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Topics - danp

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Arctic sea ice / Clear-sky 8-day Arctic mosaic
« on: July 17, 2013, 02:47:47 AM »
MODIS Terra & Aqua produce a variety of processed higher-level data products, almost all of which are then projected onto a sinusoidal tiled grid.  I had mostly been ignoring these products since the sinusoidal grid is almost unusably distorted through most of the Arctic, until I realized that the projection is area-preserving and ideally invertible.  In practice it still took some work to get reasonable results, but here's one.

The data are MOD09A1, Terra 8-day "clear-sky" tiles.  (See https://lpdaac.usgs.gov/products/modis_products_table for the full list of MODIS products). NASA takes all of its observations every 8 days and produces a best-view mosaic that has unsurprisingly exceeded my best amateur efforts.  They also do daily versions that of course have more clouds but are more up-to-date.   I reprojected to polar stereographic and produced the mosaic using the MODIS reprojection tool, and then combined bands 1, 4, 3 for RGB.  I could produce mosaics of any other band combination as well.

This particular mosaic covers days 185-193. (July 5-12).  Attached is a thumbnail image; the link is to a full-resolution zoomable version, 500m resolution.  NASA's projection from rectangular swath to sinusoidal followed by my undoing of that projection does result in some degradation of resolution, but it is not too terrible, and the procedure is much simpler than direct processing of the swath data has been.  (It also requires far less data downloading).

https://googledrive.com/host/0B2HXhBb-Jqf6NEt6Q3A4dnpzUms/

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Policy and solutions / White house meeting on Arctic ice loss
« on: April 26, 2013, 07:05:36 PM »
Commenter Boa5att posted this tantalizing tidbit on the main blog:

http://au.news.yahoo.com/thewest/a/-/wa/16886947/professor-joins-fight-to-save-arctic/

"[T]he meeting has been organised by a US brains trust on the Arctic that includes NASA's chief scientist, the director of the US National Science Foundation, representatives from the US Department of Homeland Security and the Pentagon. Joining them ... will be [Univ. of WA] Professor Carlos Duarte, who is one of 10 researchers from around the world called on to help protect the Arctic.

[Duarte] said melting of the ice was accelerating faster than any of the models could predict and the prospect of an Arctic Ocean free of ice had been brought forward to 2015, compared with a prediction in 2007 that at least one-third of the normal extent of sea ice would remain in summer in 2100."

To me the combination of top level political attendees and at least one scientist at the edge of public aggressiveness among his colleagues (2015!) is promising.  I hope some sense of alarm filters up into the executive branch and they add some synergistic messaging to their upcoming decision to ban all fossil fuel exploration in US-controlled Arctic water.   I know, at least let me dream.

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