青藏高原湖泊群湖-气相互作用及区域气候效应研究

Dominated by saline lakes and salt lakes, lake clusters in the Tibetan Plateau are consisted of lakes with the highest altitude and the largest number and occupy more than 50% lake area of China. The project will study the air-lake interaction and regional climatic effect of the alpine lake clusters. First, the parameterization scheme of roughness length over lake water-surface including the capillary wave under weak wind conditions will be established based on observations and coupled in the regional atmospheric model WRF-CLM (Weather Research and Forecasting model coupled with the Community Land model) including lake salinity parameterizations, in which the parameterization scheme of albedo over lake ice will also be improved. Thus the simulation ability of the model on water and energy exchange between lake and atmosphere will be enhanced. Then the numerical experiments will be performed with the improved WRF-CLM. Characteristics of air-lake interaction of the lake clusters and effects of altitude, lake depth, salinity of lake water will be investigated. Finally regional climatic effect of the lake clusters and the mechanism will be revealed. Study results will deepen the understanding of the land-atmosphere coupling system of the Tibetan Plateau and provide scientific references to help further improve the predictions of weather and climate.

以咸水湖和盐湖为主的青藏高原湖泊群是地球上海拔最高、数量最多的内陆湖泊群，其面积占我国湖泊总面积的50%以上。本项目以研究该高寒湖泊群湖-气相互作用及区域气候效应为目的，首先在已耦合湖泊模式盐分参数化方案的区域大气模式WRF-CLM（Weather Research and Forescating model coupled with the Community Land model）中，基于观测资料建立包含弱风条件细纹波作用的湖泊水面粗糙度参数化方案并改进湖冰反照率参数化方案，提高模式对高原湖-气水热交换的模拟能力；其次利用改进的WRF-CLM模式设计数值试验，阐明青藏高原湖泊群湖-气相互作用特征及海拔高度、湖泊深度、湖水盐度的影响；进而揭示青藏高原湖泊群对区域气候的影响及影响机理，加深对青藏高原地-气耦合系统的认识，为提高我国天气气候预测水平提供科学依据。

基于青藏高原广泛分布湖泊的湖气相互作用特征和区域气候效应受其湖泊属性影响而表现不同，而高原观测资料匮乏、湖泊模式仍需改进的情形下，在青藏高原鄂陵湖、青海湖和哈江盐池等开展了野外观测，结合数值模式和遥感数据，针对青藏高原湖泊展开了以下研究：1）揭示了弱风形成的细纹波对湖泊水面粗糙度长度的影响，确定了适合高原湖泊的粗糙度长度；明确了青藏高原湖泊反照率较低的特征，改进了湖冰反照率参数化方案，提高了WRF-CLM模式和CLM湖泊模式对高原湖泊的模拟精度，为青藏高原湖泊研究提供了有力工具；2）研究了高原典型湖泊湖气相互作用特征，揭示了高海拔导致无冰期高寒湖泊长期存在不稳定大气层结；揭示了同一气候背景下鄂陵湖、扎陵湖、哈江盐池湖温特征差异主要是由于湖泊深度及浑浊度、盐度影响，较深及透明的鄂陵湖比较浅及浑浊的扎陵湖夏季混合层更深，对大气强迫的响应更强，盐湖比同深度的淡水湖增温略快；明确了青藏高原干燥空气使得高原干旱区湖泊在夏初蒸发远大于其它地区而气温略高，导致高原干旱区湖泊春夏正-负-正的湖气温差特征；揭示了随气候变暖的高原湖泊与大气间能量交换的变化特征，高原湖泊主要成升温趋势，湖泊结冰推迟增强了湖泊对大气的加热，湖泊解冻提前使得湖泊吸收更多的能量。3）研究了湖泊对区域气候的影响及影响机理，揭示了湖泊深度、初始湖温等对湖泊效应的影响，量化了青藏高原对区域气候的影响，揭示了夏秋季湖面过程和大尺度环流背景及环境热力差异协同影响区域气候的差异。本项目共发表论文15篇，其中SCI9篇，通过本项目研究加深了对青藏高原地-气耦合系统的认识，为提高我国天气气候预测水平提供了一定的科学依据。