Collaborative Research: Observational and Modeling Studies of Overshooting Convection and Stratosphere-Troposphere Exchange
- View All
Deep convection that penetrates (overshoots) the tropopause affects the trace gas composition of the extratropical upper troposphere and lower stratosphere, which is important for global atmospheric chemistry and the Earth''s radiation balance. This study will combine more than 10 year data of ground-based radar observations with numerical model simulations to study the physical and chemical characteristics of overshooting convection. Data from approximately 100 NEXRAD radars will be composited onto a three-dimensional regional grid with high spatial and temporal resolution. Climatology of the physical characteristics of overshooting convection, such as vertical extent, geographic distribution, interannual variability, and annual and diurnal cycles will be computed from the radar observations. Overshooting convection characteristics derived from the composited radar data will be compared with estimates based on satellite IR observations. To investigate the mechanisms responsible for cross-tropopause transport and to make quantitative estimates of stratosphere-troposphere exchange, numerical model simulations with explicitly resolved convection and chemistry will be carried out for case studies and for an entire warm season. The radar data will be used along with in situ trace gas observations from aircraft to evaluate the performance of the numerical simulations.Intellectual Merit:It is well known that convection in the extratropics can penetrate the tropopause and extend into the lower stratosphere, but there is little quantitative information about its geographic distribution, frequency of occurrence, or depth of penetration into the stratosphere. The radar analyses in this study will lead to a new regional climatology of overshooting convection in the midlatitudes based on direct geometric observations at high spatial and temporal resolution. The results will be compared with satellite IR estimates of overshooting, which offer the potential to extend the regional results to a global domain. High-resolution numerical simulations of overshooting convection will be used to investigate stratosphere-troposphere exchange mechanisms and to make quantitative estimates of the transport of important trace species.Broader Impacts:This research will produce a long-term, public, dataset of radar reflectivity over a large portion of the contiguous U.S. These data will be applicable to a wide range of other hydrometeorological problems. Since convection is not resolved in current global climate models, these studies will provide guidance for developing parameterizations of stratosphere-troposphere exchange due to overshooting convection. A better understanding of overshooting convection will help to reduce uncertainties in future climate projections, which is an important economic and social problem. In addition, diagnosing convective behavior and its impact on atmospheric chemistry will lead to an improved understanding of processes affecting air quality and human health, as both increases in tropospheric ozone and depletion of stratospheric ozone are possible in overshooting storms.