This article provides a brief overview of how Optical EO has a played a part in meteorology. However, as meteorology is not dealt with in-depth in this course, there is no video to view for this topic.

Gaining a picture of the weather from above was one of the earliest applications of satellite imagery. Modern weather forecasting is conducted through a combination of surface observations, satellite imagery, satellite measurements of temperature, moisture, and wind speed, and computer modelling (known as numerical weather prediction). The improvements in weather forecasting brought about by the combination of satellite data and improved computing power and models means that our five-day forecasts are now as accurate as our three-day forecasts were thirty years ago. This often means anticipating the formation of weather systems .

Observations from the satellite record are also used for understanding climate – but climate is measured over periods of decades and centuries, so even the longest satellite records (of about thirty years) are only starting to be useful for measuring long-term change. However, weather satellite measurements can help with the starting conditions for computer models of climate .

The first TIROS missions were launched in 1960 to capture images of weather systems. Now, a combination of satellites in different orbits are used. Most of the world can be monitored at all times from geostationary orbit by satellites such as Meteosat, GOES, and Himawari. These satellites picture the Earth as a full disc along particular lines of longitude. Due to the curvature of the Earth, their view of higher latitudes is lower resolution, and beyond 65 degrees or so latitude, the images become too distorted to be of much use. These satellites use visible light during daylight hours and much longer wavelength emitted thermal infrared at night (measuring temperature, rather than brightness). They are particularly useful for what is known as “nowcasting”, when forecasters need to know information about a developing system with quick updates to alert people about weather that will affect them within minutes or hours. Meteosat, for example, normally takes an image every fifteen minutes, but during severe weather can take an image of the top one third of the disc as seen from 0 degrees longitude every five minutes. This allows imaging of convective storms which can produce damaging winds, and large hail, and are often a danger to air traffic .

Large scale atmospheric circulation
Dynamic changes in cloud patterns can be used by weather forecasters to calculate wind speeds at the top levels of the atmosphere. Occasionally, very powerful cloud formations (such as overshooting tops on thunderstorms) can also give additional information about weather on the ground. These observations can be added to the starting conditions for computer model runs to improve the accuracy and precision of the forecasts they produce.

You can view some images from the MetOp satellites in the download sheet below.