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 Texo models are less than 8.9% and 22.8%, much better than the MSIS-00 model. Exospheric temperature, the atmospheric temperature at an altitude above 300 km, is a critical parameter used in most thermospheric density models. In this study, we use different mathematical functions to construct the exospheric temperature models (ETM) named ETM, MSIS-ETM, and Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM)-ETM, respectively based on the CHAMP and GRACE density observations. The mathematical functions can be derived either using the data-driven method or using the model-driven method. Our purpose is to evaluate the performance of these constructed models in reflecting the thermosphere, and we found that all these models can provide good specification of the thermosphere such as the typical day-night, seasonal, and latitudinal variation characteristics. Overall, the ETM constructed by using the data-driven method gives a better performance than the MSIS-ETM and TIEGCM-ETM, and it can effectively simulate the physical features that are observed in the thermosphere. Our results indicate that compared with the model-driven method utilizing the sufficient data-driven PCA method to bend the exospheric temperature model is also an effective way. Exospheric Temperature Models (ETM) are constructed on the basis of CHAMP and GRACE data using different empirical orthogonal functions (EOFs)The three ETM models can provide good specification of thermospheric density after they are embedded in the MSISThe ETM with EOFs directly from the observations gives a better performance than those with EOFs obtained from the MSIS and Thermosphere Ionosphere Electrodynamics General Circulation Model models