The HWM is an empirical model of the horizontal neutral wind in the upper thermosphere. It is based on wind data obtained from the AE-E and DE 2 satellites. A limited set of vector spherical harmonics is used to describe the zonal and meridional wind components. The first edition of the model released in 1987 (HWM87) was intended for winds above 220 km. With the inclusion of wind data from ground-based incoherent scatter radar and Fabry-Perot optical interferometers (FPI), HWM90 was extended down to 100 km and using MF/Meteor data HWM93 was extended down to the ground. HWM93 was upgraded to HWM07 by including major formulation changes and the incorporation of a substantial amount of new observational data such as height profiles from NASA/UARS-WINDII and -HRDI instruments.
The new updated version of the model, HWM14, now includes extensive ground-based 630 nm FPI measurements in the equatorial and polar regions, as well as cross-track winds from the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite (~250 km altitude). As in HWM07, in the thermosphere, the model consists of two parts: a quiet-time portion, and a geomagnetically disturbed portion. The quiet-time part represents average wind conditions when ap <= 12. The disturbed part represents average perturbation winds for the specified ap input.
The model currently contains no solar activity dependence, and the F107 and F107A arguments are ignored. During the day, solar activity has a relatively insignificant effect on thermospheric winds. Variations with magnetic activity (Ap) are included.
The model currently contains no solar activity dependence, and the F107 and F107A arguments are ignored.
HWM uses geomagnetic index ap.
The model provides zonal and meridional winds for specified latitude, longitude, time, and Ap index.
Model is time-dependent.
- Neutral Wind Change
- An update to the Horizontal Wind Model (HWM): The quiet time thermosphere
- An Empirical Model of the Earth's Horizontal Wind Fields: HWM07
- Empirical wind model for the upper, middle and lower atmosphere
- Solar activity variations in midlatitude thermospheric meridional winds
Code Languages: Fortran
- Douglas Drob, NRL (Model Contact)
- Jia Yue, NASA/GSFC (CCMC Model Host)
- Katherine Garcia-Sage, NASA/GSFC (CCMC Model Host)
In addition to any model-specific policy, please refer to the General Publication Policy.