An overview of the upcoming 2010 Carbonaceous Aerosol and Radiative Effects Study (CARES) field campaign

Description

The primary objective of the Carbonaceous Aerosol and Radiative Effects Study (CARES) in 2010 is to investigate the evolution of carbonaceous aerosols of different types and their optical and hygroscopic properties in central California, with a focus on the Sacramento urban plume. Carbonaceous aerosol components, which include black carbon (BC), urban primary organic aerosols (POA), biomass burning aerosols, and secondary organic aerosols (SOA) from both urban and biogenic precursors, have been shown to play a major role in the direct and indirect radiative forcing of climate. However, significant knowledge gaps and uncertainties still exist in the process-level understanding of: (1) SOA formation, (2) BC mixing state evolution, and (3) the optical and hygroscopic properties of fresh and aged carbonaceous aerosols. Several specific science questions under these three topics will be addressed during CARES 2010. During summer the Sacramento-Blodgett Forest corridor effectively serves as a mesoscale (~100 km) daytime flow reactor in which the urban aerosols undergo significant aging as they are transported to the northeast by upslope flow. The CARES campaign observation strategy will consist of the U.S. DOE G-1 aircraft sampling upwind, within, and outside of the evolving Sacramento urban plume in the morning and again in the afternoon. The NASA B-200 aircraft carrying a High Spectral Resolution Lidar (HSRL) and a Research Scanning Polarimeter (RSP) will also be deployed to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties. The aircraft measurements will be complemented by a well-instrumented ground site within the Sacramento urban area and a downwind site in Cool, CA, to characterize the diurnal evolution of meteorological variables, trace gases/aerosol precursors, and aerosol composition and properties in freshly polluted and aged urban air. The sampling strategy during CARES will be coordinated, to the extent possible, with CalNex 2010, a major field campaign that is being planned in California in 2010 by CARB, NOAA, and CEC. In addition to obtaining new observation-based understanding from the anticipated field data, the CARES campaign strategy is centered on using the data in various focused model evaluation exercises, so that the resulting new knowledge can be integrated into regional and global climate-chemistry models.