Evaluation of ozone fields in NASA’s MERRA-2 reanalysis

Abstract:

Following the release of version 2 of the Modern Era Retrospective Analysis for Research and Applications (MERRA-2) by NASA’s Global Modeling and Assimilation Office, we present an overview of the quality of ozone in the new reanalysis. As one of the focal aspects of MERRA-2, the assimilation of ozone data constitutes a significant improvement over the predecessor reanalysis, MERRA. The observations used consist of retrieved partial columns from the Solar Backscattered UV Radiometers (SBUV) and data from two instruments onboard NASA’s Aura satellite: the Ozone Monitoring Instrument (OMI, total ozone column) and the Microwave Limb Sounder (MLS, stratospheric profiles). In this presentation we will show results of an evaluation of stratospheric and upper tropospheric MERRA-2 ozone fields against independent data. Validation of upper-tropospheric and lower-stratospheric fields is done using observations from ozonesondes and focuses on the realism of ozone gradients across the tropopause and the representation of highly dynamical vertical structures in the lower stratosphere. The stratospheric profiles are evaluated against observations from the Upper Atmosphere Research Satellite (UARS) MLS, the ENVISAT MIPAS and SAGE II instruments. Vertically integrated fields will be compared with observations from SBUV and the long record of observations made by the Total Ozone Mapping Spectrometer (TOMS). Furthermore, we will compare our results to those from other reanalyses including MERRA and discuss the implications of changes in the observing system for trend studies. We will highlight potential applications of the reanalysis ozone for scientific research of transport processes and radiative forcing by ozone.