The Observed Impact of the Upper Tropospheric/Lower Stratospheric Thermodynamic Environment on Overshooting Top Characteristics during the RELAMPAGO-CACTI Field Campaign

Abstract

Overshooting tops (OTs) are manifestations of deep convective updrafts that extend above the tropopause into the stratosphere. They can induce dynamic perturbations and result in irreversible transport of aerosols, water vapor and other mass from the troposphere into the stratosphere, thereby impacting the chemical composition and radiative processes of the stratosphere. These and other effects of OTs depend on their characteristics such as depth and area, which are understood to connect to mid-tropospheric updraft speed and width, respectively. Less understood is how static stability in the upper troposphere/lower stratosphere (UTLS) potentially modulates these OT–updraft connections, thus motivating the current study. Here, UTLS static stability and observed OT characteristics are quantified and compared using a combination of reanalysis data, observed rawinsonde data and geostationary satellite data. A strong relationship between OT depth and UTLS lapse rate and Brunt-Väisälä frequency N2 (R > 0.9, < -0.9, respectively) is found, implying that OT depth is reduced with an increasingly stable UTLS. In contrast, a weak relationship (R > 0.5) is found between OT area and UTLS static stability, implying that OT area is controlled primarily by mid to upper tropospheric updraft area. OT duration has a weak relationship to UTLS lapse rate and N2 (R = -0.27, 0.27, respectively). These relationships may be useful in describing mid- and low-level storm dynamics from satellite-observed characteristics of OTs in near real-time.