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Author Topic: Passive Microwave Sea Ice Measurements: How big an effect does cloud cover have?  (Read 12429 times)

BornFromTheVoid

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In order to keep some of the other threads on topic, I thought this subject was deserving of it's own thread.
Despite PM imagery being used, to a large degree, for it's ability to peer through clouds and provide data in the dark of the polar night, many believe that cloud cover is still a big problem; causing ice coverage to "appear" to increase when in fact it is melting and generally causing big problems with interpreting concentration data.

So, a few questions arise:
  • Is there evidence to support cloud cover having such a large impact?
  • Has something changed to make this a problem in recent years?
  • What microwave bands are best for overcoming cloud cover issues?
  • What other data sources might be used to deal with the problem?
  • Is there even a problem at all, beyond the usual noise we expect with PM imagery?

Please discuss the ideas and evidence, for and against, for cloud cover interfering with sea ice here :)
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

bbr2314

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I would argue that cloud cover has more of an impact the less sea ice we have, but this becomes especially pronounced as area decreases relative to extent (i.e., as compactness goes down).

Consider; in 2012, things were bad, but the main pack was still cohesive. Whether or not this area was covered by clouds, it appeared entirely (or almost entirely) white to the satellites, with the uniformity in concentration aiding "steadiness" in observations. Cloud cover over open ocean is easier to reduce than cloud cover over a background that is the same color.

This year, with structure of the pack completely shattered, you have -- for the very first time -- only a small area of ice that is structurally intact. While this small triangle of area N of the CAA/Greenland falls into the same category as 2012's ice, the remainder most certainly does not.

With ice that is very dispersed, as in this year, cloud cover -- especially of the low sort -- masks much of the open water in between the ice, and the satellites have a much harder time distinguishing what is real vs. what isn't, at least when clouds are overhead. Additionally, I think open water *encourages* cloud cover this far N, especially as it gives up its latent heat from the summertime, further reducing accuracy as clouds have been nearly continuous over much of the Arctic this summer.

Again, the key is the overall structural integrity of the ice.

weatherdude88

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I would argue that cloud cover has more of an impact the less sea ice we have, but this becomes especially pronounced as area decreases relative to extent (i.e., as compactness goes down).

Consider; in 2012, things were bad, but the main pack was still cohesive. Whether or not this area was covered by clouds, it appeared entirely (or almost entirely) white to the satellites, with the uniformity in concentration aiding "steadiness" in observations. Cloud cover over open ocean is easier to reduce than cloud cover over a background that is the same color.

This year, with structure of the pack completely shattered, you have -- for the very first time -- only a small area of ice that is structurally intact. While this small triangle of area N of the CAA/Greenland falls into the same category as 2012's ice, the remainder most certainly does not.

With ice that is very dispersed, as in this year, cloud cover -- especially of the low sort -- masks much of the open water in between the ice, and the satellites have a much harder time distinguishing what is real vs. what isn't, at least when clouds are overhead. Additionally, I think open water *encourages* cloud cover this far N, especially as it gives up its latent heat from the summertime, further reducing accuracy as clouds have been nearly continuous over much of the Arctic this summer.

Again, the key is the overall structural integrity of the ice.

Updates of 2012 AMSR2 data seem to have been completed. We have complete data from the first of August to 30th September. Thanks for that.

Update 20160823.

Extent: -81.4 (-123k vs 2015, -733k vs 2014, -706k vs 2013, +784k vs 2012)
Area: -8.3 (-296k vs 2015, -976k vs 2014, -946k vs 2013, +484k vs 2012)
 
You will find the updated graphs in the top post

Regional extent declined in the CAB (-32k) and Laptev (-19k).

Regional area increased in the CAB : +53k. Area declined in Laptev (-26), Chukchi (-18k) and ESS (-16k).

The attached delta map is of the Beaufort-Chukchi-ESS corner. Lots of reds and blues confirm there is a lot of ice moving around. The detachment of the Wrangek ice progresses further.

bbr2314,

Please explain why the CAB is increasing in area, whereas the ESS and Chukchi lost area. Are you hypothesizing the ice is in better shape in these region than the CAB? (Or is there even any ice there if it is in worse shape?) Additionally, with the storminess on the Russian side surely there is thicker cloud cover currently in the Laptev. So why does the Laptev also show loses? Please help me understand your "theory" works with respect to the above regions?

bbr2314

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The CAB isn't increasing in area.

weatherdude88

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The CAB isn't increasing in area.

