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Threebellies

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Re: MOSAiC news
« Reply #100 on: October 09, 2019, 11:27:28 PM »
Quote
This search for a suitable floe is ongoing

This has become a common problem for placing instruments on the Arctic ice. It also means measurements are being done under unrepresentative conditions.

Using sampling to ultimately estimate the conditions of the entire Arctic via statistical analysis requires representative (usually random) sampling but this is no longer possible. The result is likely over estimation of sea ice thickness and stability.

Not only that, it’s indicative of a paradigm shift. If ice conditions aren’t good enough to take proper samples, well, that suggests we’re a lot closer to a BOE event than some would acknowledge.

Voyages should be done like this yearly, I wish we had this back when there was actually sea ice and not slush up there.

uniquorn

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Re: MOSAiC news
« Reply #101 on: October 10, 2019, 12:30:10 AM »
crop of the mosaic multisensor map, oct7-8 showing ~20km south eastward drift since yesterday. An interesting start to this expedition. Red and white bar at the top is 20km
« Last Edit: October 10, 2019, 12:43:08 AM by uniquorn »

jdallen

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Re: MOSAiC news
« Reply #102 on: October 10, 2019, 07:28:31 AM »
It's not entirely clear that melt season is over in some parts of the Arctic Ocean.
<snippage>
It's pretty clear from the temperature data, the extent/area data and the sensor data from sources like Mosaic that the transition from melt to refreeze is no where near as distinct as it was prior to the last decade or so.

We are already seeing Arctic breakouts.  Heat intrusions above 75N are continuing pretty much unabated.  I suspect Mosaic will not show signs of either significant thickening or serious expansion of the pack into the peripheral seas for quite some time.
This space for Rent.

A-Team

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Re: MOSAiC news
« Reply #103 on: October 10, 2019, 10:14:34 AM »
Quote
transition from melt to refreeze is nowhere near distinct
Right. The 1D extent graphs don't capture geolocated nuances.

It turns out to be easy to pattern-match radar images of the Mosaic floe in early October back to visible images in Worldview in late September (before it all went dark) because in context, the floe moved as a mildly distorting rigid body over this time frame.

This enables convenient determination of the floe's provenance, daily displacements and deformations using the animation feature of WV on clear days back to 18 Mar 2019 when WV first had enough light.

Note the Mosaic radar archive goes back to Sep 8th and is cloud-free unlike visible. However its resolution is inconsistent, with a big jump on Oct 7th after the floe was selected, plus it suffers from a now-irrelevant ship track overlay. In #74, the floe is tracked back to Sept 21 in radar.

https://forum.arctic-sea-ice.net/index.php/topic,2906.msg232032.html#msg232032

However PolarView goes back even farther with its Sentinel archive. However visible and near infrared carry other information such as surface temperature, insolation history, proximity to algal blooms and wildfire soot deposition.

Because this floe will be so intensively studied over the next year, it is important to walk it back in time to better understand its 'initial state' in the Mosaic project.

The last 30 days of sea ice motion suggest that the floe has experienced very little net tendency towards resuming TransPolar Drift. The floe may have been in sub-100% concentration (light blue in OsiSaf) in mid-Sept and earlier.
« Last Edit: October 10, 2019, 12:32:29 PM by A-Team »

A-Team

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Re: MOSAiC news
« Reply #104 on: October 10, 2019, 12:47:35 PM »
Mosaic buoy data to date can be checked here. There are 16 surface velocity profilers so far; the downloads clean csv text files with hourly lat/lon to 4 decimals, drift speeds to 3 decimals in m/s, and surface temperature to 1 decimal.

However they don't triangulate the buoys nor give the ensuing Delaunay deformation over time, for which 16 Excel sheets is ideally suited (and Goog Earth Pro freeware for the graphic animation).

