Campaign : Carbonaceous Aerosol and Radiative Effects Study (CARES)

June 15, 2010 to July 15, 2010

Lead Scientist : Rahul Zaveri

Scientific Focus

The objective of the CARES campaign is to investigate the evolution of organic aerosol and black carbon mixing state and their effects on optical and hygroscopic properties.

Relevancy to ARM

The CARES campaign strategy is centered on making field measurements of different types of atmospheric carbonaceous aerosols and their climate-affecting properties, and 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.

Description of Proposed Campaign

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 (BBA), 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. Light absorption by organic aerosols in the near-UV spectrum was discovered to be a very important part of the radiation budget in a past ASP field campaign, although many questions remain. Several specific science questions under these three topics will be addressed during CARES 2010. 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. 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 the California Air Resources Board (CARB), the National Oceanic and Atmospheric Administration (NOAA), and the California Energy Commission (CEC).

During summer, the Sacramento urban plume transport is controlled by highly consistent, terrain-driven upslope winds that draw polluted air to the northeast over the oak and pine trees in the Blodgett Forest area by late afternoon. The Sacramento-Blodgett Forest corridor therefore effectively serves as a mesoscale (~100 km) daytime flow reactor in which the urban aerosols undergo significant aging due to coagulation, condensation, and photochemical processes. The CARES campaign observation strategy will therefore consist of the 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 possibly 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 source area and a downwind receptor site near 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. As opportunity allows, one or more NOAA P-3 aircraft flights will be carried out in the Sacramento plume in coordination with the G-1 flights to allow wing-tip to wing-tip inter-comparison and provide valuable additional measurements for CARES. The P-3 measurements throughout California will provide a regional context for CARES. The resulting datasets will lend themselves to focused model evaluation exercises, including local radiative and CCN closures; constrained Lagrangian modeling of SOA formation, aerosol size and composition evolution, and black carbon aging; and 3-D Eulerian modeling of radiative feedback of aerosols on meteorology and regional climate.

The second objective during CARES will be to take advantage of any natural wildfires in the vicinity to study the evolution and properties of biomass burning aerosol. Occurrence of natural wildfires is very likely all over the Central Valley during June/July. Thus, the location and timing of the CARES 2010 campaign will allow us to target such an opportunity when it arises.

ARM Resources Needed to Support Campaign

An excel file containing the lists of ACRF and additional instruments requested for the G1 aircraft and two ground sites has been emailed to Dr. Beat Schmid, PNNL.

Additional Information

The NASA B-200 aircraft carrying a High Spectral Resolution Lidar (HSRL) and possibly a Research Scanning Polarimeter (RSP) will be deployed along with the G1 aircraft during CARES 2010. The purpose of the B-200 will be to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties.

Aircraft

The NASA B-200 aircraft carrying a High Spectral Resolution Lidar (HSRL) and possibly a Research Scanning Polarimeter (RSP) will be deployed along with the G1 aircraft during CARES 2010. The purpose of the B-200 will be to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties.

Other Contacts

Co-Investigators
William Shaw
Daniel Cziczo