The Role of Aerosol-Cloud-Radiation Interactions in Regional Air Quality – A NU-WRF Study Over the United States

Aerosol plays an integrated role in the Earth’s weather and climate system. It alters the atmospheric heating profiles through absorbing and/or scattering solar radiation that leads to changes in temperature, wind, and humidity. It also serves as cloud condensation nuclei and ice nuclei to modify cloud properties and precipitation. The aerosol-induced changes in local/regional weather pattern and planetary boundary layer structure would subsequently impact atmospheric composition and air quality. Before the advent of the fully coupled air quality models, the feedbacks among aerosol, cloud, and radiation (ACR) are often ignored, and the impact of such feedbacks on air quality is less understood.

The principle purpose of this work is to assess the impact of ACR interactions on U.S. regional air quality, focusing on ozone and PM2.5, using the NASA Unified WRF (NU-WRF) modeling system. NU-WRF builds on the community WRF model with integrations of several NASA components. Specifically it couples with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model to account for ACR effects explicitly. A series of three month long simulations spanning from spring to early summer, a season laden with both local and long-range transported aerosols, have been carried out to explore the effect of ACR interactions on U.S. air quality, in which the factor separation method has been applied in order to isolate the contribution from aerosol-radiation and aerosol-cloud effect.