Ice Dwindles on the Great Lakes

March 28th, 2015
Suomi NPP VIIRS Visible Image (0.64 µm), Day Night Band Visible Image (0.70 µm) and 1.61 µm near-infrared Image  (Click to enlarge)

Suomi NPP VIIRS Visible Image (0.64 µm), Day Night Band Visible Image (0.70 µm) and 1.61 µm near-infrared Image (click to enlarge)

Clear skies over the Eastern and Midwestern United States on 28 March allowed the wide swath of Suomi NPP VIIRS to record ice conditions over the five Great Lakes. The visible and Day/Night Band imagery shows good contrast between the dark open waters and brighter melting ice. Ice strongly absorbs 1.61 µm radiation: regions in the near-infrared 1.61 µm imagery that are dark (where radiation is absorbed, not reflected/scattered) include pack ice on the lakes, and snow cover (southeast Minnesota and southwest Wisconsin; southern Ontario bordering Lake Erie; southwestern Ontario near Lake Huron; the Upper Peninsula of Michigan, northern Wisconsin and northwestern Lower Michigan) on land. Regions of clouds comprised of water droplets (extreme eastern Lower Michigan and northern Ohio, much of central Pennsylvania and the Adirondacks of northern New York) are white on all three images.

Satellite detection of ice-glazed snow cover

March 5th, 2015
Suomi NPP VIIRS 0.64 µm visible and 1.61 µm near-IR

Suomi NPP VIIRS 0.64 µm visible and 1.61 µm near-IR “snow/ice channel” images (04 March)

Comparisons of Suomi NPP VIIRS 0.64 µm visible channel and 1.61 µm near-IR “snow/ice channel” images on 04 March 2015 (above) and 05 March 2015 (below) revealed a large area of ice-glazed snow cover in the Upper Midwest. On 03 March, a northeastward surge of moisture ahead of an approaching strong arctic cold front produced areas of light snow, freezing rain, freezing drizzle, and fog across parts of southeastern Minnesota, eastern Iowa, southern and central Wisconsin, and northern Illinois — and farther to the south from northeastern Missouri into central Illinois it was warm enough for rain as the precipitation type. This precipitation fell onto a pre-existing snow cover (NOHRSC 03 March snow depth), making the skin of the snow cover icy and/or wet (depending on the air temperature); with the passage of the strong arctic cold front,  this icy and/or wet snow surface quickly froze, creating a large area of ice-glazed snow cover.

At the 1.61 µm wavelength, since ice is a stronger absorber of radiation than snow, the ice-glazed snow areas appeared darker black compared to the surrounding snow cover; areas with a dense concentration of trees (cities; river valleys) tended to diminish this darker black signal.

Suomi NPP VIIRS 0.64 µm visible and 1.61 µm

Suomi NPP VIIRS 0.64 µm visible and 1.61 µm “snow/ice channel” images (05 March)

A toggle between the 04 March and 05 March 1.61 µm snow/ice channel images (below) showed more of the darker ice-glazed snow cover area as the clouds began to clear the region on 05 March (NOHRSC snow depth: 04 March | 05 March).

Suomi NPP VIIRS 1.61 µm near-IR

Suomi NPP VIIRS 1.61 µm near-IR “snow/ice channel” images (04/05 March)

A photo of the ice-glazed snow cover in Middleton, Wisconsin (a western suburb of Madison) on 05 March is shown below.

Photo of ice-glazed snow cover in Middleton, Wisconsin (05 March)

Photo of ice-glazed snow cover in Middleton, Wisconsin (05 March)

Rapidly-melting snow in the south-central US

March 5th, 2015
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 (GOES-East) 0.63 µm visible channel images (above; click image to play animation; also available as an MP4 movie file) showed how rapidly the streaks and patches of snow cover melted across parts of the south-central US (primarily Kansas, Oklahoma, Texas, and adjacent states) on 05 March 2015. According to NOHRSC, morning snow depths (contour map | numerical snow depth values) were generally in the 2-4 inch range, with some sites reporting 5 inches on the ground.

The narrow snow band in Kansas went through the Witchita area; a 15-meter resolution Landsat-8 0.59 µm panochromatic visible image from the SSEC RealEarth web map server (below) provided a very detailed view of the snow cover in that area.

Landsat-8 0.59 µm panochromatic visible image (with and without Google Maps labels)

Landsat-8 0.59 µm panochromatic visible image (with and without Google Maps labels)

Lake effect snow band over Lake Michigan

February 26th, 2015
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 (GOES-East) 0.63 µm visible channel images (above; click image to play animation) showed the development and motion of a long single-band lake effect cloud feature over Lake Michigan on 26 February 2015. Snowfall from this band helped to boost total event accumulations (including other lake effect snow bands on the previous day) as high as 8 inches in the Chicago area, bringing this to the 3rd snowiest February on record there.

A comparison of the 18:39 UTC Suomi NPP VIIRS 0.64 µm visible channel image with the corresponding false-color Red/Green/Blue (RGB) is shown below. On the RGB image, snow, ice, and ice crystal clouds appear as varying shades of pink to red — and it can be seen that portions of the lake effect cloud band looked to be glaciated. Supercooled water droplet clouds appear as varying shades of white on this type of snow/ice-vs-cloud discrimination RGB image.

Suomi NPP VIIRS 0.64 µm visible channel and False-color RGB image (click to enlarge)

Suomi NPP VIIRS 0.64 µm visible channel and False-color RGB image (click to enlarge)

The 18:39 UTC Suomi NPP VIIRS 11.45 µm IR channel image (below) showed that cloud-top IR brightness temperatures were in the -20 to -30º C range (cyan to dark blue color enhancement) along the entire length of the lake effect cloud band, which also suggested that glaciation was likely.

Suomi NPP VIIRS 11.45 µm IR channel image (click to enlarge)

Suomi NPP VIIRS 11.45 µm IR channel image (click to enlarge)