Thunderstorms and Chemistry - Overview of the DC3 Field Project with a Focus on Scavenging of Soluble Trace Gases

Speaker: Mary Barth, NCAR

When: Wednesday, January 22, 2014, 3:30 p.m. Mountain Time
Location: Room 2A305, DSRC (NOAA Building), 325 Broadway, Boulder
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Thunderstorms provide a major pathway for transporting trace gases, aerosols, and water from the boundary layer to the upper troposphere. However, the impact of convective transport on the UTLS composition and chemistry has not been quantified nor fully characterized on the regional scale. The Deep Convective Clouds and Chemistry (DC3) field experiment was conducted in May-June 2012 to study the impact of continental, midlatitude deep convection on the upper troposphere composition and chemistry above the central to eastern U.S. for two time periods: during the lifetime of the storm itself and during the 1-36 hours after active convection occurred. In this talk I will give an overview of the DC3 field experiment, connecting the aircraft and ground-based observations to the DC3 goals. Then I will focus on the objective of estimating the scavenging of soluble trace gases. To understand trace gas scavenging by cloud particles, I will show analyses of both observations and model results (using the Weather Research and Forecasting model coupled with Chemistry, WRF-Chem). When comparing the degree of scavenging among different types of storms, we find that scavenging occurred more for high-shear, high CAPE (convective available potential energy) storms and less for a low-shear, lower CAPE storm. By comparing WRF-Chem model results with observations of inflow and outflow for a severe thunderstorm in Oklahoma, we find that WRF-Chem overpredicts the degree of HNO3 scavenging, suggesting a missing source, e.g. degassing from ice or stratosphere influx, yet underpredicts the degree of scavenging of CH3OOH and H2O2, although the H2O2 prediction does not include its aqueous-phase chemical losses.