Regional area increased in the CAB : +53k. Area declined in Laptev (-26), Chukchi (-18k) and ESS (-16k).

In layman's, if the CAB really is decreasing and the satellites are "tricked" by cloud cover, why are we not seeing this same phenomenon the last several days in the above regions where there is currently the same or thicker cloud cover?

« Last Edit: August 24, 2016, 05:44:05 PM by weatherdude88 »

bbr2314

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The CAB isn't increasing in area.

Regional area increased in the CAB : +53k. Area declined in Laptev (-26), Chukchi (-18k) and ESS (-16k).
I really don't know how to get through to you. The increase is measured from AMSR2 which does not account for all clouds.

Comparing MODIS today and yesterday clearly shows why there was a sudden apparent increase in area across the CAB. Clouds increased dramatically.

I am telling you the clouds are the reason the area increased and you are telling me the area increased... you are just full of non-sequiturs today!

weatherdude88

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I really don't know how to get through to you. The increase is measured from AMSR2 which does not account for all clouds.

Comparing MODIS today and yesterday clearly shows why there was a sudden apparent increase in area across the CAB. Clouds increased dramatically.

I am telling you the clouds are the reason the area increased and you are telling me the area increased... you are just full of non-sequiturs today!

Update 20160820.
Regional area in the CAB increased: +31k. The Laptev regions went the other way: -23k.

Update 20160821.
Same for CAB area: +63k.

CAB area has been increasing for several days now according to the Home brew AMSR2 extent & area calculation. When did the cloud cover dramatically increase? In your above post you claim a dramatic increase comparing today and yesterday? Disregarding, comparing day to day images the cloud cover does not vary much.

https://lance.modaps.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic.2016236.terra.4km

I am still also trying to understand why we are not experiencing the same "bbr2314 phenomenon" in the other regions with similar cloud cover?

« Last Edit: August 24, 2016, 06:09:17 PM by weatherdude88 »

ghoti

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This seems like such a silly argument. The literature describing each of the different sensor/algorithm  combinations makes it clear that none are perfect. There has also always been differences between them highlighting that each is providing the best data given the limitations.

Passive microwave sensor data is never used alone without other bands attempting to correct for errors due to cloud/water/temperature effects.

The big tell for me over the years have been the animations posted by A-Team and others displaying time lapse of ice cover as perceived by various instruments and algorithms. These almost always show moving bands of more "concentrated ice" traveling across the Arctic in the classic bands one normally sees in satellite animations of storm systems. Coincidence? Perhaps but I think this is why there are suggestions ice loss is being hidden by the clouds.

I'd also suggest this is why the effort is made by MASIE to evaluate ice coverage manually. In any case hopefully we'll get some clear sky conditions before freeze up so we can relax and feel more comfortable with the various SIE and SIA products.

icy voyeur

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pulled from other  Home brew AMSR2 extent & area calculation

Typo - It should have said -5C.  Since corrected.

Keep in mind, that our starting point for freezing is -1.8, not zero C.  Between -1.8 and -5C the rate of transfer of heat out of the water isn't fast enough to support robust freezing, if indeed it is possible at all.  It doesn't take much wind to disturb the surface and generate circulation in the top few meters of water, and wind is something of which we currently have aplenty of in the Arctic.

When you have "wind aplenty", doesn't that wind rechill the surface as freezing occurs? The problem with freezing at -1.8 is of course that the heat of fusion turns around and warms the water+ice mix. You're not at a constant T. If you begin with supercooled pure water at -5C and let it freeze, only about 6% of it freezes and the mix goes to 0C of water+ice. Of course if air T is -5C that differential is enough to rapidly cool things again. (no wind)

But with a steady wind you approach a constant T regime, don't you? The heat released, latent heat of fusion, gets carried away by convection.

Now add to this that if ice concentration is 80%, and it's snowing, that snow blows until it lands on open water building a fresh water slush. Drop 4cm of snow and it's as if it's 20cm of snow specifically onto the water. (@ 80% concentration).

Agreed this is competing with dynamics producing mixing. I don't know how long it takes mixing to roughly equilibrate that top layer or the wind to chill warmth that rises. Biggest effect of mixing would be increased salinity for a storm of significant duration? But sapping the warmth that rose?

Seems like many competing effects.  And thus anyone who proclaims the result is obvious, without citing precedent over a range of similar predicates, is claiming more knowledge than I would be willing to trust.


jdallen

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pulled from other  Home brew AMSR2 extent & area calculation

Typo - It should have said -5C.  Since corrected.