This is an example of where a forum member could add value to Mosaic by using the online distance tool that Uniq provided earlier. GPS positions are always given relative to the WGS84 ellipsoid of revolution rather than the earth sphere or actual geoid (available as the first 100,000 terms of a spherical harmonic expansion).

The AWI help desk writes that a more interactive version which will be online in mid November. [Hallo? Bei uns wäre diese grundlegende Softwareaufgabe erledigt gewesen, bevor das Schiff gesegelt wäre! Zur Sicherheit muss der Polarstern nahezu in Echtzeit wissen, wie sich die Belastung im Eis aufbaut, nw?]

I'm mildly astonished that oceanographers have not set up an online tool that does this.The triangle math is from the Babylonians 4000 bce, the rest was published in 1934 by a Russian descendant of a French officer captured during the Napoleonic invasion of 1812. It is not especially computationally expensive: the algos are seasoned github deposits for video gamer programmers.

The geometric set-up is very similar to USGS arrays to monitor nrt tectonic plate collision in Nevada and so earthquake strain in southern California (though some of that is interferometric as displacements are in microns). This is the PS's concern as well: sudden opening of leads and rapid formation of pressure ridges.

I could see it taking me a couple hours to start supplying the PS with nrt continuum mechanics in its immediate vicinity (but surely they have laptops on board?). Because the buoy gps is so accurate, this might improve on whatever deformation overlay they have on PS bow radar, though that would be really rt instead of hourly.

The issues are kriging up the resolution and assimilating the observed current system of S1 rifts. The ambient ice has been under extensional tension rather than compressional.

The explanation for the visualization delay must be that buoy arrays have rarely been deployed in ice: the Arctic Ocean has long been seriously under-instrumented. So three cheers for Mosaic's deployments -- this should have been done every year since Iridium went commercial in 1998.

Found a buoy forensics match to the first deployment question in #40 and chased down how we got to the words 'buoy' and 'die Boje' (plural Bojen). The English pages at Mosaic are sometimes delayed a few days.

https://data.meereisportal.de/gallery/index_new.php?active-tab1=method&buoytype=all&region=all&buoystate=all&expedition=MOSAiC&submit3=Anzeigen&lang=de_DE&active-tab2=buoy
« Last Edit: October 10, 2019, 05:00:54 PM by A-Team »

uniquorn

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Re: MOSAiC news
« Reply #105 on: October 10, 2019, 08:40:25 PM »
Nice detective work. Don't we need to see the overall buoy set up before launching into continuum mechanics? edit: not that I know how to do that ;)
Based on today's multisensor map I think I've located a buoy on or very close to Polarstern for the last few days. iabp 300234068213470. I'm not sure if this is value for MB but here is it's drift track since records started.
GFS forecast (from Nullschool) shows a yo-yo swing in temperature in the vicinity of Polarstern over the next 24 hours or so.

By 12 UTC on 8th Oct, a plume of mild arrives up from Svalbard, yielding temperatures slightly above 0 C but it is short lived and 12 hours later at 00 UTC on 9th Oct, it forecasts temperatures below -10 C as cold air is advected across the Pole from the American side towards Russia.
warmest temp was -2.4C, still quite warm. Of course, it might be sitting in the hold somewhere so the temps might not be relevant. The drift should be valid though.
edit: tech note: gif is optimised to reduce size in gimp, it may be necessary to deoptimise if downloaded. OT they must be an amusing bunch at iabp
« Last Edit: October 10, 2019, 09:38:10 PM by uniquorn »

