Atmospheric Motion Vectors
Knowledge of atmospheric motion is essential for many applications. Information on high-level atmospheric winds is of great importance for forecast models as the current state of the atmosphere has to be specified before the future state can be predicted. Winds in the upper levels can be observed using radiosondes or aircraft measurements, but those observations are limited in time and space. As satellites provide worldwide and continuous data, they are the ideal data source for regular upper atmospheric wind information.
Atmospheric motion vectors are computed by tracking clouds or moisture features from a sequence of satellite images and are thus the only observation type that provides good coverage of upper tropospheric wind data over oceans and at high latitudes. Geostationary satellites are best suited to tracking clouds as they provide data from the surface and the atmosphere with a high temporal resolution and from a non-varying satellite perspective. In the IR and VIS ranges AMVs are derived from clouds, whereas in absorption bands like the water vapor channels they are derived from moisture fields.
The routine production of AMV data started as early as in the 1970s. There have been many improvements in computation and data usage since those days: the image resolution has increased and the time interval between satellite images has decreased. The available number of satellite channels used for extracting cloud motion vectors has also increased since the 1970s. In the beginning, AMVs were produced using data from geostationary satellites only, while nowadays winds are also computed from polar orbiting satellite data.