Stratospheric Intrusion-Influenced Ozone Air Quality Exceedances Investigated in the NASA MERRA-2 Reanalysis

Stratospheric intrusions have been the interest of decades of research for their ability to bring stratospheric ozone (O-3) into the troposphere with the potential to enhance surface O-3 concentrations. However, these intrusions have been misrepresented in models and reanalyses until recently, as the features of a stratospheric intrusion are best identified in horizontal resolutions of 50 km or smaller. NASA's Modern-Era Retrospective Analysis for Research and Applications Version-2 (MERRA-2) reanalysis is a publicly available high-resolution data set (similar to 50 km) with assimilated O-3 that characterizes O-3 on the same spatiotemporal resolution as the meteorology. We demonstrate the science capabilities of the MERRA-2 reanalysis when applied to the evaluation of stratospheric intrusions that impact surface air quality. This is demonstrated through a case study analysis of stratospheric intrusion-influenced O-3 exceedances in spring 2012 in Colorado, using a combination of observations, the MERRA-2 reanalysis and Goddard Earth Observing System Model, Version 5 simulations.