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) revealed orographically-trapped waves propagating westward against the ambient flow over the Haida Strait between Haida Gwaii and British Columbia on 22 April 2019. Waves initially formed downwind of the 2000-3000 foot terrain of Haida Gwaii and moved eastward — but were then reflected back to the west by the higher 6000-8000 foot terrain farther inland over British Columbia.

Note that the wave signatures became more muted — especially over the southern portion of the Strait — as middle/upper-tropospheric moisture began to overspread the area. This moisture at higher altitudes absorbed radiation being emitted from below, re-radiating energy at the colder temperatures found within that layer of high-altitude moisture.

A plot of GOES-17 Water Vapor weighting functions calculated using 12 UTC rawinsonde data from Annette Island, Alaska (below) showed dominant peaks for Band 10 (7.3 µm, violet) and Band 9 (6.9 µm, blue) radiation in the 460-497 hPa range, so it’s likely that many of the waves resided within a layer near those pressure levels. Secondary peaks resided near the 340 hPa pressure level — the magnitude of those peaks for all 3 Water Vapor spectral bands would have increased as the aforementioned high-level moisture moved over the region.

GOES-17 Water Vapor weighting functions calculated from 12 UTC rawinsonde data at Annette Island, Alaska [click to enlarge]

from CIMSS Satellite Blog http://cimss.ssec.wisc.edu/goes/blog/archives/33014