A study of long‐term trends in mineral dust aerosol distributions in Asia using a general circulation model

Abstract

Dust events have been observed in Japan with high frequency since 2000. On the other hand, the frequency of dust storms is said to have decreased in the desert regions of China since about the middle of the 1970s. This study simulates dust storms and transportation of mineral dust aerosols in the east Asia region from 1981 to 2001 using an aerosol transport model, Spectral Radiation‐Transport Model for Aerosol Species (SPRINTARS), implemented in the Center for Climate System Research/National Institute for Environmental Studies atmospheric global circulation model, in order to investigate the main factors that control a dust event and its long‐term variation. The model was forced to simulate a real atmospheric condition by a nudging technique using European Centre for Medium‐Range Weather Forecasts reanalysis data on wind velocities, temperature, specific humidity, soil wetness, and snow depth. From a comparison between the long‐term change in the dust emission and model parameters, it is found that the wind speed near the surface level had a significant influence on the dust emission, and snow is also an important factor in the early spring dust emission. The simulated results suggested that dust emissions from northeast China have a great impact on dust mass concentration in downwind regions, such as the cities of northeastern China, Korea, and Japan. When the frequency of dust events was high in Japan, a low‐pressure system tended to develop over the northeast China region that caused strong winds. From 2000 to 2001 the simulated dust emission flux decreased in the Taklimakan desert and the northwestern part of China, while it increased in the Gobi desert and the northeastern part of China. Consequently, dust particles seem to be transported more from the latter region by prevailing westerlies in the springtime to downwind areas as actually observed. In spite of the similarity, however, there is still a large disagreement between observed and simulated dust frequencies and concentrations. A more realistic land surface and uplift mechanism of dust particles should be modeled to improve the model simulation. Desertification of the northeastern China region may be another reason for this disagreement.

Spatial distribution of dust's optical properties over the Sahara and Asia inferred from Moderate Resolution Imaging Spectroradiometer

“…As shown in Fig. 13, the dust source region in Mukai et al (2004) is in good agreement with the region identified as having large ω 0 values in our study. This region also corresponds to the Takla Makan and Gobi deserts on geological maps.…”

“…13 (Herman et al, 1997). Mukai et al (2004) also estimated that carbonaceous and dust aerosols were transported around the region with the blue box in Fig. 13.…”

“…To investigate the factors that cause the different features of ω 0 in Asia, we compare the spatial distribution of ω 0 to that of the dust emission flux as determined by Mukai et al (2004). The dust emission flux averaged over 1981in Mukai et al (2004 was estimated using a global aerosol transport model (Takemura et al, 2000(Takemura et al, , 2002a.…”

“…The dust emission flux averaged over 1981in Mukai et al (2004 was estimated using a global aerosol transport model (Takemura et al, 2000(Takemura et al, , 2002a. Figure 13 shows the region with large dust emissions in Fig.…”

“…Figure 13 shows the region with large dust emissions in Fig. 4 of Mukai et al (2004), which can be considered a dust source region and is indicated by red circles. This region is also consistent with the region containing the large vertical dust flux estimated in Kang et al (2011) on 30 March 2007.…”