Satellite Imagery – w22

Below is a quick snapshot of what the satellite imagery looked like when you checked on Friday. The image shows the west coast of the United States, up to the central coast of British Columbia.

Caption: Satellite image (infrared) for the west coast of North America. Taken from the University of Washington archives.

Interpretation

Infrared (IR) channels pick up radiation emitted by the clouds and the earth's surface. The amount of emissions depend on the temperature of the object that is emitting.  Higher clouds are colder, and are shaded brighter white.  Mid-level clouds have medium temperature, and are shaded medium grey. Low clouds are warmer, and are shaded darker grey.  Over the Pacific Ocean these low clouds are only slightly cooler than the ocean surface, hence they are only slightly lighter than the dark grey of the ocean. The hottest temperatures, such as in the central valley of California, appear as the darkest grey -- almost black.

In this image, the band of white coming down across the BC coast could be the clouds formed along a cold front trailing around a low pressure cyclonic system. Note the clouds look like they could be cycling anticlockwise around a pressure system centered just north of the upper limits of the image.