Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: Hyperion on June 30, 2018, 10:32:55 AM

Title: SMOS
Post by: Hyperion on June 30, 2018, 10:32:55 AM
Actually this thread was started by Neven. I can't accept the credit.  8)


Here's how the CMOS microwave maps look for the past 40 days.

Downloaded from: https://seaice.uni-bremen.de/data/smos/png/ (https://seaice.uni-bremen.de/data/smos/png/)
...
There is a definite trend from beige to other colours: dry -> wet

I played around a bit with those SMOS images.  I wrote a script to download the daily SMOS images for June 2010-2018 and to count the number of beige pixels in each image:

(https://i.imgur.com/fjZvZxF.png)


Average for the first 28 days of June:
(https://i.imgur.com/9Ydtklt.png)
(For what it's worth...)
Great effort Steve. But let's make sure we remember that we are/have transitioned to a predominantly bottom melt regime, rather than the meltpond surface melt regime historically. The salinity gradient and porosity of the young ice combined with the disintegrating pycnocline and more mobile ice and turbulent ocean surface mean, paradoxically that SMOS thin ice thickness maps are mostly more accurate than the were in past years where melt ponding was the norm for melt initiation. And therefore less beige Pixels were present due to melt ponds eliminating them. I love SMOS for its raw data feeds unmuddied by fiddling due to preconceived opinions of what should be presented, and what not. But the beige cutoff at levels where the error gets high, and the preemptive statement that the thickness scale should be ignored during melt season due to melt ponding making it inaccurate makes inter year comparison in a fast changing Arctic difficult.
The previous years in your chart continuing a steep descent while 2017, and more so this year not, most probably speaks more about less melt ponding and more bottom melt rather than any kind of slowdown.
Title: Re: SMOS
Post by: Tetra on June 30, 2018, 11:29:06 AM
??

Is this thread really necessary? You've already posted the same comment onto the main melting season thread.

And you are specifically talking about 2018 and it's melting season in comparison to past years.

Also "fiddling"??

Plus, you do know SMOS is just like any other tool. With all the melting shenanigans going on this year, it probably has a lot of errors.

It shouldn't be used as a holy grail to support wide scale hypothesis's about the Arctic.
Title: Re: SMOS
Post by: Jim Hunt on June 30, 2018, 12:01:42 PM
Is this thread really necessary?

A good question!

Quote
Plus, you do know SMOS is just like any other tool. With all the melting shenanigans going on this year, it probably has a lot of errors.

If memory serves, and much like CryoSat-2, SMOS maps used not to be published during the "melting season".
Title: Re: SMOS
Post by: Neven on June 30, 2018, 12:23:23 PM
Is this thread really necessary? You've already posted the same comment onto the main melting season thread.

It's better to have any discussions as to what SMOS actually means during summer over here than on the melting season thread. But I agree one of Hyperion's comments is redundant, and so I've removed the copy on the melting season thread.
Title: Re: SMOS
Post by: Rob Dekker on July 01, 2018, 06:15:11 AM
Regarding what SMOS means in summer, I found this :

Quote
The emissivity is mainly a function of bulk ice temperature, salinity and thickness. The bulk ice temperature is estimated from surface air parameters of JRA-25 reanalysis data and a zero-dimensional thermodynamic model [3]. The bulk ice salinity is estimated from a sea surface salinity weekly climatology. The sea ice thickness is corrected for the influence of the thickness distribution function to account for the invalid assumption of a uniform plane ice layer [3]. The latter correction leads to an apparent deeper penetration depth than previously reported [1]. We apply no correction for the influence of ice concentration. Thus, one can expect an underestimation of ice thickness when there is open water within the SMOS footprint. We account only for the thermodynamic influence of a parameterized snow layer on the bulk ice temperature but do not account for the direct radiative effect [4].

https://icdc.cen.uni-hamburg.de/1/daten/cryosphere/l3c-smos-sit.html

This suggests that SMOS is affected by open water between and on the ice.
More open water will trigger SMOS to report thin ice.
That means that ice concentration and SMOS in summer should have overlap (and correlate).
Low ice concentration (lots of surface melt) should thus correlate with low SMOS 'thickness' measurements.

That is consistent with the finding that SMOS in summer correlates well with low Sept extent.
Title: Re: SMOS
Post by: Steven on July 01, 2018, 08:18:04 PM
That is consistent with the finding that SMOS in summer correlates well with low Sept extent.

For what it's worth:  using the average number of beige pixels in the SMOS images in June as a predictor of the NSIDC September extent, the estimate for the September 2018 extent would be  4.74 +/- 0.68 million km2  (95% prediction interval). 

This should probably be taken with a grain of salt, since the SMOS dataset isn't supposed to be used during summer and there are only 9 years of data (2010-2018) and I only looked at the beige pixels and ignored the other colors.

For the 2018 JAXA extent daily minimum the estimate would be 4.39 +/- 0.71 million km2 (95% prediction).
Title: Re: SMOS
Post by: Hyperion on July 05, 2018, 08:33:12 AM
Nine days to the 4th.
Almost no beige pixels at all now, but for a blob compacted at the Fram entrance against Greenland.

Starting to Look a lot more like 2012. Same nine days for comparison.
And July 4th 2016, 2017.

Of course 2012 had just experienced a June Cliff, and had soggy ice and extensive melt ponding, particularly in the Pacific/ American side.

This year the signature is more likely to be from a mobile pack, with gaps and waterlogged fragments with no freeboard between the floes. It will be interesting to see what happens with the forecast out to the 9th on GFS showing an unprecedented heat and steamhosing from particularly the Russian side initially, but all directions. Perhaps some compaction will occur initially, but the cyclonic pattern taking over the whole basin is liable to cause dispersion. US Navy melt forecasts are looking extremely ominous.
Title: Re: SMOS
Post by: Hyperion on July 06, 2018, 09:45:49 AM
Here's ,3,4,5 July. And an animation of 2-7 July surface winds and temperatures. Does look to me like compaction/dispersal correlates well. Temperatures?
Title: Re: SMOS
Post by: Cid_Yama on July 06, 2018, 01:44:34 PM
30 cm is 1 ft.  So unless it's red or purple it's less than a foot thick.   

Title: Re: SMOS
Post by: oren on July 06, 2018, 02:37:30 PM
30 cm is 1 ft.  So unless it's red or purple it's less than a foot thick.
Not really, as SMOS can't measure thickness in summer
Title: Re: SMOS
Post by: Hyperion on July 06, 2018, 06:00:06 PM
Unless the ice in the the area happens to be dry and meltpond free of course. Which can happen if the air temp is below zero, and/or bottom melting in high salinity is chilling it to below the surface freezing point. But what you are getting then is the average thickness per 40x40 km area of ocean. So if its 50% concentration, then the ice in the area would be twice as thick on average as is indicated.
 The projection is conic equidistant if anyone feels like writing a script to recolor and rekey on this basis. Cryosat thickness is not available in summer for similar reasons. If surface melt charts were used to flag areas as "surface melting, thickness unknown" then actually a quite informative and plausibly accurate product could result.
At present SMOS is best for day to day comparison for information on ice movement and melting progress.
Title: Re: SMOS
Post by: Ken Feldman on July 06, 2018, 06:05:47 PM
DMI is still showing most of the pack at over a meter thick.  Visit their website here:  http://polarportal.dk/en/sea-ice-and-icebergs/sea-ice-thickness-and-volume/ (http://polarportal.dk/en/sea-ice-and-icebergs/sea-ice-thickness-and-volume/)

US Navy also has most of the pack at over a meter thick:

https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn/nowcast/ictn2018070312_2018070400_930_arcticictn.001.gif (https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn/nowcast/ictn2018070312_2018070400_930_arcticictn.001.gif)

You can get their daily maps here:  https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arc_list_arcticictn.html (https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arc_list_arcticictn.html)

Title: Re: SMOS
Post by: Hyperion on July 06, 2018, 06:40:51 PM
And their melt animations
Title: Re: SMOS
Post by: Cid_Yama on July 06, 2018, 11:47:42 PM
30 cm is 1 ft.  So unless it's red or purple it's less than a foot thick.
Not really, as SMOS can't measure thickness in summer

This is one of those common wisdoms that is actually untrue.  SMOS has high uncertainty for thick ice during the summer, underestimating the thickness of thick ice.  Uncertainty for thin ice is much lower.

New methodology has been devised in the processing of SMOS data in recent years, that has reduced the uncertainties and is now providing a useable data set in the summer.

http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4452.pdf

Alfred-Wegener has also been looking at using a synergistic interpolation of SMOS and Cryosat-2 data to reduce uncertainty as SMOS has low uncertainty with thin ice and Cryosat-2 has low uncertainty with thick ice.

https://www.ecmwf.int/sites/default/files/elibrary/2018/17987-merged-sea-ice-thickness-product-complementary-l-band-and-altimetry-information.pdf

Title: Re: SMOS
Post by: Rob Dekker on July 07, 2018, 08:09:49 AM
That is consistent with the finding that SMOS in summer correlates well with low Sept extent.

For what it's worth:  using the average number of beige pixels in the SMOS images in June as a predictor of the NSIDC September extent, the estimate for the September 2018 extent would be  4.74 +/- 0.68 million km2  (95% prediction interval). 

That's impressive, Steven.
A +/- 0.68 million km2 suggests a standard deviation of 340 k km2, which would be at the low end of the predictions at SIPN.

Did you consider submitting an entry this year based on this SMOS data ?

https://www.arcus.org/sipn/sea-ice-outlook/2018/june/call

Since SMOS is a unique, new, variable, your contribution would be very much appreciated.
Title: Re: SMOS
Post by: Hyperion on July 07, 2018, 09:59:48 AM
30 cm is 1 ft.  So unless it's red or purple it's less than a foot thick.
Not really, as SMOS can't measure thickness in summer

This is one of those common wisdoms that is actually untrue.  SMOS has high uncertainty for thick ice during the summer, underestimating the thickness of thick ice.  Uncertainty for thin ice is much lower.

