Characterizing Global Ozonesonde Profile Variability From Surface to the UT/LS With a Clustering Technique and MERRA-2 Reanalysis

Abstract

Our previous studies employing the self-organizing map (SOM) clustering technique to ozonesonde data have found significant links among meteorological and chemical regimes, and the shape of the ozone (O₃) profile from the troposphere to the lower stratosphere. Those studies, which focused on specific northern hemisphere midlatitude geographical regions, demonstrated the advantages of SOM clustering by quantifying O₃ profile variability and the O₃/meteorological correspondence. We expand SOM to a global set of ozonesonde profiles spanning 1980 to present from 30 sites to summarize the connections among O₃ profiles, meteorology, and chemistry, using the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis and other ancillary data. Four clusters of O₃ mixing ratio profiles from the surface to the upper troposphere/lower stratosphere (UT/LS) are generated for each site, which show dominant profile shapes and typical seasonality (or lack thereof) that generally correspond to latitude (i.e., tropical, subtropical, midlatitude, and polar). Examination of MERRA-2 output reveals a clear relationship among SOM clusters and covarying meteorological fields (geopotential height, potential vorticity, and tropopause height) for polar and midlatitude sites. However, these relationships break down within ±30° latitude. Carbon monoxide satellite data, along with velocity potential, a proxy for convection, calculated from MERRA-2 wind fields assist characterization of the tropical and subtropical sites, where biomass burning and convective transport linked to the Madden-Julian oscillation (MJO) dominate O₃ variability. In addition to geophysical characterization of O₃ profile variability, these results can be used to evaluate chemical transport model output and satellite measurements of O₃ profiles.