Water Vapor imagery sensing the surface in a cold/dry air mass

By Scott Bachmeier • 13 February 2020

GOES-16 Low-level Water Vapor (7.3 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) Low-level Water Vapor (7.3 µm) images (above) showed that this spectral band was able to sense the surface due to the presence of a cold and dry arctic air mass over the Upper Midwest on 13 February 2020 (the coldest surface air temperature that morning was -39ºF at Kabetogama in northern Minnesota). In North Dakota and South Dakota, the outline of the Missouri River was very evident — as well as surface warming in the western part of those states due to the onset of downslope (southwesterly) winds. Across the eastern Dakotas and Minnesota, the warmer (darker blue) “urban heat islands” of several cities and towns became more evident toward the end of the animation at 18 UTC.

The arctic air mass was so dry that Total Precipitable Water derived from rawinsonde data set record low values for the date/time (source) at a few regional sounding sites such as Bismarck ND (KBIS), Aberdeen SD (KABR) and Minneapolis/Chanhassen MN (KMPX) — and this shifted the 7.3 µm water vapor weighting functions to altitudes low enough to sense a significant amount of upwelling surface radiation (below). In fact, at KMPX the 7.3 µm water vapor weighting function actually peaked at the surface!

13 February / 12 UTC TPW climatology and water vapor weighting functions for Bismarck, ND [click to enlarge]

13 February / 12 UTC TPW climatology and water vapor weighting functions for Aberdeen, SD [click to enlarge]

13 February / 12 UTC TPW climatology and water vapor weighting functions for Minneapolis/Chanhassen, MN [click to enlarge]

Categories: GOES-16, Winter weather

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Water Vapor imagery sensing the surface in a cold/dry air mass