Possible key aeolian erodibility factors in a norther area of the Gobi Desert, Mongolia
1, Masahide Ishizuka2, Batdelger Gantsetseg3, Buyantogtoh Batjargal3, Yutaka Yamada4, Masato Shinoda5, Masao Mikami6, Dulam Jugder3
1Arid Land Research Center, Tottori University, Tottori, Tottori, Japan, 2Kagawa University, Takamatsu, Kagawa, Japan, 3Information and Research Institute of Meteorology Hydrology and Environment, Ulaanbaatar, Mongolia, 4RIKEN, Wako, Saitama, Japan, 5Nagoya University, Nagoya, Aichi, Japan, 6Japan Meteorological Business Support Center, Chiyoda-ku, Tokyo, Japan
We are making a dust observation from March 2012 in Tsogt-Ovoo (TsO), Mongolia, which is located in the northern Gobi Desert. An analysis of synoptic data shows the highest frequency of dust occurrence at TsO in East Asia. This suggests that TsO is one of important dust sources in East Asia. Kurosaki and Mikami (2007 JGR) showed narrow seasonal variations of a threshold wind speed of dust occurrence in desert regions such as the Taklimakan Desert and the Gobi Desert using synoptic data. We also can expect a narrow seasonal variation of it at TsO because of small amounts of precipitation (98.3 mm/year) and vegetation. A vegetation cover was lower than 5% on July 2011. However, we can find a clear seasonal variation of it. This result suggests that we have some aeolian erodibility factors in TsO which strongly control threshold speed. Ishizuka et al. (2012 SOLA) and Abulaiti et al. (2014 Aeolian Res) reported drastic changes in threshold speed for periods of several weeks to several months from the data of our observation, and they are discussing roles of soil crust and soil freeze-thaw process. Satellite images have captured dust emissions from topographic depressions such as valley, foot of hill, and basin in Mongolia. We have a topographic depression in TsO, whose scale is about 20 km by 10 km. We obtained an observation result that the amount of sand saltation at a 10 cm-height was 150 to 200 times larger at a topographic depression than that at its surrounding for March 10 to April 22, 2015. A PM2.5 concentration was 5 to 10 times higher at the topographic depression than that at its surrounding in a dust event at April 22, 2015. This observation result suggests that this topographic depression is the major dust source in TsO. In this study, we will discuss role of aeolian erodibility factors mentioned as above on variations of threshold speed.