Sensitivity of regional meteorology and atmospheric composition during the DISCOVER-AQ period to subgrid-scale cloud-radiation interactions

Monday, 15 December 2014
Xinzhou Huang1, Dale J Allen1, Jerold Allen Herwehe2, Kiran V Alapaty2, Christopher Loughner3,4 and Kenneth E Pickering1,4, (1)University of Maryland College Park, College Park, MD, United States, (2)U.S. Environmental Protection Agency, Durham, NC, United States, (3)Earth System Science Interdisciplinary Center, COLLEGE PARK, MD, United States, (4)NASA Goddard Space Flight Center, Greenbelt, MD, United States
Subgrid-scale cloudiness directly influences global and regional atmospheric radiation budgets by attenuating shortwave radiation, leading to suppressed convection, decreased surface precipitation as well as other meteorological parameter changes. We use the latest version of WRF (v3.6, Apr 2014), which incorporates the Kain-Fritsch (KF) convective parameterization to provide subgrid-scale cloud fraction and condensate feedback to the rapid radiative transfer model-global (RRTMG) shortwave and longwave radiation schemes. We apply the KF scheme to simulate the DISCOVER-AQ Maryland field campaign (July 2011), and compare the sensitivity of meteorological parameters to the control run that does not include subgrid cloudiness. Furthermore, we will examine the chemical impact from subgrid cloudiness using a regional chemical transport model (CMAQ). There are several meteorological parameters influenced by subgrid cumulus clouds that are very important to air quality modeling, including changes in surface temperature that impact biogenic emission rates; changes in PBL depth that affect pollutant concentrations; and changes in surface humidity levels that impact peroxide-related reactions. Additionally, subgrid cumulus clouds directly impact air pollutant concentrations by modulating photochemistry and vertical mixing. Finally, we will compare with DISCOVER-AQ flight observation data and evaluate how well this off-line CMAQ simulation driven by WRF with the KF scheme simulates the effects of regional convection on atmospheric composition.