Comparisons of WRF/Chem simulated O 3 concentrations in Mexico City with ground-based RAMA measurements during the MILAGRO period

Abstract

This work compares the WRF/Chem (Weather Research and Forecasting – Chemistry) simulated O 3 concentrations in the Mexico City Metropolitan Area (MCMA) with measurements from the ground-based RAMA network during the MILAGRO (Megacity Initiative: Local and Global Research Observations) period. The model resolves the observations reasonably well in terms of diurnal cycle and mean magnitude as reflected by high correlation coefficients and low root-mean-square errors. Stations located in the center of the MCMA generally exhibit higher correlation coefficients and lower model biases than those stations located in the peripheral of the MCMA. Large temporal variations in the observed and simulated O 3 concentrations are noted from station to station during the MILAGRO period. Sensitivity analyses of O 3 concentrations to changes in NO x and VOC emissions rates suggest that O 3 production in the MCMA is VOC-sensitive, and VOC-emissions reduction appears to be an effective strategy for reducing high surface O 3 concentrations in the MCMA.