Cloud Condensation Nuclei Activity and Hygroscopicity of Fresh Biomass Burning Particles as a Function of Burning Conditions
MEGAN MOUTON, MarkieSha James, Kotiba A. Malek, Rudra Pokhrel, Marc Fiddler, Akua Asa-Awuku, Solomon Bililign,
North Carolina A&T State University Abstract Number: 145
Working Group: Aerosols, Clouds and Climate
AbstractThe hygroscopic growth of aerosol particles is of current interest due to their effects on light scattering and absorption properties of particles which thereby affect the air quality, visibility, Earth’s radiation, and the climate. Knowledge of hygroscopic properties is essential to prediction of the role of aerosol in cloud formation, regional visibility, and lung deposition.
In this work we measure and report aerosol hygroscopicity with different instrumental techniques and metrics. A widely used parameter is the aerosol particle size hygroscopic growth factor (GF) and is the ratio of the wet particle diameter (Dp,wet) at a high relative humidity (RH) to the corresponding dry diameter (Dp,dry). The aerosol optical hygroscopic enhancement factor (f(RH)) is defined as the ratio of aerosol optical properties (aerosol extinction, scattering, or backscattering coefficients) between wet and dry conditions and is also measured and reported. Most of the studies reported used surrogate components of complex aerosols. The application to complex multi-component aerosols like biomass burning aerosols is limited.
We report aerosol hygroscopicity parameter of biomass burning aerosols derived from African biomass fuels using a humidified smog chamber into ways: Measuring extinction hygroscopic enhancement factor f(RH) for dry and wet aerosols using a cavity ring down spectrometer and deriving the hygroscopicity parameter, and directly using a Cloud Condensation Nuclei Counter (CCNC). These measurements were also made at different burning conditions representing various burning stages ranging from smoldering dominated to flaming dominated burning conditions. Results indicate that the aerosol hygroscopicity is fuel and combustion condition dependent and that the measurement and subsaturated and supersaturated conditions show an evolving aerosol hygroscopicity.