Simulated Impacts of Tropopause‐Overshooting Convection on the Chemical Composition of the Upper Troposphere and Lower Stratosphere

• Published in: Journal of geophysical research. Atmospheres 2021-11, Vol.126 (21), p.n/a
• Main Authors: Phoenix, Daniel B., Homeyer, Cameron R.
• Format: Article
• Language: English
• Subjects: Atmospheric chemistry; Chemical composition; Convection; Convection cooling; Gases; Geophysics; Lower stratosphere; Lower troposphere; Mixing ratio; Ozone; Radiation; Radiation budget; Satellite observation; Simulation; Storms; Stratosphere; Summer; Temperature; Trace gases; Tropopause; Troposphere; Tropospheric ozone; Upper troposphere; Water vapor; Water vapour; Weather forecasting
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2021JD034568

Tropopause‐overshooting convection transports air from the lower troposphere to the upper troposphere and lower stratosphere (UTLS) where the resulting chemistry and mixing of trace gases can modify the radiation budget. While recent work has examined output from model simulations as well as aircraft and satellite observations of the impacts of tropopause‐overshooting convection on UTLS composition, the range of potential impacts and their dependence on characteristics of storms and their environments is not known. Here, two 10‐day periods, one representative of springtime convection and one representative of summertime convection, were simulated with the Weather Research and Forecasting (WRF) model with Chemistry to examine the range of UTLS composition impacts from tropopause‐overshooting convection. Overall, springtime convection has a larger impact on UTLS composition than summertime convection, with a net effect of increasing water vapor (H2O) in the lower stratosphere and increasing ozone (O3) in the upper troposphere. Springtime convection frequently increases the domain average H2O mixing ratio in the lowermost stratosphere by over 20% while changes in stratospheric H2O from summertime convection are much lower (∼7%–11% increase), reflecting a dependence of the maximum possible H2O increase on UTLS temperature. Increases in upper troposphere O3 mixing ratios span the range 8%–19% from springtime convection and are minimal from summertime convection. Changes in the composition of the UTLS from tropopause‐overshooting convection are largely dependent on the height and temperature of the tropopause, with the largest changes being in environments with relatively low tropopause heights between 11 and 13 km (typical of springtime environments in the United States). Key Points Moist convection frequently reaches the tropopause in the United States and mixes air between the troposphere and stratosphere Tropopause‐overshooting convection occurring during May drastically increases lower stratospheric water vapor mixing ratios The impact that convection has on upper troposphere and lower stratosphere (UTLS) composition appears to largely depend on the height of the tropopause