Abstract:

The impact of Tibetan Plateau on the global atmospheric temperature and water vapor distribution is studied using a fully coupled climate model CESM. Comprasion of the sensitivity test without the Tibetan topography (NoTibet) and the reference experiment of realistic topography (Real) shows that the northern hemisphere becomes cold and dry in NoTibet, the southern hemisphere is much the same. Specifically, in the high latitudes of the northern hemisphere, there is a strong cooling from the surface to the stratosphere. The surface cooling centre is in the North Atlantic ocean where the mean annual temperature falls by 5ºC. Another cooling centre is at the 100 hPa which falls by 2ºC. The humidity decreases in the North Atlantic and South Asia, but increases in the South Atlantic and East Africa. Due to the reduction of ocean meridional heat transport, the meridional poleward temperature gradient strengthens, leading to the enhancement of the Hadley circulation. Then it enhances atmospheric meridional heat transport, partly compensates for the depressed northward ocean heat transport, and maintains energy balance in the mid-low latitudes of the northern hemisphere; on the other hand, the humidity reduces in the mid-high latitudes, the northern hemisphere becomes cold and dry. The study shows that Tibetan Plateau has a significant impact on the climate in the northern hemisphere, the sphere of influence can reach to the high latitude.

Key words: Tibetan Plateau, Hadley circulation, meridional heat transport

摘要：

利用耦合的气候模式CESM, 定量研究青藏高原对全球大气温度和水汽分布的影响。通过对比采用真实地形的参考实验(Real)和去掉青藏高原的敏感性实验(NoTibet)发现, 去掉青藏高原会使北半球大气变冷、变干, 对南半球的影响不明显。北半球中高纬度从地表至平流层均有强烈降温, 地表的降温中心在北大西洋, 年平均降温幅度达5ºC, 高空的降温中心在100 hPa的平流层, 年平均降温幅度达2ºC。北大西洋和南亚地区湿度减少, 南大西洋和东非地区湿度增加。北半球变冷主要是海洋向北经向热量输送减少的结果, 一方面增强了北半球的经向温度梯度, 导致Hadley环流增强, 加强了中低纬地区向北的大气热量输送, 部分补偿了海洋向北减少的热量输送, 维持了北半球中低纬度的能量平衡; 另一方面, 使得北半球中高纬度蒸发作用减弱, 大气中水汽含量减少, 北半球变得寒冷干燥。初步的研究表明, 青藏高原对北半球气候有重大影响, 影响范围可达北半球高纬度地区。

关键词: 青藏高原, Hadley环流, 经向热量输送