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DMSP SSM/I Significantly Improves Forecaster Capability

One of the newer mission sensors on the DMSP spacecraft is the SSM/I, or the Microwave Imager. The Microwave Imager contains a passive microwave radiometer that measures the thermal energy emitted and reflected by the Earth's atmosphere using the microwave portion of the electromagnetic spectrum. An advantage of microwave imagery at AFGWC indicates that storm fixes may be off by more than 200 miles if only using visual and infrared imagery.

The sensor measures microwave energies at four frequencies: 19.35 GHz, 22.235 GHz, 37.0 GHz, and 85.5 GHz. Both vertical and horizontal polarizations are used, except for 22.235 GHz, where one polarization is adequate. Various combinations of the seven channels are used to derive precipitation rates, water content in clouds and soil, land types, temperature, and wind speeds.

Multispectral Image

Multispectral Image From DMSP Visual and Thermal
Sensors Showing Hurricane Seth in its later Stages

Surface wind speeds
Color Wind Speed
Black 0-13 knots
Dark Blue 14-25 knots
Light Blue 36-30 knots
Light Yellow 31-34 knots
Red 35-49 knots

The Photo shows the surface wind speeds for Hurricane
Seth. Here the land masses are shown in black. The highest
winds are between 35 and 49 knots, depicted in red

Cloud water

Color Droplet Size
Blue 0.1-0.2 mm
Green 0.3-0.4 mm
Dark green 0.5-0.7 mm
Gray black 0.8-1.0 mm
Tan beige 1.1-1.3 mm
Red Orange 1.4 mm
Cloud water is another parameter that can be determined.
Cloud water is defined as droplets 0.1 mm or larger in diameter.
This photo shows the cloud water in the hurricane

Color Rain Rate
Black None
Dark Blue to 13 mm/hr
Light Blue 14-18 mm/hr
Light Yellow 19-40 mm/hr

This photo shows precipitation at the same time as the wind
and cloud water above. This image indicates that rainfall of up
to 13 mm/hr is falling over a wide area. The yellow around the
islands is due to shoreline contamination.

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Designed and Developed by

The Aerospace Corp.

John Bohlson, Leonard Daly, and Charles Simmons
The Aerospace Corporation
Last modified on July 03, 1997

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DMSP WebMaster - James Dixon