Swath of snow cover in the Deep South

January 20th, 2008 |

MODIS Today true color image

A Terra MODIS true color image from the SSEC MODIS Today site (above) revealed a swath of fresh snow cover across parts of Mississippi, Alabama, and Georgia on 20 January 2008. Snowfall amounts in the state of Alabama (which fell on the previous day) were as high as 5.8 inches near Verbena, 5.0 inches at Orrville, and 4.0 inches at Toxley (located on the MODIS imagery using Google Earth, below); snowfall up to 3.0 inches was reported in Mississippi, with 1.5 inches falling in Georgia.

MODIS imagery in Google Earth (Animated GIF)

AWIPS images of the MODIS visible channel, the 1.6µm “snow/ice channel”, and the Land Surface Temperature product (below) confirmed that this feature was indeed snow cover (snow is a strong absorber at the 1.6µm wavelength, and appears darker on the “snow/ice channel” image); in addition, the land surface temperatures within the area of snow cover were generally several degrees F colder (upper 20s to low 30s F, darker green enhancement) compared to the surrounding areas with bare ground (where land surface temperatures were generally in the mid 30s to around 40 F).

MODIS visible + snow/ice + land surface temperature images (Animated GIF)

Ice forming in Lake Michigan

January 20th, 2008 |

MODIS true color image

The coldest arctic air of the 2007/2008 winter season (so far) settled in over the Great Lakes region on 19-20 January 2008. Most reporting stations in Wisconsin experienced a daytime maximum temperature below 0ºF on 19 January, with the coldest overnight minimum temperature on 20 January of -34ºF at Nekoosa in central Wisconsin. As this cold air streamed eastward across Lake Michigan, ice began to form along parts of the western and southern nearshore waters as seen on the MODIS true color image (above) from the SSEC MODIS Today site. Also note that the four larger lakes in the Madison area (located toward the upper left corner of the image) had all frozen solid again — they had all frozen completely by late December, but then the largest of Madison’s lakes (Lake Mendota) began to partially open during a brief warm period in early January 2008.

In a comparison of AWIPS images of the MODIS visible and 1.6µm “snow/ice channel” (below), the lake ice (and adjacent snow-covered land surfaces) exhibited a darker signal on the snow/ice image, in contrast to the brighter signal exhibited by the supercooled water droplet lake-effect snow cloud bands that covered much of the central and eastern portion of Lake Michigan.

MODIS visible + snow/ice images (Animated GIF)