Inter-relationships between convectively generated cold pools, updraft/downdraft characteristics, and microphysical processes

 

Authors

Robert Jeff Trapp — University of Illinois at Urbana-Champaign
Steve Nesbitt — University of Illinois at Urbana-Champaign
Sonia Lasher-Trapp — University of Illinois at Urbana-Champaign
Paloma Borque — Pacific Northwest National Laboratory
Geoff Marion — UIUC
Holly Mallinson — University of Illinois at Urbana-Champaign

Category

Convective clouds, including aerosol interactions

Description

Understanding the processes controlling the characteristics of convective cold pools, and properly representing those processes in meteorological models, is imperative for improving weather and climate prediction. The main goal of this work is to identify basic inter-relationships between cold pool properties, updraft/downdraft characteristics, and microphysical processes. This study is based on the convective event that occurred on 23 May 2011 during MC3E. Analyses of the MC3E data, Oklahoma Mesonet observations, and NEXRAD, DOE-ARM, and NASA radar data were utilized, as were real-data simulations of this event using the WRF model. In addition, idealized numerical modeling of the case, using CM1 initialized with MC3E soundings and CCN data from the SGP site, were performed to study detailed microphysical processes that could not be directly observed in situ. Analysis of reflectivity composites from KTLX and KVNX radars, and of surface temperature, humidity, and wind from both the Oklahoma Mesonet and the DOE-ARM stations, led to the satisfactory detection of cold pools, some as strong as -10K, which agree with model simulated cold pool intensity. Different cold pool detection techniques were evaluated and corroborated manually with data from the NEXRAD, DOE-ARM and NASA radars. RHI scans from C-SAPR provided further information on the vertical structure of the cold pool at fine vertical resolution, as well as on attendant kinematic and hydrometeor evolution of the convective clouds in the cross-section plane. These results are compared with the numerical modeling results, which also demonstrate the evolution of sublimating, melting and then evaporating hydrometeors in the downdrafts. The potential role(s) of hydrometeor evolution on cold pool characteristics, and subsequent feedbacks into the convective evolution and the formation of new convection, were also explored via hydrometeor classification from the KVNX polarimetric datasets, and in detailed analysis of hydrometeor latent cooling terms within the idealized simulations. In addition, overshooting top depth and area from GOES-13 data were related to kinematic and microphysical processes in the storms to establish physical linkages between low- and upper-level draft structure as hypothesized by Trapp et al. (2017, JAS). Finally, GOES-13 data were analyzed over the entire MC3E campaign to relate overshooting tops to environmental characteristics as observed by the ARM sounding network.