3E: WRF-Chem Model Development

Three major developments were added to the community version of WRF-Chem (v4.0). One of the developments is a new chemistry package (T1-MOZCART), which expands the MOZART gas chemistry to better represent aromatics, terpenes, and heterogeneous chemistry. Comparisons of hourly surface ozone mixing ratios between this new chemistry package and those based on its previous version over the western U.S. show reductions in ozone of up to about 3 ppb (see Figure 1). The second development is the update of the Henry’s Law coefficients, which are important for removal of trace gases by precipitation, for the NCAR MOZART suite of chemistry options in WRF-Chem. The third development is the addition of diagnostics of integrated reaction rates (IRR) to WRF-Chem (v4.0) for MOZART chemistry packages so that analysis of ozone production, along with other atmospheric chemistry metrics, can be performed.

A new tool, EPA_ANTHRO_EMIS, was developed to create WRF-Chem emission input files directly from the Sparse Matrix Operator Kernel (SMOKE) Modeling System output. In collaboration with the U.S. EPA, the most recent 2014 US EPA National Emission Inventory (NEI) anthropogenic emissions (v2) are made available with the EPA_ANTHRO_EMIS tool. U.S. NEI emission inventories are challenging to use in WRF-Chem because they require running SMOKE (a rather elaborate effort) and then converting the created emissions to WRF-Chem compatible format. Through this new tool and the collaboration with the U.S. EPA it is now easy for a user to include the NEI 2014 in WRF-Chem simulations and its updates, and new NEI developments can be made quickly available to the WRF-Chem user community.

Plots of surface ozone.

Figure 1.

Top row: Surface Ozone (ppb) in T1_MOZCART (new chemistry option)

 


Middle row: Surface Ozone (ppb) in MOZCART

 


Bottom row: Difference in Surface Ozone (ppb) for T1_MOZCART-MOZCART

 


Project Team: Mary Barth, Gabriele Pfister, Stacy Walters, Will Vizuete (UNC), Stuart McKeen (NOAA/ESRL), Alison Eyth (U.S. EPA) and Barron H. Henderson (U.S. EPA).