Satellite-derived data helps improve the accuracy of weather forecasts. The information and pictures we can get help us to understand how weather works. They also help us to anticipate weather events better: for example, hurricane warnings.

There are two main types of satellite orbiting the Earth: Geostationary satellites remain above the same point on the Earth's surface as they rotate at the same speed as the Earth. They show you the same picture all the time - essentially a disk-shaped picture of the Earth (See an example) with a diameter of 150 degrees in latitude and longitude. Meteosat is situated above the equator on the Greenwich Meridian and it views 75 degrees north, 75 degrees south, 75 degrees east and 75 degrees west. Satellite pictures can be visible (where the sky appears black), or infrared (where the sky appears white).

Those in polar orbits orbit the Earth travelling roughly pole to pole. The orbit is in fact inclined so that it may go on one side of the North Pole and the opposite side of the South Pole. This gives a continous stream of different pictures as they scan the Earth under their orbit;they can cover the whole surface of the Earth in just three days, producing huge amounts of data. Meteorologists use powerful computers to reduce the information to a manageable form.

All kinds of different information can be read by satellites. Synthetic aperture radar mapping equipment can penetrate cloud cover. Some images are sensitive to water vapour in the Earth's atmosphere. They can be colour coded to show the differences between clouds, rain and snow. Others measure wave height, sea temperature, even sea-ice thickness. In fact they are so sensitive that they can even measure wind speed.