Impact of using the hybrid high-resolution solar reference spectrum on ozone profile retrievals from OMI measurements

We have evaluated a new high-resolution solar reference spectrum for characterizing space-borne Ozone Monitoring Instrument (OMI) measurements as well as for retrieving ozone profile retrievals over the ultraviolet (UV) wavelength range from 270 and 330 nm. The SAO2010 solar reference has been a standard for use in atmospheric trace gas retrievals; It is composed of ground-based and balloon-based solar measurements from the Kitt Peak National Observatory (KPNO) and Air Force Geophysics Laboratory (AFGL), respectively. The new reference spectrum, called the TSIS-1 Hybrid Solar Reference Spectrum (HSRS), spans 202 to 2730 nm; It is developed by normalizing high-resolution solar measurements from four independent datasets to the radiometric scale of the lower resolution Spectral Irradiance Monitor (SIM) instrument on the space-based Total and Spectral Solar Irradiance Sensor (TSIS-1) mission and on the Compact SIM (CSIM) flight demonstration mission. For the UV region of interest in this study, the high resolution measurements in the TSIS-1 HSRS are based on AFGL and ground-based solar measurements from the Quality Assurance of Spectral Ultraviolet Measurements In Europe (QASUME) campaign. In deriving on-line slit functions and wavelength shifts from OMI solar irradiances, the resulting fitting residuals show significant improvements of 0.2-0.5 % (relatively 14-42%) due to switching from the SAO2010 to the TSIS-1 HSRS. Correspondingly, in performing ozone profile retrievals from OMI radiances, the fitting residuals show relative improvements of up to ~ 5 % in 312-330 nm, with the relative differences of ~ 2 % in tropospheric ozone columns.