, and we quantify the magnitude of aerosol-cloud interactions (ACI) by vertically and horizontally colocating clouds with pollution concentrations from numerical tracer transport model output for the Arctic for a period between March and September for the years 2005 to 2010.

Here we looked at the sensitivity ACInet of arctic clouds to passive pollution plumes from distant sources rather than the sensitivity to local aerosols ACI. Precipitation can remove aerosols during long-range transport and therefore decrease the value of ACInet relative to ACI. We find that observed values of ACInet for anthropogenic pollution plumes already lie close to a theoretical maximum value of 0.33, implying that values of ACI are either similar or not significantly higher. N

Arctic clouds are more susceptible to pollution plumes than other regions. It cannot be explained by the low concentration of aerosols because the logarithm of the ACInet already take into account this effect. A hypothesis is the favorable condition of the Arctic region with high LTS. It is possible that values of ACI are particularly high in the Arctic due to elevated LTS and a reduced potential for vertical mixing with sub-saturated air. In less stable mid-latitude regions, mixing processes decrease the sensitivity of clouds to aerosols by enhancing droplet evaporation.

Regardless of the precise mechanisms, the implication of the measurements is that arctic climate may be particularly sensitive to any future changes in anthropogenic pollution concentrations. Determining the effect of aerosol-cloud interactions on surface temperatures is complicated by the unique physics of the region: increasing ? not only brightens clouds but can also lead to a higher longwave cloud emissivity; either a significant net warming or cooling occurs depending on ? , the season, and the coverage of sea-ice.

In the future, a combination of reductions in emissions of mid-latitude pollutants and increased wet scavenging in a warmer climate is anticipated to reduce the arctic aerosol burden by 61.0% by the end of the century. Based on the ACI values found here, this can be expected to correspond to an 18% decrease in ? , but with a possible compensating increase due to increasing arctic maritime transportation and industrialization. A further consideration is that the dynamic response of cloud amount to aerosols is itself a function of aerosols and meteorological conditions.The ultimate climate impact remains to be determined.

Air in the Arctic is extraordinarily sensitive to air pollution, and that particulate matter may spur Arctic cloud formation. These clouds, Garrett writes, can act as a blanket, further warming an already-changing Arctic.

"The Arctic climate is delicate, just as the ecosystems present there," T Garrett says. "The clouds are right at the edge of their existence and they have a big impact on local climate. It looks like clouds there are especially sensitive to air pollution. Early Arctic explorers' notes show that air pollution has been traveling northward for nearly 150 years or more. This pollution would naturally get blown northward because that's the dominant circulation pattern to move from lower latitudes toward the poles," he says. Once in the Arctic, the pollution becomes trapped under a temperature inversion, preventing the accumulated bad air from escaping.

Which regions contribute to Arctic pollution? Northeast Asia is a significant contributor. So are sources in the far north of Europe. They have far more direct access to the Arctic. Pollution sources there don't get diluted throughout the atmosphere."

Scientists have been interested in the effects of pollution on Arctic clouds because of their potential warming effect. In other parts of the world, clouds can cool the surface because their white color reflects solar energy back out into space. "In the Arctic, the cooling effect isn't as large because the sea-ice at the surface is already bright," Garrett says. "Just as clouds reflect radiation efficiently, they also absorb radiation efficiently and re-emit that energy back to warm the surface." Droplets of water can form around particulate matter in the air. More particles make for more droplets, which makes for a cloud that warms the surface more.

Satellite images can detect aerosol pollution in the air -- but not through clouds. "We'll look at the clouds at one place and hope that the aerosols nearby are representative of the aerosols where the cloud is," says Garrett. "They're not going to be. The cloud is there because it's in a different meteorological air mass than where the clear sky is."

So Garrett and his colleagues, including U graduate Quentin Coopman, needed a different approach. Atmospheric models, it turns out, do a good job of tracking the movements of air pollution around the Earth.

Using global inventories of pollution sources, they simulate air pollution plumes so that satellites can observe what happens when these modeled plumes interact with Arctic clouds. The model allowed the researchers to study air pollution and clouds at the same time and place and also take into account the meteorological conditions. They could be sure the effects they were seeing weren't just natural meteorological variations in normal cloud-forming conditions.

The research team found that clouds in the Arctic were two to eight times more sensitive to air pollution than clouds at other latitudes. They don't know for sure why yet, but hypothesize it may have to do with the stillness of the Arctic air mass. Without the air turbulence seen at mid-latitudes, the Arctic air can be easily perturbed by airborne particulates.

