Six Years of Aerosol Optical Hygroscopic Growth Measurements from the ARM Southern Great Plains Site: Parameter Variability and Uncertainty

 

Authors

John A. Ogren — NOAA - Earth System Research Laboratory
Anne Jefferson — NOAA- Earth System Research Laboratory
Derek Hageman — NOAA- Earth System Research Laboratory
Hadi Morrow — NOAA - Earth System Research Laboratory

Category

General Topics – Aerosol

Description

Aerosol growth from the uptake of water substantially influences direct radiative forcing. Enhanced growth from water increases the aerosol extinction, asymmetry parameter and single scattering albedo. The magnitude of this growth depends on the aerosol composition as well as its phase and the ambient RH. We report on six years of aerosol scattering hygroscopic growth, fRH, from 2009-2014 from the ARM Southern Great Plains site, SGP. The analysis includes the variability of fRH with other aerosol optical properties; sampling conditions, and season. Because of the susceptibility of these measurements to instrument design and sampling conditions we include a statistical, Monte-Carlo analysis together with the combined standard uncertainty of the instruments to estimate the measurement quality over a range of scattering coefficients. fRH was found to increase with decreasing aerosol size, increasing single scatter albedo and the ambient RH. No distinct seasonal trend was observed. The largest contribution to the measurement uncertainty is attributed to noise in the nephelometer scattering coefficient.