塔中地区一次沙尘暴过程的输沙通量估算

Estimation of Sand Transport Flux during a Sandstorm in Tazhong

以塔克拉玛干沙漠腹地塔中地区为研究区,对2008年7月19日11:29～23:56时一次沙尘暴天气过程进行野外实时输沙观测,利用经典输沙经验公式,对此次沙尘天气的输沙通量进行估算。确定了塔中地区的临界摩擦速度为0.24m/s,建立了塔中地区2m高度风速与输沙率的关系,发现Lettau输沙率公式的计算结果与实测值最为接近,塔中地区此次沙尘暴发生期间的水平输沙通量和垂直输沙通量分别为258.67×10-4kg/(m·s),40.07×10-7kg/(m2·s)。

Wind erosion occurs in many arid,semiarid and agricultural areas in the world. It is an environmental process affected by geological and climatic conditions and human activities. In general,wind erosion leads to land degradation in agricultural areas and has a negative impact on air quality. Long-distance dust emission generated by wind is the largest source of aerosols and affects directly or indirectly the atmospheric radiation balance and hence global climate change. Strong wind-erosion events,such as severe dust storm,may threaten people＇s health and cause economic loss. The Taklimakan Desert is the largest,driest and warmest desert in China. It covers an area of 337 600 km2 in the Tarim Basin,1 000 km long and 400 km wide. The Taklimakan Desert is also known as one of the largest mobile deserts in the world. About 85% desert area is covered by mobile and crescent-shaped sand dunes with height varying from 100 to 200 m,and it is virtually devoid of vegetation. Daily and seasonal temperature variation is se-vere in this arid and inland basin. Diurnal-nocturnal and winter-summer temperature differences may be as high as 20 ℃ and 30 ℃ respectively. In the center of the basin,annual precipitation is less than 10 mm. As a result of the above reasons,the desert is a main source of sandstorm in China. In this paper,a sandstorm occurred during the period from 11：29 to 23：55 on July 19,2008 in Tazhong,the hinterland of the Taklimakan Desert,is observed and analyzed. The values of sand transport flux of the sandstorm are calculated with the representative formulae. It is determined that the critical friction velocity in Tazhong is 0. 24 m/s. The relationship between wind speed and sand transport flux at height of 2 m is fitted based on the measured data. It is found that the results calculated with Lettau＇s formula are the closest to the measured values. Finally,the values of horizontal and vertical sand transport flux are calculated,and they are 258. 67 × 10 -4 kg/（ m·s） and 40. 07 × 10 -7 kg/（ m2·s） respectively.