The impact of transpacific transport of mineral dust in the United States |
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| Institution: | 1. Key Laboratory of Atmospheric Chemistry of CMA, Institute of Atmospheric Composition, Chinese Academy of Meteorological Sciences, Beijing 100081, China;2. College of Earth Science, University of Chinese Academy of Sciences, Beijing 100081, China;3. National Meteorological Center, CMA, Beijing 100081, China;4. Nanjing University of Information Science & Technology, Nanjing 210044, China;1. Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089, China;2. Environmental Meteorology Forecast Center of Beijing–Tianjin–Hebei, China Meteorological Administration, Beijing 100089, China;3. China Meteorological Administration, Beijing 100081, China;4. Beijing Municipal Meteorological Observatory, Beijing 100081, China;1. State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China;2. School of Resources and Environmental Engineering, Lu Dong University, Yantai 264025, China |
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| Abstract: | We use a global chemical transport model (GEOS-Chem) to estimate the impact of transpacific transport of mineral dust on aerosol concentrations in North America during 2001. We have implemented two dust mobilization schemes in the model (GOCART and DEAD) and find that the best simulation of North American surface observations with GEOS-Chem is achieved by combining the topographic source used in GOCART with the entrainment scheme used in DEAD. This combination restricts dust emissions to year-round arid areas but includes a significant wind threshold for dust mobilization. The model captures the magnitude and seasonal cycle of observed surface dust concentrations over the northern Pacific. It simulates the free tropospheric outflow of dust from Asia observed in the TRACE-P and ACE-Asia aircraft campaigns of spring 2001. It reproduces the timing and distribution of Asian dust outbreaks in North America during April–May. Beyond these outbreaks we find persistent Asian fine dust (averaging 1.2 μg m?3) in surface air over the western United States in spring, with much weaker influence (0.25 μg m?3) in summer and fall. Asian influence over the eastern United States is 30–50% lower. We find that transpacific sources accounted for 41% of the worst dust days in the western United States in 2001. |
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