植被恢复对黄土高原水热平衡变化及水汽内外循环影响的数值模拟研究

植被对区域气候的反馈机制是当前全球变化生态学的重要议题之一。虽然大量研究分析了黄土高原植被恢复与水文及气候的关系，但关于植被对局地气候反馈作用的认识仍十分有限，本项目旨在辨识植被对黄土高原气候的反馈方式及程度。首先，利用多源对地观测数据及气象资料，分析20世纪80年代以来黄土高原水热平衡分量及水汽收支的时空特征，明确黄土高原水汽传输的季节、年际及年代际演变特征。然后，利用地球系统模式CESM定量评估植被恢复对黄土高原能量及水量平衡的影响程度，识别植被恢复不同时期水汽收支的差异；利用气候情景预测未来的潜在植被及水循环特征，并结合植被覆盖情景敏感性试验研究植被格局与区域干旱特征的关系。最后，采用WRF模式并结合HYSPLIT模型，研究植被恢复对黄土高原水汽内循环特征的影响，追踪蒸散发水汽的去向，探究水汽传输轨迹与降水发生的联系。以期为黄土高原植被建设的合理布局及维持水资源平衡提供科学依据。

The feedback of vegetation on climate is an important scientific issue in the global change ecology. In recent decades, vegetation cover on the Loess Plateau shows a significant increasing trend, and the relationship between vegetation and hydro-climatic change has been investigated extensively, while most of previous studies focus on the responses of vegetation dynamics to climate change, and our knowledge about the feedback effects of dynamic vegetation on local climate is very limited. Thus, this project aims to quantitatively assess the feedback of vegetation restoration to the energy balance and water cycle, and discern the role of dynamic vegetation played in the local climate in the Loess Plateau region. Firstly, the spatial-temporal features of energy balance and water cycle will be analyzed since 1980s at the seasonal, yearly and decadal scale, and the moisture budget will also be investigated, using multiple land surface datasets and meteorological data. Secondly, we will perform a series of numerical simulation experiments using Community Earth System Model (CESM) in tandem with a dynamic global vegetation model to identify the contribution of vegetation restoration on water balance elements quantitatively, and the moisture budget at different restoration stage will be simulated to understand the atmospheric circulation change induced by vegetation restoration. In order to find the optimum vegetation structure and coverage to alleviate the aridity, the aridity index will be calculated using model outputs from sensitivity simulation test under different climate scenarios and vegetation scenarios with various vegetation composition and its coverage. Finally, the Weather Research and Forecasting (WRF) model were adopted to assess the impact of vegetation coverage on the internal circulation of water vapor, and the outputted water vapor and climatic data from WRF were used to run the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to trace the dispersion trajectory of evapotranspiration (ET), and the relationship between ET and local precipitation will be further analyzed. The findings of this project will enlarge current understanding on the contribution of vegetation to regional climate and thus may provide a guide for vegetation management and water balance maintenance on the Loess Plateau.