Assimilation of GOLD O/N2 Observations in WACCMX+DART

The Global-scale Observations of Limb and Disk (GOLD) imager scans the Earth in the far ultraviolet wavelengths. Spectral measurements from GOLD are used to retrieve column integrated thermospheric neutral temperature (Tdisk) and oxygen to molecular nitrogen column density ratio (O/N2) over about one fourth of the globe. The present investigation assesses the impact of GOLD O/N2 on the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCMX) using Data Assimilation Research Testbed (DART) ensemble Kalman filter. Observing System Simulation experiments (OSSEs), run with and without GOLD measurements, show that assimilating the GOLD O/N2 observations improves the root mean square error (RMSE) and bias of short-term forecast and analysis states. Assimilation of actual GOLD Tdisk observations also shows improvement when compared to independent thermosphere and ionosphere measurements. Using a Specified Dynamics WACCMX (SD-WACCMX) run as a control simulation, we found that the RMSE improvements in the analysis effective temperature and O/N2 are about 10.8% and 22.6%, respectively. Also, RMSE improvement in analysis electron column density is about 10% compared to the control simulation. RMSE improvement in the analysis O/N2 is about 23%. Also, the improvement in TEC RMSE is about 25%. These results demonstrate that assimilation of GOLD O/N2 observations have a great impact on the ionosphere-thermosphere models.