典型咸水湖及其盐分对区域气候影响的数值研究

Saline lakes and hypersaline lakes are the most typical lakes in China, which are mainly located in the west of China. These lakes have significant effects on local climate and ecosystems. Changes of water physical characteristics induced by dissolved salt in lakes will affect the balance of energy and water between lake and atmosphere, and the energy transportation of interior lake. Thus salt lake will have the different local climate compared with that of fresh lakes. The regional atmospheric model coupled with lake model has been barely employed and salinity effect has not been took into account in previous numerical studies about the saline lakes and hypersaline lakes in the west of China. In the project, we plan to parameterize the salinity effects on water characteristics in the lake module coupled into the regional atmospheric model WRF_CLM. Therefore,the lake model and its coupled regional atmospheric model are more capable to simulate the effect of saline and hypersaline lakes. Forecasting capability for weather and future climate will be improved by the regional atmospheric model in the lake area and its vicinity. Then, the regional atmospheric model including salinity parameterization will be employed to study the impact of salt on the cycle of energy and water in the typical saline lake (Qinghai Lake) in the west of China. The impact of the typical saline lake on the local climate and the mechanisms will be also studied. Study results will be helpful to protect ecological environment and reasonably utilize water resources in the west of China.

咸水湖和盐湖是我国自然湖泊的主要类型，主要分布在我国西部地区，对西部地区局地气候与生态环境有显著影响；盐分能够改变湖水的物理性质，从而影响湖气界面的能量水分交换特征及湖泊内部能量的交换方式，使咸水湖（盐湖）形成有别于淡水湖的区域气候效应。在目前对我国西部地区咸水湖、盐湖区域气候效应的数值研究中，较少应用耦合湖模式的区域大气模式，也鲜有涉及盐分的影响。本项目拟在区域大气模式WRF_CLM耦合的一维热扩散湖模式中，建立湖泊盐分参数化方案，改进湖模式与其耦合的区域大气模式对咸水湖、盐湖的模拟能力, 提高区域大气模式对湖区与周边地区天气预报能力及气候预测能力；在此基础上，利用耦合湖模式盐分参数化方案的区域大气模式，探讨盐分对我国西部地区典型咸水湖（青海湖）能量水分循环的影响,研究咸水湖对区域气候的影响，为我国西部地区生态环境保护和水资源合理利用提供参考依据。

基于青藏高原湖泊以咸水湖、盐湖为主、目前湖泊模式较少考虑盐分影响、也鲜有咸水湖、盐湖区域气候效应研究的现状，本项目主要针对含盐湖泊展开研究，1）对青藏高原青海湖、鄂陵湖和哈姜盐池等进行了观测，在区域大气模式及其耦合的离线陆面模式中建立了湖泊模式盐分参数化方案，显著提高了WRF-CLM模式或CLM湖泊模式对湖面气温、湖表温度、湖水温度的模拟精度，特别是在温度较低的寒冷冬季，为研究以咸水湖和盐湖为主的青藏高原和西部湖泊提供了有力工具。2）利用发展的模式结合观测数据，揭示了盐分对盐湖热力状态的影响及影响机理，明确了盐分对盐湖温度、蒸发和对盐湖及周边地区降水的影响。盐分在夏季将减小饱和水汽压，抑制蒸发；在冬季将降低冻结温度，增大净短波辐射，增加湖面蒸发；未冻结盐湖总体将增加区域降水，暖季淡水效应为主要贡献，冷季盐分效应为主要贡献。3）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，量化了高原大湖与周边草地水热交换的差异，改进了湖泊模型粗糙度参数化法方案；4）研究了湖泊对区域气候的影响及影响机理，量化了高原湖泊增雨效应，鄂陵湖和扎陵湖可使湖区及周边地区的年降水量最大增加49%，在青海湖西部湖泊效应增加的降水可占年降水量的50-60%；揭示了较暖湖面及较大蒸发将增加大气不稳定性、导致降水增加的机制；青海湖夏季增加降水量显著，主要为对流降水，但秋季对降水的贡献率更大，主要为大尺度降水, 夏秋季湖效应降水差异主要是由青海湖湖面过程、大尺度环流背景及环境热力差异共同形成。本项目共发表论文16篇，其中SCI 9篇。