WRF/Chem modeling of atmospheric effects of aerosols from wildfires and volcanic eruptions

Description

We have developed tools to use WRF/Chem for modeling wildfire smoke and volcanic ash. Wildfire smoke: Models for biomass burning emission and wildfire plume rise implemented online in WRF/Chem have been used to study the impact of smoke aerosols on weather. Using test cases from the extreme Alaska wildfire year of 2004 with 6.6 millions of burned acres of mostly boreal forest, it was possible to show increased large numbers of cloud condensation nuclei (CCN) in areas with high concentration of fine particulate (PM2.5). WRF/Chem runs with wildfire smoke were compared to “clean air” reference runs and showed significant differences in temperature and humidity profiles as well as in precipitation amounts. Volcanic ash: A volcanic ash plume model has been included in the source generation package for WRF/Chem. The model includes eruption source parameters for 1535 volcanoes globally. Ash particles are organized in the model in 10 bins according to their size from small particles (< 3.9 μm) to large-sized particles up to 2 mm; an umbrella-shaped vertical ash distribution is assumed to initialize WRF/Chem. The model was used to successfully predict the dispersion of volcanic ash from the recent eruptions of Eyjafjallajökull in Iceland and Mount Redoubt in Alaska. Validated atmospheric dispersion models for aerosols resulting from volcanic eruptions as well as from large wildfires are key for improving climate models. We are in the process of validating our WRF/Chem applications using remote sensing satellite data, airborne data, and data from ground-based stations. Aerosol and radiation measurements from permanent, mobile, and aerial ARM Climate Research Facilities will be a main reference for future efforts determining the characteristics and properties of volcanic and smoke aerosols.