Overview of the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES)

Abstract

Substantial uncertainties still exist in the scientific understanding of the possible interactions between urban and natural (biogenic) emissions in the production and transformation of atmospheric aerosol and the resulting impact on climate change. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Carbonaceous Aerosol and Radiative Effects Study (CARES) carried out in June 2010 in Central Valley, California, was a comprehensive effort designed to improve this understanding. The primary objective of the field study was to investigate the evolution of secondary organic and black carbon aerosols and their climate-related properties in the Sacramento urban plume as it was routinely transported into the forested Sierra Nevada foothills area. Urban aerosols and trace gases experienced significant physical and chemical transformations as they mixed with the reactive biogenic hydrocarbons emitted from the forest. Two heavily-instrumented ground sites – one within the Sacramento urban area and another about 40 km to the northeast in the foothills area – were set up to characterize the evolution of meteorological variables, trace gases, aerosol precursors, aerosol size, composition, and climate-related properties in freshly polluted and "aged" urban air. On selected days, the DOE G-1 aircraft was deployed to make similar measurements upwind and across the evolving Sacramento plume in the morning and again in the afternoon. The NASA B-200 aircraft, carrying remote sensing instruments, was also deployed to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties within and around the plume. This overview provides: (a) the scientific background and motivation for the study, (b) the operational and logistical information pertinent to the execution of the study, (c) an overview of key observations and initial results from the aircraft and ground-based sampling platforms, and (d) a roadmap of planned data analyses and focused modeling efforts that will facilitate the integration of new knowledge into improved representations of key aerosol processes in climate models

Soot superaggregates from flaming wildfires and their direct radiative forcing

“…To investigate how commonly these SAs occur in different geographical locations and atmospheric conditions, we sampled aerosols contained in wildfire smoke-laden air masses over Sacramento during the CARES (Carbonaceous Aerosol and Radiative Effects Study)27 in June 2010 and over Mexico City as part of the MILAGRO (Megacity Initiative: Local And Global Research Observations)2829 study during March-June 2006. Finally, in 2011 at Los Alamos, we sampled the downwind plumes of the Las Conchas wildfire19, the second largest wildfire in the state's history.…”

“…The sampled air mass containing biomass burning smoke particles is believed to be transported from the neighboring Sierra Nevada foothills and San Joaquin County2757 (C) The Las Conchas fire was the second largest wildfire in the state history of New Mexico burning an area of 634 km 2 . The sampled smoke plumes from this fire for this study were mostly from smoldering phase mixed with intermittent flaming phase.…”

The Arm Climate Research Facility: A Review of Structure and Capabilities

“…These include the Radiative Heating in Underexplored Bands Campaign II (RHUBC-II; Turner and Mlawer 2010) in Chile, and the Carbonaceous Aerosols and Radiative Effects Study (CARES; Zaveri et al 2012) in California. ARM field campaigns are usually colocated with ARM sites; however, several campaigns have been carried out at alternate locations to study specific processes.…”

Composition and Sources of Particulate Matter Measured near Houston, TX: Anthropogenic-Biogenic Interactions

“…Contemporary sources include biomass burning and biogenic emissions, and they include the presence of 14 C. Fossil sources include combustion and non-combustion emission sources with depleted 14 C. Ambient PM 2.5 filter subsamples were taken for analysis to give~60 µg of total organic carbon [41] for measurement of the 14 C signal on the accelerator mass spectrometer. Subsamples were acidified over hydrochloric acid using a desiccator for 12 h to remove carbonate, and dried in a muffler oven at 60˝C for one hour.…”