Transpacific transport of mineral dust: its impact in the United States

Duncan Fairlie
NASA Langley Research Center

Mineral dust in the atmosphere has important consequences for climate, tropical storm development, air quality, chemical composition, and the biosphere. Here, we examine the mobilization and transpacific transport of mineral dust from Asia, and its impact on aerosol concentrations in the United States. We use observations from ground stations, aircraft, and satellite platforms, interpreted using a global three-dimensional chemical transport model (GEOS-Chem) in which we have represented dust mobilization, transport, and deposition. We find that the best simulation of North American surface observations is achieved when we restrict dust sources to year-round arid areas, but include a significant wind threshold for mobilization. The model captures the seasonal cycle in surface dust concentrations over the northern Pacific, the outflow of dust from Asia in the free troposphere, and the timing and distribution of Asian dust outbreaks in the United States in spring 2001. We find that Asian dust persists in surface air in the West beyond episodic spring outbreaks, and accounts for 40% of the worst visibility days due to dust in the West in 2001. We discuss the consequences for the EPA Regional Haze Rule. We also consider the potential impact of climate change and land management practices on dust mobilization in Asia and its transpacific transport.