uniquorn

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Re: MOSAiC news
« Reply #106 on: October 10, 2019, 09:20:19 PM »
Thanks to meerisportal and the mosaic team, here are their prepared buoy charts.
Quote
Grosfeld, K.; Treffeisen, R.; Asseng, J.; Bartsch, A.; Bräuer, B.; Fritzsch, B.; Gerdes, R.; Hendricks, S.; Hiller, W.; Heygster, G.; Krumpen, T.; Lemke, P.; Melsheimer, C.; Nicolaus, M.; Ricker, R. and Weigelt, M. (2016), Online sea-ice knowledge and data platform <www.meereisportal.de>, Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 85 (2), 143-155, doi:10.2312/polfor.2016.011.
Now to set them all up from the same start date/time and see where they all are :)
https://data.meereisportal.de/gallery/index_new.php?active-tab1=method&buoytype=all&region=all&buoystate=all&expedition=MOSAiC&submit3=display&lang=en_US&active-tab2=buoy
(english version)
seem to have lost the buoy names somewhere....fixed
« Last Edit: October 10, 2019, 09:35:12 PM by uniquorn »

uniquorn

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Re: MOSAiC news
« Reply #107 on: October 10, 2019, 10:12:16 PM »
A brief break in the clouds. Worldview, mosaic rough location, 84.9N 135.7 (no timestamp on worldview) https://go.nasa.gov/3286OQU

A-Team

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Re: MOSAiC news
« Reply #108 on: October 11, 2019, 12:16:54 PM »
Quote
WV graticule? need final set of buoys? buoys too near the Polarstern? Physics of materials?
Spectacular VIIRS above ... but when I went to the link, it had been over-written by something unrecognizable. That happens all the time at WV as swath updates roll in. I suppose the bright networks of veins are leads (resp. thin ice) with warmer water showing through. These might be worth mapping as lead openings are recurrent weaknesses.

The 43 page explainer for the Visible Infrared Imaging Radiometer Suite is here:
https://lpdaac.usgs.gov/documents/134/VNP03_User_Guide_V1.2.pdf

WorldView doesn't do graticules well, 80º is the first latitude out from the pole with 30º increments on longitudes. Better if NASA provided options for controlling the OpenStreetMap vector graticule and fixed code so animations captured it. It's possible but inconvenient to capture the timestamp on a per swath basis which is critical to synching with other satellites.

While WV does have very accurate mouse-over lat/lon in the corner, those don't stay tied to a floe after image save or screenshot. Mosaic Multisensor offers a very nice graticule on their higher resolution images (from Oct 7th on).

For WV, if your save includes long lines intersecting the 80º circle, that chord length is enough to accurate rescale AMSR2_Large and capture its graticule as overlay for 75º and 85º plus 1º longitude increments.

/=/=/=/=/=/=

The ship itself is one big fancy drift buoy, not only reporting its GPS but also whatever parameters those six containers of atmospheric instruments in the bow are recording. Plus its azimuthal heading which the surface velocity profilers do not provide.

A rigid body can undergo translations (GPS) and rotations (azimuth changes) that are not relevant to the brittle failures of concern (opening and closing of leads, over-rafting of floes, slip-strike shearing and pressure ridges/keels).

Mosaic actually likes leads because they release ocean heat to the atmosphere and are important to study for overall energy flows, just not leads that cut LAN and power lines and strand personnel at field stations.

Taking any three buoys that define a good triangle (not co-linear, no overly acute angles), the lengths of the three sides and area enclosed do not change over time in a rigid ice pack. If the area increases, it means leads have opened under extensional forces; if the area decreases, compressional collapses have occurred.

If say 70 buoys are deployed, a goodly system of coupled triangles (the perimeter being the convex hull) emerges for monitoring regional ice deformation. Here ice brittleness increases non-linearly with colder temperatures. Since the SVPs record air temperatures at the ice surface and since the seawater underneath the ice is clamped to -1.7ºC, the temperature profile through say 2m of ice can be estimated.

Mosaic has two different buoy scales, high resolution local on and around the chosen floe and more sparsely regional. There aren't enough buoys out there to do the whole basin. There has been talk of large-scale air drops of passive devices like radar corner reflectors that would show up as points of light on Ascat etc. Hasn't happened.

