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Messages - JayW

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Arctic sea ice / Re: 2019 sea ice area and extent data
« on: June 15, 2019, 07:53:41 PM »
Slater model suggests sea ice is moving from where it's hard to melt, to where it's easy to melt. 

Arctic sea ice / Re: The Rammb Slider Thread
« on: June 13, 2019, 10:13:17 PM »
VIIRS potential for snow retrievals

Several VIIRS bands have good sensitivity to snow structure, especially SWIR bands M8,10,11
Overlaid curves show model snow albedo for various grain sizes

Link >>

Thanks for this awesome find!

An impressively dark, nearly black splotch is emerging in the northern Laptev above 80°N.  Anxiously awaiting the next frames, and how the sensors used for area and extent interpret it.

Still shot, edited to put north up.

Greenland and Arctic Circle / Re: Greenland 2019 Melt Season
« on: June 13, 2019, 08:56:41 PM »

What does the team make of the latest NWS ice map?

I think the winds made a good run at closing it back up, but fell short, at least so far.  The pack becoming more disperse is allowing the complex currents to reveal themselves.  I'd say a non icebreaker can still safely navigate, but others may have a different opinion on what's considered open.

Contrast boosted for detail

Arctic sea ice / Re: The Rammb Slider Thread
« on: June 13, 2019, 11:34:24 AM »

I don't know if it's surface temperature or snow wetness or a combination of both.

I did saw the ESS darkening in M8 and M10 band like 2 days before melt ponds became visible in Sentinel.

Also the Greenland darkening Jay posted, corresponds directly to rising temperatures.

I did a bit of poking around, trying to read stuff well above my pay grade.  This one paper explains a lot I think.  Ultimately, it appears we are likely looking at grain size.  Fresh snow generally falls as dendrites, the pretty, six sided geometric shapes we see portrayed in Christmas movies that's highly reflective.  Over time, the snow metamorphosizes due to factors such as temperature, humidity, compaction, etc.  It turns out that the 1240nm wavelength is sensitive to the grain size (larger grains better absorb this part of the spectrum).  Anyone who has watched a lot of snow melt will have likely noticed that as snow warms to the point of melting, it turns into "corn snow", large grainy snow that loosely resembles ball bearings (at least it reminds me of them). 

I believe that this must be what we are seeing, the metamorphosis from a more flake-like structure, to larger, coarser grains that occurs as a snowpack begins going through thaw-freeze cycles.  So while the sensor is picking up on the increased absorption of the 1240nm wavelength by larger grains, it coincides with the temperature rising above freezing, or any other process that would increase grain size like rain or even compaction.

Arctic sea ice / Re: The Rammb Slider Thread
« on: June 13, 2019, 04:14:49 AM »
Amazing animation.
So does the dark color represent wet surface or warmed surface?

I believe band M8 is considered to be in the near infrared spectrum, so it's possible that's is sensitive to surface temperatures, but as it is called the "cloud/snow" band, it's also possible is picking up on some property of wet snow.  Maybe some of both.  My hunch is that it's the snowpack "ripening", right at the threshold of melting.  So perhaps it's sensitive to temps near 0°C, or dampness, but I can't say for certain.  Only thing that I'm sure of, is that's is picking up on something.   :)  sorry I can't be more informative..

Arctic sea ice / Re: The Rammb Slider Thread
« on: June 13, 2019, 03:52:09 AM »
Greenland, band M8.
Needs click

Arctic sea ice / Re: The 2019 melting season
« on: June 12, 2019, 08:58:26 AM »
The Laptev is going to take it on the chin.  Look at those closely packed isobars, latest euro continues the push towards the Atlantic with the 970s cyclone, while keeping the Siberian side toasty.  The Beaufort low might pump some warmth into the CAA as well, as it stirs up the Beaufort sea, trading surface melt for bottom. 

Arctic sea ice / Re: The Rammb Slider Thread
« on: June 12, 2019, 03:04:41 AM »

32 hour loop, the frontal passage and associated wind shift is quite evident, it also removes all doubt from my mind that it's clear sailing for a non-icebreaker.

How do you make a loop with the stills filtered out? On ezGIF?
No filter,.I omit the frames when the satellite doesn't image the area by taking screenshots, it's a bit tedious, but makes for a better finished product in my opinion.