New methodology has been devised in the processing of SMOS data in recent years, that has reduced the uncertainties and is now providing a useable data set in the summer.


Very interesting Cid. I wonder if their archive has been reprocessed with the new algorithm. Or are comparisons with past years now made more difficult.
Anyhow. Freshly loaded to the Bremen servers. Here's the latest. As predicted a beige spot north of Siberia from the offshore winds causing compaction.
Don't expect it to last. The monster low in place in the Beaufort is going to disperse it back into the ESAS and Chukchi kill zones. The beige clump compacted against mid CAA is being fried and blown out to sea right now. And if the forecast for the next five days holds true, that low is going to grow into a monster covering the whole Arctic and spend the week winching in the whole north sea, with winds blowing all the way from Florida, and filling the whole gap from Greenland to Europe. Waves will be spectacular, as will the surface surge of hot water into the Atlantic killzone.
Title: Re: SMOS
Post by: Steven on July 07, 2018, 08:10:05 PM
That's impressive, Steven.
A +/- 0.68 million km2 suggests a standard deviation of 340 k km2, which would be at the low end of the predictions at SIPN.

Did you consider submitting an entry this year based on this SMOS data ?

https://www.arcus.org/sipn/sea-ice-outlook/2018/june/call

Since SMOS is a unique, new, variable, your contribution would be very much appreciated.

Thanks, Rob.  But since I used only 8 years of data in the regression analysis (2010-2017), I'm not sure how seriously those numbers should be taken.

Actually I have more confidence in NSIDC sea ice concentration as a predictor of the minimum.  That gives an estimate of 5.0 +/- 0.8 million km2 for the NSIDC September extent, as I posted in the poll thread (https://forum.arctic-sea-ice.net/index.php/topic,2340.msg161754.html#msg161754) last Sunday.
Title: Re: SMOS
Post by: Steven on July 07, 2018, 08:18:42 PM
Not really, as SMOS can't measure thickness in summer

This is one of those common wisdoms that is actually untrue.  SMOS has high uncertainty for thick ice during the summer, underestimating the thickness of thick ice.  Uncertainty for thin ice is much lower.

New methodology has been devised in the processing of SMOS data in recent years, that has reduced the uncertainties and is now providing a useable data set in the summer.

http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4452.pdf

It's obvious that SMOS grossly underestimates sea ice thickness in summer.  Nothing in your link suggests otherwise.  Note that they are talking about determining sea ice concentration from SMOS data in summer, not thickness.
Title: Re: SMOS
Post by: Hyperion on July 07, 2018, 11:42:43 PM
My guess is they have reprocessed the historic data all of the early files were modified end of October 2017.
Steven, if you have 1% of an area of ocean covered by small floes averaging 2m thick, with sub 200m gaps between them, should you say this is 100% area, 100% extent, and 100% concentration of 2m thick ice?
This is what we are being asked to swallow on every chart and metric, but SMOS.
Its meltponds SMOS has problems with in summer. With thin, young, porous, fragmented, and highly salinity stratified ice,  meltponding is improbable now. But far more prevalent in 2012. Less so every year.
Title: Re: SMOS
Post by: Hyperion on July 08, 2018, 10:52:18 AM
Today's SMOS is in,  and results are as expected.

On the seventh the Beaufort cyclone has already detached the blob of beige from mid CAA. And compacted the pack in the north Beaufort through dispersing floes in the direction of the pole.

The winds blowing out of Fram strait and around the top of Greenland have shifted the beige blob off the northeast tip of Greenland and compacted floes in the mouth of Nares.

Winds out of Bering straight are withering Pago's bridge in the Alaskan coastal Chukchi- Beaufort border.

In general, melt is progressing at pace around the whole periphery of the pack.
Title: Re: SMOS
Post by: Hyperion on July 09, 2018, 07:02:33 PM
Today's latest.
That cyclone mixing is wreaking havoc. Obviously not meltponding confusing SMOS over where the sea level height is going on here. Waves, warm, wet, windy whupping under cloud and fog veil huh?
Title: Re: SMOS
Post by: Hyperion on July 10, 2018, 01:24:17 PM
Today's SMOS. It seems all the central basin ice is being expelled towards kill zones where either incoming ocean and Atmospheric heat is being soldly accelerated into, or Ocean heat and waves already exist enough to finish the deal.
Title: Re: SMOS
Post by: Hyperion on July 12, 2018, 10:40:08 PM
It near as dammit is a blue ocean event already Neven. I bet my left nut that anything near the periphery, extending now to a Chukchi to Barents strip right across the pole where meltponding is being reported is actually open water, and satellites being fooled by wave action.
And what I cannot stand is bullying. Which is what you supported.
If it wasn't for the south Asian low pressure zone acting as a giant cross equator Hadley cell with the southern hemisphere whole Indian ocean high, it would be all over already. But that looks to be changing as the Arctic low pressure is merging with it
 And a single high pressure covering north Atlantic, America, and Pacific combined with that is a dipole covering half the planet, and the Arctic sea ice the meat in the sandwich.
I am only posting here because its not fair that Nevens inability to distinguish between deliberate concern troll attacks and actual naivety deprive others of factual reports.


Title: Re: SMOS
Post by: Hyperion on July 13, 2018, 08:02:13 AM
https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/beaufortictn_nowcast_anim30d.gif

https://seaice.uni-bremen.de/data/smos/png/?C=M;O=D
Title: Re: SMOS
Post by: Neven on July 13, 2018, 10:59:30 AM
It near as dammit is a blue ocean event already Neven. I bet my left nut that anything near the periphery, extending now to a Chukchi to Barents strip right across the pole where meltponding is being reported is actually open water, and satellites being fooled by wave action.
And what I cannot stand is bullying. Which is what you supported.

As said, if there's a BOE event this year (it's already practically there according to you), I will apologize. Conversely, if there's no BOE, you'll get banned from this forum.
Title: Re: SMOS
Post by: RikW on July 13, 2018, 11:35:49 AM
https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/beaufortictn_nowcast_anim30d.gif

How reliable is this animation? Because if this is true almost all ice outside 80 degree is below 1m, thus doomed. Or there is a lot of open water, which lowers the ice thickness, which also isn't very good news I'd say.

Too bad we have a lot of clouds on Worldview. Any suggestions for layers/overlays to increase the visibility? I've been checking worldview and animated last month for some parts, I can only say for sure that Kara sea is doomed, which isn't a big surprise and I think the beaufort isn't an ice sheet but just a lot of floes, most of them much smaller than I would like.

For example 2 pictures of beaufort/cab 4 days ago, low on clouds, doesn't look that good. I think it's among the worst years for this region around this date (2015 and 2016 beging the other 2 worst years) but I think the 'bad' region extends closer to the pole (but those clouds...)
Title: Re: SMOS
Post by: Peter Ellis on July 13, 2018, 12:11:00 PM
It near as dammit is a blue ocean event already Neven. I bet my left nut that anything near the periphery, extending now to a Chukchi to Barents strip right across the pole where meltponding is being reported is actually open water, and satellites being fooled by wave action.
Blue is ice, white is clouds.  Why even bother to post something so easily disproven? The people that built and run SMOS say that during the summer it doesn't accurately measure ice thickness, and that is the only factual report here.
https://go.nasa.gov/2NKVaF7
Title: Re: SMOS
Post by: oren on July 13, 2018, 12:13:26 PM
It near as dammit is a blue ocean event already Neven. I bet my left nut that anything near the periphery, extending now to a Chukchi to Barents strip right across the pole where meltponding is being reported is actually open water, and satellites being fooled by wave action.
Seriously Hyperion, this is utter nonsense. A blue ocean event is defined in these parts of the world as <1 million square km of sea ice extent. Do you claim that we are there or very near that? Just note that JAXA is currently reporting >8.5 million sqkm of extent. It's not a BOE and will not be a BOE by September either.
About the "satellites being fooled by wave action", why not just open worldview and take a look for yourself? The white or bluish white of ice is easily distinguishable from dark waves. Your bet doesn't seem to be a good one.
Title: Re: SMOS
Post by: echoughton on July 13, 2018, 12:38:48 PM
Me thinks Hypernion is going to lose a precious jewel.  :-\ :-\ :-\
Title: Re: SMOS
Post by: Pmt111500 on July 13, 2018, 02:48:54 PM
Ah, SMOS, new ice product? What does it measure? Remaining thickness of first-year ice? The numbers are anyway quite a lot off of some of the other products. And they also differ from each other. Not so long ago there was a thickness map that looked like it measured the thickest bits remaining, maybe this does the same for thinnest bits.
Title: Re: SMOS
Post by: Hyperion on July 13, 2018, 02:58:17 PM
I tried to post this gift on the melting forum but Nevz just deleted it.  These are entering the Arctic Basin as over hundred kmph over 22 second over 600m wavelength Waves. They are not showing up on Nullschool or other wave charts because of higher,  short period waves that they show automatically instead. But these have come fro the southern ocean, are being accelerated and lengthened by strong cross equatorial winds blowing north out of the south Atlantic, and the strong  north Atlantic southerlies blowing into the Arctic from off the US coast. The massive highs pressure systems covering the Atlantic basins are culpable.
These waves are about a meter high entering the ice, and should be easily capable of penetrating right through to the Chukchi. The reflection off shelves and refraction around shallows like Svalbard causes complex crossing and reinforcing patterns. The Pyramid waves I have mentioned before. No question that waterlogged  and fragmented icefields, with sea showing through  gaps, holes and puddles connected to the Ocean raised relative to the troughs nearby would fool radar Altimetry into thinking there was more free board than there is, more thickness and meltponds on the ice.
Sure, blue ocean already is a bit far measuring by jaxa extent definition. But on actual area, If I'm right about this it could be getting close.
Title: Re: SMOS
Post by: RikW on July 13, 2018, 03:04:24 PM
It measures thickness in a reliable way if there are no melt ponds and/or open water is absent. So underestimation in the summer. Although it gives an indication if melt is happening, because when thickness decreases fast during summer, there are either a lot of melt ponds, a lot of open water between floes or thickness is really decreasing.