Someone posted a great animation (can't relocate :() of the ice temperature profile behavior under an upper sinusoidal (seasonal) boundary conditions, plus an explicit solution of the governing heat equation. Thus if the a curve is fitted to the buoy's hourly temperatures, each term in its fourier expansion will have an exact solution -- and these are additive solutions.

However real ice has many issues such as surface snow and its complex aging status, frozen-in air bubbles, variable salinity inclusions, brine pockets, crystal dislocations, adherent algae and copepods etc etc meaning that the heat conductivity parameter isn't constant or known. So it is easier just to freeze in a string of thermistors below the buoy.

/=/=/=/=/=/=

We can do a lot better than that cramped meereisportal visual just with a drag-n-drop of all the buoy lat/lon columns onto google earth pro. The advantage of GEP is the liquid rescaling to any zoom, a free parameter for temperature or thickness and mouse-over popups; the disadvantage is there does not seem to be a digitized daily ice edge line around. However there is a way of auto-generating that from say the AMSR2 blue edge.

GEP barely pauses loading a kml file with 250,000 lat/lon waypoints. That would be 30 buoys reporting hourly for a year. Hourly is a bit much given slow drift speeds but it is great for dynamic triangles. There is very little overhead to drawing lines between buoy pairs with the same timestamp.

/=/=/=/=/=/=

The AMSR2 images below compare the ice edges on the Siberian side south of the Polarstern on Oct 10th for 2013-2019 (the 2012 is not provided by the UHH archive). The large format 3.125 km does notably better on growing landfast ice. This narrow strip is difficult to image because of the irregular coastline can occupy part of rectangular gridded pixels.

Clearly autumn 2019 is off to a very slow start; the magenta overlay line on earlier years shows how much open water is still left in the Laptev, the star at bottom shows the Polarstern location. I don't expect the 500 km reach of open water to freeze over any time soon because shallow shelf water been increasingly affected by Atlantification. The Laptev had frozen over completely in 2012-13 by the first of the year.
« Last Edit: October 11, 2019, 07:44:40 PM by A-Team »

macid

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Re: MOSAiC news
« Reply #109 on: October 11, 2019, 01:47:19 PM »
Animations of buoys drift speed attached, code on my github, it should be possible to take a set of buoys and calculate their movements respective of each other.. interesting idea

there's accelometer data in the buoy data as well, I assume this can be related to wave height or ice bits bumping into each other?

Also if anyone has good data files for ice concentration/movements please let me know. I saw AMSR2 has hdf files but they're a bit of a pain, preferably something with coordinates.

uniquorn

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Re: MOSAiC news
« Reply #110 on: October 11, 2019, 08:06:40 PM »
Good step forward on buoy analysis :).
polarstern temps for niall, half a yoyo
« Last Edit: October 11, 2019, 08:12:08 PM by uniquorn »

A-Team

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Re: MOSAiC news
« Reply #111 on: October 11, 2019, 08:28:37 PM »
Quote
should be possible to take a set of buoys and calculate their movements respective of each other
Quick and easy way to do that on a massive scale -- # of buoys and # of times -- is a database mail merging into kml template (keyhole markup language, human readable text like html), let Google Earth do the scalable display over a bathymetry background plus calculate all the distances and polygonal areas for you to very high WGS84 accuracy and then load it up on a web browser so clients don't need GE installed.

Just look at the attached txt file for the triangle ... it's so easy, it's so easy to parse it out and drop into their display engine.

The SVP buoy 2019P152_300234068218450_proc.csv weighs in at just 16 kb for 299 lines. The three buoy triangle, 1 kb. So not talking serious text wrangling here with a few dozen buoys for a year; in SV days our group was knocking out 16 terabyte based scientific displays, trillions of buoys.

« Last Edit: October 11, 2019, 09:36:02 PM by A-Team »

Niall Dollard

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Re: MOSAiC news
« Reply #112 on: October 11, 2019, 10:31:18 PM »
Good step forward on buoy analysis :).
polarstern temps for niall, half a yoyo

Thanks for that plot Uniquorn. So didnt quite reach positive values.

