Transpacific
transport of mineral dust: its impact in the United States
Duncan
Fairlie
NASA
Langley Research Center
Abstract:
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.