Radiative Impact of Observed and Simulated Aerosol Layers Over the East Coast of North America

Wednesday, 17 December 2014
Larry K Berg1, Jerome D Fast2, Sharon P Burton3, Duli Chand4, Jennifer M Comstock2, Richard Anthony Ferrare3, Johnathan W Hair3, Chris A Hostetler3, John Hubbe4, Evgueni Kassianov4, Raymond R Rogers3, Arthur J Sedlacek III5, John E Shilling4, Jason M Tomlinson1, Jacqueline Mary Wilson6 and Alla Zelenyuk4, (1)Pacific Northwest National Lab, Richland, WA, United States, (2)Pacific Northwest Natl Lab, Richland, WA, United States, (3)NASA Langley Research Center, Hampton, VA, United States, (4)Pacific Northwest National Laboratory, Richland, WA, United States, (5)Brookhaven National Lab, Upton, NY, United States, (6)Battelle Pacific Northwest, Richland, WA, United States
The vertical distribution of particles in the atmospheric column can have a large impact on the radiative forcing and cloud microphysics. A recent climatology constructed using data collected by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) suggests elevated layers of aerosol are quite common near the North American east coast during both winter and summer. The Two-Column Aerosol Project (TCAP), conducted from June 2012 through June 2013, was a unique study utilizing both in situ and remotely sensed measurements designed to provide a comprehensive data set that can be used to investigate science questions related to aerosol radiative forcing and the vertical distribution of aerosol. The study sampled the atmosphere at a number of altitudes within two atmospheric columns; one located near the coast of North America (over Cape Cod, MA) and a second over the Atlantic Ocean several hundred kilometers from the coast. TCAP included the yearlong deployment of the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) located at the base of the Cape Cod column, as well as summer and winter aircraft intensive observation periods (IOPs) using the ARM Aerial Facility. One important finding from the TCAP summer IOP is the relatively common occurrence (during four of the six nearly cloud-free flights) of elevated aerosol layers in both the Cape Cod and maritime columns that were detected using the nadir pointing second-generation NASA Langley Research Center High-Spectral Resolution Lidar (HSRL-2). These elevated layers contributed up to 60% of the total observed aerosol optical depth (AOD). Many of these layers were also intercepted by the aircraft configured for in situ sampling, and the aerosol in the layers was found to have increased amounts of biomass burning material and nitrate compared to aerosol found near the surface. Both the in situ and remote sensing observations have been compared to simulations from the regional Weather Research and Forecasting model coupled with chemistry (WRF-Chem). The model simulated the observed layers well in some cases, but in other instances there were differences in the altitude, mass loading, and aerosol water associated with regional scale transport and the representation of the aerosol lifecycle.