Optical and Chemical properties of atmospheric aerosols in California

Three aircraft field campaigns were performed in California: CALNEX based in Los Angeles area during May 2010, CARES based in Sacramento during June 2010 and CALWATER2011 based in Sacramento during February 2011. These studies demonstrated a large contrast in the aerosol properties between the northern and southern regions of California. Southern California, especially the Los Angeles basin, has a dense population and is a heavy polluted area, whereas northern California is less populated and has more rural regions, making it less polluted. The aerosol chemistry is strongly affected by these differences. In this study we compare the optical measurements of the aerosols (absorption and scattering coefficients, and therefore extinction coefficient), as well as the chemical composition of the single particles measured with an aerosol time-of-flight mass spectrometer (ATOFMS). A total of 18 flights during CALNEX, 22 flights during CARES, and 28 flights during CALWATER2011 have been analyzed and the fundamental differences in mixing state and sources and impact on optical properties are discussed. For comparison and validation purposed, we also have inferred mixing state from California aerosols using AERONET.