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Topics - Nightvid Cole

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Arctic sea ice / Overdue for a 'monster' spring volume melt?
« on: March 02, 2018, 04:08:08 PM »
It looks like we haven't really had a warm spring in the Arctic since 2010. Here is the April-June temperature for the region north of 75 degrees latitude:

https://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries.pl?ntype=1&var=Air+Temperature&level=1000&lat1=75&lat2=90&lon1=0&lon2=360&iseas=1&mon1=3&mon2=5&iarea=1&typeout=2&Submit=Create+Timeseries

It is also true that 2010 had the largest spring volume drop on PIOMAS of all time:

https://14adebb0-a-62cb3a1a-s-sites.googlegroups.com/site/arctischepinguin/home/piomas/grf/piomas-trnd3.png?attachauth=ANoY7cpnGfvdXIX8LPaNeN2TTx4i88IJgME3gaEISrD7kWYWSJVd5tV-ydfcVrf9SCEl1gGtWsFF5TRnxv5uUysZn_vqxQ_VP1LNk6OfFuXqUhDMvBt6t_jPO6SqEbt7dt0gd78wAP7d_3Cw1noBJW27uQ8EZxv6xy_Lffjc4H03QJmz8CBGYPCwz9KAOevGtyYtW9TnywFLHygz3JTssrAYBHzTT9HcD54MxB3NSmoKEO2X5trcoOqOXvoIMCB-3Hp3bmKOleBB&attredirects=0

Since the trend has been for warming springs since at least 1990, this raises the question of whether we are overdue for a monster spring volume melt. Even a spring melt identical to 2010 puts us on the fast track to shattering the 2012 volume minimum. If we have a spring warmer than 2010, it seems that we could approach near ice free conditions in a single year. What gives? 

2
Arctic sea ice / The 2016 melting season
« on: March 08, 2016, 04:45:17 PM »
The sun is slowly returning to the Arctic, as we prepare for another melting season. The ice is thinner than last year on the Alaskan side, according to DMI, though there is less very thin ice around the North Pole:

http://ocean.dmi.dk/arctic/icethickness/thk.uk.php




3
Arctic sea ice / Arctic sea ice OPTICS
« on: July 24, 2015, 08:00:07 PM »
Even snow-covered sea ice is not a Lambertian reflector, since at shallower incidence angles not only is the illumination nearer the surface and thus more photons escape without absorption, but also the individual snow crystals scatter preferentially in the forward direction and thus at shallow incidence angles you can get more single-scatter-escaping photons. For these reasons, light at shallow incidence angles has a higher % reflected.

When snow melts and leaves bare ice, there is still a surface scattering layer, though it has a lower air/ice ratio than snow does, but the same phenomena occur.

When you replace it with melt ponds, albedo drops, but a water surface also has higher albedo at shallower incidence angles (see https://en.wikipedia.org/wiki/Fresnel_equations).

Finally, when you have a field of low-concentration but irregular ice, shallow-incidence-angle light is almost certain to hit the peak of a floe before reaching the liquid water, while steep incidence angle light has a good shot at actually hitting liquid surface.

There are several consequences of this. One interesting consequence is that when the sun is low in the sky, clouds may actually *enhance* the absorbed insolation rather than reducing it, because more light is coming from higher in the sky (steeper incidence angles), particularly when the ice is still covered by snow and thus the total illumination doesn't decrease much on account of multiple reflections between surface and clouds.

However, when the sun is at higher angles, clouds of course reduce it.

Another consequence of this is that while the north pole may be getting more insolation than the peripheral Arctic near the Solstice, less energy is absorbed, because almost all of it is coming in at shallow incidence angles. At lower latitudes such as 70N or 75N, the time of day with the most insolation also has the lowest albedo, so the net effect is larger absorbed energy.

A truly accurate understanding of energy balance of sea ice must use proper optics - a single "albedo" figure will never be physically reasonable.

4
DMI puts it in mid-August, while PIOMAS puts it in September! Do we have clues from submarine data or other sources as to which one is right and which is wrong?

5
Permafrost / NH snow cover for June is second lowest on record
« on: July 08, 2015, 04:03:14 AM »
See chart. (Note: This only includes land snow, not snow on sea ice, so this is a separate measurement from the very low June snow seen on sea ice this year).


6
Developers Corner / Cloud masking?
« on: June 29, 2015, 06:46:14 PM »
Anybody know how to get cloud data that's used to create declouded TERRA images over the Arctic? I'd like to be able to decloud other Arctic data as well - i.e. to create declouded AMSR2 maps and the like.

7
Greenland and Arctic Circle / Summer 2015 Alaska Wildfire Thread
« on: June 28, 2015, 03:21:05 PM »
It has now gotten so bad that air quality in Fairbanks has reached dangerous levels:

