Sensitivity of Convective Cloud Properties and Evolution to Model Physics during ESCAPE: Case Studies

The lifecycle of convective clouds, from initiation to maturity and eventually to dissipation, is driven by a combination of thermodynamic, microphysical and radiative processes that are strongly coupled. To improve our understanding of the lifecycle of convection and aerosol-cloud interactions in deep convective clouds, the Experiment of Sea breeze Convection, Aerosols, Precipitation and Environment (ESCAPE) field campaign took place around the Houston area in June 2022. An ensemble of high-resolution Weather Research and Forecasting (WRF) model simulations was performed for the entire period of ESCAPE. To closely examine the sensitivity of convection to model physics, additional sets of WRF simulations with higher output frequency (10-min) were conducted for 2 selected cases determined by the convection type, location and timing of convection initiation. The two cases are June 2 and 16, 2022, which are representative of convections triggered by a frontal system and the sea breeze circulation, respectively.

For the June 16 case, the WRF simulations demonstrated substantial sensitivity to both the planetary boundary layer (PBL) schemes and initial forcings. While for the June 2 case, in addition to sensitivity to the PBL and initial forcings, sensitivity to the microphysics scheme was also evident. To elucidate the mechanisms underlying these sensitivities, the model simulations were compared to various observational products including NCEP/EMC Stage IV precipitation, MRMS radar observations, and airborne instrumentations collected during the campaign. Moreover, cloud cell tracking was performed both on the model simulations and MRMS data to better understand errors in the timing and location of convection initiation, as well as how the convective cloud structures compared between the model simulations and observations.