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We have studied the Asian dust emitted from a hotspot in the Gobi Desert by a lidar network, analyses of Himawari-8 Dust RGB and meteorological fields, and a field survey since 2013. We found a remarkable dust hotspot in the Gobi Desert by the filed survey and analysis. The Himawari-8 Dust RGB imagery shows that the dust storm occurred in an orographic convergence zone sandwiched between the Khangai, Altai, and Gurvan Saikhan Mountains in the Gobi Desert. The lidar network operating in Dalanzadgad, Sainshand, and Zamyn-Uud, Mongolia shows a dust layer development over the Gobi Desert in association with a cold frontal system and the long-range transport of the dust. We estimated the massextinction conversion factor MECF (g m-2) from simultaneous observations using an optical particle counter (OPC) installed on a tethered balloon and a ceilometer in the Gobi Desert. The MECF values decreased from the Asian dust source (Dalanzadgad 1.91 g m-2) to the lee-side areas (e.g., Tsukuba 1.18 g m-2) due to the gravitational settling of large dust particles.

A lidar network captured the evolution of a dust layer in the Gobi Desert on 22–23 May 2013. The lidar network consists of a ceilometer and two AD-Net lidars in Mongolia. The dust layer was generated by a strong wind due to a cold front and elevated over the surface of the cold front by an updraft of the warm air in the cold-front system. It was evolving from the atmospheric boundary layer to the free troposphere while moving 600 km through the desert with the cold front.

Asian dust is transported over a long range via the mid-latitude westerlies when dust is lifted to the free troposphere over the source regions, whereas dust remaining in the atmospheric boundary layer is not transported far. In the Gobi Desert, a major source region of Asian dust, a ceilometer (compact lidar) monitors the vertical distribution of dust at Dalanzadgad, Mongolia. On 29-30 April 2015, the ceilometer observed a developed dust storm over the ground, followed by a dust layer within a height of 1.2-1.8 km. The dust storm had already developed in the upwind region before reaching Dalanzadgad. This feature was also shown in the ceilometer observation data. The dust layer remained at almost the same height for 12 h, because the dust became trapped within an inversion layer at a height of 1.2-1.5 km over cold air. This result suggests that the inversion layer prevented the dust from reaching the free troposphere, thereby restraining the long-range transport of the dust via the westerlies. This is the first paper that reports this type of vertical distribution of dust in the source region based on observation data. [ABSTRACT FROM AUTHOR]

The Gobi Desert is one of the major sources of Asian dust, which influences the climate system both directly and indirectly through its long-range transport by the westerlies. In this desert, three ground-based lidars are operated in Dalanzadgad, Sainshand, and Zamyn-Uud, Mongolia. This study firstly combined these lidars into a lidar network and shows the spatial development of a dust layer over the desert and the long-range transport of the dust during 22-23 May 2013 via the lidar network. During this dust event, a cold front accompanying an extratropical cyclone moved southeastward across the desert and sequentially passed through Dalanzadgad, Sainshand, and Zamyn-Uud. In Dalanzadgad, in the central part of the desert, a dust storm occurred owing to the strong wind (6-10 m s-1) associated with the cold front and reached a top height of 1.6 km. Some of the dust floated at a height of 0.9-1.6 km along the cold frontal surface. In Sainshand and Zamyn-Uud, in the eastern part of the desert, the dust layer extended from the atmospheric boundary layer (ABL) to the free troposphere in the updraft region of warm air in the cold frontal system. Overall, while the dust layer was moving across the desert with the cold frontal system, it was developing up to the free troposphere. The mechanism of this development can be explained by the combination of two processes as follows: (1) the continuous emission of dust from the desert surface to the ABL by the strong wind around the cold front and (2) the continuous transport of the dust from the ABL to the free troposphere by the updraft of the warm air in the cold frontal system. This mechanism can contribute to the long-range transport of dust by the westerlies in the free troposphere. [ABSTRACT FROM AUTHOR]

A dust event occurred in the Gobi Desert on 22-23 May 2013 due to strong wind reaching a speed of 16 m s-1. The strong wind was caused by a developing low pressure system and a cold front. The vertical structures of the dust layer and cold frontal system were observed by a ceilometer installed at Dalanzadgad, Mongolia, which is located in the central part of the Gobi Desert. The dust layer had extended over the ground surface for 12 hours, and its top height reached 1.8 km above ground level (AGL). During the dust event, the cold front passed, and the cold air mass replaced the warm air mass. The top height of the cold air mass was less than 1.8 km AGL. In addition, the observational results suggest that some dust was transported from the atmospheric boundary layer to the free troposphere by the warm air ascending along the surface of the cold front. [ABSTRACT FROM AUTHOR]