One factor the clouds were not sensitive to, however, was smoke from forest fires. "It's not that forest fires don't have the potential," Garrett says, "it's just that the plumes from these fires didn't end up in the same place as clouds."

Air pollution attributable to human activities exceeded the influence of forest fires on Arctic clouds by a factor of around 100:1.

Particulate matter is an airborne pollutant that can be controlled relatively easily, compared to pollutants like carbon dioxide. Controlling current particulate matter sources could ease pollution in the Arctic, decrease cloud cover, and slow down warming.

All of those gains could be offset if the Arctic becomes a shipping route and sees industrialization and development. Emissions from those activities could have a disproportionate effect on Arctic clouds compared to emissions from other parts of the world, Garrett says.

"The Arctic is changing incredibly rapidly," he says. "Much more rapidly than the rest of the world, which is changing rapidly enough."

47
Arctic sea ice / Re: Latest PIOMAS update (January update)
« on: January 05, 2018, 11:21:55 PM »
Effect of Snow Salinity on CryoSat-2 Arctic First-Year Sea Ice Freeboard Measurements
V Nandan et al 17 October 2017 DOI: 10.1002/2017GL074506

Sea ice thickness retrievals at the CryoSat-2 frequency require accurate measurements of sea ice freeboard from the main radar scattering horizon is at the snow/sea ice interface.

Using an extensive snow thermo-physical dataset from [measured] late winter conditions in the Canadian Arctic, we examine the role of saline snow on first-year sea ice on the location of radar scattering, its ability to decrease radar penetration depth, and its impact of exaggerating FYI thickness estimates.

Based on the dielectric properties of saline snow commonly found on FYI the vertical shift in scattering is ~7 cm. A thickness-dependent snow salinity correction factor for FYI freeboard estimates significantly reduces CryoSat-2 FYI retrieval error.

Relative error reductions of ~11% are found for an ice thickness of 0.95 m and ~25% for 0.7 m. Our method also helps to close the uncertainty gap between SMOS and CryoSat-2 thin ice thickness retrievals. Our results indicate that snow salinity should be considered for FYI freeboard estimates.

During the formation of seasonal first-year sea ice (FYI), a small amount of brine is expelled upward, resulting in a thin brine layer on the ice surface. With subsequent snow accumulation, there is an upward wicking of brine into the snow cover. This wicking produces brine-wetted snow, primarily within the bottom 6–8 cm, which have salinities ranging from 1 to 20 parts per thousand.  The brine within the snow alters the dielectric and microwave scattering properties of the snow leading to significantly reduced radar penetration.

With the recent and rapid decline of MYI, and its replacement by FYI, the role of snow salinity should be considered whenever FYI freeboard is estimated using CryoSat-2 on local to pan-Arctic scales. [paraphrased selections]

48
Arctic sea ice / Re: The 2017/2018 freezing season
« on: January 05, 2018, 03:38:49 PM »
Meanwhile, still some open water in the Chukchi on the 4th of January according to 3.125 km resolution UH AMSR2 (which is also seen in the U Bremen product, inset). Also a very small amount in the Beaufort but as pull-away polynyas rather than hasn't-yet-frozen.

Green indicates the extent of solid ice (100% concentration). Here the image will display at full height with a click without opening a new tab. Ice thickness is also rather meagre for this date though there's considerable annual variability, second image UH SMOS 03 Jan 18. The same date is available for 2011-2017 as both full scale animation (needs a click to animate today) and small scale all-in-one.

49
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: January 05, 2018, 03:01:49 PM »
no huge files
The mp4 works some major magic through different compression that exploits visual illusions, reducing a 48 MB gif to a 1.8 MB mp4. So in theory could run the Ascat for 5 consecutive years and still stay within bounds. However other things break as the number of individual frames gets too large.

It is all playing fine in the Opera browser (which I use because of its totally effective code level ad blocker).

50
Arctic sea ice / Re: Latest PIOMAS update (January update)
« on: January 05, 2018, 02:26:01 PM »
It seems you need to click, even with size less than 700x700
It sometimes helps to save, crop off one column of pixels from an edge, optionally do a gif-differencing, then re-save and re-load to forum. Though today nothing seems to help. It is uploading all the gif frames today rather than only the first as it sometimes does.

Here is the matching Ascat for the same 32 days. Click to view. Piomas does fairly well on Fram export but isn't effectively displaying the action over at the narrower Nares Strait.

Note the ice being exported out the Fram is a merge of two ice streams, one originating from the Laptev and the other thick coastal CAA ice. (Textbook depictions invariably show ice moving out from the Chukchi along a 'Transarctic Drift' but 20 years of sea ice age animations and buoy tracking do not.)

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