Mechanisms that propagate polar satellite-derived atmospheric motion vector information into lower latitudes

The use of Atmospheric Motion Vectors (AMVs) in NWP (Numerical Weather Prediction) models continues to be an important source of information in data sparse regions. These AMVs are derived from a time-sequence of images from geostationary and polar orbiting satellites. NWP centers have documented positive impact on model forecasts not only in regions where the AMVs are measured, but elsewhere as well. One example is the effect of the Moderate Resolution Imaging Spectroradiometer (MODIS) polar winds on forecasts in the middle and subtropical latitudes.

Using a pre-operational version of the National Centers for Environmental Prediction's (NCEP) Global Forecast System (GFS), a side-by-side experiment was run for a six week period, with and without the MODIS polar winds. Several cases within this period have been examined to determine how winds in the polar regions may affect the height and wind fields in lower latitudes. Two basic possibilities were addressed: a) An adjustment in the mass field by the three-dimensional variational (3DVAR) assimilation system and b) Dynamical considerations in the vicinity of the polar jet stream.

By using a combination of model analyses and forecasts, with sophisticated visualization techniques, an attempt is made to separate and quantify the relative importance of each effect. The status of the current research will be presented.