32 hour loop, the frontal passage and associated wind shift is quite evident, it also removes all doubt from my mind that it's clear sailing for a non-icebreaker.

18:22 UTC

Is it?

I think that front blew a path through the slush, but until all the clouds clear, can't be 100 percent positive.  There's a real chance the winds blow the pack back in, and I'm not sure if that would nullify any "open" path.   I'll let others decide.

Arctic sea ice / Re: The 2019 melting season
« on: June 09, 2019, 02:44:18 PM »

I guess this illustrates a cold low over Beaufort and a warm low over Laptev (edit: warm front)
We should expect now some acceleration in area decline, compactness down. Beaufort is still cold but that low scattering the floes and stirring the preheated waters is slow bottom-melt slaughter we have seen other years.

I think there's still question as to how cold that Beaufort low will be.  Looking at 2m temps on the ecmwf, it appears the relatively long lived cyclone becomes fairly occluded, mixing out much of the cold surface air.
This is roughly a 6 day loop, temp in celcius.

Arctic sea ice / Re: The 2019 melting season
« on: June 09, 2019, 12:24:52 PM »
Some fast ice is beginning to pulled away in the ESS. (First attachment,  band I1 with I3 overlay.

Second attachment is the EURO ensemble 5 day average sea level pressure. It screams slow extent loss.  Winds have reversed int the Chukchi already, and an amazing ice edge is visible inch thr RAMMB slider.  We should also see ice getting dispersed in the Beaufort for the time being.  The one constant is the push towards the Atlantic.  The ESS and Laptev will see persistent southerlies, and likely the most impressive extent declines.
  This isn't to say melting will halt, in fact, is should transport ice to areas it could melt quicker.  It'll be interesting to watch the floes reaction in the Chukchi in particular.

Cloud when you really don't need it.

Reminds me of Monty Python's "Total Eclipse of the Sun 1972".... "Rain... Rain".

I think we may get lucky and get some clearing around 15Z.

10 hour loop

Arctic sea ice / Re: Latest PIOMAS update (May 2019)
« on: June 05, 2019, 12:15:55 AM »
May PIOMASS thickness distribution falls short of being encouraging.

Arctic sea ice / Re: The 2019 melting season
« on: June 03, 2019, 12:29:24 PM »
925 Vector wind anomaly for May.

yup.  kinda stalled out there (animates on click)
Worldview images from consecutive days can be as little as 51 minutes apart or a much as 47.5 hours apart, it depends on which orbital swath the image was taken from.

If you look at it with sub daily imagery, it marches along unabated.
13.5 hour loop

Arctic sea ice / Re: The Rammb Slider Thread
« on: June 01, 2019, 10:27:48 PM »

I remember seeing little cyclonic features like that in 2013...14?

There was some discussion but no conclusions.

I suspect they are fairly common, but exist in the lowest part of the atmosphere along frontal boundaries.  Since they are so low, higher clouds likely obscure them normally.

Speaking of swirls, some neat, fractal-like ones in the Greenland sea today.

Needs click, band I2, because it's the highest resolution.

Arctic sea ice / Re: The 2019 melting season
« on: June 01, 2019, 07:48:47 PM »
These large floes don't seem to have the strength like 2016 in the Beaufort.  I hope this isn't the thicker, multi year ice that's been discussed.

This was the largest chunk. (Requires a click)

14 hour loop, ending on June 1, 01 UTC

Arctic sea ice / Re: The Rammb Slider Thread
« on: June 01, 2019, 12:03:45 AM »
Plenty of streaks showing NE of Utqiagvik.
Band 8, needs click.

12 hour loop.

 most recent VIIRS image.

Edit: I am in the June 1-7 camp.

Arctic sea ice / Re: The Rammb Slider Thread
« on: May 30, 2019, 01:23:24 PM »
Here's the area in the Kara Sea where more darkening in band M8 is evident.  I hypothesize that the thin, low clouds produced drizzle (liquid), wetting the snow, where the thicker clouds were able to generate higher precipitation rates, and thus snow, leaving behind the white streaks.

