Primary Biological Aerosol Particles (PBAPs): modeling at Southeast and Southern Brazil cloud physics processes using BRAMS

Abstract

Destructive hailstorms have caused significant damages to agriculture and infrastructure in Brazil, with losses over 2 billion reais in the last decade. Numerous studies suggest that extreme rainfall events in South-Southeastern Brazil, the most hail-prone region in the country, can be produced by mesoscale convective complexes, extratropical cyclones, and heat and moisture transport, especially by the South American low-level jet. However, aerosol particles that have the ability to act as Cloud Condensation Nuclei (CCN) or Ice Nuclei (IN) such as Primary Biological Aerosol Particles (PBAPs) have not been taken into account in those studies, and their impacts on the formation of severe storms with hail precipitation remain challenging. An analysis combining model simulations for aerosol-cloud interactions with field experiments is therefore essential to handle the research question here proposed. The Brazilian Regional Atmospheric Modeling System (BRAMS) model coupled with the two-moment cloud microphysics schemes RAMS/CSU and Thompson, and the Weather Research and Forecasting (WRF) model coupled with the Spectral-Bin Microphysics (SBM) scheme will be used as modeling tools to account for cloud and aerosol lifecycle processes associated with the formation of severe storms and hail formation. Aerosol composition and size distribution data collected during aerosol sampling campaigns will be used as input parameters in the microphysics and aerosol modules to properly represent the observed conditions. In order to quantify the impact of aerosol activation processes on ice formation, model simulations with different prescribed aerosol data (initial concentrations, homogeneous or heterogeneous fields, etc.) will be compared and evaluated against satellite-based and aircraft observations. (AU)