For yo-yo temperatures, it's hard to surpass the eastern slopes of the Rockies. Denver drop of 39.5 C in 36 hours !

blumenkraft

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Re: MOSAiC news
« Reply #113 on: October 12, 2019, 07:41:02 PM »
Life aboard the RV Akademik Fedorov

Link https://www.mosaic-expedition.org/mosaic-school-week-2/
Refugees welcome

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Re: MOSAiC news
« Reply #114 on: October 13, 2019, 01:18:15 AM »
Update: the differencing of successive days of AMSR2_large is an effective way of visualizing closure of the open gap between the Polarstern and the Siberian shoreline: central ice pack edge growth meets growing landfast ice. Growth of that is just now kicking in.

I was just barely able to scale down mosaic.multisensor to overlay the Polarstern drift path on the 3.125 km resolution AMSR2; this require downsizing the radar original to 0.45% to get the path scaled (no sign of TPD yet).

There are a lot of ways to slice and dice the buoy data, the first substantial nrt data set we’ve had to work with, other than satellite products, since the ice penetrating radar archive for Greenland. In past years, 0-1 buoys have been reporting, often defectively, in the entire Arctic Ocean whereas now we have a large active coupled buoy array in the vicinity of the Polarstern..

The data archiving is still a bit rough, for example the second set of buoys below don’t measure snow depth or ice thickness as their meereisportal table indicates. However provisional graphs of temperature and speed are provided as a convenience and updated daily.

The Polarstern itself behaves as a giant buoy since being stably moored on Oct 4th. No hourly database for it accompanies the others. The radar image archive shifted to high resolution on Oct 7th. The pixel dimensions shifted inexplicably from 3500 x 4304 to 3498 x 4302 between the 7th and 9th, causing stacking issues. (Inexplicable because the crop tool has a fixed-size checkbox in all known image software.) The timestamps are all 0500 UTC; lat/lon of the Polarstern are not provided in the extensive legend.

The Sentinel images have different pixel offsets each day. Lagrangian coordinates (co-moving with ship) are being used; they cause havoc with the graticule and drift course overlay. It's more common on satellite series to use fixed eulerian coordinates to illustrate floe and lead dynamic development.

https://data.meereisportal.de/download/buoys/photos/2019P191_deployment.pdf

The first set of RSAQUA-type SVP buoys was deployed by Chinese scientists. These measure GPS position every hour along with temperature. From lat/lon they derived displacements (not shown) by an unknown equation (vincenty? haversine?), from which speeds were determined hourly. These buoys do not carry a wave heave accelerometer. Tides in the open Arctic are too low and slow to give a reading.

I checked into measurement error. One degree difference in latitude on the WGS ellipsoid is 111,111 meters. The GPS is reported to 1 part in 10,000, meaning 85.1234º can barely be distinguished for 85.1235º. Thus the positional uncertainty is 11.1 meters which is inadequate for a cruise missile but plausible this far north.

In calculating items like the changing sides and angles of a delaunay triangulation array, no purpose is served by exceeding the accuracy of the data.

It appears the buoys do not track azimuth. That is, unlike a ship, there is no natural axis unless the floe itself is stably asymmetric. Rotation of the floe in which the buoy is frozen is thus difficult to disentangle from translation.

We have measured large floes spinning around and around in the Beaufort arm eddies in previous autumns. In the vicinity of the Polarstern, the ice is mainly moving en bloc. The arm is forming nor this month and will likely extend up the Alaskan coast to the Chukchi before turning north. The ice will not move in a gyre, it hasn't for over a decade.

