WHAT ARE SATELLITE IMAGES?
Most meteorological satellite images are taken from satellites which are in
geosynchronous orbit, which means they are at a fixed spot high above the earth, usually
about 36,000km. METEOSAT takes images of Europe and Africa and is located above the equator
and Greenwhich, which gives it a location of 0°N and 0°E. Other geosynchronous
satellites include :
- GOES for North and South America and the east Pacific and west Atlantic
- GMS for Asia and the west Pacific<
- INDOSAT for the Indian Ocean and southern Asia and India
There are other types that orbit at lower altitudes and they orbit the earth from a few hours to once or twice a day
taking pictures of hurricanes and thunderstorms, etc.
Different types of pictures are taken, depending which part of the visible or non-visible part of the electromagnetic
spectrum is being used. Visible images show pictures as humans would see them (although most are in black and white).
Infra-red pictures are very useful since infra-red pictures are almost the same as visible, yet the temperatures of clouds are really being photographed. How are temperatures
depicted, well, the higher the clouds are in the atmosphere, the colder they will be and the whiter they appear on the image. Low, warm clouds, like
stratus and fog, is hardly seen on infra red images. Infra red images are most useful since they do not depend on sunlight, and hence, are invaluable at night when visible images are useless.
Finally, water vapour images show where the moisture is located in the atmosphere. The camera on the satellite only seeks out the water vapour wavelengths in the electromagnetic spectrum, hence
huge river-like swirls of moisture are seen on these images, enabling forecasters to see where the moisture is being transported to.
Satellite images can now be animated, thanks to the computer power of today, however, this site carries no animations, as they are far too large for easy and fast download over conventional 28.8kbps modems.
GLOBAL SATELLITE LINKS
