The first -40F temperatures of the winter season in the Lower 48 states
Posted by JAC on 2/1/2011, 3:58 pm
http://cimss.ssec.wisc.edu/goes/blog/ A major surge of arctic air from Canada helped to produce the first surface air temperatures of -40 F (-40 C) or colder over the Lower 48 states during the Winter of 2010/2011 - the coldest official minimum temperature was -46 F (-43 C) at International Falls, Minnesota on the morning of 21 January 2011, with a number of locations across northern Minnesota and northern Wisconsin in the -30 F (-34 C) to -40 F (-40 C) range. A series of AWIPS images of 1-km resolution POES AVHRR 10.8 m IR and MODIS 11.0 m IR data (above) shows the increase in areal coverage of surface IR brightness temperatures of -40 C and colder (purple to white color enhancement). The coldest surface IR brightness temperature on the images was -49 C (-56 F) at 08:41 UTC - but surface IR brightness temperatures do not always correlate well with surface air temperatures (which are generally measured in a shelter at a height of about 5 feet above the surface). Note the significantly warmer waters along the north shore of Lake Superior (yellow to red color enhancement) - MODIS Sea Surface Temperature values there were still in the low to middle 30s F. On the 04:29 UTC MODIS image, some features of curiosity are the 3 northwest-to-southeast oriented "streaks" that resemble plumes near Hibbing (station identifier KHIB). These could be plumes from industrial sites (mining, or power plants) - in fact, we have seen similar plumes coming from that same area in the past on 1-km resolution MODIS fog/stratus product imagery. A comparison of MODIS 11.0 m IR and MODIS Land Surface Temperature (LST) product images (below) shows that the "plumes" exhibited LST values near -20 F (darker blue color enhancement), compared to adjacent LST values in the -30s F (violet color enhancement). |
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