Evaluating the influence of deep convection on tropopause thermodynamics and lower stratospheric water vapor: A RELAMPAGO case study using the WRF model

Abstract

Troposphere to stratosphere exchange is generally driven by deep convection capable of overshooting tropospheric materials contributing to stratospheric chemistry. The La Plata Basin region in South America is known for organized deep convection and mesoscale convective systems. This study employs the Weather Research and Forecasting model to simulate deep convection during the RELAMPAGO field campaign in Argentina. This work investigates upper troposphere – lower stratosphere (UTLS) thermodynamics, specifically double tropopause events, and identifies lower stratospheric hydration related to deep convection. Results show that lower stratospheric hydration occurred during two organized convective types, a mesoscale convective complex (MCC) and squall line, which coincided with strong low level jet moisture transport. However, the lower stratosphere was not hydrated during discrete cells. While UTLS moisture was present in all three convective types, during the discrete cell, ice and water vapor were mixed, inhibiting net positive buoyancy and the transport of tropospheric material aloft. During the MCC and squall line events, UTLS moisture was stratified. A dry layer in the tropopause was collocated with an ice layer where net positive buoyancy contributed to stratospheric hydration as high as 20 km.