Issued by The National Weather Service
Fairbanks, AK
Fri, Jun 26, 5:21 pm AKDT
... AIR QUALITY ALERT IN EFFECT UNTIL 5 PM AKDT MONDAY...
THE FAIRBANKS NORTH STAR BOROUGH AIR QUALITY DIVISION HAS ISSUED AN AIR QUALITY ALERT... IN EFFECT UNTIL 5 PM AKDT MONDAY.
THE FAIRBANKS NORTH STAR BOROUGH AIR QUALITY IS CURRENTLY CLASSIFIED AS UNHEALTHY AND EXCEEDS THE EPA HEALTH LIMIT FOR FINE PARTICULATE POLLUTION. PEOPLE WITH RESPIRATORY OR HEART DISEASE... THE ELDERLY AND CHILDREN SHOULD AVOID PROLONGED EXERTION; EVERYONE ELSE SHOULD LIMIT PROLONGED EXERTION.
FOREST FIRE SMOKE AND LOCAL AIR QUALITY CONTINUES TO REMAIN HIGHLY VARIABLE. THE NATIONAL WEATHER SERVICE HAS FORECAST HIGHER HUMIDITY AND RAIN SHOWERS OVER THE WEEKEND... WHICH WILL HELP TO IMPROVE AIR QUALITY... BUT WILL NOT COMPLETELY ELIMINATE THE SMOKE. SO THE FAIRBANKS NORTH STAR BOROUGH IS FORECASTING AIR QUALITY TO VARY FROM UNHEALTHY TO MODERATE AS SMOKE MIXED WITH RAIN SHOWERS MOVES THROUGH THE AREA. IN ORDER TO MORE ACCURATELY JUDGE THE PARTICULATES FROM SMOKE IN YOUR IMMEDIATE AREA... PLEASE USE THE JUDGING PARTICULATE LEVELS CHART FOUND ON THE FAIRBANKS NORTH STAR BOROUGH AIR QUALITY WEBSITE.
NOTE THAT AIR QUALITY READINGS ARE FROM MONITORING STATIONS IN FAIRBANKS AND NORTH POLE AND MAY NOT BE REPRESENTATIVE IN YOUR AREA. PARTICULATE CONCENTRATIONS WILL BE HIGHER IN THE COOLER OVERNIGHT HOURS... AND WILL VARY WITH WIND DIRECTION AND PROXIMITY TO A FIRE. IF YOU ARE SENSITIVE TO RESPIRATORY PROBLEMS AND EXPERIENCE ANY EFFECTS PLEASE FOLLOW THE INSTRUCTIONS OF YOUR PHYSICIAN.



Above: Smoke has also moved to North parts of the state, as seen on this TERRA image taken from NASA web site (Scroll bar is at bottom of image).


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Arctic sea ice / How does PIOMAS function without melt ponds?
« on: March 30, 2015, 05:34:48 PM »
It's quite puzzling to me how PIOMAS does so well despite having no melt ponds whatsoever in the model  (!!!) despite the fact that multiple other simulations have shown marked improvement when melt ponds are added (September Arctic sea-ice minimum predicted by spring melt-pond fraction:

 http://www.nature.com/nclimate/journal/v4/n5/full/nclimate2203.html?WT.ec_id=NCLIMATE-201405 )

Is there an explanation for this? Is there some effect PIOMAS overestimates that almost perfectly cancels out its lack of melt ponds due to pure happenstance?

10
Arctic sea ice / Is first year ice getting slushier?
« on: March 09, 2015, 01:19:11 AM »
It used to be that the lower concentration red, orange, yellow, and green areas on the CT maps had more to do with weather during the summer, for instance:

http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh?fm=08&fd=21&fy=2008&sm=08&sd=21&sy=2009

Now, the past couple years, it seems you can almost "see through" the first-year ice, as the lower concentration areas line up with the first year ice:

http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh?fm=08&fd=21&fy=2013&sm=08&sd=21&sy=2014

Look carefully, in particular, at the large contiguous "purple" areas on these maps. It seems now they are virtually identical to the second-year and multi-year packs, cf. the Tschudi maps

http://ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age2013_34.gif

and

http://ftp://ccar.colorado.edu/pub/tschudi/iceage/gifs/age2014_34.gif

. (Sorry for the problems with the links; using [img] did not work and you have to get rid of "http://" in the URL to access the last two images...)   This seems unprecedented in the CT record - earlier years had lots of "red" areas in late summer but never so well aligned with the first-year portion of the pack.

Have we reached a point where the Arctic simply cannot re-grow ice over the winter that can join the main pack and remain "fully solid" through the summer?

11
Arctic sea ice / Happy GAC2012 day!
« on: August 07, 2014, 08:46:37 PM »
Two years ago today, remember?  :)

Anybody want to describe their experience watching it?

12
Arctic sea ice / Effect of coming 'warm wave' in the Arctic
« on: March 02, 2014, 03:39:56 PM »
Has anyone else here looked at the long-range ECMWF or other forecasts? It looks as though ALL the Northern Hemisphere's cold air over the next 10 days is about to be pulled into North America, and then out over the Atlantic to die a quick death over the open water.

If this happens, does it mean 'game over' for thickening the ice, for the most part?

14
Arctic sea ice / Clouds blocking passive microwave sensing?
« on: July 06, 2013, 11:05:16 PM »
If you look closely at the DMI ice concentration animation, it looks like you can see clouds and weather systems going by and blocking the signal.

If you look closely at the MODIS visible images for the same date, the clouds seem to be in the same positions as the transient white streaks on the DMI concentration maps.

If so, how does this not defeat one of the supposed advantages of using microwave data as opposed to visible?

15
Arctic sea ice / PIOMAS forecast: how reliable?
« on: June 22, 2013, 02:39:40 AM »
PIOMAS initialized on June 1 predicts a very strange spatial distribution of ice in September:

http://www.arcus.org/files/search/sea-ice-outlook/2013/06/pdf/pan-arctic/zhang_lindsay.pdf

with a piece of ice against the Siberian coast failing to melt at all. This hasn't happened since what, 1998?

I am highly skeptical...

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