AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Assessing the Accuracy of Parameterized Aerosol Extinction Estimates during the HAGiS (Hygroscopic Aerosol Growth in winter Study) Field Campaign
TIMOTHY GORDON, Nick Wagner, Bernard Mason, Ann M. Middlebrook, Charles Brock, Mathews Richardson, Frank Erdesz, Daniel Murphy, CU CIRES - NOAA ESRL
Abstract Number: 314 Working Group: Aerosols, Clouds, and Climate
Abstract In situ measurements of ambient aerosol extinction are essential for validating aerosol optical depth (AOD) estimates from ground-, lidar- and space-based remote sensors, which are in turn used to constrain earth system models. Typically, ambient extinction is calculated by multiplying measured dry extinction by a hygroscopic growth factor. Various growth factor parameterizations (e.g., the so-called gamma and kappa parameterizations) have been employed, but relatively few studies have assessed the closure between growth-factor derived ambient extinction and direct ambient extinction measurements. Furthermore, obtaining robust growth-factor derived extinction estimates in near-saturated conditions is notoriously difficult because these parameterizations asymptotically approach infinity. During the March-April 2015 HAGiS (Hygroscopic Aerosol Growth in winter Study) field campaign in Boulder, Colorado, direct ambient extinction measurements from a novel open-path aerosol extinction cavity ringdown spectrometer (AECRDS) were compared with different growth-factor derived extinction estimates from a closed-path AECRDS to evaluate the accuracy of these growth factor parameterizations. We present comparisons for a range of atmospheric conditions, including ambient humidities between 10%-100% and both organic- and inorganic-dominated aerosol.