Keep in mind, that our starting point for freezing is -1.8, not zero C.  Between -1.8 and -5C the rate of transfer of heat out of the water isn't fast enough to support robust freezing, if indeed it is possible at all.  It doesn't take much wind to disturb the surface and generate circulation in the top few meters of water, and wind is something of which we currently have aplenty of in the Arctic.

When you have "wind aplenty", doesn't that wind rechill the surface as freezing occurs? ...
<snippage>
Seems like many competing effects.  And thus anyone who proclaims the result is obvious, without citing precedent over a range of similar predicates, is claiming more knowledge than I would be willing to trust.

Rational questions deserving more time than I have currently, but absolutely agree with your last point.

The answers to your others are best summarized by the phrases "it depends" and "it's complicated".  I'll try to put some thoughts together.

 ;D
This space for Rent.

weatherdude88

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Seems like many competing effects.  And thus anyone who proclaims the result is obvious, without citing precedent over a range of similar predicates, is claiming more knowledge than I would be willing to trust.

One thing it shows pretty clearly is that we have no SST's currently across the central arctic below -5C.  That indicates pretty definitively that the transfer of heat is not yet high enough to support a refreeze. 

My -5C claim is in part historical, in part from work presented elsewhere by others on these forums, and actually is shaded on the conservative side.  I've read from others here that the threshold may actually be a bit lower, at -10C. 

No need to be conservative because we have never had liquid water surface temps across the arctic at -5C as suggested by your first post. The initial map posted shows a large area of uniform 2 meter surface temperatures.

Andreas T

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I find this discussion quite puzzling because we have had discussions before in which all the relevant facts have been talked about.
In AMSR animations there is darkening and brightening which turns out not to be caused by changes in ice cover when we can get cloud free visual observation. The main cause of AMSR showing no ice where there clearly is, is of course water on the ice surface. The most plausible explanation (examples of which can be seen in the footage from Obuoy14) is that the storm brought about significant areas of wet broken ice which was seen as water by the AMSR data processing. In calmer conditions, with cold air and some snowfall the microwave emissivity goes up and the ice is seen again.

Freezing up in the sense of ice cover forming on ice free sea water is highly improbable when air temperatures are not below -5oC and water is not close to freezing point (approx -1.8oC) all the way to the bottom (or a halocline) the main reason for that is density driven convection of cooled surface water down and warmer water up.
Colder air temperatures can freeze the surface of warmer water but in present conditions water convection preventing freezing beats air convection taking heat from the surface.


seaicesailor

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Thank you Andreas. Great explanation, never understood well the effect of convection on this problem until now.

Andreas T

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sorry, I should have mentioned heat loss by radiation to deserve that praise. Cloud cover is keeping it low now but clear skies will change that.

Nick_Naylor

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We should also keep in mind that as ice is blown around, it can cross regional boundaries between the CAB and peripheral regions.

So an increase in the CAB accompanied by decreases elsewhere might simply be "immigration".
Perhaps we should build a wall.

Link to map of Arctic regions: http://forum.arctic-sea-ice.net/index.php/topic,153.msg73543.html#msg73543

icy voyeur

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Colder air temperatures can freeze the surface of warmer water but in present conditions water convection preventing freezing beats air convection taking heat from the surface.
And wind speed? Clearly wind speed increases the rate of heat exchange at the air::water/ice interface.

-2C @ 10 km/hr wind -6C wind chill,
-2C @ 25 km/hr wind -8C,
-2C @ 40 km/hr wind -10C 

Not to take those Ts literally but the effect should correlate (subject to humidity but if it's high then there's lots of snow)
 I'm sure this is old hat to some, I can relocate to stupid questions if necessary.

bbr2314

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Colder air temperatures can freeze the surface of warmer water but in present conditions water convection preventing freezing beats air convection taking heat from the surface.
And wind speed? Clearly wind speed increases the rate of heat exchange at the air::water/ice interface.

