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 From DMSP Visual and Thermal
Sensors Showing Hurricane Seth in its later Stages
|
|
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
|
|
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.
[ To Beginning |
Backward |
Forward |
To End ]
Designed and Developed by
John Bohlson, Leonard Daly, and Charles Simmons
The Aerospace Corporation
Last modified on July 03, 1997
Please send any questions or comments regarding this service or content to
DMSP WebMaster - James Dixon