The Influence of Convection on Upper Troposphere Lower Stratosphere Composition from Multiple Years of Trajectory-Matched Ground-Based Radar Observations and Satellite-Based Trace Gas Profiles

Five years of hourly, high-resolution radar observations over the contiguous US are matched with downstream trace gas profiles from the Aura Microwave Limb Sounder (MLS) via large-scale trajectory calculations driven by MERRA-2 winds to reveal the influence of convection on upper troposphere lower stratosphere (UTLS) composition. Two populations are defined for analysis, one based on trajectories initialized within radar-observed convection that reaches altitudes observed by the Aura MLS and the other based on trajectories randomly initialized within regions observed by radar that did not contain storms (i.e., a null population). To ensure that the null population adequately indicates a lack of convective influence when matched with MLS observations, storm-free trajectories that travel within close proximity to downstream convection during the transit from initialization to coincidence with an MLS profile are discarded. Comparison of trace gas distributions from these two trajectory-matched populations in altitudes relative to the tropopause reveals the influence of convection on the UTLS.

Preliminary analysis shows that, as expected, convection results in an increase in water vapor (H2O) throughout the UTLS compared to air masses without recent convective influence. Carbon monoxide (CO) concentrations are also found to generally increase within convectively influenced regions, especially in the UT. Ozone (O3) concentrations mostly decrease in the UTLS, with some considerable differences observed between environments that are more extratropical (low altitude, warm tropopauses) or tropical (high altitude, cold tropopauses) in nature. Results will be presented based on environment, season, and storm intensity, and will include analyses of H2O, O3, CO, methyl chloride (CH3Cl), chlorine monoxide (ClO), hydrogen chloride (HCl), nitrous oxide (N2O), and temperature from the Aura MLS. The perceived significance of these results and relevance to global composition will be discussed.