-2C @ 10 km/hr wind -6C wind chill,
-2C @ 25 km/hr wind -8C,
-2C @ 40 km/hr wind -10C 

Not to take those Ts literally but the effect should correlate (subject to humidity but if it's high then there's lots of snow)
 I'm sure this is old hat to some, I can relocate to stupid questions if necessary.
wind chill is perceived by humans and animals not inanimate objects

Michael Hauber

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wind chill is perceived by humans and animals not inanimate objects

The physics of heat transfer affect humans, animals and inanimate objects exactly the same way.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

Darvince

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The physics of heat transfer affect humans, animals and inanimate objects exactly the same way.
The difference would be that humans and animals are far warmer than the environment, while inanimate objects (and ice/ocean especially) are usually only a few C warmer than the environment, if they are warmer at all.

icy voyeur

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wind chill is perceived by humans and animals not inanimate objects

No. It's more like wet bulb versus dry bulb temps. Please quit asserting things with such bombast when you are so far out of your depth. Please. Everything else aside, as a career scientist, your language is like fingernails on a chalkboard. Was a time the elders taught an arrogant pup like you a lesson, took some of the starch out of your collar, [metaphor of one's choice]. I'm particularly reminded of of story from South Africa where some rescued elephants turned into the equivalent of a teenage mob and were killing rhinos. The upshot was that this is what happens when young elephants turn into the equivalent of teenagers without the supervising effects of older males to bitch slap the unruly ones. But on the internet, the unruly ones ignore the slapdowns. I've said too much, but please, learn to behave.

budmantis

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wind chill is perceived by humans and animals not inanimate objects

The physics of heat transfer affect humans, animals and inanimate objects exactly the same way.

I think the key word used by BBR is "perceived". Can inanimate objects perceive anything?

budmantis

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wind chill is perceived by humans and animals not inanimate objects

No. It's more like wet bulb versus dry bulb temps. Please quit asserting things with such bombast when you are so far out of your depth. Please. Everything else aside, as a career scientist, your language is like fingernails on a chalkboard. Was a time the elders taught an arrogant pup like you a lesson, took some of the starch out of your collar, [metaphor of one's choice]. I'm particularly reminded of of story from South Africa where some rescued elephants turned into the equivalent of a teenage mob and were killing rhinos. The upshot was that this is what happens when young elephants turn into the equivalent of teenagers without the supervising effects of older males to bitch slap the unruly ones. But on the internet, the unruly ones ignore the slapdowns. I've said too much, but please, learn to behave.

You might not agree with an individual's assertion, that's fine. You might not like an individual, that's fine too. You might even feel repulsed by someone, that's also fine, but your response to BBR is inappropriate and you should apologize.

bbr2314

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wind chill is perceived by humans and animals not inanimate objects

No. It's more like wet bulb versus dry bulb temps. Please quit asserting things with such bombast when you are so far out of your depth. Please. Everything else aside, as a career scientist, your language is like fingernails on a chalkboard. Was a time the elders taught an arrogant pup like you a lesson, took some of the starch out of your collar, [metaphor of one's choice]. I'm particularly reminded of of story from South Africa where some rescued elephants turned into the equivalent of a teenage mob and were killing rhinos. The upshot was that this is what happens when young elephants turn into the equivalent of teenagers without the supervising effects of older males to bitch slap the unruly ones. But on the internet, the unruly ones ignore the slapdowns. I've said too much, but please, learn to behave.

<removed funny, but offensive gif; N.>
« Last Edit: August 25, 2016, 12:29:36 PM by Neven »

bbr2314

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wind chill is perceived by humans and animals not inanimate objects

No. It's more like wet bulb versus dry bulb temps. Please quit asserting things with such bombast when you are so far out of your depth. Please. Everything else aside, as a career scientist, your language is like fingernails on a chalkboard. Was a time the elders taught an arrogant pup like you a lesson, took some of the starch out of your collar, [metaphor of one's choice]. I'm particularly reminded of of story from South Africa where some rescued elephants turned into the equivalent of a teenage mob and were killing rhinos. The upshot was that this is what happens when young elephants turn into the equivalent of teenagers without the supervising effects of older males to bitch slap the unruly ones. But on the internet, the unruly ones ignore the slapdowns. I've said too much, but please, learn to behave.

You might even feel repulsed by someone, that's also fine, but your response to BBR is inappropriate and you should apologize.

Considering BBR's response to Icy Voyeur's post, perhaps I should add "or not" to the above paragraph! He certainly had it coming BBR, but you might be in a spot of trouble with the headmaster.
I messaged Neven. I am sick of these random personal attacks and am entitled to defend myself. Yesterday I was attacked by wxdudewhatever and today I get called a stupid young elephant worthy of a bitch slap.

