November 4, 2021 - Cloud Streets over Foxe Basin

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Foxe Basin
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Frigid air and strong wind over Nunavut, Canada drew stunning patterns
in the clouds over Foxe Basin in early November 2021. The Moderate
Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua
satellite acquired this true-color image on November 2.

Foxe Basin sits north of Hudson Bay along the Northwest Passages.
Approximately 310 mi (500 km) across at its maximum width, the shallow
Foxe Basin is one of the richest and most biologically diverse areas of
the Canadian Arctic, supporting such species as Sabine’s Gull, bearded
seal, walrus, and a summering area for a variety of whales, despite
being covered with snow and ice most of the year.

In early November, warm summer temperatures had emptied the waters of
Foxe Basin of most of their ice cover, but autumn set the stage for
falling temperatures. By November 3, temperatures hovered around -9˚C
(15.8˚F) during the daytime as light snow fell over most of the region.
Air temperatures over the waters of the Northwest Passages remained
relatively warm and moist compared to land. As a steady wind pushed
frigid, dryer air from above the land across the water, the stage was
set for a spectacular show in the clouds.

As the cold air mass moved over the relatively warm water, it quickly
gained warmth and moisture necessary to form clouds. But these are not
your typical cumulus clouds. Notice how they line up in organized rows
parallel to the direction of the wind. These “cloud streets” are the
result of nature trying to balance differences in energy.

Cloud streets occur when columns of heated air—thermals—rise through
the atmosphere and carry heat away from the sea surface. The moist air
rises until it hits a warmer air layer (a temperature inversion) that
acts like a lid. The inversion causes the rising thermals to roll over
on themselves, forming parallel cylinders of rotating air. On the
upward side of the cylinders (rising air), water vapor condenses and
forms clouds. Along the downward side (descending air), skies remain
clear.

Cloud streets align along the path of the prevailing wind and usually
start slightly offshore. This is because the cold air mass needs some
time and distance moving over the water to pick up enough moisture for
cloud formation. As the air moves over islands, turbulence occurs, and
clouds take on a more rippled appearance. Where there is little wind,
the clouds take the form typical of a layer of marine stratocumulus
clouds.

Image Facts
Satellite: Aqua
Date Acquired: 11/2/2021
Resolutions: 1km (1.5 MB), 500m (4.8 MB), 250m (13.5 MB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2021-11-04

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