So based on the satellite images you can safely state the ice is in a bad condition
Title: Re: SMOS
Post by: Pmt111500 on July 13, 2018, 03:20:33 PM
It measures thickness in a reliable way if there are no melt ponds and/or open water is absent. So underestimation in the summer. Although it gives an indication if melt is happening, because when thickness decreases fast during summer, there are either a lot of melt ponds, a lot of open water between floes or thickness is really decreasing.

So based on the satellite images you can safely state the ice is in a bad condition

Thanks, so to calibrate it's position in the scale of true values, we'd need to check the numbers against other products during winter. Granted currently the compactness is pretty bad according to some other measures so this would underestimate thickness of remaining ice quite a bit. Say 50% open ocean on a grid cell could then mean the SMOS thickness is 50% smaller than the renaining ice on a grid cell? Anyway compactness is low currently. Interesting product this SMOS, looks almost designed to state the precariousness of the Arctic Ice
Title: Re: SMOS
Post by: Hyperion on July 13, 2018, 10:58:12 PM
The advantage SMOS has on thin and fragmented ice is its penetration of freshwater is good. Salinity in the water decreases penetration I the xband microwave frequency markedly. So clouds and fog have little influence, unlike with Amsr2. But the saltier meltponds that can cause it to see the sea level a fraction higher than it is.
But the influence of wave tilt, porous first year ice etc is likely to make the overestimation of sea level quite small. Especially with the surface  being pegged to below freezing point by the high salinity water melting the floes from below. These charts have shown little or no sign of exaggerated thinness from hot and wet coastal atmospheric influx to my eye.
I think it would be fairer to call this a summer volume product than thickness as it is showing average thickness over over a mix of ocean and ice. If we were to plot a new chart that took the US Navy thickness and SMOS volume, and used them to colour pixels by the percentage difference, then we might get a more accurate area chart than presently presented. The US navy has the best under ice sonar resources so like SMOS their charts are unlikely to be as badly compromised by the swell influence I've pointed out. Which BTW IMO is the main reason piomass has been overestimating thickness, particularly north of Svalbard. And over the outer ESAS.
So if SMOS says 20cm and US navy 1m, then we might have around 20% actual area.  If this was the average Arctic wide then Area would be really only 20% of extent. Thus my point about being darn close to a blue ocean event right now.
Title: Re: SMOS
Post by: Hyperion on July 13, 2018, 11:51:45 PM

Today's SMOS, and the most famous pyramid wave images in the world. I strongly recommend reading the following paper, for help in understanding wave, land and wind interaction relevant to today's arctic.

http://rsnr.royalsocietypublishing.org/content/63/2/119

WHAT KIND OF A WAVE IS HOKUSAI’S GREAT WAVE OFF KANAGAWA?
by
JULYAN H. E. CARTWRIGHT
1,*AND HISAMI NAKAMURA
2,*
1Instituto Andaluz de Ciencias de la Tierra, CSIC–Universidad de Granada,
Campus Fuentenueva, E-18071 Granada, Spain
2Chuo University, 742-1 Higashi Nakano, Hachioji, Tokyo 192-0393, Japan

The great wave off Kanagawa by Katsushika Hokusai is probably the most famous image in
Japanese art. It depicts three boats in heavy seas on the point of encountering the eponymous
wave, while Mount Fuji is glimpsed in the distance. ;)
Title: Re: SMOS
Post by: Hyperion on July 14, 2018, 05:21:13 PM
And the 13th.
Title: Re: SMOS
Post by: Wherestheice on July 14, 2018, 10:32:29 PM
And the 13th.

SMOS is a better way to look at the state of the Arctic instead of extent....
Title: Re: SMOS
Post by: Neven on July 14, 2018, 11:38:02 PM
An even better way is to look at them both. And then compare, compare, compare to what has happened in the recent past.

That SMOS graph doesn't mean much if it isn't compared to the ones from 2007-2017.
Title: Re: SMOS
Post by: Hyperion on July 15, 2018, 02:45:32 AM
An even better way is to look at them both. And then compare, compare, compare to what has happened in the recent past.

That SMOS graph doesn't mean much if it isn't compared to the ones from 2007-2017.

I agree about the recent past. But if we are going to compare with previous years back to 2010 when SMOS started, then we have to remember that since 2013 the ice has been increasingly younger and more porous. Meaning years like 2012 would have far more meltponds, hence SMOS would have overestimated sea level, and underestimated ice volume. It should be far more accurate now.

But lets compare SMASS directly with US Navy thickness for the 13th of July.

It actually looks to me like the SMASUSnavthik ratio would give Area estimate closer to 10% coverage over most of the Pacific-American side of the pole.
Hmm. I'll pm Steven. If I resize these better and reduce the number of colours it should be easy to get accurate    smasusnathik figures and plots from them.

Edit: attached a few hours work with an unfamiliar gimp. May be usable.
Title: Re: SMOS
Post by: Hyperion on July 15, 2018, 12:46:42 PM
Here's 12, 13, 14 July of both SMASS and USNavThik.
In unadulterated, and reduced to 16 colour plots. These can be split into frames at ezgif.com
This looks like a better way to do this than gimps over sophisticated posterising stuff. If I hadn't had four computers stolen in the last 12 months, it would be a walk in the park to write a pixel counting Smasusnavthik plotter. Anyone who wants to try should have no problems. Just finish the edit by cropping at the 70 degree north line, as per top left corner, and resizing to match.
Title: Re: SMOS
Post by: Wherestheice on July 19, 2018, 05:50:09 AM
can someone upload a link to find the SMOS data?
Title: Re: SMOS
Post by: Random_Weather on July 19, 2018, 06:01:44 AM
https://seaice.uni-bremen.de/data/smos/
Title: Re: SMOS
Post by: slow wing on July 19, 2018, 06:07:17 AM
The maps are here:
https://seaice.uni-bremen.de/data/smos/png/ (https://seaice.uni-bremen.de/data/smos/png/)

I've used the ones ending in _hvnorth_rfi_l1c.png, though I don't know why they differ from the _hvnorth_l1c.png ones, nor do I know if there is any reason to prefer one over the other.

By inspection, they look similar but not identical. I'm guessing the "rfi" ones have some extra processing but that's just a guess. Does anyone know?

Title: Re: SMOS
Post by: Wherestheice on July 19, 2018, 06:23:05 AM
Thank you both! Very helpful
Title: Re: SMOS
Post by: Hyperion on July 19, 2018, 07:19:03 AM
The maps are here:
https://seaice.uni-bremen.de/data/smos/png/ (https://seaice.uni-bremen.de/data/smos/png/)

I've used the ones ending in _hvnorth_rfi_l1c.png, though I don't know why they differ from the _hvnorth_l1c.png ones, nor do I know if there is any reason to prefer one over the other.

By inspection, they look similar but not identical. I'm guessing the "rfi" ones have some extra processing but that's just a guess. Does anyone know?
The rfi version has the radio frequency interference from high powered radar systems processed out of it. I've been posting the plain unadulterated version. Call me quirky, but I prefer raw data feeds as little processed as possible. It seems to be outside the pack that gets any and only occasional effect anyway. And I guess I kind of like seeing when and where these probably mainly military radar systems are being used. ::)

The last seven days. With a funky fade between frames and a little enlargement, seems to help visually track the changes.
Title: Re: SMOS
Post by: RikW on July 19, 2018, 09:08:38 PM
So massive thickening in the CAB, so I presume melt season somehow ended already?
Title: Re: SMOS
Post by: Wherestheice on July 19, 2018, 09:32:04 PM
So massive thickening in the CAB, so I presume melt season somehow ended already?

i think its just the ice compacting.
Title: Re: SMOS
Post by: Hyperion on July 19, 2018, 10:42:19 PM
So massive thickening in the CAB, so I presume melt season somehow ended already?

i think its just the ice compacting.
Yes. There has been strong winds and heat coming in on the Pacific side for a few days and a ring of small cyclones around the Russian coast and a larger one in Chukchi-Beaufort.
The big area of blue at the eastern end of the Chukchi is where the remnant Beaufort circulation is. That's quickly going poof. So where the compaction is happening isn't at all great for the ice surviving. Its been shifted to where warm salty Atlantic water is available at shallow depth and its also vulnerable to wave mixing and breaking from the Atlantic.
And lined up for the Fram, Nares, and CAA export and kill zone.
Title: Re: SMOS
Post by: Hyperion on July 19, 2018, 11:02:38 PM
Those were 16,17,18,19 1000hpa winds and temperature.
This is today.
Title: Re: SMOS
Post by: Tor Bejnar on July 19, 2018, 11:38:57 PM
from July 1 (above)
Quote
SMOS is affected by open water between and on the ice.
I think what is useful is the beige areas which show 'dry' ice.  I presume this is local freeze, new snow or compaction.
Title: Re: SMOS
Post by: Hyperion on July 20, 2018, 10:42:33 AM
You really should expect the majority of the ice surface in the estuary to be dry in the current regime Tor. Ice conducts heat better than water. And with the consistent high atmospheric energy input over the whole estuary surface. The salinity differential bottom to top. Its a bottom melt surface freeze paradigm we are in. Remember the Arctic Estuary is only 2.7% of the earths surface. Insolation directly on the estuary is not significant in a thin, young ice regime.

Wikipedia:
The Arctic Ocean is the smallest and shallowest of the world's five major oceans.[1] The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it a mediterranean sea or an estuary of the Atlantic Ocean.[2][
Title: Re: SMOS
Post by: Peter Ellis on July 20, 2018, 12:09:05 PM
So massive thickening in the CAB, so I presume melt season somehow ended already?
It's not thickening.  SMOS doesn't measure thickness accurately during the melt season.
(This could be posted as a followup to every other post in this thread, so let's just assume it was)
Title: Re: SMOS
Post by: oren on July 20, 2018, 12:11:54 PM
I get the feeling RikW's comment was missing a  ;)
Title: Re: SMOS
Post by: binntho on July 20, 2018, 12:12:23 PM
You really should expect the majority of the ice surface in the estuary to be dry in the current regime Tor.