Click to run

Arctic sea ice / Re: The Rammb Slider Thread
« on: May 30, 2019, 10:32:51 AM »
worldview terra modis corrective reflectance 367 picks up the same striations on may26-28. I'm thinking peak sunlight through different layers of cloud combined with warm air temperature for a shortish time period. (click to run)
Melt ponds between pressure ridges, my 2 cents worth.
That's kinda my thinking as well, although I think that the dark is wet snow, not quite liquid water. 

The pressure from the Beaufort ice getting shoved westward by the winds must've piled the ice up somewhere.  As the pressure ridges rose up, the extra weight then lowered the troughs between ridges, allowing see water to saturate the snow.

I noticed the same with the other dark spots too.

Could it caused by rain?

I'm coming around to the idea that the dark areas in band M8 are representing wet snow, and whiter areas are drier/colder snow.  I think in many of these cases, we are seeing the snowpack "ripen", meaning that it has softened to the piont it's melting so that it's surface is wet, but it's still very white, as the water can't pool on the surface yet.  That's why everything looks white in the visible bands, but picked up by the near infrared bands and displays as darker.

Today's interesting area of darkening is SE of Wrangel Island.  Here we see a storm passing through, but offering is a window through the dry slot.  A close look reveals some white bands that follow the cyclonic curvature of the storm. My interpretation is that the majority of precipitation that fell was a mixture of rain and snow, this wet down the snow (dark patches).  The whiter arcs are areas where the the precipitation came down hard enough that it was able to stay snow.  This is very common for storms where the temperatures are neat 0°C, the heavier stuff creates more cooling in the column and can drag down enough cold to keep it snow.

There's some similar patterns emerging in the Kara Sea this morning, but waiting for a few more images to load for that area.

Edit: added the Bremen cause color, as it picked up on the "torching" in the Chukchi where I feel the rain/snow mixture fell.

Requires a click

Getting closer

Arctic sea ice / Re: The Rammb Slider Thread
« on: May 28, 2019, 12:36:44 PM »

Arctic sea ice / Re: The Rammb Slider Thread
« on: May 27, 2019, 11:48:57 PM »
Okay, instead of clogging up the melting thread with my speculative post, this fits well here.  I was perusing the arctic using band M8 ("snow/cloud"), and was struck by some features on the Pacific side, these also show up in the two "snow/ice" bands. As an aside, the "I" bands are 375m resulting, "M" bands are 750m.  They are clearly features of the ice, not atmospheric, but I'm not willing to go as far as saying it is wetness, as much as I'm tempted.  The satellite definitely "sees" something, but I can't discern if it's a roughness thing, a temperature thing, or a wetness thing, or even a combination.  I've reattached the NPP satellites a bit, but haven't gained clarity.  Incidentally, the area that uniquorn referenced at 85.3N, 96.5E shows as a dark spot. (Third attachment, still image)

First attachment is north of the Chukchi. (Click it)
Link to are area

Second is further north. (Click it)

Arctic sea ice / Re: The 2019 melting season
« on: May 27, 2019, 04:36:52 PM »
Plotted the average skin surface temp from May 1-25 for the last 8 years. Sorry about the resolution, I was trying to save space.  2012 is upper left, 2019 lower right.

Arctic sea ice / Re: 2019 sea ice area and extent data
« on: May 26, 2019, 04:03:17 PM »
"Compactness" running on the low side.

Arctic sea ice / Re: The 2019 melting season
« on: May 26, 2019, 02:27:23 PM »
Dove-tailing with the melt pond and snow cover discussion, here's a couple of screen grabs of the snow cover model from Climate Reanalyzer; the first is today, the second is for June 1st.

The takeaway is, GFS predicts snow cover over the next 6 days will be hammered, seriously.

A lot of that melt - 6-10CM worth - will be on the snowpack in the CAB.

I'm wary of the *raw* GFS data and its handling of snowmelt, especially on the ice.  The GFS is not coupled to sea ice, and also has issues dealing with boundary layer (the part that interacts with earth's surface) temperatures.

First attachment
The plots provided by the NOAA/ESRL Physical Sciences Division, Boulder, CO from their Web site at , which are forced by the GFS forecast, but with a markedly different result. Note that the upper right panel, "GFS ice area", remains unchanged through the 7 day forecast, as its un-coupled"

Second attachment (Requires a click) is the 10 day sea ice forecast from the ECMWF, available at , this is a coupled model.

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