Energy and Water Cycle over the Land Surface in the Tibetan Plateau

为了理解和模拟亚洲夏季风的季节和年际变化，必须解决水文过程，特别是大尺度水汽的起源和循环、降水场和青藏高原地表水文过程。由于蒸发量与土壤湿度的非线性关系，利用空间平均土壤湿度计算的蒸发量在干燥条件下小于实际蒸发量，而在潮湿条件下较大。青藏高原因滞留而导致的大范围土壤水分分布的影响用土壤水分标准差的线性函数来表示（Hirose et al., 2000）。这一结果为扩大非均质陆面过程提供了一种方法。由于青藏高原地面观测站相对较少，只有通过卫星遥感才能实现对整个高原的有效监测和时空采样的连续性。反过来，实地观测和过程研究有助于作为基于卫星的检索算法的地面真实信息来源。为了实现上述过程和模式研究的目标，GAME-Tibet侧重于开发和验证降水、辐射收支、地表通量、土壤湿度和雪的卫星算法。

To understand and model the seasonal and interannual variability of the Asian summer monsoon, it is important to address the hydrological processes, especially the origin and circulation of water vapor at large scale, the precipitation fields, and the land surface hydrological processes in the Tibetan Plateau.Due to the non-linear relationship between evaporation and soil moisture, calculated evaporation by using spatially averaged soil moisture is smaller than actual one under dry condition and larger under wet condition. The effects of the wide range of the soil moisture distributuion due to the presence of detention in the Tibetan Plateau is expressed by a linear function of the standard deviation of soil moisture(Hirose et al., 2000). This result suggests a method for scaling up heterogeneous land surface processes.Because of the relatively few ground observation stations over the Tibetan Plateau, efficient monitoring and continuity in space-time sampling over the complete plateau are only possible by satellite remote sensing. In turn, the field observations and process studies help serve as sources of ground-truth information for satellite-based retrieval algorithms. To meet the objectives of the process and modeling studies reported above, GAME-Tibet focused on the development and validation of satellite algorithms for precipitation, radiation budget, surface fluxes, soil moisture and snow.