What estuary are we talking about here?  The areas that seem to be dry in the SMOS image are not over any known estuaries.

And with the consistent high atmospheric energy input over the whole estuary surface.

What estuary?

The salinity differential bottom to top. Its a bottom melt surface freeze paradigm we are in.

Again, where? On the "dry" part of SMOS? And by "bottom melt surface freeze paradigm" do you mean that the surface is freezing as a consequence of bottom melt, or that some third factor is causing both? Any evidence?

Remember the Arctic Estuary is only 2.7% of the earths surface.

Oh! The "Arctic Estuary" is not on any known maps. An estuary is defined as the tidal mouth of a large river and is obviously not a useful label for the Arctic Ocean which does in deed cover 2.7% of the earth's surface.

Insolation directly on the estuary is not significant in a thin, young ice regime.

But no entrainment? Baseless claim without evidence and flouting the laws of physics.
Title: Re: SMOS
Post by: Ned W on July 20, 2018, 04:04:11 PM
Oh! The "Arctic Estuary" is not on any known maps. An estuary is defined as the tidal mouth of a large river and is obviously not a useful label for the Arctic Ocean which does in deed cover 2.7% of the earth's surface.

Well, this 2012 paper does analogize the Arctic Ocean to an estuary:

https://link.springer.com/article/10.1007/s12237-010-9357-3

But it also calls the Arctic a "beta ocean," in contrast to other "alpha oceans".  Which seems ... not so nice.
Title: Re: SMOS
Post by: Hyperion on July 20, 2018, 04:11:52 PM
<snip, no endless quoting, please; N.>

Binntho, this is the third time you have appeared to be deliberately wasting forum space and my time by claiming that I am making baseless claims, and demanding evidence belligerently while quoting me providing that evidence in the same post. Please read Wikipedia's article on the Arctic ocean for yourself. And the references provided there as to why oceanographers describe it as an estuary. Which is a body of lower and often  stratified salinity water where one or more riverine freshwater entries mix with ocean water before entering the ocean through a constricted exit.

<snip, stop playing the victim, please; N.>
Title: Re: SMOS
Post by: binntho on July 20, 2018, 04:18:51 PM
Oh! The "Arctic Estuary" is not on any known maps. An estuary is defined as the tidal mouth of a large river and is obviously not a useful label for the Arctic Ocean which does in deed cover 2.7% of the earth's surface.

Well, this 2012 paper does analogize the Arctic Ocean to an estuary:

https://link.springer.com/article/10.1007/s12237-010-9357-3

But it also calls the Arctic a "beta ocean," in contrast to other "alpha oceans".  Which seems ... not so nice.

I think the "estuary" metaphor is not meant to be taken seriously. The Arctic Ocean is more than 14 times bigger then the largest sea (the Mediterranean) but 10 times smaller then the largest ocean (the Pacific).

The Arctic Ocean is 64% of the size of the Southern Ocean, and 5 times smaller than the Atlantic. So based on size alone, the Arctic Ocean seems to be properly named.

On the other hand, it is mostly enclosed by land while the other Oceans communicate more or less freely with each other with large "ocean-border" areas.
Title: Re: SMOS
Post by: RikW on July 20, 2018, 04:34:53 PM
does the atlantic ocean communicate freely with the other oceans?
Title: Re: SMOS
Post by: gerontocrat on July 20, 2018, 04:56:49 PM
does the atlantic ocean communicate freely with the other oceans?

The Arctic for one, the Southern Ocean for two, the Indian Ocean for three (saw it 35 years ago at the tip of Africa - amazing how you could see the difference and the boundary between the two).
Title: Re: SMOS
Post by: binntho on July 20, 2018, 05:02:58 PM
does the atlantic ocean communicate freely with the other oceans?

--- edit: Misread the question, thought you were asking about the Atlantic Arctic (doh!)... ---

I guess it depends on what you mean by "freely" ... much more so than the Mediterranean, less than e.g. the Southern Ocean.

The Arctic body of water is either an ocean or a sea. Most of the worlds seas (as named) are actually subdivisions of oceans or other, larger seas,, such as e.g. the Norwegian Sea and the Ionic Sea, but the Black, Mediterranean, and the Caribbean seas are more or less cut off from other seas/oceans (and the Caspian totally ...).

Based on size, the Arctic Ocean is properly named as such, being much closer to the next-smallest ocean than the biggest sea. If, on the other hand, a sea was to be defined as having little or restricted communication with other seas or oceans, then the Arctic Sea might be better. But then again, if such a definition was to be adopted, what would happen to the Sargasso sea which lies more or less in the middle of the Atlantic without touching land!
Title: Re: SMOS
Post by: Pmt111500 on July 20, 2018, 05:07:10 PM
does the atlantic ocean communicate freely with the other oceans?
I think Indian ocean provides most of the surface waters, intermediate waters and northern Atlantic bottom waters come mostly from interaction with Arctic ocean and some northern bottom water and all of southern bottom water come from interaction through acc and southern ocean. Mediterranean is mostly a water sink and would dry up if Gibraltar and Suez were blocked. Simplified.
Title: Re: SMOS
Post by: gerontocrat on July 20, 2018, 05:18:00 PM
If the Arctic was demoted to a sea - what becomes of the seas of the Arctic Ocean? Chukchi, Beaufort, ESS etc - ponds?

Pluto it is not - no demotion on the horizon. It has been, is, and will be an ocean, until it is ice-free for at least most of the year. Then perhaps someone will say - it is now totally Atlantified (horrible word) - so is part of the Atlantic Ocean.
Title: Re: SMOS
Post by: Dharma Rupa on July 20, 2018, 06:08:21 PM
Pluto it is not - no demotion on the horizon. It has been, is, and will be an ocean, until it is ice-free for at least most of the year. Then perhaps someone will say - it is now totally Atlantified (horrible word) - so is part of the Atlantic Ocean.

Atlantisized?
Title: Re: SMOS
Post by: binntho on July 20, 2018, 06:19:11 PM
Pluto it is not - no demotion on the horizon. It has been, is, and will be an ocean, until it is ice-free for at least most of the year. Then perhaps someone will say - it is now totally Atlantified (horrible word) - so is part of the Atlantic Ocean.

Atlantisized?

The Atlantic is of course named after the giant Atlas who holds the world on his shoulders (cf. the mythical "Atlantis" in ancient Greek is Ἀτλαντὶς νῆσος (Atlantic nisos, literally the Island of Atlas).

So to follow tradition (cf. Sargasso Sea), once blue ocean is reached, we could rename the Arctic Ocean the Atlasso Sea, being a part (or sea) of the Atlantic after beging Atlassoed (presumably with one hand) by Atlas.
Title: Re: SMOS
Post by: Hyperion on July 21, 2018, 07:59:06 AM
Really there is one world ocean. With Antarctica in the middle of it. Since for most of the last few million years, the Arctic has been an icelocked pond with almost no communication with the world ocean, its probably quite fair to call it a deep brackish tidal lagoon or estuary. My point in pointing this out is that at only 2.7% of the earths surface and less than half of that in annual insolation. Insolation is no where near as important as the energy coming in and out from surrounding landmasses.
I wrote an extensive post about this on the melting thread.
Title: Re: SMOS
Post by: binntho on July 21, 2018, 10:28:56 AM
I don't think the Arctic Ocean can be called a "deep brackish tidal lagoon or estuary" at 14 million square kilometers, an average depth in excess of 1 km, maximum depth 4.5 kilometers.

My point in pointing this out is that at only 2.7% of the earths surface and less than half of that in annual insolation. Insolation is no where near as important as the energy coming in and out from surrounding landmasses.

What you did say was "Insolation directly on the estuary is not significant in a thin, young ice regime" which is a baseless claim, i.e. without evidence. It also goes against the laws of physics,  since a "thin young ice regime" would be more affected by direct sunlight than thicker ice.

Now you make another claim, based on percentages, i.e. that insolation over the Arctic Ocean is nowhere near as important as the energy coming in and out from surrounding landmasses. Again this is without evidence, and seems to go against the consensus. But it depends on circumstances - if the Arctic Ocean is covered with clouds and strong low-pressure areas, sunlight will not reach the ice but warm air will be sucked in from surrounding landmasses.

But that has nothing to do with 2.7% or any other figure you might want to put forward.

As for me criticizing your post, the "estuary" remarks were what we adults call "sarcasm" and the factual claims you keep making are large, strange and without evidence, and I see it as my duty to point this out before this forum becomes a fantasy free-for-all.
Title: Re: SMOS
Post by: Peter Ellis on July 21, 2018, 10:38:50 AM
...the factual claims you keep making are large, strange and without evidence, and I see it as my duty to point this out before this forum becomes a fantasy free-for-all.
Quite. As far as I can tell from Hyperion's ramblings, warm air currents are supposed to magically cause bottom melt without top melt, so the ice surface stays dry.  A contention that's trivially disproved with a large dry martini and a hairdryer.