Maybe he wouldn't be so angry if he knew the definition of wind chill. LOL!

budmantis

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About five minutes after I posted my last comments, I removed them. Now I wish I had left them. I don't know what Voyeur's problem was, but its his problem, not yours. Heck, even Lucy agrees with me and I didn't have to bribe her with more food!LOL

TerryM

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bbr
Please remove your graphic graphic


Thank you
Terry

bbr2314

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bbr
Please remove your graphic graphic


Thank you
Terry
Satisfied?

Neven

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Okay, I'm at my 'holiday' address, and I write 'holiday' because I still need to work here half days because my girls hope to stay a week longer this year.

So, naturally, I'm getting fed up with all this bickering. I've told bbr2134 that he will get pushback because he crosses the edges. You get a certain reputation, and then you got certain reactions. You have to accept that, it's only logical. Try not to retaliate by shooting back insults. It will get you banned for good.

As for others: Pushback is fine, but leave the effing insults out of it, as it only complicates matters. I'm willing to ban people, I just don't do it straight away. bbr2314 writes something about wind chill, and then we get some bullshit about elephant slapdowns. It's an interesting anecdote and 'elephant slapdown' sounds funny, but it's not helpful! It only makes bbr2314 more defensive and not willing to learn, and things get out of hand.

I don't want any more bickering because of some stupid details. Let's just wait and see what happens for the remainder of this melting season without drawing unwarranted conclusions all the time!
Il faut comparer, comparer, comparer, et cultiver notre jardin

bbr2314

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Okay, I'm at my 'holiday' address, and I write 'holiday' because I still need to work here half days because my girls hope to stay a week longer this year.

So, naturally, I'm getting fed up with all this bickering. I've told bbr2134 that he will get pushback because he crosses the edges. You get a certain reputation, and then you got certain reactions. You have to accept that, it's only logical. Try not to retaliate by shooting back insults. It will get you banned for good.

As for others: Pushback is fine, but leave the effing insults out of it, as it only complicates matters. I'm willing to ban people, I just don't do it straight away. bbr2314 writes something about wind chill, and then we get some bullshit about elephant slapdowns. It's an interesting anecdote and 'elephant slapdown' sounds funny, but it's not helpful! It only makes bbr2314 more defensive and not willing to learn, and things get out of hand.

I don't want any more bickering because of some stupid details. Let's just wait and see what happens for the remainder of this melting season without drawing unwarranted conclusions all the time!
I have no axe to grind, just confused as to why I should expect pushback when all I did was state a dictionary definition... it's the equivalent of telling someone they should expect anger if they say the sky is blue or evolution is real. ???? Don't understand at all how that is crossing an edge.

Neven

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I have no axe to grind, just confused as to why I should expect pushback when all I did was state a dictionary definition... it's the equivalent of telling someone they should expect anger if they say the sky is blue or evolution is real. ???? Don't understand at all how that is crossing an edge.

I've explained to you in a PM. People get a certain interpretation of you as a forum member and then view everything through that lens. That's what you get for going out on a limb and declaring the Arctic will go ice-free or records will be broken for sure at an early point during the melting season. You then get pushback with almost everything you say. It's only logical, don't take it too personal.

No more insults, not even if it's funny GIFs. End of discussion. Let's watch the ice.
Il faut comparer, comparer, comparer, et cultiver notre jardin

Andreas T

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Colder air temperatures can freeze the surface of warmer water but in present conditions water convection preventing freezing beats air convection taking heat from the surface.
And wind speed? Clearly wind speed increases the rate of heat exchange at the air::water/ice interface.

-2C @ 10 km/hr wind -6C wind chill,
-2C @ 25 km/hr wind -8C,
-2C @ 40 km/hr wind -10C 

Not to take those Ts literally but the effect should correlate (subject to humidity but if it's high then there's lots of snow)
 I'm sure this is old hat to some, I can relocate to stupid questions if necessary.
wind chill is perceived by humans and animals not inanimate objects
instead of bizarre emotional blow outs maybe we can look at the scientific merit of statements and correct where we know better.
Yes, rate of heat transfer increases when there is forced convection (wind) whether from animate and inanimate objects makes no difference (focussing on the word wind chill is just dodging the point of the discussion)
What is important is that air of -2 can cool an object of -1 down to -2 but not further regardless how strong the wind blows.
That is different for a wet object where evaporation can cool the object below the air temperature (like a wet bulb thermometer). But that depends on how dry the air is, the more humid it is the lower the cooling rate. The  relative humidity seen at the Obuoys over the years is fairly constantly around 90%.

