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Meteorological Models
For air quality modeling purposes, meteorological grid models are used in conjunction with chemical transport models to provide gridded output of chemical species and/or pollutant data. Meteorological models use physical formulations and parameterizations to simulate atmospheric processes and their change with time. These meteorological parameters are calculated at distinct spatially equidistant points over an area of interest which is called a grid. When these models are applied in a retrospective mode (i.e. modeling a past event) they are able to blend ambient data with model predictions via four-dimensional data assimilation, thereby yielding temporal and spatially complete data sets that are grounded by actual observations.
There are several commonly-used meteorological grid models that can develop inputs for air quality models. These grid models differ in their simulation of atmospheric processes but each produce gridded meteorological parameters. There are also several post-processors which are needed to convert the raw meteorological modeling output to suitable air quality model input. A few of the most commonly used meteorological models and post-processors are briefly described below.
The EPA's Air Quality Modeling Group has completed modeling applications for several years over multiple domains. Those gridded meteorological data which have been used in an EPA rulemaking are available from EPA as described below, along with documentation describing the methodology and evaluation of these simulations.
| Gridded Meteorological Models and Post-Processors |
MM5 The Fifth-Generation Penn State University / National Center for Atmospheric Research mesoscale model (commonly referred to as MM5) is a frequently-used meteorological model for historical episodes. It is a limited-area, nonhydrostatic, terrain-following sigma-coordinate model designed to simulate or predict mesoscale and regional-scale atmospheric circulations. Databases 2001 Continental U.S. MM5 at 36 km resolution 2001 Eastern U.S. MM5 at 12 km resolution 2002 Continental U.S. MM5 at 36 km resolution 2002 Eastern U.S. MM5 at 12 km resolution 2002 Western U.S. MM5 at 12 km resolution (from Western Regional Air Partnership (WRAP)) 2005 Continental U.S. MM5 at 36 km resolution 2005 Eastern U.S. MM5 at 12 km resolution 2005 Western U.S. MM5 at 12 km resolution Documentation Comparison of MM5 Model Estimates for February and July 2001 Using Alternative Input Databases Annual Application of MM5 to the Continental U.S. for 2001: Modeling Protocol Annual Application of MM5 to the Continental U.S. for 2001: Final Report and Evaluation Annual Application of MM5 for Calendar Year 2001 at 12 km Resolution 12 km Model Performance Evaluation for an Annual MM5 Simulation Regional and Local-scale Evaluation of 2002 MM5 Meteorological Fields for various Air Quality Modeling Applications Regional and Local Scale Evaluation of MM5 Meteorological Fields for various Air Quality Modeling Applications Draft Final Report: Annual 2002 MM5 Meteorological Modeling to Support Regional Haze Modeling of the Western United States Meteorological Modeling Performance Evaluation for the Annual 2005 Continental U.S. 36-km Domain Simulation Meteorological Modeling Performance Evaluation for the Annual 2005 Eastern U.S. 12-km Domain Simulation Meteorological Modeling Performance Evaluation for the Annual 2005 Western U.S. 12-km Domain Simulation |
| WRF Over the next few years it is expected that both real-time and historical meteorological modeling will begin to use the Weather Research and Forecast (WRF) modeling system. This state-of-the-art system will serve as an update to MM5. It is designed to be a flexible, state-of-the-art atmospheric simulation system that is portable and efficient on available parallel computing platforms. WRF is suitable for use in a broad range of applications across scales ranging from meters to thousands of kilometers. |
| MCIP EPA developed the Meteorology-Chemistry Interface Processor (MCIP) tool to convert MM5 and WRF output into CMAQ input. Because most meteorological models are not built for air quality modeling purposes, MCIP deals with issues related to data format translation, conversion of units of parameters, diagnostic estimations of parameters not provided, extraction of data for appropriate window domains, and reconstruction of meteorological data on different grid and layer structures. MCIP provides a complete set of meteorological data needed for CMAQ air quality simulations. |
Note about available data: At present, only the 2001 and 2002 datasets are available. EPA's preferred approach of distributing the data is as follows: First, send an e-mail to Pat Dolwick (dolwick.pat@epa.gov) requesting the specific dataset(s) you are interested in with a brief description of your intended use of these data. Second, send an external hard drive (USB or USB/Firewire combo) or drives to EPA w/ enough space to write the data. The process takes about 1-2 weeks for each 36km dataset and 2-3 weeks for each 12km dataset. The eastern U.S. 12km datasets are ~ 1.4 Tbytes per year. The continental U.S. 36km datasets are ~ 450 Gbytes per year. (We can provide details on how to access the western U.S. 2002 data.) EPA does not presently have the capability of extracting subsets of the data in terms of specific variables or geographic subdomains. It may be possible to extract subsets of the data in terms of time periods, though this will be handled on a case-by-case basis.