Assessing GEOS-CF Analysis of Ozone Profiles as a Priori for Hyperspectral BUV Ozone Profile Retrievals

Abstract

Satellite remote sensing of ozone has progressed from daily global observations by polar-orbiting platforms to hourly regional monitoring by geostationary platforms. However, retrieving detailed vertical profiles remains challenging because satellite measurements have inherently limited vertical sensitivity. Within the optimal estimation (OE) framework, a priori information constrains the retrieval, preventing unphysical deviations driven by measurement uncertainties while supplementing the limited information content of the observations. In this study, we evaluate ozone profiles from the Goddard Earth Observing System Composition Forecasting (GEOS-CF) system as an alternative a priori to the tropopause-based (TB) ozone profile climatology. To ensure a robust assessment, retrieval experiments are performed across multiple satellite platforms, including OMI, TROPOMI, and GEMS. The GEOS-CF ozone analysis systematically exhibits a systematic positive bias in the troposphere relative to ozonesonde soundings, but agreeing with limb observations within a few percent throughout most of the stratosphere, particularly between 50 and 1 hPa. Larger discrepancies are found in the tropopause region (>100 hPa) and in the upper atmosphere (<1 hPa). These characteristics are reflected in the satellite retrievals: the positive tropospheric bias in the GEOS-CF a priori propagates into the retrieved ozone profiles, whereas the improved representation of the stratosphere in GEOS-CF reduces the retrieval biases associated with the TB a priori. These results support a hybrid a priori strategy that combines the tropospheric stability of the TB climatology with the improved stratospheric representation of GEOS-CF.