![\"Suomi](\"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-content\/uploads\/sites\/5\/2018\/09\/180901_180902_suomi_npp_viirs_InfraredWindow_AK_anim.gif\")
<\/a>Suomi NPP VIIRS Infrared Window (11.45 \u00b5m)<\/em> images on 01 and 02 September [click to enlarge]<\/p><\/div>A low moved eastward across the Beaufort Sea on 01 September 2018, bringing a cold front southward across the North Slope and Brooks Range in far northern Alaska (surface analyses<\/strong><\/a>). A sequence of Suomi NPP VIIRS Infrared Window (11.45 \u00b5m) images (above)<\/strong><\/em> showed the clearing of high\/cold clouds in the wake of the frontal passage.<\/p>\n The upslope flow of cold air helped to generate accumulating snowfall across that region — prompting a Winter Storm Warning to be issued for the eastern Brooks Range, where 4-8 inches was expected at higher elevations — and some of the resulting snow cover was seen on a Suomi NPP VIIRS Day\/Night Band<\/strong><\/a> (0.7 \u00b5m) image at 1415 UTC or 6:15 am local time on 02 September (below)<\/strong><\/em>. A comparison with the corresponding VIIRS Infrared Window<\/strong><\/a> (11.45 \u00b5m) image and Topography<\/strong><\/a> is also shown. The darker shades of brown on the topography image correspond to elevations of 6000-8000 feet in the Brooks Range.<\/p>\n Suomi NPP VIIRS Day\/Night Band (0.7 \u00b5m),<\/em> Infrared Window (11.45 \u00b5m)<\/em> and Topography images [click to enlarge]<\/p><\/div>Later in the day on 02 September, additional clearing of patchy low clouds revealed more of the snow cover, as seen in a toggle between VIIRS Visible<\/strong><\/a> (0.64 \u00b5m), Shortwave Infrared<\/strong><\/a> (3.74 \u00b5m) and Topography images (below)<\/strong><\/em>. Supercooled water cloud droplets are efficient reflectors of incoming solar radiation, making patches of low cloud appear darker shades of gray<\/em> on the Shortwave Infrared image (helping to identify low clouds over snow cover).<\/p>\n Suomi NPP VIIRS Visible (0.64 \u00b5m),<\/em> Shortwave Infrared (3.74 \u00b5m)<\/em> and Topography images [click to enlarge]<\/p><\/div>At 2124 UTC (or 1:24 pm local time), a 30-meter resolution Landsat-8 False Color Red-Green-Blue (RGB) image viewed using RealEarth<\/strong><\/a> (below)<\/strong><\/em> provided a more detailed view of a portion of the snow cover. Snow and ice appear as shades of cyan in this type of RGB image — which is created by combining Landsat bands 6 (1.61 \u00b5m), 5 (0.865 \u00b5m), and 4 (0.655 \u00b5m) as Red, Green, and Blue — and numerous small ice floes can also be seen off the coast.<\/p>\n Landsat-8 False Color RGB image [click to enlarge]<\/p><\/div>On a side note, farther to the west an interesting pattern of contrails was seen in VIIRS Visible<\/strong><\/a> and Infrared Window<\/strong><\/a> images at 2046 UTC (below)<\/strong><\/em>. On the Visible image, note that the darker contrail shadows cast onto the surface are displaced about 15 miles to the north (due to the low sun angle); the contrail features exhibited Infrared brightness temperatures of -10 to -15\u00baC. These contrail patterns were generated by military aircraft performing training exercises: similar features have been noted over California<\/a><\/strong> and North Dakota<\/a><\/strong>. <\/p>\n Suomi NPP VIIRS Visible (0.64 \u00b5m) and Infrared Window (11.45 \u00b5m) images [click to enlarge]<\/p><\/div>A curved portion of one of these contrails was seen on web camera images looking south from Atqasuk (below)<\/strong><\/em>.<\/p>\n Webcam from Atqasuk earlier. @AlaskaWx<\/a> pic.twitter.com\/VJbbLaqtJm<\/a><\/p>\n \u2014 Brian Brettschneider (@Climatologist49) September 3, 2018<\/a><\/p><\/blockquote>\n<\/a><\/a><\/a><\/a>\n