艾比湖干涸湖底风扬粉尘的发生及其在边界层的扩散特征研究

Lake in arid land, which plays an incredible role in maintaining of the regional ecosystem balance, is an important part of the arid ecosystem and is highly sensitive to climate change and environment evolution. In the context of climate change, intense human activity leaded lakes to shrink and even dry up, followed by environmental degradation and serious desertification. As a result, frequent dust storms occurred. This project is aimed to understand the mechanism of eolian dust from the playa of Ebinur lake and its diffusion characteristics in the atmosphere boundary layer, three key questions are urgent to be answered, i.e., how do the key parameters that affect the eolian dust change? What is the spatial pattern of key processes that control the dust emission from the playa? And what are the main features of dust spread in the atmosphere? Within the selected Ebinur lake playa, quantitative studies will be implemented through statistical analysis, positioning observations and model simulations to gain the land surface parameters and aerodynamic parameters and their variation, to understand spatial differences of the process that control the dust generation near the surface, and to define the pathways and range of dust suspended in the atmospheric boundary layer. This project will identify the main factors influencing the occurrence of eolian dust, reveal regional differences of eolian dust generation in complex underlying surface thoroughly, and interpret dust release characteristics and its diffusion characteristics scientifically, and increase understanding and awareness of the important dust source in the evolution process of lakes in arid land. Meanwhile, results of this project could provide a reference for tail-end lake area to take effective measures to defense eolian dust, as well as provide a scientific basis for construction and management of ecosystems in the tail-end lake area.

干旱区湖泊是干旱区生态系统重要组成部分，对气候与环境变化具有高度敏感性。气候变化背景下，随着人文过程的加强，尾闾湖逐渐萎缩甚至干涸，导致区域环境恶化，尘暴频发。本项目针对深入理解尾闾湖干涸湖底风扬粉尘发生机理及扩散特征的科学目标，围绕影响干涸湖底风扬粉尘发生的关键参数、控制粉尘释放的关键过程和粉尘扩散的关键特征三个问题，选择新疆艾比湖干涸湖底为研究区，通过数值分析、定位观测和模型模拟，开展地气界面地表参数和空气动力学参数变化特征、近地表层风扬粉尘发生过程的空间差异、大气边界层粉尘扩散路径和范围的定量研究，识别风扬粉尘发生的主要影响因素，深入揭示风扬粉尘发生的区域差异，明确粉尘潜在扩散范围和主要路径，科学阐释干旱区湖泊演变过程中风扬粉尘发生特征，提高对干涸湖底这一重要粉尘源区的理解和认识，为干旱区尾闾湖地区防风固尘采取有效的生物和工程措施提供参考，为尾闾湖地区生态系统建设和管理提供科学依据。

干旱区湖泊是干旱区生态系统的重要组成部分，对气候与环境变化具有高度敏感性。气候变化背景下，不断增强的人类活动导致尾闾湖泊不断萎缩，风扬粉尘事件频发，造成区域环境恶化。本项目通过数值分析、定位观测和模型模拟，在干涸湖床地表参数和空气动力学参数变化特征、近地表层风扬粉尘发生过程的空间差异、大气边界层粉尘扩散路径和范围的定量研究方面取得了重要研究进展：.（1）艾比湖干涸湖床不同地表覆盖类型空气动力学参数等表现出显著的区域差异。东北部的白梭梭荒漠和红砂荒漠的空气动力学粗糙度可达5.15 cm和5.45cm，耕地和无植被覆盖地区的空气动力学粗糙度分别为0.003 cm和0.001 cm。西北部的琐琐砾漠、东南部芦苇草甸的起动摩阻风速值分别为127.53 cm/s和167.47 cm/s，是10种地表覆盖类型中较大的。红砂荒漠的摩阻风速为71.4 cm/s，为10种地表覆盖类型中摩阻风速的最大值。.（2）艾比湖干涸湖床西北部的琐琐砾漠和北部的红砂荒漠由于较粗的粒径组成和较大的起动摩阻风速导致很难释放粉尘。在没有水分和植被影响下，无植被覆盖区域的粉尘释放通量达到153 g/(km2·s)，耕地在无作物种植时期的粉尘释放通量达到83.8 g/(km2·s)。.（3）艾比湖干涸湖床的粉尘潜在扩散具有显著的季节分异。春季和夏季的潜在扩散范围最大，秋季和冬季1000 m以下扩散范围较小，1000 m高度以上低密度气团轨迹扩散范围较大；不同季节的粉尘潜在扩散表现出明显的方向性：风扬粉尘主要有两个扩散通道，春季和夏季的主要扩散方向为东南方向；秋季和冬季的主要扩散方向在较低层为东北方向。.（4）通过与咸海、柴窝堡湖等干旱区典型尾闾湖泊MODIS和MISR气溶胶光学厚度及扩散特征的比较表明，亚洲中部干旱区干涸湖床有潜力释放大量的粉尘。作为气溶胶长期悬浮于大气中，除造成近源区空气污染，增加大气浮尘和大气气溶胶之外，含盐粉尘在天山山区沉降，与气候变化效应叠加会显著的加速雪冰消融。作为亚洲风尘系统研究的重要内容之一，对干涸湖床的粉尘释放的研究会对亚洲风尘系统研究提供一定的借鉴意义。