High density winds are produced at six hourly intervals from both the GOES-8 and GOES-9 satellites, operated by the National Oceanic and
Atmospheric Administration (NOAA). The two satellites are the latest geostationary weather satellites operating in the U.S., and employ
the latest technology in spacecraft and instrument capabilities. They orbit the earth directly over the
equator, at a speed equal to the earth's rotation. To an observer on the ground, they would appear stationary (thus the term geostationary). GOES-8 is
fixed relative to longitude 75W, providing coverage over the Eastern U.S., Central and South America, and the Atlantic Ocean, and GOES-9 is fixed relative to
longitude 135W, to provide coverage over the Western U.S. and Pacific Ocean.
Satellite images of clouds, water vapor fields and surface features are obtained by instruments capable of measuring infrared energy emitted by the earth's atmosphere and surface, as well as reflected sunlight in the visible spectrum. The amount of infrared energy reaching the satellite's instruments is affected by the surface temperature, and the vertical temperature and humidity structure of the atmosphere. Two distinct frequencies (or channels) of infrared energy are used in the derivation of the high density winds. One is highly correlated with atmospheric moisture (designated the 'water vapor' channel), and the other with the temperature of the land, oceans and clouds (known as the 'window' channel).
Wind estimates are produced by tracking features in the GOES-8/9 water vapor and infrared
window channel data, (clouds) and are designated as ' water vapor` and 'cloud drift' winds. Automated pattern recognition software is used to detect and
track features in three successive images, each 30 minutes apart. Each wind vector, consisting of speed and direction, is assigned a height above the earth's
surface based on the infrared energy signatures and
guidance from corresponding numerical weather forecast parameters.
For more information contact: