Signature of ice accrual across South Dakota and Minnesota

January 1st, 2019 |

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) Near-Infrared “Snow/Ice” (1.61 µm) images (above) revealed a darker swath — oriented southwest to northeast, from central South Dakota to central Minnesota — highlighting areas which received an accrual of ice (from freezing rain/drizzle) during a 30 December31 December 2018 mixed precipitation event (surface analyses). Light to moderate Freezing Rain was reported at Watertown SD (KATY) for 3.5 consecutive hours (plot | text).

As seen in a plot of ABI Spectral Response Functions (below), snow and ice are efficient absorbers of radiation (and therefore exhibit a low relectance) at the 1.61 µm wavelength, making them appear darker on the Snow/Ice imagery — and since ice absorbs more strongly than snow, it appears as the darkest shades of gray/black. Strong northerly winds in the wake of the precipitation event then swept the residual ice-crusted snow cover clear of any new snowfall.

Plots of Spectral Response Function for ABI Bands 1-5 [click to enlarge]

Plots of Spectral Response Function for ABI Bands 1-5 [click to enlarge]

A higher spatial resolution view using VIIRS Near-Infrared “Snow/Ice” (1.61 µm) images from NOAA-20 (at 1839 UTC) and Suomi NPP (at 1931 UTC) is shown below. The darkest areas on the Snow/Ice images appeared to be over the southern/western portion of Deuel County in South Dakota and much of Chippewa County in Minnesota.

VIIRS Near-Infrared

VIIRS Near-Infrared “Snow/Ice” (1.61 µm) images from NOAA-20 (at 1839 UTC) and Suomi NPP (at 1931 UTC) [click to enlarge]

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