青藏高原土壤湿度—降水反馈及其机理研究

The project takes the aim at studying the impacts and response of soil moisture change on precipitation over the Tibetan Plateau in China. Firstly, by using the satellite-derived soil moisture, precipitation, the atmospheric profile and reanalysis products, combining with the mechanisms of soil moisture-precipitation feedback, the lead-lag interactions between soil moisture and precipitation will be investigated by using statistic method, to determine the time scale and regional difference of the interactions. And then, numerical simulations will be designed to simulate the response of precipitation to soil moisture by applying the satellite-derived soil moisture variations. According to the simulations, quantitative assessment of soil moisture change on regional climate in the source of the Three Rivers will be performed, taking the time scale and the mechanisms of soil moisture-precipitation feedback as the prior knowledge and getting rid of the impacts of the large-scale background field. Furthermore, the potential influences of soil moisture change on future precipitation change in this region will be investigated and forecasted. Thus, the impacts and responses of soil moisture change caused by the human activities and global warming on precipitation over the Tibetan Plateau will be better understood from three different aspects including the interactive time scale, the physical mechanism and the quantitive contribution to precipitation. It will provide a reliable reference for management of water resources and addressing climate change on the Tibetan Plateau under global warming.

拟申请项目以研究土壤湿度非均匀分布及其变化对青藏高原区域气候的响应和影响为目的，首先利用遥感获取的土壤湿度、降水、大气廓线及再分析等多源资料结合土壤湿度—降水反馈机理分析青藏高原地区土壤湿度—降水反馈过程，明确其作用的时间尺度、机理及其在地域上的差异；然后以此为先验知识、设计数值试验，模拟土壤湿度时空变化对青藏高原区域降水的影响。根据模拟结果，在除去大尺度环流背景的影响下进行比较分析，定量评估其影响。从而在理论和事实的框架下，从时间尺度、影响机理和影响程度三个不同层面深入理解全球变暖背景下青藏高原土壤湿度时空变化对降水的响应和影响，为提出全球变化情景下的青藏高原地区水资源合理利用和保护及应对气候变化提供依据。

根据项目任务，利用观测资料、卫星遥感、探空观测结合一维大气边界层模型和WRF模式细致研究了青藏高原夏季土壤湿度对降水的响应及其对午后对流降水的影响，取得以下主要研究成果：.发展了一种用降水观测评估土壤湿度遥感产品的方法；提出了欧空局土壤湿度产品在青藏高原应用时存在的问题和产品改进建议；定量评价了青藏高原夏季土壤湿度对气候变化的响应及其机理；细致研究了青藏高原土壤湿度对午后对流降水触发的机理、区域差异及其成因；明确了观测资料、卫星遥感和WRF模式中触发午后对流降水的土壤湿度阈值；定量评估了青藏高原土壤湿度触发午后对流降水的强度及其对极端降水事件的影响。最后，项目通过整合分析，提出了青藏高原土壤湿度触发午后对流降水概念框架。