Using satellites to help create weather forecasts

Introduction to weather satellites

To produce our forecasts we need a range of observational data to monitor the Earth's atmosphere, ocean and land surface. Satellite measurements are a vital and integral part of the current global observing system that directly affects the skill of the forecasts we produce.

The skill of our two-day forecasts is now the same as our one-day forecasts were ten years ago, and this is partly because of a variety of new satellite measurements introduced to our forecasting systems over the past decade.

The launch of the first weather satellite in 1960 demonstrated the potential of satellites to provide information about the atmosphere even in the most remote areas. In 1969 the first temperature profile information estimated from satellite measurements were introduced to a computer model. Even in those early days the new satellite measurements improved forecasts in the southern hemisphere.

During the 1970s and 1980s a wide range of satellite missions were launched, from which many different meteorological quantities could be estimated. Some satellite instruments allowed improved estimation of moisture, cloud and rainfall. Others allowed estimation of multi-level winds, by tracking features such as clouds in the imagery, or ocean surface winds from scattered microwave signals from the sea surface.

From the 1990s the measurements made by the satellite instruments began to be used by computer models in their raw form instead of derived products. At this time data assimilation systems had advanced to the point where a measurement of the Earth's radiance in narrow spectral bands could be directly assimilated, in the same way as in-situ measurement of atmospheric temperature. This development significantly increased the impact of satellite data for weather forecasting.

What the Met Office does

We are constantly improving the way we use established satellite observations and preparing for the use of new measurements from space. We are engaged in:

• assimilating a wide range of satellite data into NWP computer models
• producing new imagery products for forecasters, such as fog coverage, cloud top height and precipitation
• creating environmental products, such as volcanic ash monitoring
• generating products for climate monitoring, such as sea-surface temperature
• leading the EUMETSAT NWP Satellite Application Facility
• providing advice, to the space agencies, on our requirements for future weather satellites