3A: WRF-Chem Model Development

A major effort is underway to implement a new NCAR chemistry package (MOZART-T1), which builds on the MOZCART and MOZART-MOSAIC chemistry currently in WRF-Chem V3.9. The updated chemistry package (MOZART-T1) expands the chemistry to more explicitly treat aromatics and terpenes as well as heterogeneous chemistry on aerosols. Importantly, the MOZART-T1 chemistry package is a product of the Chemistry Café database that produces consistent chemical reaction mechanism input files for both WRF-Chem and CAM-Chem simulations.

As part of this effort, the Henry’s Law coefficients describing the ability of the trace gases to dissolve into water have been updated and now include dissolution of several organic compounds that were not previously part of the wet or dry deposition schemes. These coefficients are also part of the Chemistry Café database. In the updated chemistry package, these Henry’s Law constants are consistently used by different WRF-Chem subroutines describing dry deposition, wet deposition, and aqueous-phase chemistry in parameterized convection.

Other WRF-Chem development includes adding a suite of diagnostics, called integrated reaction rates (IRR). These diagnostics store the rates of each of the gas-phase reactions from the NCAR MOZART chemistry packages. The IRR diagnostics are written to a separate output file, which can then be analyzed. NCAR scientists are collaborating with William Vizuete (UNC) to use his process analysis tool, PERMM, which can calculate a variety of atmospheric chemistry metrics such as ozone production efficiency, “chain length” (number of cycles of using a radical, e.g. OH or NO, for producing ozone), and identify which volatile organic compounds are responsible for producing ozone.

Project Team: Mary Barth, Gabriele Pfister, Stacy Walters, Will Vizuete (UNC).