Numerical Experiments for the Influence of the Surface Drag Effect of the Qinghai Xizang Plateau on the General Circulation in Spring
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摘要: 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(300 hPa和500 hPa)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250 hPa层)。在青藏高原南侧的25°N的250 hPa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。Abstract: 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 circulation.
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