长江源卓乃湖流域沙尘释放过程模拟

Modelling of sand/dust emission process in the Zhuonai Lake Watershed,the source of the Yangtze River

由于碎屑物质的堆积,干涸湖盆和河道往往会成为干旱和半干旱地区主要的沙尘源区。目前关于干涸湖泊沙尘释放过程的研究多集中在干旱半干旱地区,青藏高原由于其气候和下垫面特点,以往的研究往往忽略其沙尘释放过程。然而近年来受暖湿化趋势的影响,青藏高原降雨增多,洪水事件频发,从而导致地表可蚀性沉积物增多,在其高风能环境影响下极易导致沙尘事件的发生。为了提出科学的风沙防治对策,需明确沙尘释放的时空分布过程。因此,研究以长江源卓乃湖流域为研究区,基于气象、遥感、陆面同化等数据,利用综合风蚀模拟系统(Integrated Winderosion Modelling System,IWEMS)和沙尘释放与沉积模型(Dust Entrainment and Deposition,DEAD),模拟了卓乃湖流域2000—2020年的沙尘释放过程。结果显示:①卓乃湖流域沙尘释放年内变率较大,高值一般发生在冬春季节,低值多在夏秋季节。湖泊溃堤前沙尘释放年际波动较大,溃堤之后,沙尘释放呈显著上升趋势,说明溃堤后,退水湖岸为沙尘释放提供了丰富的物源。②就空间分布而言,卓乃湖沙尘释放具有较大的空间异质性,湖泊沿岸的沙尘释放率明显高于其他地区,湖泊溃堤之后,沙尘释放的高值区逐渐由湖泊北岸向东南岸迁移。③湖泊溃堤之后,风速对沙尘释放的影响机制发生了较大的变化,沙尘释放过程更易发生。

Due to the accumulation of detrital materials,dry lake basins and rivers often became the main sand/dust emission source areas in arid and semi-arid regions.At present,the research on the sand/dust process of dry lakes is mostly concentrated in arid and semi-arid areas.Due to the climate and underlying surface characteristics of the Qinghai-Tibet Plateau(QTP),previous studies often ignore the sand/dust emission process.However,in recent years,affected by the trend of warming and humidification,the rainfall in the QTP has increased,and flood events have occurred frequently,resulting in an increase in surface erodible sediments.Under the influence of its high wind energy environment,it is easy to cause ssand/dust events.In order to put forward scientific sand/dust control countermeasures,it is necessary to clarify the spatio-temporal distribution process of sand/dust emission.Therefore,based on meteorological,remote sensing,global land data assimilation systems and other data,the IWEMS(integrated wind-erosion modelling system)and DEAD(dust entrainment and deposition)were used to simulate the sand/dust emission process in the Zhuonai Lake Watershed from 2000 to 2020.The results show:1)The seasonal variation rate of sand/dust emission in Zhuonai Lake watershed is large.The high value of sand/dust emission generally occurs in winter and spring,and the low value is mostly in summer and autumn.The annual variation of sand/dust emission was large before the Zhuonai Lake broken,and after the break event,the sand/dust emission showed a significant upward trend,indicating that after the lake burst,the backwater lake bank provided a rich source of sand/dust emission.2)From the perspective of spatial distribution,the sand/dust emission in the Zhuonai Lake has great spatial heterogeneity,and the sand/dust emission rate along the lake coast is significantly higher than that in other areas.After the lake burst,the high value area of sand/dust emission gradually moves from the north bank to the southeast bank.3)After the lake burst,the influence mechanism of wind speed on sand/dust emission has changed greatly,and the sand/dust emission process is more likely to occur.The results provide a theoretical basis and data support for the prevention and control of wind and sand/dust disasters in the Zhuonai Lake Watershed.