Global Model Simulations of the Transport of Asian and Sahara Dust: Total Deposition of Dust Mass in Japan

We simulated the global transport of dust emitted from all major dust source regions on earth by using a global three-dimensional chemical transport model for the year 2000. A modified dust emission flux scheme and an advanced nonlocal diffusion scheme for accurately determining the atmospheric eddy diffusivity in the atmospheric boundary layer were implemented to improve the chemical transport model. We specifically examined and analyzed dust storms that occurred in China and northern Africa. Four scenarios representing the global transport of dust from dust storms originating in the Loess region and the Gobi, Takla Makan, and Sahara deserts, respectively, were simulated. The results of each scenario were then compared with those resulting from all major dust source regions on earth, to identify which deserts have a major impact on dust transport and its deposition in Japan. The dust from the Sahara desert, most from the western part that was found in this study, reached Japan in 9–10 days, while Gobi and Loess region dust took 2 to 3 days, and 4 days for Takla Makan dust. The model-calculated monthly total deposition of dust mass from all major dust source regions was compared with comprehensive measurements of total deposition collected at sampling stations distributed over Japan, and good agreement was generally found. From these analyses, it was also indicated that dust emitted from other deserts, including the Turkestan, Iranian, and Arabian, could have a significant impact on dust deposition on Japan.