青藏高原地面拖曳效应对春季大气环流影响的数值研究

用一个在ＮＣＡＲ的气候模式ＣＣＭ１（Ｒ１５Ｌ１２）基础上改进和发展起来的ＣＣＭ１（Ｒ１５Ｌ７）－ＬＮＷＰ长期数值预报模式，以国家气象中心１９９２年４月１日客观分析资料和ＮＣＡＲ的固定个例（１９７５年１月１６日）为初始场，进行长期数值预报试验，研究了青藏高原地面拖曳效应对春季大气环流的影响．结果表明，当月平均的青藏高原地面拖曳系数与全球其它陆面月平均拖曳系数之差由０．０００８增大至０．００４时，预报效果得到了明显改进．青藏高原至巴尔喀什湖之间的（３００ｈＰａ和５００ｈＰａ）温度差可增大３℃，从孟加拉湾一带至青藏高原的温度差可减小１．５℃，使得在青藏高原及其北侧高空西风增强（增强中心在４０°Ｎ的２５０ｈＰａ层）．在青藏高原南侧的２５°Ｎ的２５０ｈＰａ出现西风的减弱中心，有利于晚春季节东亚南支西风急流的北移．青藏高原的地面拖曳效应有利于在春季加大其迎风坡和背风坡效应，加强北半球经向三圈环流及全球经向环流．

Numerical Experiments for the Influence of the Surface Drag Effect of the Qinghai Xizang Plateau on the General Circulation in Spring

This long range numerical experiments for the influence of the surface drag effect of the Qinghai Xizang Plateau on the general circulation in spring by using a CCM1(R15L7) LNWP model based on CCM1(R15L12)are carried out. The results show that the prediction results can be improved when difference of the mean monthly drag coefficient between Qinghai Xizang Plateau and other land areas increases from 0.0008 to 0.004. The surface drag effect of the Plateau is advantageous to the increasing of the temperature over the Plateau and the decreasing at the north of the Plateau, which induce to the enhancing of the westerly wind in the upper levels over the Plateau and its north side, and the weakening centers of the westerly appear on the south side of the Plateau, which are favorable to the northward shift of the southern subtropical westerly jet in East Asia. It is also beneficial to the enhancement of the Northern Hemispheric three circle and global meridional circulations.