Forward Model and Sensitivity Analysis for Limb-Scattered Radiation of Mesospheric OH Radicals Emission in Ultraviolet Band

Hydroxyl, one of the principal oxidants in the atmosphere, determines the density of ozone and other greenhouse gases even the change of climate. In order to achieve high resolution vertical profiles of OH radical in mesosphere, an accurate forward model should be built up for its retrieval. In this paper, this forward model simulates limb-scattered signal including OH solar resonance fluorescence around 309 nm. We calculate OH band rotationalemission rate factor g based on molecular spectroscopy theory, and combine it with OH slant column calculated by SCIATRAN to synthesize OH fluorescence emission spectra. By superimposing atmospheric background signal and do a convolution with instrument line shape function, we could obtain a simulated spectra containing OH concentration information. These results are in good agreement with previous measurements by MAHRSI (Middle Atmosphere High-Resolution Spectrograph Investigation) and SHIMMER (Spatial Heterodyne Imager for Mesospheric Radicals). Then we analyze several factors that may influence the forward model. By modifying these parameters, forward model could be more accurate and closer to the actual radiative transfer process in the future.