非均匀风场与急流强迫的水体涡旋动力特征模拟  

A simulation study on dynamic characteristics of eddies forced by non-uniform wind fields and jet currents

作　　者：王坚红[1] 冯呈呈[1] 苗春生[1] 李洪利[1] 耿珊珊[2] 

机构地区：[1]南京信息工程大学,江苏南京210044 [2]国家海洋信息中心,天津300171

出　　处：《大气科学学报》2013年第6期653-665,共13页Transactions of Atmospheric Sciences

基　　金：国家自然科学基金资助项目(41276033);国家科技支撑计划项目(2012BAH05B01);公益性行业(气象)科研专项(GYHY201206068);南京气象雷达开放实验室研究基金(BJG201105);江苏省科技支撑项目(BE2012774);江苏高校优势学科建设工程资助项目(PAPD)

摘　　要：通过数值模拟有限区域水气界面由强迫作用驱动形成的水体涡旋及环流动力结构特征,分析非均匀风场、水体急流、两者叠加以及环境边界和地转偏向力等因子的综合影响,探讨此类水体涡旋结构和动力特征。风应力驱动的水体涡旋尺度大,相对深厚,正涡旋具有下凹表面,负涡旋具有上凸表面。水体急流驱动的涡旋形成在急流两侧,对应急流所在深度及厚度尺度相对较小,也较浅,但流速与强度均大于风场驱动的涡旋环流。地形阻挡起着引导涡旋环流走向的作用;同时在北半球地转偏向力对急流侧向负涡旋形成和强度增强更为有利。此外正涡旋对应的辐合辐散势函数强于负涡旋,有利于正涡旋区垂直上升运动强于负涡旋中垂直下沉运动。非均匀风场及水体急流两种强迫叠加作用下,涡旋数量增加、尺度减小,底层的流场形态及强度与表层差异增大。形成的水体涡旋结构呈现多种形态:深厚的整层一致;浅薄的仅维持在上层,或上下层环流相反等。风应力驱动的涡旋以正压性为主,水体急流驱动的涡旋因急流的垂直强切变而具有强的斜压性,在正斜压动能的转换中,正压性涡旋区有斜压动能向正压动能转换,斜压性涡旋区有正压动能向斜压动能转换,均有利于这两个区域正负涡旋的维持。By simulating the dynamic and structural characteristics of water eddies in a limited area, the paper analyzed the functions of impact factors like non-uniform wind field, water jet current, their super- position, environmental boundary, Coriolis force and etc. The eddies generated by wind fields are of lar- ger size and deeper depth. Cyclone is of concave surface and anticyclone is of convex surface. The ed- dies generated by water jet appear on both sides of the jet and accord with the jet thickness. Their size is smaller and thickness is shallower, but their flow and strength are stronger. Topographic boundary plays a guiding role in the movement of eddy. The Coriolis force in the Northern Hemisphere is beneficial for the enhancement of negative eddy. Meantime the potential function presenting convergence and diver- gence of eddies for cyclone is stronger than that for anticyclone. It is more effective to cause the vertical upward motion for cyclone than to cause the downward motion for anticyclone. When non-uniform wind field overlapped water jet, the number of eddies increase, their size decreases and their patterns at bottom are of more obvious difference from those on the surface layer. There are many types of eddy structures：for some the whole layer is consistent;for some others consistency only existence on the up- per layer;for still some others the upper and lower circulations reverse, etc;The eddies generated by wind field are mainly barotropic, the eddies forced by water jet are manly baroclinic. In kinetic energy exchange, it happens that the barotropic kinetic energy transforms into baroclinic kinetic energy at baro- tropic eddy area, and the barotropic kinetic energy transforms into baroclinic kinetic energy at baroclinic eddy area. Both kinetic energy transformations are beneficial for the maintenance of the two kinds of eddies.

关 键 词：非均匀风场 水体急流 涡旋结构 正斜压动能转换 

分 类 号：P447[天文地球—大气科学及气象学]