Earth from space

Observations from space

18 July 2012

"I don't think any forecaster would argue with the fact that satellite data and imagery are absolutely critical to every weather forecast we produce at the Met Office."

These are the words of Stewart Turner, Space Programme Manager. It's his job to coordinate Met Office activity relating to satellites, in collaboration with a large number of people across the Met Office, the UK and overseas. There are a great many satellites orbiting Earth at any one time, taking pictures and collecting data - some of which are used by the Met Office to predict future weather patterns. In fact, satellites are behind a huge proportion of the information used in weather forecasting around the world today.

Satellite receiver

Essentially, forecasters use satellites in two different ways.

The first involves measuring a range of different variables in the atmosphere such as wind, temperature, humidity and cloud, and also the temperature of the Earth's surface.

Meteorologists use this information together with data from non space-based observing systems to develop the best possible understanding of the current state of the atmosphere. This is used to 'initialise' numerical models which are used to forecast future weather conditions.

"Satellite data underpin everything we do."

The second use of satellite information is actual imagery - pictures of the weather. Forecasters use these to monitor rapidly developing weather events and to verify that weather systems are developing in the way predicted by the numerical models.

The combined results are used to produce the forecasts that are communicated to the general public.

"Satellite data underpin everything we do," says Stewart. "In terms of contribution to the numerical modelling, they're responsible for something like 64% of the accuracy of the short-range forecast."

A worldwide effort

Satellite

Satellite programmes are very expensive to run. So organisations that need satellite information often form partnerships. The Met Office, representing the UK as one of the 27 Member States of EUMETSAT (The European Organisation for the Exploitation of Meteorological Satellites), uses satellites from many different agencies around the world, including EUMETSAT and NOAA (the US National Oceanic and Atmospheric Administration).

Partnerships such as these mean that a wide range of countries can benefit from the output of satellites, without having to invest in their own, individual programmes. "It's essentially a way of opening the technology up to many different parties, in a way that we can all afford and mutually benefit from," says Stewart.

Satellite image

This is especially true for developing countries. Due to their position, the best images that geostationary satellites provide are of the equatorial regions. For example, they're ideally placed to gain a perfect view of Africa.

EUMETSAT and the European Commission are working together to help African countries benefit, working with local meteorological services to make use of the enhanced forecasting data and providing the relevant training to help get them up and running. In addition to the imagery, these satellite communications provide a wide range of information to forecasters and disaster managers in Africa, including forecast model products and surface-based observations.

Uses beyond everyday forecasting

"Satellite images look through a lot of different spectral channels, or wavelengths of light, by adding and subtracting various spectral channels, meteorologists can identify vital information."

Satellite image 1

Although satellites are primarily intended for weather forecasting, the images they produce can also be used for other purposes.

"Satellite images look through a lot of different spectral channels, or wavelengths of light," Stewart explains. "By adding and subtracting various spectral channels, meteorologists can identify vital information, such as the location of particular air masses - or volcanic ash, for example."

The images can also be tuned to highlight features such as ice on the Earth's surface, which has a number of useful applications - including in the field of climate change.

So whether it's using satellites to capture a high-resolution image of a striking pattern of weather, or compiling very rapidly detected data for fast-moving forecasting purposes, there's no doubt satellites are here to stay as a vital part of meteorology.

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