摘要
斯里兰卡岛以东海域在西南季风期间常会出现一对低频涡旋偶极子(即斯里兰卡穹顶气旋涡和反气旋涡),对当地的海洋生态系统及气候有着重要影响。基于(1/12)°分辨率的混合坐标海洋模式(Hybrid Coordinate Oceanic Model,HYCOM)再分析资料以及多尺度子空间变换(MWT)和基于MWT的正则传输理论等方法,分析了它们的生成发展机制。结果发现这2个涡旋发展所需能量最终都来源于海表风应力做功,但具体可取3条完全不同的路径:①风应力直接驱动涡旋;②风应力驱动背景场的西南季风流,其后西南季风流发生正压不稳定以提供涡旋所需的涡动能;③西南季风流通过风应力做功获得的动能转换为有效位能,其后通过斜压不稳定给涡旋提供位能。涡旋最终衰亡的主要原因包括风应力对涡旋做功的减少、西南季风流正压不稳定的减弱、涡旋的能量频散以及低频涡向更高频扰动的正向能量级串。
The low-frequency vortex dipoles,namely,the Sri Lanka Dome(SLD)and Anticyclonic Eddy(AE),a recurring phenomenon that is generated during southwest monsoon season east of Sri Lanka,have great influences on local ecosystem and climate.A recently developed multiscale analysis methodology is used to investigate the genesis and evolution mechanisms underlying the low-frequency vortex dipoles,on the basis of the HYCOM reanalysis data with a horizontal resolution of(1/12.5)°.It is found that the dynamical processes of the two eddies are similar,with the ultimate driving force traced back to the wind stress.They may,however,choose one or more of the following three completely different energy pathways:①eddies are directly driven by the wind;②the wind first drives the background southwest monsoon current(SMC),while the SMC feeds the eddies via a barotropic instability;③the SMC obtains energy from the wind,and then convert that part of kinetic energy to available potential energy(APE),which through a baroclinic instability is transferred to eddy APE,facilitating the growth of the eddies.The two eddies may decay due to either a reduction in strength of the external wind forcing,or a weakening of the barotropic instability of the background flow,or a nonlocal dispersion of the eddy energy,or an intense dissipation through forward energy cascading.
作者
何蔚邦
杨洋
梁湘三
HE Wei-bang;YANG Yang;LIANG Xiang-san(School of Marine Sciences,Nanjing University of Information Science&Technology,Nanjing 210044,China;Department of Atmospheric and Oceanic Sciences,Fudan University,Shanghai 200438,China;Institute of Atmospheric Sciences,Fudan University,Shanghai 200438,China)
出处
《海洋科学进展》
CAS
CSCD
北大核心
2022年第3期379-398,共20页
Advances in Marine Science
基金
国家自然科学基金项目——黑潮延伸体低频变异的能量学特征及其机理研究(41975064)和多尺度子空间交互作用与北大西洋涛动(NAO)动力过程研究(41806023)
2015年江苏双创团队项目——江苏沿岸海洋环境对人为与自然变化的多尺度响应
江苏省特聘教授项目。
关键词
斯里兰卡穹顶
西南季风流
多尺度过程
正压失稳
斜压失稳
孟加拉湾
Sri Lanka Dome(SLD)
Southwest Monsoon Current(SMC)
multiscale window transform
barotropic instability
baroclinic instability
Bay of Bengal(BOB)
