Photochemical models are widely used to determine the level of VOC and NOx emissions reductions required to attain the National Ambient Air Quality Standard for ozone (O3). Modeled O3 concentrations, (O3), are affected by photochemical production of O3, by NOx and VOC precursor emissions, and by meteorological processes that included horizontal transport, vertical mixing, cloud effects on actinic flux, and deposition of O3 and its precursors. In this study, the authors conduct a series of sensitivity experiments with the Regional Acid Deposition Model (RADM) using changes in meteorological inputs, such as PBL height and cloud effects, to examine their impact on (O3) and on O3 production efficiency. Using each of these modified meteorology scenarios as a 'base case' the authors then evaluate the effect of meteorology on the effectiveness of emissions controls by running additional model simulations with 15% and 50% reductions in NOx or VOC emissions.