本文利用全球海气耦合模式,设计并进行了7组高原不同隆升情景的数值试验,集中研究了青藏高原隆升在欧亚内陆干旱演化中的作用。在无高原试验中,亚洲副热带干旱区为东西对称的纬向型分布;随着高原高度的增加,一方面有助于东亚季风降水的向北扩展,另一方面导致欧亚大陆西风强度显著减弱,使得亚洲副热带气候纬向不对称性增加,同时欧亚中纬度干旱面积增加。其原因是,高原隆升导致近地层气温下降,进而大气含水量减小;同时,地形的阻挡效应导致纬向和经向的环流减弱,这两个因素综合导致内陆地区水汽输送的减弱是中亚干旱区范围增加的主要动力学机制。与以往大气模式试验一致,海气耦合试验支持了高原隆升是亚洲内陆水汽输送和降水减少,以及内陆干旱化加剧的重要原因的科学认识。
As one of the most important geological events in the Cenozoic Era, the Tibetan Plateau (TP) uplift not only exerts profound influences on its own environment evolution, but also plays a key role in driving the global weather and climate evolution. The effect of the TP uplift in forming the mid-latitude dry climates has been demonstrated by a growing number of geologic evidences and numerical experiments. However, most of experiments are based on atmospheric general circulation model (AGCM), and the coupled atmosphere-ocean model(CGCM)experiments have not been widely undertaken. In order to address this issue, the Community Earth System Model (CESM) of National Center for Atmospheric Research(NCAR)is used to design seven simulations in total. The CESM consists of atmosphere, land, ocean, and sea ice components that exchanges state information and fluxes through a coupler. The low-resolution (about 3.75°×3.75°) version of CESM is less computationally expense and widely used for a variety of applications. In seven experiments, various TP heights are used: 0 % (no TP), 20 %, 40 %, 60 %, 80 %, 100 % (modern TP), and 120 % of the modern TP heights. The other boundary conditions are the same for all experiments. All the experiments are integrated for more than 500 model years and have reached an equilibrium state. The analysis of regional average of precipitation and soil moisture changes over the Asian inland is performed in this study. In addition, the method of vertically integrated moisture transport across the four boundaries of the Asian inland is used to quantitatively measure the total moisture budget in this area. Systematic changes in precipitation pattern and circulation fields as well as total moisture fluxes occurred along with progressive mountain uplift. In the experiment without TP, the subtropical belts of aridity in Asia are nearly zonal distribution. With the uplifting of mountain, the East Asian monsoon intensifies and extends northward, while the westerlies into