Transport of Urban and Rural Boundary Layer Aerosol Particles within Deep Convective Storm Systems

Aerosol particles are integral to the development of deep convective storm systems through their effects on microphysical, dynamical, and radiative processes. Many significant sources of different types of aerosol particles are located in the boundary layer, but the degree to which the aerosols produced by these sources are transported into convective storms by convective cold pools, lower-level convergence, and other boundary layer processes is not well-understood. The goal of this study is to analyze the extent to which aerosols produced within the boundary layer by different mechanisms are entrained into deep convective systems, as well as to understand the spatial and temporal evolution of their distribution within these systems.

To address this goal, the release and subsequent transport of aerosols in both urban and rural regions are modeled using conserved, massless tracers in the Regional Atmospheric Modeling System (RAMS), a compressible non-hydrostatic cloud-resolving model. The tracers are neither microphysically nor radiatively active in order to specifically isolate the transport of these particles from subsequent feedback effects that they may have on storm development. Several storm morphologies, including deep isolated convection, supercells and squall lines, are simulated using high-resolution simulations (with vertical and horizontal grid spacings of 100 m). For each storm morphology, a number of sensitivity simulations are conducted in which the location, timing, release rates and magnitude of the aerosol sources are varied. The parameterization of these aerosol sources is guided by observations from three field campaigns: BioAerosols and Convective Storms (BACS), TRacking Aerosol Convection interactions ExpeRiment (TRACER), and Experiment of Sea breeze Convection, Aerosols, Precipitation, and Environment (ESCAPE). BACS examined the release and transport of bioaerosols by convective cold pools, while TRACER and ESCAPE focused on the impacts of urban and maritime aerosols on isolated storms developing around Houston. The use of data from these different field campaigns provides a physical basis from which to model the aerosol sources in both the urban and rural simulations. Quantification of the tracer budgets in different parts of the storm and how they vary as a function of aerosol source and storm morphology will be presented, and through this analysis the processes driving boundary-layer aerosol transport will be elucidated. Understanding the transport of these tracers within deep convective storms provides an important next step in our understanding of the relationship between boundary layer aerosol sources and subsequent storm-aerosol interactions.