A column for changing bearing angle can be added using batch online tools (or spreadsheet formula). I did this for 2019P152 using positions 24, 48 and 72 hours apart; to the extent calculated bearings change more than the track implies, the floe has rotated. Bearing, heading and course are a source of perpetual confusion but see:

https://www.movable-type.co.uk/scripts/latlong.html

There is no column for changes in drift speed (acceleration) but that is implicit as the slope of the tangent line to the speed graph (below). The one I looked at 2019 has a puzzling periodicity. Obviously if other 11 buoys don’t follow in parallel, they are diverging/converging and the ice in between is deforming.

2019P152
2019P155
2019P156

D Watkins, a grad student at Oregon State who studies ‘Arctic lower tropospheric temperature inversions in the CESM large ensemble’ deployed a second set of nine buoys (brand not provided) from the helicopter of the Akademik Federov.

2019P188  2019P196
2019P190  2019P198
2019P191  2019P200
2019P192  2019P203  2019P206

These buoys apparently do have an onboard accelerometer, though the column heading is "accelometer_variance ()" with units omitted but values ranging from 5 to 15. It’s not clear why the buoy should expect any waves in the next 8 months. I tracked down an explanation of sorts from NDBC not specific to this particular buoy:

Quote
How are spectral wave data derived from buoy motion measurements?
https://www.ndbc.noaa.gov/wave.shtml

NDBC-reported wave measurements are not directly measured by sensors on board the buoys. Instead, the accelerometers or inclinometers on board the buoys measure the heave acceleration or the vertical displacement of the buoy hull during the wave acquisition time. A Fast Fourier Transform (FFT) is applied to the data by the processor on board the buoy to transform the data from the temporal domain into the frequency domain. Note that the raw acceleration or displacement measurements are not transmitted shore-side. Response amplitude operator (RAO) processing is then performed on the transformed data to account for both hull and electronic noise. It is from this transformation that non-directional spectral wave measurements (i.e., wave energies with their associated frequencies) are derived. Along with the spectral energies, measurements such as significant wave height (WVHGT), average wave period (AVGPD), and dominant period (DOMPD) are also derived from the transformation.
« Last Edit: October 13, 2019, 01:55:03 PM by A-Team »

blumenkraft

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Re: MOSAiC news
« Reply #115 on: October 13, 2019, 05:12:40 AM »
The official trailer is quite heroic.  ;D

Refugees welcome

gandul

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Re: MOSAiC news
« Reply #116 on: October 13, 2019, 01:28:16 PM »
The official trailer is quite heroic.  ;D
It's just this Zimmer-esque soundtrack that is used for almost everything now, even for Trump Twitter videos.
I see science heroic but on the quiet side. But well OK.
No me lo trago

A-Team

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Re: MOSAiC news
« Reply #117 on: October 13, 2019, 05:54:10 PM »
Mosaic is posting the daily location radar in quasi-lagrangian coordinates, with the point position of the Polarstern and the North Pole determining the moving axis. In normal ship-based lagrangian coordinates, the bow-stern center line and main mast would determine the coordinate system (alternately some asymmetry axis on the floe to which the Polarstern is afixed). The difference is in how rotation is represented.

We are more used to eulerian coordinates in satellite archives where the graticule stays fixed. We went through this all before in the time of Ptolemy and Galilleo.

Whoever painted on the red lines and circle, over-writing the value of the most important pixels, seems not have centered them accurately on the ship which shows clearly as a bright white dot (all that metal reflecting Sentinel's beam back). Perhaps those circles reference a valid timestamp but one different from the S1 which would appear in its file name had it been correctly cited.

At any rate, I adjusted the six dates for which for which they archived S1 at higher resolution, so from Oct 7th to Oct 12th so far. As noted above, some of these are either mis-cropped or slightly rescaled from the others. The Polarstern tied on Oct 4th but those dates are missing (4-6 Oct).

We need to go back to the original files and do this over, right. I am not sure though that all of them are S1 as it does not seem that polarview carries them all at the needed resolution. If so that would mean a tedious navigation deep through the ESA server.

