Daniel Phoenix-March 14

Impacts of Tropopause-Penetrating Convection on the Chemical Composition of the Upper Troposphere and Lower Stratosphere

Tropopause-penetrating convection is capable of rapidly transporting air from the lower troposphere to the upper troposphere and lower stratosphere (UTLS). Since the vertical redistribution of gases in the atmosphere by convection can have important impacts on the chemistry of the UTLS, the radiative budget, and climate, it has become a recent focus of observational and modeling studies. Despite being otherwise limited in space and time, recent aircraft observations from field campaigns such as the Deep Convective Clouds and Chemistry (DC3) experiment have provided new high-resolution observations of convective transport. Modeling studies, on the other hand, offer the advantage of providing output related to the physical, dynamical, and chemical characteristics of storms and their environments at fine spatial and temporal scales.

To examine the impact of tropopause-penetrating convection on the chemical composition of the UTLS, a 10-day period of high frequency, tropopause-penetrating convection over the Central United States was simulated using the Weather Research and Forecasting model with Chemistry (WRF-Chem). The overall direction of transport is troposphere-to-stratosphere transport such that convection increases water vapor (H₂O) concentrations and decreases ozone (O₃) concentrations in the UTLS. During this period, high concentrations of H₂O were consistently injected from the troposphere into the lower-most stratosphere (between the 350 K and 380 K isentropes) such that the mean concentration of H₂O increased by 50% in that layer over the domain. In the vicinity of convection, air containing high concentrations of ozone (O₃) from the overworld stratosphere (above the 380 K isentrope) is transported downward to the UTLS. This air may also contain high concentrations of inorganic chlorine (Cl_y) that can destroy O₃ in high H₂O, low temperature regimes. The possibility of this catalytic destruction process is discussed as an aim of future work.