Meteorological satellites are our "weather eyes in the sky". The perspective of space is unique; a satellite image can often provide views of broad-scale weather systems in their entirety. A geosynchronous satellite, high above the equator at an altitude of 23,000 miles and revolving in the same direction as the earth rotates, remains fixed over the same scene on earth. Individual views of the planet below or a rapid sequencing of such images as animation, can display surfaces and clouds associated with weather systems.
Weather satellite sensors are basically tuned to two types of radiation: visible light and infrared. Visible light views are like black-and-white television. Dark surfaces reflect little sunlight and appear dark, while clouds and snow cover are highly reflective, appearing bright. However, clouds, fog, and surface features (forests, mountain ranges, major rivers) are usually visible from space only during daylight hours.
Infrared (heat) radiation is emitted by a surface at a rate directly proportional to its temperature. Consequently, thermal infrared images can be interpreted as temperature maps of the underlying surfaces and clouds. Because heat emissions are continuous, these satellite images are available day and night. Water and ground surfaces are generally warm and appear dark while middle level clouds are cool and look gray. The highest, coldest clouds such as thunderstorm tops are bright white. These temperature ranges may be enhanced by assigning various color schemes for television and computer display.
Specially tuned infrared sensors can even detect invisible water vapor in the middle troposphere. Regions of the atmosphere with little water-vapor content appear dark on "vapor channel" images while high vapor content areas are milky white. Clouds also show as bright white in vapor images.
To view satellite images, and for more details concerning satellite imagery, turn to the satellite views and the Tuesday optional electronic Supplemental Summary Information available on the DataStreme Homepage.
To be submitted on the lines for Tuesday on the Study Guide, Part B, Applications, Week 3 Chapter Progress Response Form, under section B. Daily Summary.