Abstract:

The southeast Atlantic Ocean provides an excellent natural laboratory to study aerosol-cloud and aerosol-radiation interactions, a large driver of uncertainty in climate projections. This region features near-permanent stratocumulus clouds and a massive persistent smoke source during the agricultural burning in the Austral winter. The physical and chemical evolution of the smoke, its transport, and its tendency to function as CCN in warm clouds all present important targets to constrain uncertainty in predictions of aerosol’s climate impacts.

To understand these important smoke processes, we compare observations from the ORACLES, CLARIFY, and LASIC field campaigns to two earth system models (CESM and E3SM) and a regional climate model (WRF-Chem-CAM5). Using airborne measurements of 3D-winds, clouds, and aerosols, we find that there is a strong sensitivity of modeled cloud droplet number concentration (CDNC) to marine boundary layer (MBL) turbulence, in both the mean turbulent updraft velocity and its distribution, which together drive CDNC biases in models. We also find that models are improved by parameterizing the observed photolytic oxidation of organic aerosol in the free-troposphere that drives chemical and physical aging. Boundary layer aerosol composition is also significantly influenced by marine by marine emissions of sulfate gases, even during extremely smoky periods. Finally, we will pivot to examine the potential for US wildfire emissions to be improved by analyzing Doppler weather radar data.