New Method Improves Simulation of Dust Particles over Western United States
Dust from soils is an important “natural” source of aerosols, contributing a major portion of aerosol scattering (cooling) and absorption (warming) of solar radiation. However, capturing the correct source amount and sizes of aerosols as the wind blows dust from different soil and desert sources into the atmosphere is a challenge in climate models. A multi-institutional team, including a U.S. Department of Energy scientist from Pacific Northwest National Laboratory, applied a new particle size distribution (PSD) of emitted dust, improving previous estimates of remote dust contributions. The new PSD is based on a simple, but physical fragmentation relation and is constrained using measured sizes. Fine surface particulate matter in the western United States is influenced not only by local sources, but also by trans-Pacific transport of Asian and African dust, with Asian dust contributing between 0.2 and 1.0 mg/m3 in the spring. The new PSD was applied to the GEOS-Chem chemical transport model and applied globally to all dust source regions. The team found that the new PSD for emitted dust in the GEOS-Chem model reduced large discrepancies between the simulated surface-level fine dust amount measured in the western United States. They also improved the ratio of fine to coarse dust, something that simply adjusting the total dust emissions did not accomplish. The model with the new PSD better simulates fine dust surface concentrations in the western United States, which is important when considering sources contributing to non-attainment of air quality standards, as well as for simulating climate and hydrological changes.
Zhang, L., J. Kok, D. Henze, Q. Li, and C. Zhao. 2013. “Improving Simulations of Fine Dust Surface Concentrations over the Western United States by Optimizing the Particle Size Distribution,” Geophysical Research Letters 40(12), 3270–75. DOI: 10.1002/grl.50591.