Improving the Thermosphere Ionosphere in a Whole Atmosphere Model by Assimilating GOLD Disk Temperatures

Global-Scale Observations of Limb and Disk (GOLD) disk measurements of far ultraviolet molecular nitrogen band emissions are used to retrieve column integrated disk temperatures (T_disk), which are representative of the lower-and-middle thermosphere. The present work develops a new approach to assimilate the T_disk in the whole atmosphere community climate model with thermosphere-ionosphere eXtension using the data assimilation research testbed ensemble adjustment Kalman filter. Nine days of data, 1–9 November 2018, are assimilated. Analysis state variables such as thermospheric effective temperature (T_eff, airglow layer integrated temperature), ratio of atomic oxygen to molecular nitrogen column densities (O/N₂), and column electron content are compared with a control simulation that is only constrained up to ∼50 km. It is observed that assimilation of the GOLD T_disk improves the analysis states when compared with the control simulation. The analysis and model states, particularly, T_eff, O/N₂, and electron column density (ECD) are compared with their measurement counterparts for a validation of the assimilation. T_eff and O/N₂ are compared with GOLD T_disk and O/N₂. While, the ECD is compared with ground based total electron content measurements from global navigational satellite system receivers. Root mean square error (RMSE) improvements in T_eff and O/N₂ are about 10.8% and 22.6%, respectively. The RMSE improvement in analyses ECD is about 10% compared to the control simulation.