Measurements of pollutants and their spatial distributions over the Los Angeles Basin

Despite great progress in mitigating air pollution in the past few decades, the Los Angeles Basin is still facing significant air quality problems. The ability to monitor air pollution levels throughout the South Coast Air Basin is very important, and until now has been limited to ground monitoring stations. However this approach lacks significant spatial coverage, and is limited to surface observations which are often affected by local emissions. There is a pressing need to conduct long-term continuous observations with greater spatial coverage. In this presentation we show initial results of Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of pollutants from the California Laboratory for Atmospheric Remote Sensing (CLARS) at Mt. Wilson Observatory overlooking the Los Angeles Basin. Capable of pointing in any direction, the UCLA MAX-DOAS instrument can map out the spatial distributions of pollutants and aerosol extinction over the Los Angeles air basin by measuring the column densities of trace gases from solar radiation reflected at the ground and scattered light from the sky. Positioning of the instrument on top of a mountain overlooking the entire LA basin provides a unique setting for long-term continuous monitoring of the region. During the CalNex field campaign in May and June of 2010, the MAX-DOAS conducted measurements of the spatial and temporal distributions of NO2, HCHO, glyoxal, and aerosol extinction (through O4 measurements) in the Los Angeles basin. Here we present column densities of these trace gases and discuss how our observations can greatly improve our ability to monitor concentrations, emissions and distributions of trace gases throughout the Los Angeles Basin. Preliminary comparisons with column results from the WRF-Chem model simulations will also be shown.