This magical bottom-only melt arises because "Ice conducts heat better than water", and so it will conduct the atmospheric energy through to the water under the ice, allowing the ice to melt from the bottom, but not the top.  This is drivel.  Heat cannot of itself pass from one body to a hotter body. i.e. if the ice is conducting heat downwards, then the top of the ice is hotter than the bottom, so the top will melt first.
Title: Re: SMOS
Post by: Hyperion on July 21, 2018, 10:45:55 AM
...the factual claims you keep making are large, strange and without evidence, and I see it as my duty to point this out before this forum becomes a fantasy free-for-all.
Quite. As far as I can tell from Hyperion's ramblings, warm air currents are supposed to magically cause bottom melt without top melt, so the ice surface stays dry.  A contention that's trivially disproved with a large dry martini and a hairdryer.
Actually proven with a handful of salt, some ice cubes and some water to float them, while you use your hairdryer Peter. Its how everyone did freezers before electric ones.
Title: Re: SMOS
Post by: oren on July 21, 2018, 11:02:10 AM
They are just that, ramblings, which is why I mostly don't bother to respond.
Title: Re: SMOS
Post by: Tor Bejnar on July 21, 2018, 02:39:48 PM
The second sentence in the Wikipedia article on Arctic Ocean:
Quote
The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it a mediterranean sea or an estuary of the Atlantic Ocean.[2][3]


Quote
...
2."'Arctic Ocean' - Encyclopædia Britannica". Retrieved 2012-07-02. "As an approximation, the Arctic Ocean may be regarded as an estuary of the Atlantic Ocean."

I was surprised too...
Title: Re: SMOS
Post by: slow wing on July 21, 2018, 02:49:20 PM
This magical bottom-only melt arises because "Ice conducts heat better than water", and so it will conduct the atmospheric energy through to the water under the ice, allowing the ice to melt from the bottom, but not the top.  This is drivel.  Heat cannot of itself pass from one body to a hotter body. i.e. if the ice is conducting heat downwards, then the top of the ice is hotter than the bottom, so the top will melt first.

Commenting in this discussion, this is my understanding of the situation.

Hyperion is technically correct - this situation is possible under some circumstances.

The quote above is correct that the top will be 'hotter' than the bottom, because that is where the heat is coming from.

However, it is incorrect in claiming that means the top will always melt first. The reason is the presence of salt at the bottom, but not at the top, which lowers the melting point at the bottom.

E.g the top will melt at 0 degrees C if there's no salt, but the bottom may melt at -1.8 degrees C at a reasonable salinity for sea water.

So the situation of bottom melt in Arctic sea ice with heat carried from a dry top is theoretically possible.

In practice, on the other hand, I suspect that such a scenario is presumably unlikely to make a big contribution to the overall melt.

The reason is that the thermal conductivity of ice is not all that good: it's around 2.2 W/(mK). (https://www.engineeringtoolbox.com/ice-thermal-properties-d_576.html) So there is going to be a non-negligible temperature gradient in order to carry a non-negligible flow of heat down through the ice.

Consider this scenario, chosen to be a type of threshold case:
1 meter thick ice
0 degrees at the top
-1.8 degrees at the bottom
With both top and bottom at the threshold temperature for melting.

Linearizing for simplicity, the thermal gradient is 1.8 degrees/meter.

This implies a heat flow of ~2.2 W/(m.K) x 1.8 K/m = 4 W/m^2

The heat of melting of ice is 334 kJ/kg (same reference as above).

So rate of melting is ~4 J/(s.m^2) x / (334,000 J/kg x 900 kg/m^3) ~ 1.3e-8 m/s
(presuming a density of 900 J/kg)

A month is ~pi x 10^7s / 12 (using a useful mnemonic for approximate number of seconds in a year)

So that rate of melting would be 1.3e-8 m/s x pi x 10^7 / 12 ~ 3.5e-2 m/month = 3.5 cm/month.

So this threshold situation would be a bottom melt rate of only 3 or 4 cm per month.

If the bottom melt rate is:
a) Above this, then the top will be wet;
b) Below this, then the top can be dry even when the bottom is melting from heat carried downwards.

This is obviously a simplified situation - it is not rigorous - and is for ice that is 1 meter thick.
(If the ice is thinner\thicker then the melt rate can be more\less, in approximately inverse proportion to the thickness.)


But it illustrates the general point that ice dry at the top cannot be carrying much heat down to be melting the bottom.

SUMMARY:

Consider a situation for the Arctic sea ice where the heat to melt ice is coming from above. Then:

1) Bottom melt can only be fast, or even moderately fast, if the top is wet; and

2) The maximum bottom melt rate where a dry top is even possible (where the heat comes from above, & holding to some sort of long term equilibrium) is only of order a few cm/month.

So bottom melt with a dry top but still using heat arriving through the ice and from the top, while physically possible, is likely not the dominant scenario for Arctic sea ice.
Title: Re: SMOS
Post by: FishOutofWater on July 21, 2018, 05:05:23 PM
After the snow on top melts, light passes through the ice warming the water below the ice. That's physically possible when the sun is at a high enough angle. There's also advection of Atlantic water into the Arctic ocean. There's also the transport of ice over Beaufort & Chukchi sea summer water. We don't need to invent non-physical processes to get bottom melting. Sometimes that will happen when the top surface isn't melting, but generally not in July.
Title: Re: SMOS
Post by: slow wing on July 21, 2018, 11:13:18 PM
Agree, Fish, that there are other processes - that you have given - that can cause a lot of bottom melt even when the top of the ice is dry.

The above discussion relates specifically to heat conduction down through the ice when the top is heated by warm winds.

Parenthetically, there are also a couple of other issues that work against lots of heat transfer by that mechanism: air can carry only very little heat per unit volume - orders of magnitude less than water, and the thermal coupling to the ice will usually be poor. (Water vapour in the air helps though.)
Title: Re: SMOS
Post by: johnm33 on July 22, 2018, 01:06:37 AM
OT but 'Atlas' carried the sky on his shoulders, actually inside his head he was a navigator in the days before maps and atlas's curiously. Without complete star knowledge sailors got lost.
Title: Re: SMOS
Post by: RoxTheGeologist on July 22, 2018, 01:32:53 AM

I would think there is a gradient, the base of the ice is fixed at >-1.8°C and the top of the ice at <0°C which would match a salinity gradient through the ice. If you heat the basal water (insolation, pushing the ice over warm sea) then the ice melts from the bottom.

If you heat the ice from the top, insolation, warm air, warm rain, then you might be in a thermodynamic environment to cause bottom melt. I could easily see water on top of the ice causing bottom melt, as it freezes and releases heat of fusion and then ice conducting that energy to the base. Perhaps that is one mechanism by which ice becomes fresher as it ages. In reality, at equlibrium, the ice surface should be 'dry', it refreezes at 0°C causing bottom melt.
Title: Re: SMOS
Post by: Peter Ellis on July 22, 2018, 02:44:12 AM
Bottom melt happens primarily near the edges of floes, and the heat source is from radiation absorbed by the open water between the floes.  The onset is generally quite late in the season, but because of the huge thermal mass of the ocean, it can continue even after atmospheric temperatures have dropped below freezing at the transition from summer to autumn.

Anything other than the above is a mere detail in the small decimal places. This forum used to know stuff like this!
Title: Re: SMOS
Post by: Hyperion on July 22, 2018, 04:06:52 AM
When the ice is a fractured and mobile pack of porous honeycombed ice, as per today's arctic, there's a lot more complexity than a one dimensional conduction calculation can give good approximations from s-wing.
Like the thermo karst effect. The densest fresh water is 4-6 degC. So it is quite normal for the top of waterlogged cavities to be at zero degrees, or even frozen over,  whilst deeper down there is warmer water burrowing deeper. You might call this subsurface micro-meltponding

Under the floe a similar but salinity driven process works as warmer saltier water below is exchanged and turned over as it gives energy to the ice and is freshened by melt in a non uniform process. One can even envisage outward flow of freshened melt from the edges of floes drawing up warmer more saline stuff from below in the middle. Exactly like the process tunneling under the ice shelves of Antarctica and Greenland.
Algal growth into the porous bottom of the ice absorbs solar energy, metabolic heat and antifreeze secretionsthat lower the melting point still further, increases porosity, and of course warm salty water rises.
These convection processes should vastly increase the   thermal transfer through the average 1m ice.

And then there is radiative energy transfered in microwave and ultraviolet spectra that ice is near transparent to.
Title: Re: SMOS
Post by: Hyperion on July 22, 2018, 11:38:36 AM
16 to 21 July. Apart from the major disintegration of the pac-ruski quadrant, major changes appear to be compaction into the CAA garlic press and Svalbard region killing grounds.
Title: Re: SMOS
Post by: FishOutofWater on July 22, 2018, 06:30:29 PM
Generally, in the Arctic the density gradient is controlled by salinity not temperature. The light fresh water floats above the saline layers. Thus the process you propose generally does not happen in the Arctic.

"Under the floe a similar but salinity driven process works as warmer saltier water below is exchanged and turned over as it gives energy to the ice and is freshened by melt in a non uniform process."
Title: Re: SMOS
Post by: Neven on July 22, 2018, 07:11:11 PM
Hyperion can't answer, because he's banned from the ASIF.
Title: Re: SMOS
Post by: FishOutofWater on July 22, 2018, 08:14:05 PM
Neven, that will improve the signal to noise ratio around here.
Title: Re: SMOS
Post by: Hefaistos on July 22, 2018, 09:54:50 PM
It near as dammit is a blue ocean event already Neven. I bet my left nut that anything near the periphery, extending now to a Chukchi to Barents strip right across the pole where meltponding is being reported is actually open water, and satellites being fooled by wave action.
And what I cannot stand is bullying. Which is what you supported.

As said, if there's a BOE event this year (it's already practically there according to you), I will apologize. Conversely, if there's no BOE, you'll get banned from this forum.
So already now we know for sure there will be no BOE this year :)
Title: Re: SMOS
Post by: Neven on July 22, 2018, 10:34:46 PM
No, it was simply taking up too much time and energy, reading the posts from beginning to end, deciding whether to approve, editing out the bad parts, replying to angry mails.

If there's a BOE, I will reinstate Hyperion and apologise. In fact, I will do so if I ever think there could be a BOE (and I hope I will be able to see it coming).
Title: Re: SMOS
Post by: Steven on July 22, 2018, 10:40:14 PM
I updated my pixel-counting calculations with SMOS images that were quoted in the topmost post of this thread.  First, I counted the number of beige pixels for each daily SMOS image for July 2010-2018:

(https://i.imgur.com/QlMGbgf.png)


Clearly 2013 and 2014 stand out.  But in general the number of beige pixels in July is quite small. 

