Ozone predictabilities due to meteorological uncertainties in Mexico City basin using ensemble forecasts

Abstract. The purpose of the present study is to investigate the sensitivity of ozone concentration ([O3]) predictions in Mexico City to meteorological initial uncertainties and planetary boundary layer (PBL) parameterization schemes using state-of-the-art meteorological and photochemical prediction models through ensemble forecasts. The simulated periods (3, 9, 15, and 29 March 2006), represent four typical meteorological episodes ("South-Venting", "O3-North", "O3-South" and "Convection-North", respectively) in the Mexico City basin during the MCMA-2006/MILAGRO campaign. Our results demonstrate that uncertainties in meteorological initial conditions have significant impacts on O3 predictions, including the peak time [O3], as well as the horizontal and vertical [O3] distributions, and temporal variations. The ensemble spread of the simulated peak [O3] averaged over the city's ambient monitoring sites can reach up to 10 ppb. The magnitude of the ensemble spreads varies with different PBL schemes and meteorological episodes. The uncertainties in O3 predictions caused by PBL schemes mainly come from their ability to represent the mixing layer height, but overall, these uncertainties are smaller than those from uncertainties in meteorological initial conditions.