Tidal analysis of modeled thermospheric winds to improve agreement with measurements over South Africa

Abstract

This thesis presents studies of thermospheric winds obtained using ground-based Fabry-Perot interferometers (FPIs). Using data from four different sites across the globe, we evaluate the performance of the Horizontal Wind Model (HWM) at each location, focusing on a new FPI recently deployed to South Africa. Through this analysis, we find that the model is able to better represent winds at or near locations where the model was constrained by data during its development. For those locations far from any model constraints, there is an apparent phase shift between model and data. This finding is particularly apparent for all months of data collected from South Africa. We describe a method to reduce these differences between model and data by extracting the diurnal, semidiurnal, and terdiurnal tidal components from the model output and shifting the phase of the terdiurnal tide so that model output better represents the data. This method is applied to the model output at four different sites, and the improvement in fit, quantified by the Taylor diagram distance, is discussed.