As an alternative, I included more pixel colors from the color legend of the SMOS images.  More specifically, I lumped together all the beige, purple, red and yellow pixels of the SMOS images in the pixel counting algorithm:


(https://i.imgur.com/bb95jZf.png)


Average number of pixels for the first 21 days of July:

(https://i.imgur.com/WrFZ6VL.png)
Title: Re: SMOS
Post by: AvantGuardian on August 13, 2018, 03:10:57 AM
Looks like this is the place where usnavy and German data is not unwelcome. So someone needs to post the SMOs and us navy stuff here huh.
Title: Re: SMOS
Post by: Neven on August 13, 2018, 11:07:11 AM
Looks like this is the place where usnavy and German data is not unwelcome. So someone needs to post the SMOs and us navy stuff here huh.

That's right, and it would be even better if you could compare it to previous years.
Title: Re: SMOS
Post by: AvantGuardian on August 14, 2018, 12:58:58 AM
11, 12 Aug smas


Re: SMOS
« Reply #88 on: Today at 01:35:38 PM »
Note: This message is awaiting approval by a moderator.
I've asked my professors and C/O about your questions sir. Thank you for asking sir.
They believe this seems to show the results of the hot and humid winds that blew from the Atlantic front, for most of the preceding week right across the pole to the  Chukchi and Siberian theatre. This pushed a lot of the floes in the central pack 20-40 degrees to the right of the wind direction, and caused a lot of surface melting in the active corridor also. A lot of meltwater was pushed out of the pack onto the ESAS, and into the CAA, because winds move the surface waters faster than ice floes. And large gaps within the pack allowed the high winds to create a large storm surge. Now that the winds have reversed direction, the cooling effect of them blowing over heavily fractured ice distributed in  highly saline surface waters, is causing surface crusting on the floes, and meltwater flooded surface channels and ponds of the central pack causing this area to read as thicker than it actually is.
Regarding how this compares with SMOS datasets from previous years. My superiors suggest that the high surface salinity and fragmented pack is causing SMOS to overstate thickness relative to previous years.
Title: Re: SMOS
Post by: Neven on August 14, 2018, 08:39:51 AM
What does this show and how does it compare to previous years?
Title: Re: SMOS
Post by: AvantGuardian on August 15, 2018, 01:35:38 PM
I've asked my professors and C/O about your questions sir. Thank you for asking sir.
They believe this seems to show the results of the hot and humid winds that blew from the Atlantic front, for most of the preceding week right across the pole to the  Chukchi and Siberian theatre. This pushed a lot of the floes in the central pack 20-40 degrees to the right of the wind direction, and caused a lot of surface melting in the active corridor also. A lot of meltwater was pushed out of the pack onto the ESAS, and into the CAA, because winds move the surface waters faster than ice floes. And large gaps within the pack allowed the high winds to create a large storm surge. Now that the winds have reversed direction, the cooling effect of them blowing over heavily fractured ice distributed in  highly saline surface waters, is causing surface crusting on the floes, and meltwater flooded surface channels and ponds of the central pack causing this area to read as thicker than it actually is.
Regarding how this compares with SMOS datasets from previous years. My superiors suggest that the high surface salinity and fragmented pack is causing SMOS to overstate thickness relative to previous years.

Can you ask your professors/superiors for the images of previous years (2012 to now, preferably) and put them side by side, so we can all compare them, instead of having to rely on their word and convoluted theories where 2-3 days of wind cause massive shifts at ultra-high speed?

Note: This message is awaiting approval by a moderator.
No Sir, there seems to be no longer a website at https://seaice.uni-bremen.de/
Perhaps they have decided there is no more sea ice.

And with respect sir. If sir had ever tried to paddle a small boat in a wind, on even a harbour or lagoon, sir would understand that the surface of the water can blow very fast in a wind. This in fact is how waves are generated.
Title: Re: SMOS
Post by: Neven on August 16, 2018, 10:39:59 AM
Can you ask your professors/superiors for the images of previous years (2012 to now, preferably) and put them side by side, so we can all compare them, instead of having to rely on their word and convoluted theories where 2-3 days of wind cause massive shifts at ultra-high speed?
Title: Re: SMOS
Post by: AvantGuardian on August 16, 2018, 01:28:36 PM
No Sir, there seems to be no longer a website at https://seaice.uni-bremen.de/
Perhaps they have decided there is no more sea ice.

And with respect. If you had ever tried to paddle a small boat in a wind, on even a harbour or lagoon, you would understand that the surface of the water can blow very fast in a wind. This in fact is how waves are generated.
Title: Re: SMOS
Post by: Cid_Yama on August 17, 2018, 06:32:26 AM
SIC comparison
https://sites.google.com/site/arcticseaicegraphs/concentration-maps/sic0819
Title: Re: SMOS
Post by: Rob Dekker on August 19, 2018, 09:56:45 AM
Let's just wait until Bremen SMOS comes back on-line.
Then we can do the proper year-by-year comparisons.
https://seaice.uni-bremen.de/data/smos/png/
Title: Re: SMOS
Post by: Steven on August 20, 2018, 09:07:05 PM
The SMOS images are back online.  Here are some updated graphs obtained using a pixel-counting script.

First, here's a look at the beige pixels, which are at the far right end of the SMOS color legend:

(https://i.imgur.com/XDqX3MC.png)

(https://i.imgur.com/Vrzs4se.png)


The graph below counts more pixel colors, lumping together all the pixel colors from beige to green in the SMOS color legend (including the intermediate yellow, red and purple colors).  At this time of year, this graph has a good correlation with the September minimum extent.


(https://i.imgur.com/vXwLMxi.png)

(https://i.imgur.com/RH0Ats6.png)


Finally, here is a weighted average of all pixels in the SMOS image, with each pixel weighted according to its numerical value in the color legend:


(https://i.imgur.com/aO6CSCF.png)
Title: Re: SMOS
Post by: Rob Dekker on August 21, 2018, 09:20:00 AM
That's great work, Steven. Thank you.

It appears that 2018 ranks rather high on your various SMOS graphs, suggesting less "water" on the ice than in previous years (some even suggesting a resemblance to 2013/2014).

Also, just eye-balling the results, it seems to me that the SMOS data bears clear resemblance to the "ice concentration" data, as visualized by Wipneus (the "compactness" graph) here :
https://sites.google.com/site/arcticseaicegraphs/regional
which is also been high for much of the summer.

With the side-note that some of your SMOS data graphs appears to have less "noise" than the concentration data.

Do you know (did you calculate?) which metric (SMOS or ice "concentration") has better predictive skill for determining the minimum in September, especially this late into the melting season ?
Title: Re: SMOS
Post by: Steven on August 21, 2018, 11:03:11 PM
It appears that 2018 ranks rather high on your various SMOS graphs, suggesting less "water" on the ice than in previous years (some even suggesting a resemblance to 2013/2014).

Also, just eye-balling the results, it seems to me that the SMOS data bears clear resemblance to the "ice concentration" data, as visualized by Wipneus (the "compactness" graph) here :
https://sites.google.com/site/arcticseaicegraphs/regional
which is also been high for much of the summer.

It also agrees with the JAXA AMSR2 melt graphs (https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/grf/jaxa-amsr2-melt-extent-ratioD.png) on Wipneus' website, which suggest that surface melting has been relatively weak this melt season.

Regarding compactness, there were also some anecdotes from the Swedish icebreaker Oden, which traveled from Svalbard to the North Pole earlier this month.  The captain of the ship reported (http://www.sjofartsverket.se/pages/111200/Veckobrev%20fr%C3%A5n%20Isbrytaren%20Oden%202018-08-09.pdf) that the sea ice is very compact and that he had not seen such high compactness in more than a decade.  That seems to be due to the prevalent weather conditions during this melt season: a reverse dipole anomaly with ensuing northward sea ice drift (and compaction) on the Atlantic side of the CAB.


Do you know (did you calculate?) which metric (SMOS or ice "concentration") has better predictive skill for determining the minimum in September, especially this late into the melting season ?

This late in the melt season, I would just use the extent trajectories for previous years.  That suggests about 4.7 million km2 for the September 2018 NSIDC extent.  As for the SMOS data, the second graph I posted yesterday suggests a slightly higher value, about 4.9.  That is also similar to what Slater's method predicts.  The skill of those 3 different methods seems to be rather similar in mid-August.
Title: Re: SMOS
Post by: Steven on June 05, 2019, 05:06:07 PM
The 2019 melt season is now well underway.  Like last year (https://forum.arctic-sea-ice.net/index.php/topic,2278.msg161413.html#msg161413), I run a pixel counting algorithm on the SMOS images. 

In summer SMOS is sensitive to surface melting.  The beige pixels in the SMOS images would correspond to sea ice with a dry surface (without melt ponds).  During June, the number of beige pixels in the images tends to decrease fast as surface melting becomes more widespread in the Arctic Ocean.

Based on this metric, surface melting in 2019 has been mediocre in the last few weeks (slightly weaker than the 2010s average).  But it's still early in the season and a lot can happen.

(https://www.dropbox.com/s/fl2xs6aeop3ioen/SMOS_beige_pixels.png?dl=1)

https://www.dropbox.com/s/fl2xs6aeop3ioen/SMOS_beige_pixels.png

To keep this graph up-to-date, I uploaded it on dropbox.com and it will be updated every day with the latest data.
Title: Re: SMOS
Post by: Sterks on June 05, 2019, 05:28:35 PM
The 2019 melt season is now well underway.  Like last year (https://forum.arctic-sea-ice.net/index.php/topic,2278.msg161413.html#msg161413), I run a pixel counting algorithm on the SMOS images. 

In summer SMOS is sensitive to surface melting.  The beige pixels in the SMOS images would correspond to sea ice with a dry surface (without melt ponds).  During June, the number of beige pixels in the images tends to decrease fast as surface melting becomes more widespread in the Arctic Ocean.

