AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Evaluating Simulated Profiles of Aerosol Optical Properties Using Measurements Collected during the Two Column Aerosol Project (TCAP)
JEROME FAST, Larry Berg, Jerome Barnard, Duli Chand, Richard Ferrare, Connor Flynn, Chris Hostetler, Arthur J. Sedlacek, John Shilling, Jason Tomlinson, Alla Zelenyuk, Pacific Northwest National Laboratory
Abstract Number: 408 Working Group: Aerosols, Clouds, and Climate
Abstract Relatively large uncertainties remain in climate model predictions of aerosol radiative forcing. Climate models are usually evaluated using column-integrated measurements collected by instruments at the surface or from satellites because measured profiles of aerosol optical properties are limited. Adequately simulating the vertical distribution of aerosols and their effect on the radiation budget is also important since it affects how the meteorological conditions respond to aerosol radiative effects. In this study, we compare simulated profiles of aerosol optical properties obtained from the WRF-Chem model with those obtained from both in situ and remote sensing measurements during the Department of Energy’s (DOE) Two-Column Aerosol Project (TCAP). TCAP was designed to investigate changes in aerosol mixing state, CCN concentration, aerosol radiative forcing, and cloud-aerosol interactions in two atmospheric columns: one over Cape Cod, Massachusetts and another located approximately 200 km to the east. TCAP was the first science mission for the Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) spectrometer and the second generation downward looking High Spectral Resolution Lidar (HSRL-2). Two types of simulations are performed, the first with predicted aerosols and the second in which aerosol mass, composition, and size distribution measurements are used to drive the aerosol optical property module. Differences in scattering and absorption are quantified between the second simulation and the measurements will arise from assumptions employed by the aerosol optical property module (e.g. mixing rule, refractive indices, internal versus external mixing state). By comparing the results of the two types of simulations, we can identify the factors that contribute to errors in simulated optical depth, single scattering albedo, and angstrom exponent that are used by radiation modules. The model is also used to investigate reasons for changes in aerosol properties between the two columns, as aging alters aerosol optical properties as they are transported over the ocean.