青藏高原蒸散年际变化及其对西风和季风环流的响应

在评估4种蒸散格点资料（GLDAS，GLEAM，MERRA-2，CRET）在青藏高原适用性的基础上，以精度最高的CRET（R²为0.83，RMSE为14.76 mm）及同期气象环境数据，在年际尺度上分析了青藏高原蒸散变化特征及其受大尺度西风和季风环流的影响.结果表明，青藏高原年平均蒸散为414.2±18.32 mm，具有明显的年际变率和变化趋势，且区域（西风区、季风区和过渡区）间差异明显.蒸散年际变化与西风和季风环流强弱的年际变化密切相关，且季风和西风对蒸散的影响存在显著的区域差异.西风和季风通过调节局地气候环境因子影响蒸散：土壤湿度、归一化植被指数（NDVI）和风速三个局地气候环境要素是青藏高原蒸散主要调控因子，蒸散与土壤湿度和NDVI呈显著正相关，与风速在高原西部呈显著负相关、在高原东部呈显著正相关；研究WYI（Webster-Yang Index）和WI（Westerly Index）与影响蒸散的主导气候环境因子的关系发现，WYI与土壤湿度和NDVI呈显著正相关，且WYI与NDVI的相关系数在高原中部和南部较大，使得WYI对蒸散影响在中部分过渡区和南部季风区较大，WI也与土壤湿度和NDVI呈显著正相关，但WI与NDVI的相关系数在中部和北部较大，WI对蒸散影响在中部过渡区和北部西风区较大，同时，WI与风速在大部分高原显著相关，WI在高原东部通过风速对蒸散变化具有正贡献，使得季风区东部蒸散年际变化也受WI影响，最终使得WI对蒸散的影响在除季风区西部以外的区域较大.该研究结果可加深认识青藏高原水循环变化及其机理，为区域水资源和生态系统管理提供科学依据.

Inter-annual variability of evapotranspiration and its response towestly and monsoon circulation over the Tibetan Plateau

In this paper, on the basis of the evaluation of the applicability of four gridded evapotranspiration datasets (GLDAS, GLEAM, MERRA-2, CRET) on the Tibetan Plateau, the most accurate CRET (R2 of 0.84 and RMSE of 15.67 mm) and contemporaneous meteorological data are used to analyze the variability of evapotranspiration on the Tibetan Plateau on an interannual scale and its responses to the large-scale westerly and monsoonal. The results show that the annual mean evapotranspiration on the Tibetan Plateau is 414.2±18.32 mm, with obvious interannual variability and trends, and significant differences among regions (westerlies, monsoons and transition zones). The interannual variation of evapotranspiration is closely related to the interannual variation of the strength of the westerly and monsoon circulation, and there are significant regional differences in the influence of the monsoon and westerly winds on evapotranspiration. The westerlies and monsoons influence evapotranspiration by regulating local climatic environmental factors: soil moisture, normalized vegetation index (NDVI) and wind speed are the three main local climatic environmental factors regulating evapotranspiration on the Tibetan Plateau. The correlation coefficients between WYI and NDVI are large in the central and southern parts of the plateau, which makes the influence of WYI on evapotranspiration greate in the middle transition zone and the southern monsoon zone. WI is also significantly and positively correlated with soil moisture and NDVI, but the correlation coefficient between WI and NDVI is large in the central and northern parts, and the effect of WI on evapotranspiration is large in the middle transition zone and the northern westerly zone. Meanwhile, WI is significantly correlated with wind speed in most of the plateau, and WI has a positive contribution to evapotranspiration variation through wind speed in the eastern part of the plateau, making the interannual variation of evapotranspiration in the eastern part of the monsoon zone also influenced by WI, which finally makes the effect of WI on evapotranspiration is large in most of the Tibet Plateau other than the western part of the monsoon region. The results of the study can deepen the understanding of water cycle changes and their mechanisms on the Tibetan Plateau, and provide a scientific basis for water resources and ecosystem management.