Impact of GOLD Disk Temperatures on a Whole Atmosphere Data Assimilation Model

Abstract:

GOLD scans the Earth's disk from geostationary orbit for about 18.5 hours a day, from 0610 UT to 0040 UT. The daylight disk measurements of N₂ Lyman‐Birge‐Hopfield (LBH) bands can be used to retrieve thermospheric neutral temperatures over about one fourth of the globe. The present investigation assesses the impact of GOLD disk temperatures on the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCMX) using Data Assimilation Research Testbed (DART) framework. Two Observing System Simulation experiments (OSSEs), one with and one without assimilating GOLD thermospheric neutral temperatures, show that assimilating GOLD thermospheric temperatures decreases the model bias and spread by 71% and 49%, when compared to forecast. But compared to lower atmosphere only assimilation the bias and spread is improved by 94% and 83%. Specification of the amplitudes of global DW1 and local diurnal tide in WACCMX+DART are improved by about 7% and about 17%, respectively, when GOLD temperatures are assimilated. Improvements are also observed in ionospheric states and the model states at times and locations where there are no GOLD observations. These results will be presented along with some results from assimilation of actual GOLD disk neutral temperature observations.