Sensitivities of Midlatitude Overshooting Convection, Above-Anvil Cirrus Plume Formation, and Irreversible Transport to the Lower Stratosphere Environment

Abstract:

Tropopause-overshooting convection in the midlatitudes can result in the injection of cloud material (and tropospheric air) into the lower stratosphere, at times resulting in expansive plumes of cirrus cloud residing above the anvil and observable in satellite imagery. These above anvil cirrus plumes (AACPs) have been studied for their importance as a link to severe weather and impacts on upper troposphere lower stratosphere (UTLS) composition. There is currently limited knowledge in how injection of lower tropospheric air and cloud material by convection (and the extent of AACPs) varies in different UTLS environments. This study uses the Bryan Cloud Model (CM1) to conduct a sensitivity study on AACP production and troposphere-to-stratosphere transport in overshooting convection to UTLS temperature (stability) and wind environments. Namely, four idealized CM1 supercell convection simulations are carried out in which the tropospheric environment is equivalent, but two of the environments contain a single tropopause and two a double tropopause. The two simulations for each tropopause environment differ in wind profile: one has a strong storm-relative jet in the LS, driving frequent gravity wave breaking and AACP formation, and the other a weak storm-relative jet, preventing gravity wave breaking and AACP formation. Here, AACP and troposphere-to-stratosphere transport sensitivity to tropopause environment are evaluated for the first time. Sensitivities to the wind profile within a single tropopause environment have been diagnosed in previous studies, but the evaluation of sensitivities to the wind profile within a double tropopause environment is also diagnosed for the first time.