Monitoring the weather

Satellite-based data has made an immense contribution to Australian meteorology and is essential to weather forecasting and climate research.

There are two basic types of weather satellites.

a) Polar-orbiting satellites take measurements from an altitude of 850 km,at several wavelengths.

In the visible region of the spectrum the photographs are of the earth and its clouds during daylight hours. Infra-red images measure the temperature of the surface of the earth, and clouds, night and day.

Such satellite images give information on the extent of fog, flood waters, snowfields and pack ice; on sea surface temperatures and wave characteristics; on temperatures, humidities and pressures throughout the troposphere; and on winds, which can be derived from cloud movements. The images display cloud formations associated with cyclones, cold fronts and other weather systems, and also capture smaller features like thunderstorms.

b) Geostationary satellites revolve around the earth at a height of 36,000 km over the equator at the same speed as the earth rotates. From earth they appear to hover over the same point.

The Japanese Geostationary Meteorological Satellite over Indonesia provides sequences of selected images. Successive images provide a moving picture of the clouds as they form, are carried by the winds, and disappear. Wind speed and direction at different levels in the atmosphere can be calculated from such sequences. These hourly wind fields are particularly important when forecasting tropical cyclone position and intensity.

Click on either of the links below to view animated satellite images of the earth in your computer movie player.
Quicktime movie file 2.2MB
AVI movie file 1.9MB