Evaluation of the Exospheric Temperature Modeling From Different Empirical Orthogonal Functions

In this paper, we constructed the Exospheric Temperature Models (ETM) on the basis of CHAMP and GRACE data using different empirical orthogonal functions (EOFs). The EOFs of the exospheric temperature can be derived either from satellite data directly or from the outputs of the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) and MSIS models by applying the Principal Component Analysis method. Then, the thermospheric mass densities calculated from ETM are used to compare with the observed data in order to evaluate the performance of different ETM models. It was found that all these three models can provide good specification of thermospheric density including day-night, seasonal, and latitudinal variations. However, the ETM based on CHAMP and GRACE data gives a better performance in modeling the Equatorial Thermospheric Anomaly and the Midnight Density Maximum features than the MSIS-ETM and TIEGCM-ETM. Specifically, independent SWARM-C data comparison showed that the Relative Deviations and corresponding Root-Mean-Square-Errors of our T_exo models are less than 8.9% and 22.8%, much better than the MSIS-00 model.