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Atmospheric Science & Global Change


photo collage depicting the types of particulates being modeled

What is WRF-Chem?

The Weather Research and Forecasting (WRF) model is a next generation meteorological model being developed collaboratively among several agencies (NOAA/NCEP, NOAA/ESRL, NCAR). WRF-Chem is a version of WRF that also simultaneously simulates the emission, turbulent mixing, transport, transformation, and fate of trace gases and aerosols. The WRF Atmospheric Chemistry Working Group is guiding the development of WRF-Chem.

Take a Tour of the WRF-Chem tutorials or contact for documentation describing how to use PNNL modules in WRF-Chem


  • Integrate WRF-Chem simulations and a wide range of field campaign measurements to develop a better understanding of local and regional-scale evolution of particulates and aerosol radiative forcing that are sub-grid scale processes for global climate models
  • Employ the modeling framework of WRF-Chem to develop new treatments of aerosol processes for global climate models
  • Perform process studies investigating aerosol aging, aerosol-cloud interactions, and aerosol radiative forcing
  • Explore the feasibility of using a version of WRF-Chem as a regional climate model


As part of an internal PNNL project, the trace gas and aerosol chemistry modules of the PNNL Eulerian Gas and Aerosol Scalable Unified System (PEGASUS) [Fast et al., 2002; 2006] were implemented into the WRF framework during 2004 and 2005. An "off-line" coupling of meteorology and chemistry is employed in PEGASUS so that the meteorological fields are read from files at specified time intervals; however, the "on-line" coupling of meteorology and chemistry in WRF more accurately represents of the evolution of trace gases and aerosols and permits the inclusion of feedback processes important for climate applications. Aerosol-radiation-cloud feedback processes, cloud chemistry, and cloud-aerosol interactions were incorporated into WRF-Chem during 2005 and 2006. Merging chemistry and aerosol process modules into the WRF framework have enabled PNNL scientists to better understand the uncertainties associated with aerosol radiative forcing and the impact of aerosols on clouds, distribute PNNL research among the scientific community, and promote collaborative activities with other research groups.


Atmospheric Science & Global Change

Fundamental & Computational Sciences