WRF/Chem Analyses and Comparisons With In Situ, Aircraft and Satellite Data During MILAGRO

During March 2006, the Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign was conducted over the Mexico City area in collaboration with several national and international agencies. The main objective of MILAGRO was to conduct measurements of Mexico City gaseous pollutants (CO, O3, NOx, SO2, etc.) and aerosol particles (PM2.5, PM10), and to study the atmospheric processes leading to the formation of secondary aerosols from precursor gases, and the transport and transformation of these gases and aerosols on local, regional, and global scales. Coordinated aircraft-based and ground-based measurements were made during MILAGRO supported by extensive satellite observations and modeling activities at various scales. The goal of this study is to examine and compare fully coupled WRF/Chem (Weather Research and Forecasting Chemistry) model simulations at 3-km resolution with in situ, aircraft and satellite data during MILAGRO. Emissions inventories from NCAR and PNNL are used for this study. Preliminary analyses suggest that the model simulations during workdays agree reasonably well with observations in terms of pollutant concentrations and diurnal cycles when the PNNL emissions inventory is used; however, the model tends to overestimate the pollutant concentrations when using the NCAR emissions inventory. On weekends and holidays, appreciable discrepancies are noted between the model simulations and observations using either of the emissions inventories, pointing to the need for weekend and workday specific emissions inventories. Work is underway to constrain Mexico City emissions using formaldehyde (HCHO) and NO2 measurements from the Ozone Monitoring Instrument (OMI) on NASA's EOS-Aura satellite. In this study, we will also discuss emissions control strategies for alleviating pollution problems in Mexico City based on model sensitivity results.