AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Biomass Burning as a Modulator of Droplet Number in the Southern Atlantic
MARY KACARAB, Steven Howell, Jennifer Griswold, Kenneth Thornhill, Rob Wood, Jens Redemann, Athanasios Nenes, Georgia Institute of Technology
Abstract Number: 286 Working Group: Aerosols, Clouds, and Climate
Abstract Aerosols play a significant role in local and global air quality and climate. Their ability to scatter and absorb radiation and to act as cloud condensation nuclei (CCN) has a substantial impact on the earth’s radiation balance and is a large source of uncertainty in global climate predictions. Biomass burning organic aerosol (BBOA) can drastically elevate CCN concentrations, but the response in cloud droplet number may be suppressed, or even reversed, due to low supersaturations that can develop from strong competition for water vapor (Bougiatioti et al. 2016). Understanding and constraining the magnitude of droplet response to biomass burning plumes is an important component of understanding aerosol-cloud interaction. The southeastern Atlantic (SEA) cloud deck provides a unique opportunity to study these cloud-BBOA interactions for marine stratocumulus, as it is overlain by a large, optically thick biomass burning aerosol plume from Southern Africa during the burning season. The interaction between these biomass burning aerosols and the SEA cloud deck is being investigated in the NASA ObseRvations of Aerosols above Clouds and their intEractionS (ORACLES) study. Measurements of CCN concentration, aerosol size distribution and composition, updraft velocities, and cloud droplet number in and around the SEA cloud deck and associated BBOA plume were taken aboard the NASA P-3 aircraft during the first and second years of the ORACLES study in September 2016 and August 2017. Here we evaluate the predicted and observed droplet number sensitivity to the aerosol fluctuations and quantify, using the data, the drivers of droplet number variability (vertical velocity or aerosol properties) as a function of biomass burning plume characteristics. This work seeks to contribute to an increased understanding of how CCN and aerosol properties affect the radiative and hydrological properties and impact of the cloud.