Characteristics of near-surface wind speed and sand-dust flux at northeast edge of Ulan Buh Desert

Abstract: Deserts are the main source of dust storms in the surface layer, aeolian sand-dust transport is a serious problem in many arid and semi-arid regions in the world, and it is considered to be a significant part of global biogeochemical cycle. Aeolian dust transport processes are closely related to the variation of the height of near-surface horizontal and deposition dust flux. Ulan Buh Desert is one of the 8 largest deserts in China, and is also one of the important dust source regions in northern China. In this paper, fixed monitoring stations were set up in both the desert-oasis ecotone and the oasis at the northeast edge of Ulan Buh Desert, the near-surface (0-50 m) wind speed and sand-dust flux data obtained from the dust observation tower at the Inner Mongolia Dengkou Desert Ecosystem Research Station of the State Forestry Administration in 2013 were analyzed to reveal the spatio-temporal variation characteristics of wind speed and sand-dust flux at the northeast edge of Ulan Buh Desert. The results showed as follows: 1) Both the average wind speed of the year and the average wind speed of different seasons of the near-surface layer in both desert-oasis ecotone and oasis increased with the increase of the height, and the wind speed profile characteristics could be expressed by power exponential function. The wind speed in the desert-oasis ecotone was significantly higher than that in the oasis. 2) The near-surface horizontal sand-dust flux and dust-falling amount in both desert-oasis ecotone and oasis decreased with the increase of the height, and the distribution characteristics also accorded with power exponential function. The horizontal sand-dust flux in the oasis-desert ecotone was significantly higher than that in the oasis, which obviously indicated that the protection forest in the oasis has the effects of weakening the transportation of sand dust. The horizontal sand-dust flux and dust-falling amount in the desert-oasis ecotone had a linear correlation relationship, while the horizontal sand-dust flux and dust-falling amount in the oasis showed an exponent relationship. 3) The variation characteristics of horizontal sand-dust flux and dust-falling amount in the artificial oasis and the oasis-desert ecotone were gradually decreased with the increase of the height in the 4 seasons of a year, the horizontal sand-dust flux and dust-falling amount were concentrated in spring, followed by summer, while those in autumn and winter were relatively low; the horizontal dust flux and the dust-falling amount of oasis-desert transition belt were significantly higher than the inner oasis. The horizontal dust flux and dust-falling amount in the oasis-desert ecotone were significantly higher than that in the oasis in all 4 seasons of a year. The results reveal the spatio-temporal variation rules of near-surface wind speed and sand-dust activity, and illuminate the mechanism of the effects of oasis protection forest on weakening surface wind speed and sand-dust activities, which can help to provide a theoretical basis and reference for the desertification combating and the establishment of oasis protection forest.