CIMSS Satellite Blog

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images, with topography [click to play animation | MP4]

GOES-17 (GOES-West) Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images (above) displayed subtle thermal signatures of some of the highest-elevation western and central portions of the Alaska Range on 28 February 2019.

Plots of GOES-17 Water Vapor weighting functions, calculated using 12 UTC rawinsonde data from Anchorage, are shown below. Even with a very large satellite viewing angle (or zenith angle) of 70.1 degrees — which would tend to shift the Water Vapor weighting functions to higher altitudes —  the presence of dry air within the entire mid-upper troposphere brought the weighting function peaks downward to pressure levels corresponding to those of the higher elevations of the Alaska Range.

GOES-17 Water Vapor weighting functions, calculated using 12 UTC rawinsonde data from Anchorage [click to enlarge]

The dry air aloft helped to provide a remarkably cloud-free day over much of south-central Alaska, as seen in GOES-17 “Red” Visible (0.64 µm) images (below). In addition, an example of the transient spikes in daytime solar reflectance that are seen during this time of year was evident in the Visible imagery — note the brief brightening of a few of the images centered at 2115 UTC. Additional details about this effect are available here.

GOES-17 “Red” Visible (0.64 µm) images [click to play animation | MP4]

from CIMSS Satellite Blog http://cimss.ssec.wisc.edu/goes/blog/archives/32118