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/N-2), and column electron content are compared with a control simulation that is only constrained up to similar 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/N-2, and electron column density (ECD) are compared with their measurement counterparts for a validation of the assimilation. T-eff and O/N-2 are compared with GOLD T-disk and O/N-2. 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/N-2 are about 10.8% and 22.6%, respectively. The RMSE improvement in analyses ECD is about 10% compared to the control simulation.