The weather is the state of the atmosphere measurable by its temperature, humidity, precipitation, and other atmospheric variables. To forecast the weather is a major branch in the field of meteorology. In comparison to climate, weather can only be predicted for a short period of time (minutes to month), because it describes the state of the atmosphere for specific days at specific locations. For a reliable weather forecast, a good numerical prediction model with precise initial conditions is needed. Models are sensitive to changes in the initial condition, that is why at the moment weather predictions are only accurate for few days. However, both models and the determination of initial conditions are steadily improved. EO makes a significant contribution to improving the initial conditions by providing global information several times a day. As the quality of the EO products improves, the weather forecast also improves.
Since decades, satellites are used to monitor and forecast weather. Therefore, it is one of the most established sectors of satellite data applications. There are geostationary and polar-orbiting weather satellites that measure all kinds of meteorologically relevant variables, e.g. cloud coverage, wind speed [...] via passive or active imagery. However, not only satellites are used to collect information, but also other remote sensing techniques that can be airborne or ground-based such as Lidar.
Weather forecasts are used by citizens for decisions in everyday life, in agriculture for crop cultivation decisions and in the stock markets. Other domains of applications are hydrometeorology, aviation, maritime navigation, and the military and nuclear sectors.