On the generation of North Brazil Current rings
On the generation of North Brazil Current rings
复制标题
论巴西北流环的生成
DOI：
10.1357/002224003322005050
复制
发表时间：
2003
影响因子：
0.5
通讯作者：
P. Malanotte‐Rizzoli
中科院分区：
文献类型：
--
作者：
M. Jochum;P. Malanotte‐Rizzoli
采用高分辨率大气环流模式（OGCM）研究了北巴西洋流（NBC）环的生命周期。研究的重点是解释环的产生机制及其垂直结构。OGCM用于尽可能简化的锥状天气，但能够再现真实的热带大西洋平均环流。三种数值实验分析：无风；稳定的风;季节性变化的风。随着风的作用，一个一致的情景出现了NBC环的产生。结果表明，东北环流是正压不稳定的，辐射第1斜压模态的罗斯比波，周期为63天（稳定风）或50天（变风）。这些波浪在巴西海岸形成，每年产生约6 - 7个反气旋。由于潜在涡度守恒，这些反气旋在沿着巴西海岸向西北传播并成为NBC环时变得更加强烈。其中，每年约有一次深度低于1000米。这些深环是由一个表面的NBC环和一个中间涡合并而成的。中间涡旋是由中间西边界流（IWBC）产生的，它在穿过赤道时变得不稳定。
A high resolution general circulation model (OGCM) is used to investigate the life cycle of North Brazil Current (NBC) rings. The focus of the study is on explaining the generation mechanisms of the rings and their vertical structure. The OGCM is used in a cone guration simplie ed as much as possible but capable of reproducing a realistic mean circulation of the tropical Atlantic. Three numerical experiments are analyzed: no wind; steady wind; seasonally varying winds. With wind forcing, a consistent scenario emerges for the generation of NBC rings. It is shown e rst that the NECC is barotropically unstable, radiating Rossby waves of the e rst baroclinic mode with a period of 63 days (steady wind) or 50 days (variable wind). These waves ree ect at the Brazilian coast and create about 6‐ 7 anticyclones per year. These anticyclones intensify as they propagate northwestward along the Brazilian coast because of potential vorticity conservation and become NBC rings. Among them, about one per year reaches a depth below 1000 m. These deep rings are created by the merger of a surface NBC ring with an intermediate eddy. The intermediate eddies are produced by the Intermediate Western Boundary Current (IWBC) which becomes unstable upon crossing the equator.