HWM Neutral Wind Model from NSSDC

The HWM87 is an empirical model of the horizontal neutral wind in the upper thermosphere analogous to the MSIS model for neutral temperature and density. It is based on wind data obtained from the Atmosphere Explorer E and Dynamics Explorer 2 satellites. A limited set of vector spherical harmonics is used to describe the zonal and meridional wind components. The data base was not adequate to detect solar cycle effects but the model does include magnetic activity effects. Mid- and low- latitude data are reproduced quite well by the model. The polar vortices are present, but not to full detail. Currently the model is intended for winds above 220 km altitude; it does not include altitude variations. The model software provides zonal and meridional winds for specified latitude, longitude, time, and Ap-index. The model code is distributed by NSSDC on magnetic tape, on diskettes for use on PCs, and online on NSI/DECNET.