湖陆环流对博斯腾湖蒸发影响的数值模拟研究
Numerical study on the influence of lake-land circulation on evaporation in Bosten Lake
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摘要: 新疆地区地处亚欧大陆腹地,气候条件干燥,水资源时空分布不均,可用水资源匮乏。湖泊是新疆水资源主要贮存方式之一,其通过多界面、多要素大气边界层物理过程调控区域水热物质交换与循环,对缓解干旱区沙漠化发挥不可或缺的作用。本文以博斯腾湖为研究对象,利用WRF-CLM模拟2020年夏季6月~8月共计92天的局地环流形势,分析近地面风场、水汽分布并结合去湖试验,获得局地环流对湖面蒸发的影响机制,具体表现为:盛行湖风时,湖面蒸发的水汽会在上岸气流的携带下向陆地输送,同时在湖风锋的上升气流影响下向高空扩散,在山谷风等背景风的综合作用下,湖风环流会携水汽下沉并聚集于湖岸形成离散分布的水汽聚集区,这些区域的比湿保持在较高水平。博斯腾湖的水汽聚集区分布于湖区西侧,这些区域具有边界层高度较周边其他陆面边界层低,下垫面多为植被覆盖等特点。Abstract: Xinjiang is situated in the interior of the Eurasian continent. It is characterized by arid climatic conditions, presenting an uneven spatial and temporal distribution of water resources and a paucity of accessible water resources. Lakes constitute one of the primary means of water resource storage in Xinjiang. They play a pivotal and irreplaceable role in combating desertification within the arid region. Through complex multi-interface and multi-factor physical processes occurring within the atmospheric boundary layer, lakes modulate the regional exchange and circulation of water and heat materials. In this research endeavor, Bosten Lake was chosen as the focal point. The WRF-CLM model was employed to simulate the local circulation patterns over a span of 92 days from June to August in the summer of 2020. By meticulously analyzing the near-surface wind fields and water vapor distribution, and in conjunction with lake-removal experimental setups, the mechanism underlying the influence of local circulation on the evaporation of the lake surface was unearthed. The details unfold as follows: When the lake breeze holds sway, the water vapor that evaporates from the lake surface is ferried towards the land, propelled by the onshore air currents. Concurrently, under the sway of the updraft at the lake breeze front, it disperses into the upper atmosphere. Under the combined forces of the valley wind and background wind, the lake breeze circulation drives the water vapor downward, congregating it along the lakeshore to form discretely scattered water vapor accumulation zones. The specific humidity within these areas persists at an elevated level. The water vapor accumulation area of Bosten Lake is predominantly distributed on the western flank of the lake. Notably, the boundary layer height in these regions is lower than that of the neighboring land surfaces, and the underlying surface is largely blanketed by vegetation.