Snow and ice across the Tennessee Valley and mid-Atlantic regions

January 31st, 2010 |
MODIS visible channel + MODIS Red/Green/Blue (RGB) false color images

MODIS visible channel + MODIS Red/Green/Blue (RGB) false color images

A large winter storm spread heavy snowfall, sleet, and freezing rain from Texas and Oklahoma to the East Coast of the US during the 28-30 January 2010 period. AWIPS images of the MODIS visible channel and a MODIS false-color Red/Green/Blue (RGB) image using the visible and the 2.1 µm near-IR “snow/ice” channels (above) showed the resulting wide swath of snow cover across the Tennessee Valley and mid-Atlantic regions on 31 January 2010. This example also offers a glimpse at the type of RGB image capability that should be available with the upcoming AWIPS II software.

Snow cover (which appears as brighter white features on the visible image) is a strong absorber at the 2.1 µm wavelength — so it appears red on the false-color RGB image. However, ice is an even stronger absorber, so areas that received a significant accrual of ice (from freezing rain, freezing drizzle, and/or sleet) appeared as an even darker red band along the southern periphery of the broad area of snow cover — this darker red band was especially evident across parts of southern Tennessee, southern North Carolina, and extreme northern South Carolina. In contrast, supercooled water droplet clouds appear as brighter features on the RGB image.

A MODIS true color image from the SSEC MODIS Today site (below; viewed using Google Earth) showed the locations of some of the heaviest snowfall amounts in each state, as well as 2 locations that received the highest accruals of ice (0.75 inch at Wallace in North Carolina, and 0.5 inch at Franklin in Tennessee).

MODIS true color image (viewed using Google Earth)

MODIS true color image (viewed using Google Earth)