Impacts of Aerosols on UV Radiation and Ozone Formation and Analysis of Chemical Processes using a 3-D Chemical Transport Model in the Mexico City Metropolitan Area

The influence of aerosols on UV radiation is investigated by calculating the photolysis rate coefficients using the NCAR tropospheric ultraviolet and visible radiation model (TUV) constrained by aerosol extinction vertical profiles as well as other optical properties provided by Lidar and spectroradiometer observations. The calculated photolysis rates are validated by measured values for key species. The computed photolysis rates are incorporated into a 3-D chemical transport model CAMx (Environ) to assess the impacts of aerosols on O3 formation in the Mexico City Metropolitan Area. Understanding the chemical processes governing O3 formation and the sensitivity of O3 to emissions reductions is a key issue in formulating an effective O3 control strategy . We performed episodic simulations using the CAMx model and analyzed the chemical processes in terms of the budgets of free radicals, NOy and O3, and O3 production rate and efficiency, which gave us useful information about important chemical processes controlling O3 production and sensitivity to precursor reductions. We analyzed as well the effects of chemistry, transport and deposition on O3 production in Mexico City.