Biot-Savart流体力学理论与索马里低空急流形成机理的研究  

Biot-Savart law and the formation mechanism of Somali low-level jet

作　　者：冯士德[1] 冯涛[2] 

机构地区：[1]中国科学院大气物理研究所云降水物理与强风暴实验室,大气科学和地球流体力学数值模拟国家重点实验室,北京100029 [2]北京市气象局,北京100089

出　　处：《物理学报》2011年第2期810-817,共8页Acta Physica Sinica

基　　金：国家自然科学基金重点和面上项目(批准号:40927002,40875036,40675029)资助的课题~~

摘　　要：首先利用格子Boltzmann模型模拟了越赤道索马里低空急流对我国青藏高原东部大气环流的影响,再借助于Biot-Savart定律和流体力学理论以及美国国家环境预报中心的数据资料,研究分析了下垫面感热条件与索马里低空急流发生和发展的关系.太阳直射从南回归线逐渐向北移动过程中,索马里半岛和阿拉伯半岛地表温度逐渐增高;而在此期间,西北印度洋海表温度却增加缓慢.两半岛地表温度高的区域就会使空气上升,而海表低温区域空气就会下沉.海陆温差的增加有利于Rayleigh-Benard对流环流的生成和发展,也使得陆地和海面上正负垂直相对涡强度Γ增强.根据Biot-Savart定律,涡强度Γ的增强必然诱导出相应强大的水平速度.两半岛和海面上这一对正负相对涡度场耦合成一部高效率的"索马里抽气泵".这一抽气泵将气流从南半球吸入,在索马里沿岸附近排出.索马里半岛和阿拉伯半岛地表增温以及与西北印度洋海表温差是驱动索马里抽气泵运转的主要能源.Firstly,we investigate the impact of cross-equatorial Somali low-level jet on the atmospheric circulation in the east of Tibet Plateau using lattice Boltzmann model simulation. Secondly,we study the relationship between thermal conditions on the bottom boundary and the formation of Somali jet based on Biot-Savart law using the data from National Centres for Environmental Prediction （ NCEP）. As the radiation from the Sun gradually moves from the southern meridian,the temperature on the ground surface of Somali Peninsular and Arabic Peninsular gradually increases. During the same period the surface temperature of the Northern Indian Ocean increases much slower. It is shown that this increase in the temperature difference between the land and sea is inductive to the formation and development of Rayleigh-Benard convection and leads to the increasing relative vorticity strength between positive and negative vertical vortices over the land and sea. According to Biot-Savart law,the increase in vorticity strength will induce correspondingly a large horizontal velocity. The pair of positive and negative vorticity fields over the two Peninsulars and the sea surface is effective in forming and maintaining this current. This mechanism is referred to as＂Somali suction pump＂. It draws air continually from the Southern hemisphere and releases it at the coastal area of Somali.

关 键 词：索马里低空急流 Biot-Savart定律 索马里抽气泵 

分 类 号：P458.121.1[天文地球—大气科学及气象学]