Seven Years of Aerosol Scattering Hygroscopic Growth from SGP: the relationship to aerosol size, optical properties and chemistry
Author
Anne Jefferson — NOAA- Earth System Research Laboratory
Category
Microphysics (cloud and/or aerosol)
Description
Hygroscopic growth fit parameter gamma plotted against the aerosol organic mass fraction. The colors indicate the ratio of inorganic nitrate to sulfate ions. Fit lines are for each denomination of nitrate/sulfate mass ratio.
Aerosol extinction is closely coupled to the ambient relative humidity with the aerosol water uptake and hence size and extinction increasing with RH. This enhancement in the extinction coefficient strongly influences the direct radiative forcing via changes in the aerosol optical depth, asymmetry parameter, and single scattering albedo. In addition, changes in relative humidity can modify the gas to aerosol partitioning of semi-volatile compounds and moderate aqueous reactions within the aerosol that significantly alter the aerosol mass and optical properties. We present long-term measurements of aerosol scattering hygroscopic growth from the Southern Great Plains (SGP) site in Lamont, OK. The hygroscopic growth is closely coupled to aerosol chemistry, ambient relative humidity and size; factors that also control the aerosol phase and morphology. These relationships along with changes in the aerosol optical properties can be a tool to predict aerosol hygroscopic growth in environments with a limited range of measurements or low aerosol loading with high measurement uncertainty.
