Implications of Sea Breeze Circulations on Boundary Layer Aerosols in the Southern Coastal Texas Region

Abstract. The Sea Breeze Circulation (SBC) influences atmospheric processes at multiple scales in coastal regions. Understanding how SBCs impact the aerosol number budget and aerosol impact on perturbation of incoming solar radiation is essential. This study investigates sea breeze-aerosol interactions (SAIs) during 46 summertime SBC events using data from the TRacking Aerosol Convection Interactions Experiment (TRACER) field campaign across rural and urban sites in southern Texas. Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) simulations complement observations to explore spatio-temporal meteorological controls on boundary layer aerosols. During the campaign, Sea Breeze Fronts (SBF) penetrating inland transported cool, moist air over the land, introducing air masses with distinct properties compared to the preexisting continental air. These SAIs cause variability in number concentrations of up to a factor of two, with events typically lasting ~5 hrs before returning to background conditions. SAI’s impact on aerosols varies with site’s proximity to the sea and the preceding sea breeze (SB) history, primarily affecting the marine-influenced accumulation mode. The coastal site reflects stronger marine influence, while the inland site reflects SB air masses that regain continental characteristics. Model outputs show that the regional SAIs extend ~50 km inland and reach up to the boundary layer height. SBC further influences the local aerosol radiative impacts by changing the aerosol number budget. SAIs modify cloud condensation nuclei in ~20 % of events during SBF passage. For the typical TRACER SBF passage, the local aerosol radiative forcing was also found to change by up to 40 %.