The DTM-2013 thermosphere model

Aims – The Drag Temperature Model (DTM) is a semi-empirical model describing the temperature, density, and composition of the Earth’s thermosphere. DTM2013 was developed in the framework of the Advanced Thermosphere Modelling and Orbit Prediction project (ATMOP). It is evaluated and compared with DTM2009, the pre-ATMOP benchmark, and the Committe on Space Research (COSPAR) reference model for atmospheric drag JB2008. Methods – The total density data used in this study, including the high-resolution CHAMP, GRACE and GOCE data, cover the 200–900 km altitude range and all solar activities. DTM2013 was constructed with the data assimilated in DTM2009, but with more GRACE data, and low-altitude GOCE data in particular. The solar activity proxy, F10.7 in DTM2009, has been replaced with F30. The bias and precision of the models is evaluated by comparing to the observations according to a metric, which consists of computing mean, RMS, and correlation. Secondly, the residuals are binned, which procedure aids in revealing specific model errors. Results – This evaluation shows that DTM2013 is the least biased and most precise model for the data that were assimilated. Comparison to independent density data shows that it is also the most accurate model overall. It is a significant improvement over DTM2009 under all conditions and at all altitudes, but the largest improvements are obtained at low altitude thanks to GOCE data. The precision of JB2008 decreases with altitude, which is due to its modeling of variations in local solar time and seasons in particular of the exospheric temperature rather than modeling these variations for the individual constituents.