A42B-04
Source Attribution of Observed Absorption Profiles During the Two Column Aerosol Project (TCAP) Using a Regional Model
Thursday, 17 December 2015: 11:05
3004 (Moscone West)
Jerome D Fast1, Larry K Berg1, Duli Chand1, Richard Anthony Ferrare2, Connor Joseph Flynn3, Chris A Hostetler2, Jens Redemann4, Arthur J Sedlacek III5, John Shilling1, Yohei Shinozuka6, Jason M Tomlinson1 and Alla Zelenyuk1, (1)Pacific Northwest National Laboratory, Richland, WA, United States, (2)NASA Langley Research Center, Hampton, VA, United States, (3)PNNL, Richland, VA, United States, (4)NASA Ames Research Center, Moffett Field, CA, United States, (5)Brookhaven National Lab, Upton, NY, United States, (6)Bay Area Environmental Research Institute Sonoma, Sonoma, CA, United States
Abstract:
Relatively large uncertainties remain in climate model predictions of absorption resulting from black carbon (BC) and brown carbon (BrC). In this study, we focus on comparing simulated profiles of BC, biomass burning aerosols, absorption, and other aerosol optical properties obtained from the regional WRF-Chem model with in situ and remote sensing measurements made during the Department of Energy’s Two-Column Aerosol Project (TCAP). TCAP was designed to investigate changes in aerosol mixing state, aerosol radiative forcing, CCN concentration, and cloud-aerosol interactions in two atmospheric columns: one over Cape Cod, Massachusetts and another located approximately 200 km to the east over the ocean. Measurements from the NASA second-generation airborne High Resolution Spectral Lidar reveal the presence distinct aerosol layers associated with the marine boundary layer, residual layer transported over the ocean and in the free troposphere. Analyses of SP2 and aerosol optical measurements indicate that particles in the free troposphere were more ‘aged’ and had a lower single scattering albebo than for aerosol layers at lower altitudes; however, BC concentrations aloft were lower in the free troposphere. Instead, particle classes derived from the miniSPLAT single particle measurements suggest that the increased absorption aloft may be due biomass burning aerosols. The model suggests that ambient winds likely transported smoke from large wildfires in central Canada as well as smoke from other fires into the sampling domain. The simulated percentage of biomass burning aerosols was consistent with the miniSPLAT data, but the model currently treats all organic matter as non-absorbing. Therefore, we perform sensitivity simulations to examine how the model’s absorption and AOD responds to assumptions used for BrC associated with biomass burning and whether the predicted profiles agree with absorption data and wavelength dependent AOD data from 4STAR.
