Assessing the Impacts of Assimilating GOLD Disk O/N2 Observations on the
Thermosphere-Ionosphere System
Abstract
The Global-scale Observations of Limb and Disk (GOLD) imagers scan the
Earth‘s Thermosphere-Ionosphere (TI) in the far ultraviolet wavelengths.
Measurements from GOLD daylit spectrum are used to retrieve the column
integrated atomic oxygen to molecular nitrogen density ratio (O/N2) over
about one fourth of the globe. The present investigation assesses the
impact of assimilating GOLD disk O/N2 on the Whole Atmosphere Community
Climate Model with thermosphere-ionosphere eXtension (WACCMX) using the
Data Assimilation Research Testbed (DART) ensemble adjustment Kalman
filter. Two Observing System Simulation Experiments (OSSEs) are
performed, and improvements are quantified by calculating root mean
square error (RMSE) and bias with respect to a true run. One of the
OSSEs assimilates only the lower atmosphere (LA, <100 km)
observations, referred to as LA experiment, and the second assimilates
GOLD O/N2 and LA observations, referred to as Whole Atmosphere (WA)
experiment. The WA-analysis O/N2 RMSE and bias are about 60% and 87%
better compared to LA-analysis. Also, the O/N2 RMSE and bias for the
WA-analysis are about 23% and 54% better compared to WA 1 hr
forecasts. The improvement in WA electron column density (ECD), a model
equivalent of Total Electron Content (TEC), is about 24% compared to
the LA experiment. These results demonstrate that the assimilation of
GOLD O/N2 improves both the thermosphere and ionosphere in a whole
atmosphere data assimilation system.