At any rate, despite the visual competition from the crazy graticule and red paint, it was possible to re-register six days of imagery. The four gifs below present the data at four levels of zoom. A lot could be said about leads opening and closing, scene deformation, rotation of the PS floe and so on. These run at 150 ms per frame; download and view frame by frame. I also prepared a single concatenate mp4 that has a better controller but am out of attachments here.

be cause

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Re: MOSAiC news
« Reply #118 on: October 13, 2019, 08:24:01 PM »
https://sabvabaa.nersc.no/  is taken from Andreas T's post on the abandoned Mosaic project thread and covers a similar journey a few years ago .. a good read . b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

A-Team

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Re: MOSAiC news
« Reply #119 on: October 13, 2019, 11:31:20 PM »
New snow buoy deployed by Mosaic on Oct 11th. These seem to work by taking four sonar measurements from above, with calibration of actual snow at time of deployment. The sonar footprint is about 10 sq meters ... necessary because the snow pack is quite variable and subject to drift accumulations (or bare ice spots).

Again, the manufacturer of the device are not provided; very likely the listed contact M Hoppmann of AWI can provide details. However the device is probably very similar to snow buoy 2014S12, deployed during Polarstern cruise PS82 though that one also measure internal ice temperature. Again, it is not the ice mass balance buoy that meereisportal keeps referencing (crossed out below).

https://doi.pangaea.de/10.1594/PANGAEA.875328

The database fields here can be readily integrated with the other 16 sea ice drift buoys in the growing array and its track displayed in GEP as before. Since all the buoys so far are reporting hourly on the hour, that can be used as the indexed field for a single composite flatfile db with just the essential lat,lon column + one additional parameter of choice.

This will allow individual tracks of the entire 17-buoy array to be displayed over bathymetry and coastline with either Voronoi or Delauney triangulation, with easy updating since the year is just getting started. This is just a paste into a kml template, not rocketry science.

https://data.meereisportal.de/gallery/index_new.php

time hourly on the hour   
latitude (deg) to 4 decimals
longitude (deg) to 4 decimals
distance_to_surface_1 (m)   
distance_to_surface_2 (m)   
distance_to_surface_3 (m)   
distance_to_surface_4 (m)   
barometric_pressure (hPa)   
temperature_air (degC)   
temperature_surface (degC)
« Last Edit: October 14, 2019, 12:00:17 AM by A-Team »

A-Team

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Re: MOSAiC news
« Reply #120 on: October 13, 2019, 11:44:09 PM »
Here are those additional floe tracking time series mention a couple of posts back. The first concatenates four levels of zoom into a movie with frame controller; the second presents 07-12 Oct 2019 data in eulerian coordinates that are better if overlays with other satellites are planned.

Here I used the .avi export option out of ImageJ and converted to mp4 with the free online tool:
https://cloudconvert.com/avi-to-mp4

The concept of a massively coupled buoy array is new and not fully implemented at meereisportal. The buoys are already experiencing glitches -- whether at the level of sensors, Iridium transmission or IT processing station at AWI I couldn't say -- that result in missing timestamps, eight in a row (4 hrs) for P152 and one for P188 (below).

These data gaps are not indicated by NaN or dashes as they should be; the csv files just skip the lines with no indication. Consequently, each person using the files has to run a separate detector for them (a new column subtracting consecutive time stamps sorted for anomalies).

The gaps then need to be filled in, most easily by linear interpolation from the lines above and below. If the csv isn't repaired, graphic representation of the buoy will be misleading and worse, be out of temporal synch forever more with locations of the other 16 buoys.

Some of buoys are reporting hourly, others twice hourly. If this seems excessive, it can be reduced to every 4, 8, 12, 24 hours by windowing with an appropriate fill-down averaging column followed by remainder (modular) arithmetic in the spreadsheet that consolidates all the individual buoy reports.

