Excess reactive nitrogen can have detrimental effect for the environment, including eutrophication, greenhouse gas effect, over-fertilization, particulate matter formation and so on. In this study, the Weather Research and Forecasting (WRF) model is used to provide inputs to Chemical Transport Models, which will be used to estimate atmospheric particle matter concentrations and reactive nitrogen deposition over Midwest USA. One-way nesting is used at a spatial resolution of 4 km x 4 km for a nested domain. A separate run with a coarser spatial resolution (12 km x 12 km) was also completed. Such comparison is of interest to investigate how spatial resolution affects the predictions of WRF.

North American Meso-scale Forecast System data from National Oceanic and Atmospheric Administration are used as the lateral and boundary conditions. Surface observation data are incorporated to improve the first guess of model predication using objective analysis. Different physics schemes available in WRF model are tested to identify the best combination for Midwest USA. Finally, the WRF model predications will be compared with weather stations data to check the reliability of the WRF model.