5.2 Improvements to the Noah land surface model in WRF-CMAQ, and its application to future changes in the Chesapeake Bay region

Campbell, Patrick, Jesse Bash, Chris Nolte, and Tanya Spero, U.S. Environmental Protection Agency

Regional, state, and local environmental regulatory agencies often use Eulerian meteorological and air quality models to investigate the potential impacts of climate, emissions, and land use changes on nutrient loading and air quality. The Noah land surface model in WRF can be used with the Community Multiscale Air Quality (CMAQ) model for such investigations, but WRF/Noah does not output all of the data required by CMAQ. In this work, we modified Noah in WRFv3.8.1 to improve its linkage to CMAQv5.2 by adding variables from WRF/Noah to the WRF output, updating the WRF soil and vegetation reference tables that influence CMAQ wet and dry photochemical deposition processes, and decreasing WRF/Noah's top soil layer depth to be consistent with CMAQ's dust and bi-directional ammonia emission modules. In this presentation we will show that the modified WRF/Noah-CMAQ can meet or improve model performance for near surface temperature, 10-m wind speed, sensible heat flux, and ambient concentrations of ozone and sulfur dioxide compared to the default WRF/Noah-CMAQ. Finally, we apply the modified WRF/Noah-CMAQ system to dynamically downscaled climate change and emissions, and present projected impacts on meteorology, air quality, and nitrogen deposition in the Chesapeake Bay region in the 2050s.