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

Abstract 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 (∼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.