A meridional wind climatology from a fast model for the derivation of meridional winds from the height of the ionospheric F2 region

Results of a semi-empirical model of neutral wind speeds in the upper thermosphere are presented. The derived wind speeds will be useful in studies of ionospheric behavior and for validating thermospheric general circulation models. The Meridional Wind Model is based on a refinement of the technique of Miller et al. (1986, 1993) who used the height of the peak electron density in the ionosphere (hmF2) and a comprehensive ionospheric model to deduce thermospheric winds. Computation requirements were drastically reduced by parameterizing the essential aspects of the ionospheric model while preserving the accuracy of the original method. The model can accept hmF2 directly or calculate it from fundamental scaled ionosonde parameters to produce winds locally. It also includes the capability to produce winds on a global scale by using the International Reference Ionosphere (IRI) model. Since there is no provision for electric fields, the model is accurate only at mid-latitudes. The Meridional Wind Model is used to examine the long-term averages of meridional winds at different levels of solar activity. The winds are derived from F2-layer heights from an ionosonde data base that extends from 1958 to 1990. Results show smaller nighttime winds when the solar flux is greatest. Daytime wind speeds increase with latitude and vary by season, but are not as strongly dependent on solar flux. Winds from the ionosonde data base and derived using the IRI are in general agreement with the winds from the Horizontal Wind Model (HWM90). There are, however, significant differences, especially at higher latitudes.