Black Carbon From Wildfires Shown to Warm Southern California Skies

RELATED TO: A51J-08 • FRIDAY, DEC. 18, 9:45 A.M. • MOSCONE SOUTH 309 "THE EFFECT OF WILDFIRES ON ATMOSPHERIC HEATING RATES AS MEASURED BY UNMANNED AIRCRAFT" As wildfires raged through California in July 2008, a pair of specially outfitted aircraft flying in formation recorded the effects of the airborne particles produced by the blazes, making an unprecedented profile of the atmospheric effects of black carbon around one of the country's largest urban centers. Scripps Institution of Oceanography, UC San Diego scientists will present results from the California AUAV Air Pollution Profiling Study (CAPPS), which deployed autonomous unmanned aerial vehicles (AUAVs) to gather meteorological data between April 2008 and September 2009. The project sought to evaluate how long-range transport of pollutants including ozone, soot and other particulates mix with local pollution and influence air quality and regional climate. Most of the flights originated at Edwards Air Force Base near Rosamond, Calif. in the Mojave Desert. For the first time-direct measurements of the heating rate over California and the heating rate from wildfire plumes were directly measured by utilizing the ability of AUAVs to fly in precise stacked formations. Scripps scientist Craig Corrigan said that data from the two stacked AUAVs, flying through regionally disperse smoke plumes, suggested that particulates in the air over the base contributed an additional 0.6 degree Celsius per day of heating in the lowest three kilometers (~10,000 feet) of the atmosphere. An unmanned aircraft passes the face of a crescent moon during a CAPPS data-gathering flight. "Our absorption data suggested that 80 percent of the aerosol heating came from black carbon, or dark soot, and 20 percent from dust and light-absorbing organic carbon," Corrigan said. Scripps Atmospheric and Climate Sciences Professor V. Ramanathan, lead scientist of the California Energy Commission-funded study, said the direct measurements of atmospheric heating by soot from wild fires link such fires with regional climate and climate change, and is in part due to details of Southern California climate and meteorology, which is influenced by its dry weather and its tendency to trap rather than export smog. Those factors could make it especially prone to climate change consequences of air pollution such as accelerated snowmelt and dimming at ground level; however, additional measurements are needed before definitive conclusions can be made, he said. CAPPS represents another successful use by Ramanathan's team of AUAVs to gather meteorological data. The researchers revolutionized the gathering of atmospheric data in 2006 when they first successfully deployed the aircraft in the Maldives AUAV Campaign (MAC). Miniaturized instruments on the aircraft, which typically flew in formations of three, measured a range of properties such as the quantity and size of the aerosols on which cloud droplets form. The instruments also recorded variables such as temperature, humidity and the intensity of light that permeates clouds and masses of smog. It was the first time such comprehensive measurements were made at a cost that was very low relative to traditional manned flights. Subsequently the aircraft have been deployed in other locations around the world, including during the 2008 Summer Olympics in Beijing, during which authorities enacted strict anti-smog measures around the city. The California Energy Commission's Public Interest Energy Research (PIER) program will employ CAPPS results in an analysis of the potential future economic and ecological consequences of Southern California air pollution. Scientists also hope to combine CAPPS results with satellite data to better understand the role of aerosols at a larger regional scale. "As we learn more about the air we breathe and seek solutions to reduce greenhouse gases, this important atmospheric research will help us address the serious challenges to California's water resources, ecology and the health of our residents," said California Energy Commissioner Arthur Rosenfeld. "With this study, California continues to demonstrate its commitment as a national leader in climate change research." • Video related to the project is available. • For more information see Scripps explorations magazine story: http://explorations.ucsd.edu/Research_Highlights/2008/May/CAPPS/