全球地形影响大气和海洋经圈环流的耦合模式研究

利用气候系统模式(CESM1.0)研究陆地地形改变对大气?海洋经圈环流的影响。模式首先给出真实海陆分布及陆地地形情况下的大气?海洋气候态, 然后给出平板陆地情况下(陆地海拔均匀10 m)的气候态。与真实世界相比, 平板陆地情形下大气?海洋经圈环流发生重大改变: 首先, 年平均大气对流中心南移到赤道附近, 使得大气哈德雷环流相对于赤道对称; 其次, 海洋的经向翻转流变强, 大西洋经向翻转流完全消失, 取而代之的是在太平洋出现强大的经向翻转流及热盐环流。在平板陆地情形下, 北半球中高纬度大气抬升减弱, 向北的大气热量输送减少, 北半球温度降低, 大气对流中心因而向赤道迁移; 同时, 海洋向极地的热量输送也减弱, 中高纬度海洋变冷, 北太平洋海水密度增加很多, 北大西洋海水密度降低, 导致海洋经向翻转流从大西洋转移到太平洋。

Coupled Model Studies of the Topography Effect on the Global Meridional Overturning Circulations

The atmospheric and oceanic meridional circulation in both the flat and real world are studied using the fully coupled Community Climate System Model version 1.0 (CESM1.0). Two global mean climate are obtained from two topography experiments named Flat (the land of the whole planet is set as 10 meters above sea level without ups and downs) and Real (just simulated to the real world). There is significant difference in both the atmospheric and oceanic meridional circulation relative to the real world. Hadley Cells is more symmetric as a result of the southward shift of the center of the time averaged atmospheric convection. The oceanic meridional overturning circulation is greatly increased with deep PMOC (the Pacific meridional overturning circulation) and THC (thermohaline circulation) replacing AMOC (the Atlantic meridional overturning circulation). These are caused by the decrease in both the atmospheric and oceanic heat transport from equator to Arctic in mid-high latitude of the Northern Hemisphere (NH). At the same time, it is found that the air rising is weakened and much colder climate is observed in the flat world, which result in the increased sea water density in the Pacific opposite to the Atlantic.