Atmos. Chem. Phys. Discuss., 9, 1329-1376, 2009
© Author(s) 2009. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Comparisons of WRF/Chem simulations in Mexico City with ground-based RAMA measurements during the MILAGRO-2006 period
Y. Zhang1, M. K. Dubey2, and S. C. Olsen3
1Climate Impacts Group, University of Washington, Seattle, Washington, USA
2Earth and Environmental Science Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
3Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA

Abstract. Comparison of the WRF/Chem (Weather Research and Forecasting – Chemistry) model simulations at 3-km resolution with measurements from the ground-based RAMA monitoring network during the MCMA-2006/MILAGRO field campaign is presented. The model resolves reasonably well the observed surface temperature, relative humidity and wind speed; however, large discrepancies are identified between the simulated and the observed surface wind direction for wind speeds below 2 m s−1. The simulated chemical species concentrations (CO, O3, NO, NO2 and NOy) compare favorably with the observations with the notable exception of SO2. Simulated O3 concentrations agree especially well with the observations. The model performs much better during daytime than nighttime for both chemical species and meteorological variables, although the model tends to underestimate daytime temperature and overestimate nighttime relative humidity. It is noted that the simulated nocturnal planetary boundary layer (PBL) height using the Yonsei University PBL scheme is unrealistically low. However, no combination of the available PBL schemes and land surface models (LSMs) is distinctly better than the others in reproducing the observations. The simulated meteorological fields under the O3-South, O3-North and EI Norte weather episodes exhibit similar correlation coefficients and biases for the same variable. However, the model performs best for the O3-South episode and performs poorest for the El Norte events in resolving the observed chemical species.

Citation: Zhang, Y., Dubey, M. K., and Olsen, S. C.: Comparisons of WRF/Chem simulations in Mexico City with ground-based RAMA measurements during the MILAGRO-2006 period, Atmos. Chem. Phys. Discuss., 9, 1329-1376, doi:10.5194/acpd-9-1329-2009, 2009.
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