Since we are talking about cooling the ocean surface we need to compare rate of heat transfer from the surface by convection and evaporation and radiation with rate of heat transfer to the surface from the bulk of the ocean to the surface. (thats why my comment talked about "competition") Wind will increase convection in the ocean as well as in air so I don't expect wind above -5 to freeze the ocean surface but please correct me if anybody has evidence to the contrary.

johnm33

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My 2c, I thought it was pretty much accepted that ice only becomes established with air temps. below -11c. This came from Wayne D. who lives in the arctic iirc. There are 800c of separation between ice and water, in a manner of speaking,  so between -1.8 and -11 a lot of room for 'flux', plus ice type crystals form in water at all temperatures and -charged or turbulent water is particlarly prone, so any specific snapshot is likely to have it's own idiosyncratic errors.

ghoti

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-11C is the temperature below which open water generally freezes but Wayne also has pointed out that heavy snow fall onto water below freezing will remain frozen and float. This creates a thin somewhat insulating layer of ice under some conditions much earlier than water freezing in place.

ghoti

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The guide to sea ice concentration provided by the AMSR2 algorithm at:

https://climatedataguide.ucar.edu/climate-data/sea-ice-concentration-data-amsr-e-amsr2-ssmis-u-bremen-and-u-hamburg-asi-algorithm

says
Quote
The high-frequency (89 GHz) channel is more sensitive to weather effects (atmospheric water vapor and cloud liquid water) than the low-frequency channels employed by other sea ice products.
but they also say
Quote
High-frequency channels (89GHz)-mainly measuring surface emission-make the retrievals potentially less influenced by snow layering than algorithms using lower frequencies
and
Quote
Nonetheless, the ASI includes adjustments intended to correct for weather using the lower-frequency channels.

They do an amazing job of it too. Just don't demand that they provide a noise free instantly complete picture on any particular day. The seasonal progression and inter-annual comparisons of sea ice cover they provide are invaluable.

Blizzard92

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Here is a link to the latest SIPN webinar ("Uncertainty in Satellite-Derived Sea Ice Extent Estimates")... which may be relevant for some. Presentation is by Walt Meier of NASA Goddard.
Current - Postdoctoral Researcher - Colorado State University - Atmospheric Sciences
UC Irvine - Earth System Science Ph.D.
Cornell University - Atmospheric Sciences B.Sc.

Twitter: @ZLabe
Website: https://sites.uci.edu/zlabe/

longwalks1

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As posted previously July 10 

https://forum.arctic-sea-ice.net/index.php/topic,1457.msg82931.html#msg82931   reply #491

Quote
This is freely accessible, but very technical (not very accessible in that sense). But it gives an impression what algorithms do and how they can give different results by dealing with weather and surface conditions differently.
 It is also useful to be aware that the seaice concentration plots that we look at are the result of processes which have to interpret the brightness temperature data coming in (have a look at AMSR2 data on worldview) which do not give by themselves straightforward ice/ no ice information.


Satellite passive microwave
measurements of sea ice concentration:
an optimal algorithm and challenges

N. Ivanova , L. T. Pedersen , R. T. Tonboe , S. Kern , G. Heygster , T. Lavergne ,
A. Sørensen 5 , R. Saldo 6 , G. Dybkjær 2 , L. Brucker 7,8 , and M. Shokr 9

doi:10.5194/tcd-9-1269-2015

which mentions the 89 mhz also. 

I have been spending weekends sitting with mentally challenged individuals in hospital all too much lately.  I read this over August long weekend.  Much was over my head, it was a difficult slog through it, but I did learn some and appreciate 5 day values more. 

Thanks for the above sources of info.


A-Team

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Quote
puzzling, we've gone over all this many times before, cloud artefacts sweeping across sea ice concentrations are obvious on animations and confirmed by their channels.
Amen to that. Of the seven later articles citing the above 2015 paper, this one using VIIRS (visible and infrared) on Suomi for vastly better resolution (requires clear skies though) is probably the most relevant to us. http://www.mdpi.com/2072-4292/8/6/523/htm

I expect the active radar on Sentinel 1AB to eat Suomi's lunch at all wavelengths as it has a great orbit, vastly better resolution, and is minimally affected by atmospheric and surface artifacts. While it doesn't have 1-day coverage of the whole Arctic Ocean, its swaths provide the tools for correction of satellites that do.