Based on this metric, surface melting in 2019 has been mediocre in the last few weeks (slightly weaker than the 2010s average).  But it's still early in the season and a lot can happen.

(https://www.dropbox.com/s/fl2xs6aeop3ioen/SMOS_beige_pixels.png?dl=1)

https://www.dropbox.com/s/fl2xs6aeop3ioen/SMOS_beige_pixels.png

To keep this graph up-to-date, I uploaded it on dropbox.com and it will be updated every day with the latest data.
Great stuff! By mid June 2012 had only 1/5 of the surface “dry”. Let’s see how this year will go, my feeling is that it will get there but with some days of lag. Obviously if the lag is too long, we get into July and the possibility of keeping pace with 2012 will be nil.
Title: Re: SMOS
Post by: Brigantine on June 06, 2019, 11:51:14 AM
That graph is exactly what I needed!

But... is the map from this date 2012 accessible somewhere too?
Title: Re: SMOS
Post by: Neven on June 06, 2019, 12:15:31 PM
Yes, here (https://seaice.uni-bremen.de/data/smos/png/).

Thanks for reminding me of Steven's great graph. I see it is still updated, and will try to insert it in the ASIG daily graphs page.
Title: Re: SMOS
Post by: Sterks on June 10, 2019, 01:51:07 PM
Bumping this live plot,  one click less away. Thank you Steven.
In summer SMOS is sensitive to surface melting.
(https://www.dropbox.com/s/fl2xs6aeop3ioen/SMOS_beige_pixels.png?dl=1)

https://www.dropbox.com/s/fl2xs6aeop3ioen/SMOS_beige_pixels.png
Title: Re: SMOS
Post by: Steven on June 18, 2019, 11:57:45 PM
The number of beige pixels for 2019 has been slightly below 2012 in the last 3 days.  But it may also be interesting to have a look at the other colors in the SMOS images.  Note that 2019 currently has relatively many of the purple/violet/red/orange-ish pixels, especially when compared to 2012.  To quantify this, I run a pixel-counting algorithm for several color segments of the SMOS color legend, for the date 17 June, see the bottom chart below (blue pixels are ignored, and I made some heuristic corrections for data gaps for the years 2010 and 2011).

(https://i.imgur.com/UBVf4lr.png)


(https://www.dropbox.com/s/8zb473ihgiz4z3x/smos_colors_pixel_count.png?dl=1)
Title: Re: SMOS
Post by: Rich on June 19, 2019, 02:43:16 AM
The number of beige pixels for 2019 has been slightly below 2012 in the last 3 days.  But it may also be interesting to have a look at the other colors in the SMOS images.  Note that 2019 currently has relatively many of the purple/violet/red/orange-ish pixels, especially when compared to 2012.  To quantify this, I run a pixel-counting algorithm for several color segments of the SMOS color legend, for the date 17 June, see the bottom chart below (blue pixels are ignored, and I made some heuristic corrections for data gaps for the years 2010 and 2011).

(https://i.imgur.com/UBVf4lr.png)


(https://www.dropbox.com/s/8zb473ihgiz4z3x/smos_colors_pixel_count.png?dl=1)

This is extremely cool. Have you considered running a simulated volume with this?

Simply multiply the pixel count by my implied thickness and area. For the beige, make an assumption of average thickness (perhaps 75-100 cm).

You're making a good point here that all of pixel colors matter.... it's not just beige v. other.
Title: Re: SMOS
Post by: oren on June 19, 2019, 02:59:26 AM
Steven thanks for your analysis of SMOS chart (and for the automated dropbox link for the "beige index"). I agree an aggregate SMOS index taking all the colors with some kind of weighting could be quite useful in summer. Just don't call it volume, as it doesn't represent thickness at this stage, but mostly surface wetness.
Title: Re: SMOS
Post by: Rich on June 19, 2019, 03:41:20 AM
Just don't call it volume, as it doesn't represent thickness at this stage, but mostly surface wetness.

I respectfully disagree with this point Oren.

The sensors are still picking up enough information that allow it to assign a thickness to the ice which conforms to a common sense understanding of where we expect the thickness to be.

If it was simply measuring a binary state of wet v. dry, the map would only have two colors.

The presence of water on the surface might impair the precision of the thickness data, but there is still something functional going on there which allows the sensor to assign a thickness output resembling reality.

It's a tall order to ask, but if someone wanted to reconcile the SMOS pixel counts with past PIOMAS data, I'm guessing they could find a good fit.
Title: Re: SMOS
Post by: Tor Bejnar on June 19, 2019, 05:15:58 AM
I imagine (= guess - based on what I've been hearing for years) when the sensor responds with "purple", it is sensing an area that has more dry spots than when it responds with "red", and has 100% nothing to do with ice thickness (except for where it is sensing actually dry thin ice).
Title: Re: SMOS
Post by: oren on June 19, 2019, 05:36:43 AM
Check out this post by A-Team in the Test Space thread for some more information.
https://forum.arctic-sea-ice.net/index.php/topic,2558.msg206386.html#msg206386 (https://forum.arctic-sea-ice.net/index.php/topic,2558.msg206386.html#msg206386)
Quote
Smos and Smos-Smap can't help but still report ice thinness but that is overlain -- and overwhelmed -- by other factors contributing dielectric. Note the color sequence in the palette is maintained south to north, with the periphery 'thinner'. This does not agree well with melt pond distribution (blueish in WorldView) because a number of other factors contribute to the overall artifact picture, such as ice surface roughness and floe vs open water distribution relative to instrument ground resolution.

Both are passive satellite instruments that do not use altimeters. In winter, they measure the change in stokes parameters as emitted blackbody radiation from the upper cms of ocean water passes through the anisotropic ice above. Like so many hand-me-down Arctic tools, Smos and Smap have been re-purposed from their originalmission design which required a near-polar orbit and so provided accidental coverage of the Arctic Ocean.

Smos and Smap in summer have been wrongly written off in journals. There is still information there if you 'let go' of ice thinness; inter-year comparisons must indicate something (but what?). A glance at the non-beige colors above the CAA (where the ice is entirely >0.5m) shows an interesting correlation with a dramatic shift in Ascat brightness. So it is an interpretive matter of what the colors are telling us.

The gif investigates an overlay of SMOS and high-resolution WV visible on a clear day. Again, it is not clear what visible features on the ice surface correlate with Smos and Smap map colors.
Title: Re: SMOS
Post by: Rich on June 19, 2019, 05:58:28 AM
I imagine (= guess - based on what I've been hearing for years) when the sensor responds with "purple", it is sensing an area that has more dry spots than when it responds with "red", and has 100% nothing to do with ice thickness (except for where it is sensing actually dry thin ice).

Studying the map closely reveals that the story you imagine is probably wrong.

The pixels are arranged in a continuum according to thickness.

They run from thinnest to thickest as follows

dark blue
light blue
light green
dark green
yellow
orange
red
purple
beige

The pattern on the map reveals no deviation in the continuum. You don't see any purple areas adjacent to any green areas. Yellow always has green on one side and orange / red on the other. This is exactly what one  would expect to see with a body of ice that is thickest in the center and melting from the shallow sections toward the thick sections.
.
It is unrealistic to expect that surface moisture would appear along a continuum like that. .

This appears to be an ASIF legend that has gotten traction over the years. I'm challenging the legend.
Title: Re: SMOS
Post by: binntho on June 19, 2019, 07:01:15 AM
This is exactly what one  would expect to see with a body of ice that is thickest in the center and melting from the shallow sections toward the thick sections.

Sounds reasonable. But the thickness distribution that we "know" from products like Piomas does not match the color distribution of the SMOS graph.

It seems to me that the more reasonable explanation for the colour gradiation is that hot air flows from one area to another, and cools down as it reaches the coldest parts (in the center). Surface melts then mostly follows the temperature of the hot air.

This can be seen happening very clearly north of CAA and Greenland where we know that the thickest ice is.
Title: Re: SMOS
Post by: oren on June 19, 2019, 07:49:27 AM
I recommend to read
https://seaice.uni-bremen.de/thin-ice-thickness/ (https://seaice.uni-bremen.de/thin-ice-thickness/)
Quote
SMOS
The thickness of thin sea ice (SIT) is daily retrieved from observations of the L-band microwave sensor SMOS (Soil Moisture and Ocean Salinity). Horizontal and vertical polarized brightness temperatures in the incidence angle range of 40° to 50° are averaged. The ice thickness is then inferred from the polarization difference and the intensity using an empirical method (Huntemann et al., 2014).

Thin sea ice occurs during the freezing season. In the melting season, the thickness of sea ice is highly variable and the emission properties in the microwave change due to the wetness of the surface and occurrence of melt ponds in the Arctic. Therefore, thickness data are calculated only during the freezing season, that is from October to April in the Arctic and from March to September in the Antarctic. During the melting season, the procedure does not yield meaningful results.

As the resolution of SMOS at the used incidence angle range is about 40 km, only larger regions of thin ice will be retrieved correctly. The rim of thin ice shown in many cases not necessarily indicates thin ice, but can also be caused by the smearing effect (convolution) of the low resolution.

Each day of ice thickness data product are calculated twice to ensure that all swath files were available in the archived product. First processing is done directly on the next day with only about 7 hours delay. At this time it can happen that not all swath files are available and another processing of the same day is initiated 23 hours later. In more than 50% of the time the first processing does not include all swath but usually provides sufficient coverage for Arctic and Antarctic regions.

This service has been developed in the framework of the EU project SIDARUS. After completion of the SIDARUS project end 2013, the service is continued on a best effort base in the context of the Polar View and of the Arctic Regional Ocean Observing System (Arctic ROOS).

