29 January 2015

Aerosol Indirect Effect on the Grid-Scale Clouds in the Two-Way Coupled WRF–CMAQ


Atmospheric emissions from burning fossil fuels have impacts on both climate and air quality. These particles influence the climate directly, by scattering and absorbing incoming solar radiation and terrestrial outgoing radiation. They influence the climate indirectly by affecting cloud radiative properties through the aerosol role as cloud condensation nuclei and ice nuclei. A team of researchers, including Department of Energy scientists at Pacific Northwest National Laboratory, found that including indirect aerosol effect treatments in the Weather Research and Forecasting Community Multiscale Air Quality model (WRF-CMAQ) represents a significant advancement for studies modeling air quality and its interaction with regional climate. This improved modeling framework is also useful for investigating the impact of emission controls on the regional hydrological cycle and climate. The team implemented first, second, and glaciation aerosol indirect effects on resolved clouds in the two-way coupled WRF-CMAQ modeling system by including parameterizations for both cloud drop and ice number concentrations, based on CMAQ-predicted aerosol distributions and WRF meteorological conditions. They conducted the numerical experiments over the continental United States and compared simulations with satellite and in-situ observations. The results showed that including the aerosol indirect effect improves both air quality and meteorological simulations. This study shows that including the aerosol indirect effect is important for modeling air pollutants and also their interaction with the regional climate.