Impacts of Vertically Varying Aerosol Layers on MCS Cold Pool and Precipitation Processes

Each year during the Northern Hemisphere springtime, aerosol particles sourced from widespread biomass burning in Central America are lofted and transported at various altitudes into the Southern Great Plains of the United States, where they can interact with cloud systems. Of the cloud systems that are prevalent in the Southern Great Plains, mesoscale convective systems (MCSs) play one of the most important roles in the regional hydrological and energy cycles. As such, it is important to assess the impacts of these elevated aerosol layers on MCS development.

To accomplish this goal, cloud-resolving model simulations of two MCS events that transpired during the Midlatitude Continental Convective Cloud Experiment (MC3E) were performed using the Regional Atmospheric Modeling System (RAMS). For each MCS event, three simulations were completed with varying initial aerosol profiles. Specifically, the three initial aerosol profiles have the same vertically integrated aerosol mass and number, but have peak aerosol concentrations at three different elevations – the surface, 1 kilometer above ground level (AGL) and 5 kilometers AGL, respectively. These profiles were based on data from the Navy Aerosol Analysis and Prediction System (NAAPS).

Results from the six simulations are intercompared to assess aerosol-MCS interactions. Initial results demonstrate that MCSs ingest higher concentrations of aerosol particles in simulations with peak aerosol concentrations near the surface. However, the entrainment of aerosol particles at middle and upper tropospheric levels also provides a significant source of aerosol particles for the MCS at localized elevations. Aerosol particles act as cloud condensation and ice nuclei, and therefore, aerosol concentrations and ingestion locations will impact the microphysics and resulting dynamics of the simulated MCSs. Changes in microphysical and dynamical processes between simulations will be presented with a focus on understanding how vertically varying aerosol layers impact MCS cold pool and precipitation feedbacks.