Potential Influences of Aerosol Concentrations on Mode and Degree of Development in Mid-continental Convective Clouds during POLCAST4

The Polarimetric Cloud Analysis and Seeding Test (POLCAST4) field project was conducted during July 2012, focusing primarily on convective clouds in eastern North Dakota. Primary project objectives for POLCAST4 were: (1) to better understand the effects of cloud base hygroscopic cloud seeding on convective clouds; and (2) to better elucidate the microphysical processes, including interactions with aerosols, that are involved in the development (or lack of) of convective clouds in the Northern Plains. The project involved the University of North Dakota (UND) polarimetric Doppler weather radar, the KMVX Doppler radar (recently upgraded to dual-polarization capability) and in situ sampling from airborne and surface-based instrumentation.

While we expect this suite of observations to be useful for understanding cloud-aerosol interactions that play a role in development of continental convective clouds (as well as their suitability for seeding), greater understanding can be obtained by comparative analysis of these observations with simulations using a model that can incorporate aerosol physics and chemistry. The Weather Research and Forecasting Model with Chemistry (WRF-Chem) is one such model. WRF-Chem can also be effectively used as a means of examining the sensitivity of the results to changes in the aerosol concentration, composition and treatment of cloud-aerosol interactions. In this presentation, we will present preliminary results from WRF-Chem simulations for one or more cloud systems during the week of 8 July, validating the simulations against the cloud and aerosol properties derived from the in situ and dual-polarization radar observations. The results from the combined observational/modeling analysis will be used to make inferences regarding the role of aerosols in the evolution of the convective cloud system.