This master spreadsheet has one column for common time, lon and lat columns for track plotting, a column for displacement and a free column depending on what the particular buoy measures (air temp, snow depth etc). So far I have only put 4 of the 17 into a master. It starts 04 Oct 19 when the Polarstern first moored.

Then there is the matter of updating, say adding incoming data once a week. It's probably better to start from scratch rather than just appending because some of the data gaps might have been repaired and new buoys might have been deployed.

Meereisportal has not implemented the Polarstern itself as a buoy. While it is surely collected, I don't where that location data is posted in a compatible format.

Since the buoys are quite co-localized now, there may be grid regularization advantages in setting up companion files for virtual buoys (stable features on ice radar). This could only be done once a day, not hourly, and involves manual observation and recording.

The initial locations at deployment of the 17 buoys (at various dates) are shown in a broader context in the GE screenshot (orange polygon). The magenta and green circles show the largest possible free rotations of the ice pack without coming up against fixed land; green is restricted by the de Longa islands. The centers, called the poles of inaccessibility have been determined very accurately in recent papers.

Sort Active     Name       Long     Lat
 5   07.10.19   2019P188   135.99   84.71
10   05.10.19   2019P193   135.97   84.77
 7   07.10.19   2019P190   135.29   84.69
14   07.10.19   2019P200   135.06   85.00
15   07.10.19   2019P203   134.84   85.07
16   07.10.19   2019P206   134.48   84.97
13   07.10.19   2019P198   134.29   85.07
17   02.10.19   2019S92    134.24   84.78
12   07.10.19   2019P196   133.98   85.00
 6   05.10.19   2019P189   132.59   84.70
 9   07.10.19   2019P192   132.57   84.65
11   05.10.19   2019P194   132.07   84.71
 8   05.10.19   2019P191   131.71   84.66
 1   29.09.19   2019P152   125.86   84.24
 2   29.09.19   2019P155   125.23   83.78
 3   28.09.19   2019P156   121.26   82.09
 4   26.09.19   2019P157   119.25   81.39


GE line formatted:
134.29,85.07,0 134.84,85.07,0 133.98,85.00,0 135.06,85.00,0 134.48,84.97,0 134.24,84.78,0 135.97,84.77,0 132.07,84.71,0 135.99,84.71,0 132.59,84.70,0 135.29,84.69,0 131.71,84.66,0 132.57,84.65,0 125.86,84.24,0 125.23,83.78,0 121.26,82.09,0 119.25,81.39,0
« Last Edit: October 14, 2019, 04:16:28 PM by A-Team »

A-Team

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Re: MOSAiC news
« Reply #121 on: Today at 01:05:26 AM »
The first image breaks the latest radar image of the Polarstern's route into daily segments by using successively earlier dates (which have to be moved to align under their co-moving frame reporting).
Once again, we see that net travel over a week is far too long to resolve actual distance drifted by a factor of 3x here.

A junior scientist onboard twittered their initial mooring position in decimal minutes (!) as "84º04.582' 134º25.769' at 9:30 pm Friday boat time (!!)". I could not confirm that ship time used is UTC but would hope so. The PS may know its GPS position better than the buoys: 84.07637 134.42948 which suggests 1.1 m accuracy but that is not entirely clear.

ftp://ftpsrv2.awi.de/sea_ice/mosaic/jpg/large/mosaic_multisensor_map_2019-10-13_hr_NoOverlay.jpg

If the adjacent ice pack were moving as a rigid non-deforming block, the buoys would all change speeds in concert. They don't quite (slide show, 4 PRIC buoys).

Esther Horvath has been taking some great photos from the PS. The ice thickness looks barely able to support some of the heavy gear that has to be set up on the ice, such as the 'Ocean City' electric hub.

https://follow.mosaic-expedition.org has high resolution photos on the side.
https://mosaic.colorado.edu/blogs has good posts from the Polarstern
« Last Edit: Today at 03:26:12 AM by A-Team »