三江源区植被变化与区域气候反馈及其机理研究

The project takes the aim at studying the impacts and responses of vegetation change on regional climate change of the source of the Three Rivers (including the Yangtze River, the Yellow River and the Lancang River) in China. Firstly, the lead-lag interactions between the vegetation fraction, its induced surface albedo and climate factors will be investigated by using statistic method, to determine the time scale and regional difference of the interactions. And then, numerical simulations will be performed to simulate the regional climate change of the source of the Three Rivers by combining with the remote sensing data in a temporal and spatial series. According to the simulations, quantitative assessment of vegetation change on regional climate in the source of the Three Rivers will be performed, taking the time scale and the regional difference of the responses of vegetation change to regional climate as the prior knowledge and getting rid of the impacts of the large-scale background field. Finally, the impacts of vegetation change on surface water- and heat- transfer and regional climate change and its interactive mechanism will be further discussed based on the surface energy balance equation,large-scale and convective precipitation processes. Furthermore, the potential influences of vegetation change on future climate change in this region will be investigated and forecasted. Thus, the impacts and responses of vegetation change caused by the human activities and climate change on regional climate in the source of the Three Rives will be better understood from three different aspects including the interactive time scale, the influencing extent and the physical mechanism. It will provide a reliable reference for proposing countermeasures of eco-construction, environment protection and sustainable land use in the source of the Three Rivers under global change.

拟申请项目以研究植被变化对三江源区区域气候的影响和响应为目的，首先利用统计分析方法研究该地区植被覆盖度及其引起的地表反照率变化与气候因子之间的超前-滞后相互作用，明确其作用的时间尺度和地域性差异；然后设计数值模拟方案，结合遥感资料的时空序列，模拟三江源区区域气候变化。根据模拟结果，以三江源区地表植被对气候变化响应的时空尺度为先验知识，在除去大尺度环流背景的影响下进行比较分析，定量评估三江源区植被变化对区域气候变化的影响；最后，基于地表能量平衡方程及大尺度和对流降水物理过程，探讨植被变化对地表水热传输和区域气候变化的影响，深入研究其作用机理，进一步揭示和预测对该区域未来气候变化的可能影响。从而在时间尺度、影响程度和物理机制三个不同层面深入理解人类活动和气候变化影响下的植被变化对三江源区区域气候的响应和影响，为提出全球变化情景下的三江源区生态建设、环境保护和土地可持续利用等对策提供依据。

根据项目任务，利用观测资料、卫星遥感、和WRF模式细致研究了青藏高原三江源区植被变化对区域气候的影响及其机理，取得以下主要研究成果：.利用观测资料研究了三江源区草地覆盖和湖泊下垫面对蒸发的影响，提出土壤湿度和植被变化对蒸发的影响；结合观测资料建立了青藏高原包括三江源区蒸发长时间序列数据集（1961-2010），并指出近年来蒸发变化趋势及其影响因子。利用WRF模型将MODIS随时空变化地表反照率和叶面积指数（LAI）引入WRF模型，研究了三江源区植被和地表反照率对区域气候的影响，特别是重点阐述了地表反照率和植被覆盖变化对区域气候的影响及其影响机理。最后，项目通过整合分析，提出了三江源区植被及反照率对午后对流降水影响机理示意图。