戈壁沙漠沙尘向青藏高原传输路径和传输机制:以2020年4月一次沙尘事件为例

Transport of dust from Gobi Desert to the Tibetan Plateau and its dynamic mechanism: a case study of a dust event in April of 2020

戈壁沙漠是沙尘天气频发区域,也是东亚沙尘暴的关键源地。青藏高原毗邻东亚和南亚两大沙源区,是全球气候变化的敏感地区。然而戈壁沙漠沙尘向青藏高原传输路径以及传输机制尚不清晰。基于区域空气质量模式WRF-Chem、FNL再分析资料并结合HYSPLIT后向轨迹模型,以2020年4月戈壁沙漠一次强沙尘事件为例,探讨了戈壁沙漠沙尘向青藏高原传输路径以及传输机制。结果表明:在此次沙尘事件期间,青藏高原东坡和北坡是戈壁沙漠沙尘传输至青藏高原的重要通道。受环流形势和高大地形的影响,青藏高原北坡沙尘传输效率大于东坡,而东坡沙尘垂直运动较北坡旺盛。500 hPa乌拉尔山以东的气旋系统和蒙古气旋共同控制中高纬度带,影响沙尘输送过程。随着中高纬气旋系统的东移,500 hPa新疆脊被破坏,青藏高原上空短波槽开始建立。短波槽前低层辐合的环流场有利于700 hPa闭合低压的维持,促使青藏高原北坡的偏北大风产生,有利于北坡沙尘向青藏高原输送。200 hPa高空急流动量下传引起河西走廊近地东风盛行,有利于戈壁沙漠沙尘从东坡向青藏高原输送。此环流形势构成了戈壁沙漠沙尘向青藏高原传输的有利风场。该研究成果进一步完善了戈壁沙漠沙尘的传输路径,为研究沙尘影响青藏高原及其周边地区的天气气候变化提供了科学支撑。

The Gobi Desert is a region known for its frequent sandstorms,and is one of the key sources of sandstorms in East Asia.The Tibet Plateau is adjacent to the two major sand source regions of East Asia and South Asia,and is one of the most sensitive regions to climate change in the world.However,the transmission path and mechanism of the Gobi Desert dust to the Tibet Plateau are still unclear.Based on the regional air quality mode WRF-Chem,FNL reanalysis data and the HYSPLIT backward trajectory model,a strong dust event in April of 2020 was used to explore the dust transmission path and transmission mechanism from the Gobi Desert to the Tibet Plateau.The results showed that during this dust event,the east and north slopes of the Tibet Plateau were important channels for dust transmission from the Gobi Desert to the Tibet Plateau.Affected by the circulation situation and the high terrain,the dust transmission efficiency on the north slope of the Tibet Plateau is greater than that on the east slope,while the vertical movement of dust on the east slope is stronger than that on the north slope.The 500 hPa cyclone system east of the Ural Mountains and the Mongolian cyclone jointly control the middle and high latitudes and affect the dust transport process.With the eastward movement of the mid-high latitude cyclone systems,the 500 hPa Xinjiang ridge was destroyed,and the short-wave trough over the Tibet Plateau began to be established.The low layer convergent circulation in front of the short-wave trough is conducive to the maintenance of the 700 hPa closed low pressure,which promotes the northerly wind on the northern slope of the Tibet Plateau,and is conducive to the transport of dust from the northern slope to the plateau.The downward transmission of the 200 hPa upper-level jet stream caused the near-ground easterly wind to prevail in the Hexi Corridor,which was conducive to the transport of the Gobi Desert dust to the plateau.This circulation situation constitutes a favorable wind field for dust transmission from the Gobi Desert from the eastern slope to the Tibet Plateau.The research results further improve the transmission path of the Gobi Desert dust,and provide scientific support for the study of the weather and climate change of the dust influence on the Qinghai-Tibet Plateau and its surrounding areas.