The overarching goal of this prject is to advance the understanding of the processes impacting regional and global climate change and air quality. This will be accomplished by addressing 5 subgoals: 1) Measurement of the 4D distribution of NO2, HCHO, CO, SO2, glyoxal, the greenhouse gases CH4, N2O, CO2, and aerosol extinction from Mt. Wilson, 2) Development and application of novel methods to simulate and assimilate trace gas slant column densities into regional 3D models. 3) Determination of the emissions of NOx, VOC, CO, CH4, and tentatively N2O in the Los Angeles basin during CalNex 2010, 4) Study of the transport of pollutants and greenhouse gases in and out of the Los Angeles Basin, and 5) Quantification of the trace gas levels and chemistry above the Southern Californian boundary layer. A novel approach to monitor the spatial distribution of greenhouse gases and air pollutants using remote sensing measurements in the UV-vis and the near IR from an mountain location 1.7km above the LA basin will be developed and applied. The data will be analyzed with novel tools to simulate the measured path integrated absorption with a chemical transport model, assimilate the data into the model, and employ adjoint techniques to derive quantitative information. With this combined observational/modeling approach a number of science objectives identified in the CalNex 2010 white-paper will be addressed.