Other useful links which I haven't read in full yet:
https://icdc.cen.uni-hamburg.de/1/daten/cryosphere/l3c-smos-sit.html (https://icdc.cen.uni-hamburg.de/1/daten/cryosphere/l3c-smos-sit.html)
Uni Hamburg SMOS page.

http://seaice.de/Kaleschke_2016.pdf (http://seaice.de/Kaleschke_2016.pdf)
SMOS sea ice product: Operational application and validation in the
Barents Sea marginal ice zone

https://www.the-cryosphere.net/13/675/2019/tc-13-675-2019.html (https://www.the-cryosphere.net/13/675/2019/tc-13-675-2019.html)
Combined SMAP–SMOS thin sea ice thickness retrieval

Title: Re: SMOS
Post by: Rich on June 19, 2019, 08:46:02 AM
This is exactly what one  would expect to see with a body of ice that is thickest in the center and melting from the shallow sections toward the thick sections.

Sounds reasonable. But the thickness distribution that we "know" from products like Piomas does not match the color distribution of the SMOS graph.

It seems to me that the more reasonable explanation for the colour gradiation is that hot air flows from one area to another, and cools down as it reaches the coldest parts (in the center). Surface melts then mostly follows the temperature of the hot air.

This can be seen happening very clearly north of CAA and Greenland where we know that the thickest ice is.

If you want to prove your point, it might be better to out up a current PIOMAS chart next to the current SMOS chart and identify areas which are different.

Comparing May 2018 PIOMAS to current SMOS isn't very scientific.

Title: Re: SMOS
Post by: Rich on June 19, 2019, 09:02:52 AM
Thank you Oren for providing the quotes from A-Team and the links.

The interpretations of those is vague.

I have acknowledged that the surface moisture impairs the thickness measurement which may reduce the precision to a point where the folks in Bremen may not consider it meaningful.

That doesn't mean that it still isn't producing an output which is representative of thickness.
Title: Re: SMOS
Post by: Neven on June 19, 2019, 10:26:11 AM
If you want to prove your point, it might be better to out up a current PIOMAS chart next to the current SMOS chart and identify areas which are different.

Comparing May 2018 PIOMAS to current SMOS isn't very scientific.

Coincidentally, Wipneus just posted a mid-month PIOMAS update.
Title: Re: SMOS
Post by: Tor Bejnar on June 19, 2019, 06:38:47 PM
I imagine (= guess - based on what I've been hearing for years) when the sensor responds with "purple", it is sensing an area that has more dry spots than when it responds with "red", and has 100% nothing to do with ice thickness (except for where it is sensing actually dry thin ice).

Studying the map closely reveals that the story you imagine is probably wrong.

The pixels are arranged in a continuum according to thickness.

The pattern on the map reveals no deviation in the continuum. You don't see any purple areas adjacent to any green areas. Yellow always has green on one side and orange / red on the other. This is exactly what one  would expect to see with a body of ice that is thickest in the center and melting from the shallow sections toward the thick sections.
.
It is unrealistic to expect that surface moisture would appear along a continuum like that. .

This appears to be an ASIF legend that has gotten traction over the years. I'm challenging the legend.
I think I am probably approximately correct, still.  From SMOS (via Oren (https://forum.arctic-sea-ice.net/index.php/topic,2341.msg206759.html#msg206759))
Quote
In the melting season, the thickness of sea ice is highly variable and the emission properties in the microwave change due to the wetness of the surface and occurrence of melt ponds in the Arctic.
My experience of drawing topographic maps from surveying data tells me that a map with a 40 km grid with points of presumed thickness (or wetness) across it can have a topographic-like map drawn over it, creating continuous lines of demarcation between areas of equal thickness (wetness).

Old fashioned reason tells me that the juxtaposition of the thickest ice on the Arctic Ocean (residing perennially in the area north of the CAA) with a zone of SMOS-determined thin ice (presuming non-beige color means variations on thin) is not tenable.  Given that the publishers of the SMOS data declare their data is not useful for thickness determination during the melting season, I can conclude that the colored zones do not describe any aspect of thinness when the surface has degrees of wetness.

This does not mean I am right.  But you are probably wrong.  The ASIF legend lives a little longer!  :)
Title: Re: SMOS
Post by: lurkalot on June 21, 2019, 01:51:58 PM
A large proportion of Arctic ice is no more than 2m thick, we are told. This would have a freeboard of around 25cm, which ought to be reachable by any self-respecting wave in the vicinity. Is SMOS capable of distinguishing between ice that is wet from melting, from waves or indeed from rain?
Title: Re: SMOS
Post by: oren on June 21, 2019, 02:31:38 PM
As floes can easily be hundreds of meters across, and some reach tens of kilometers across, the effect of wave-induced wetness should be negligible.
Title: Re: SMOS
Post by: Tor Bejnar on June 21, 2019, 04:51:28 PM
I know little about SMOS, but their sensors do detect "salinity".  So conceptually, it would register surface melt differently from a salt water wash.  However, SMOS reports on a 35 or 40 km grid (I've read both; I presume it is one or the other, unless it is latitude dependent), so the sensors-to-data-output-system is doing a great deal of averaging.  As open water is very wet, as soon as SMOS looks at floes that are 'small' (and not perfectly packed together), it starts averaging (convoluting) thickness with wetness and the thickness output becomes seriously/totally irrelevant (per SMOS literature).  As Oren suggested, a salt water wash will occur mostly along the edges of floes, so the salinity SMOS detects from open water might be very slightly exacerbated by salty water on a floe.  I conclude with Oren, "negligible", and add "irrelevant after review."
Title: Re: SMOS
Post by: Steven on June 21, 2019, 09:19:27 PM
an aggregate SMOS index taking all the colors with some kind of weighting could be quite useful in summer

Below is a first version.  In this graph, I weighted the pixels according to their numerical value on the color legend of the SMOS maps.  So the non-beige pixels are weighted by a factor between 0 (for dark blue pixels) and 0.5 (for light purple pixels).  For the beige pixels I used a weighting factor 0.6 for now.  That is somewhat arbitrary, but I'm not sure if there is a better choice.

I excluded 2010 and 2011 from this graph for now, since I haven't automated the correction of data gaps for those 2 years.  (For the beige pixel graph, I did some manual corrections for that, but that would be more complicated for the weighted version).  Perhaps I'll include those 2 years later if I have some time.

(https://www.dropbox.com/s/97j1gbr7zdostz8/smos_weighted.png?dl=1)
Title: Re: SMOS
Post by: prokaryotes on June 21, 2019, 11:03:38 PM
Just curious, but can this pickup on flaw polynyas?

Quote
Areas of flaw polynyas in the ESAS increased dramatically (by up to five times) during the last decades, and now exceed the total area of Siberian wetlands.
Link (https://www.mdpi.com/2076-3263/9/6/251/htm)
Title: Re: SMOS
Post by: oren on June 22, 2019, 12:07:57 AM
Thank you very much Steven.
I think the beige pixels should carry a larger weight, I would put it at around 0.75. Beyond that, the other factors make sense and the graph is useful as a complement to the beige-only graph.
Is there any way for you to generate a permanent link for this one as well?
Title: Re: SMOS
Post by: Tor Bejnar on June 22, 2019, 12:24:40 AM
I don't recall ever seeing the term "flaw polynya" before, and it took some searching to find a definition, finally (from here (https://skepticalscience.com/arctic-methane-outgassing-e-siberian-shelf-part1.html)):
Quote
flaw polynyas (band-like ice-free areas), which form
simultaneously with land-fast ice in November. Flaw polynyas
reach tens of kilometres in width and migrate out of fast ice
hundreds of kilometres northward (Smolyanitsky et al., 2003),
and here (https://www.collectionscanada.gc.ca/obj/s4/f2/dsk2/ftp03/MQ53200.pdf)
Quote
A polynya is defined as any nonlinear-shaped area of open water and/or sea ice cover < 30 cm thick enclosed by a much thicker ice cover (WMO 1970). It can be restricted on one side by a coast, terrned shore polynyas, or bounded by fast ice, termed flaw polynyas.
Title: Re: SMOS
Post by: Steven on June 22, 2019, 12:22:30 PM
I think the beige pixels should carry a larger weight, I would put it at around 0.75. Beyond that, the other factors make sense and the graph is useful as a complement to the beige-only graph.
Is there any way for you to generate a permanent link for this one as well?

The link is here:
https://www.dropbox.com/s/97j1gbr7zdostz8/smos_weighted.png?dl=0

I guess the weighting for beige pixels would depend on the time of year.  A large contiguous group of beige pixels would probably have higher numerical values in the middle of the group than at the edges.  Anyway there isn't much beige left at this time of year so they get less important for the calculation.

P.S.  To illustrate the problems with 2010 and 2011, see e.g. this image (https://seaice.uni-bremen.de/data/smos/png/20100618_hvnorth_rfi_l1c.png) for 2010.  The pole hole for those 2 years is larger than for the years 2012-2019.  Moreover 2010 and 2011 have some irregular data gaps at other places (e.g. Greenland Sea) which vary from day to day.
Title: Re: SMOS
Post by: Steven on June 30, 2019, 02:47:38 PM
I excluded 2010 and 2011 from this graph for now, since I haven't automated the correction of data gaps for those 2 years

Update: I made some improvements to the pixel counting algorithm and included 2010 and 2011 in the graph.  Note that those two years were very low at this time of year.  That is consistent with some other datasets that are also showing strong surface melting in 2010/2011 at the end of June, see e.g. Worldview bands 7-2-1 (https://worldview.earthdata.nasa.gov/?p=arctic&l=MODIS_Terra_CorrectedReflectance_Bands367(hidden),MODIS_Aqua_CorrectedReflectance_Bands721,VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2010-06-28-T00%3A00%3A00Z&z=3&v=-6473728,-2402304,4716544,2979840) or NSIDC sea ice area, where 2010 was also the lowest on record in the past few days.

(https://www.dropbox.com/s/97j1gbr7zdostz8/smos_weighted.png?dl=1)
https://www.dropbox.com/s/97j1gbr7zdostz8/smos_weighted.png