Stratosphere-Troposphere Exchange of Air Masses and Ozone Concentrations Derived from Observations

This research presents the estimation of the stratosphere-troposphere exchange (STE) of air mass and ozone from 2007 to 2010, wholly derived using observational data. The STEs of ozone and air masses, mainly controlled by the Brewer-Dobson Circulation, have important implications for the global tropospheric ozone budget. However, modern reanalyses have considerable uncertainty in their current quantification of ozone STEs. This uncertainty has been attributed to the diabatic heating at the isentropic surface fitted to the tropical tropopause. Here we derive the STEs of air mass and ozone by using observational datasets include temperatures from the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2), ozone and water vapor concentrations from the Aura Microwave Limb Sounder (MLS), and the cloud radiative effects based on CALIPSO and CloudSat measurements. The radiative heating rates in the clear-sky condition are derived using a radiation model with observed inputs of temperatures, water vapor and ozone. The derived air mass and ozone STEs are compared against the Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA2) and the European Center for Medium-range Weather Forecasts (ECMWF) ERA5 STEs of ozone and air masses. We present results in three distinct regions, the northern hemisphere extratropics, southern hemisphere extratropics, and tropics, along with global averages. We will further quantify the uncertainties in STEs from ERA5 and MERRA2 using observed temperatures, ozone concentrations, and clear-sky radiative heating rates derived from observations for 2006-2022.