Monday, September 2, 2013

Summer 2013 850mb Temperatures

A useful measure for estimating surface temperatures is to look at the temperature a little above the ground. The 850mb geopotential height temperature (approximately 5,000') is commonly used to extrapolate the temperature down to surface level. While many charts and tables will be generated to display the surface temperatures for 2013, I thought it would be interesting to look at the temperatures at 850mb and where they rank in comparison to other summers. 

The first chart below shows the summer temperature anomaly from the NCEP/NCAR reanalysis. The bull's eye for greatest difference from normal is just north of Yakutat along the Yukon border.

The next map show the actual upper air sounding temperatures for the months of June, July, and August at the 14 sounding locations for Alaska. The overall summer ranking is shown for each station. Only Kodiak recorded their warmest summer at the 850mb level. Every other station was in the top 10. Again, not really a surprise given the surface temperatures were in the top 10.

On June 18th, Anchorage set an all-time record for the warmest 850mb temperature with a reading of 18.4C. No other station set their all-time 850mb temperature record but several came close. The 17.4C in Bethel and 17.2 in McGrath (both on June 19th) were the second highest 850mb temps for each station.

Finally, here is a picture from the top of South Suicide Peak (5,005') near Anchorage on one of the very warm 850mb temperature days. The pressure level was 851mb and the temp was 18C (64.4F). It is not exactly a free-air temperature but it was very, very warm.

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