Background

Numerical models used for weather forecasts need continuous ingestion of observations of current weather status to provide reliable estimates. Among the input variables, updated and accurate wind observations play a crucial role in Numerical Weather Prediction (NWP) models, as wind has a long-lasting effect on all the other variables. One technique to estimate atmospheric wind is through the computation of Atmospheric Motion Vectors (AMVs).

A new demonstrator with Sentinel-3

AMV is a product that is continuously generated from geostationary and low Earth orbit satellites. AMVs are computed by tracking clouds or areas of water vapour and calculating the relative motion of similar features in consecutive satellite images and therefore the technique is applicable in overlapping satellite tracks (e.g. satellites in tandem or in a constellation).

In December 2020 EUMETSAT developed the first demonstrator of a tropospheric wind AMV generator from Sentinel-3 SLSTR (Surface Temperature and Sea Surface Temperature) data. The scientific validation of the SLSTR AMV products is documented in Barbieux, et al. (2021).

AMV benefits in tropical cyclone forecasts

Recent impact experiments at the Met Office and elsewhere have shown that the AMV data enables to offer higher accuracy in forecasts and in hurricane track forecasts. (e.g. Soden et al. 2000).

Alternative sources of wind information are derived from the mass field, which is easy to observe and can be used to derive the wind field in the extra-tropics areas. However, for the tropics and smaller-scale features the data is less accurate as the coupling is weaker. For best results, models require information on both the mass field and the wind field.