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MODELS-3/CMAQ APPLICATIONS WHICH ILLUSTRATE CAPABILITY AND FUNCTIONALITY
Citation:
LeDuc, S K., K L. Schere, J M. Godowitch, AND G L. Gipson. MODELS-3/CMAQ APPLICATIONS WHICH ILLUSTRATE CAPABILITY AND FUNCTIONALITY. Presented at Millennium NATO/CMS International Technical Meeting on Air Pollution Modeling and Its Application, Boulder, CO, May 15-19, 2000.
Impact/Purpose:
The goal of this task is to thoroughly characterize the performance of the emissions, meteorological and chemical/transport modeling components of the Models-3 system, with an emphasis on the chemical/transport model, CMAQ. Emissions-based models are composed of highly complex scientific hypotheses concerning natural processes that can be evaluated through comparison with observations, but not validated. Both performance and diagnostic evaluation together with sensitivity analyses are needed to establish credibility and build confidence within the client and scientific community in the simulations results for policy and scientific applications. The characterization of the performance of Models-3/CMAQ is also a tool for the model developers to identify aspects of the modeling system that require further improvement.
Description:
The Models-3/CMAQ developed by the U.S. Environmental Protections Agency (USEPA) is a third generation multiscale, multi-pollutant air quality modeling system within a high-level, object-oriented computer framework (Models-3). It has been available to the scientific community since July 1998 with annual releases since that date. The system was designed to be flexible and modular. The science has been documented (USEPA, 1999a) and a user guide prepared for the framework (USEPA, 1999b). Current users of Models-3/CMAQ have tried various options in their applications, some of which will be shared at the First Annual Models-3 Workshop to be held in June 2000 (http://www.epa.gov/asmdnerl/models3).
The Models-3/CMAQ has considerable capability at this time. The user may select from multiple chemical mechanisms which are provided as well as edit or revise those mechanisms. Two chemical mechanisms have been evaluated thus far in Models-3/CMAQ: RADM2 and Carbon Bond IV. Emissions for these mechanisms are generated using the Models-3 Emission Processing and Projection System (MEPPS). MEPPS can be executed using the framework "Study Planner" (USEPA, 1999b) which directs and monitors multiple execution steps. MEPPS which invokes both SAS and ARC/INFO can also be executed outside the framework. Emission control strategies can be developed within the MEPPS or can be created outside MEPPS by adjusting emission files. The latter approach was used to simulate uniform emission reductions as described on the poster. A Plume-in-Grid capability is also available in Models-3/CMAQ which contains a Lagrangian reactive plume model to simulate subgrid scale pollutant plumes from major point sources within an Eulerian grid. Plume concentrations are integrated into the concentration in a grid cell after the plume segment reaches model grid size.
Open-source visualization tools, Vis5D (http://www.ssec.wisc.edu/ billh/vis5d.html), PAVE
(http://envpro.ncsc.org/OTAGDC/pave_letter.html) and Data Explorer (DX), (http://www.research.ibm.com/dci/software.html) are integrated into the Models-3/CMAQ and are used for analyzing and displaying the results. Evaluations of the accuracy and patterns of the simulations have been done using SAS.
The Model-3 framework requires either a Sun workstation, Windows NT on a PC, or Silicon Graphics workstation. The framework Study Planner allows for model simulations to be conducted on computer platforms other than the one running the framework. The science codes will execute on other computing platforms and model execution can be performed on various platforms by using scripts without the Models-3 framework. However, the user must manually make changes in the script that would otherwise be made by the framework. Cray computers, both vector and parallel, have been successfully used with the standalone scripts as well as with the Study Planner in the system framework.