CAJ | 학술논문

搅拌是海水混合的重要组成,其强度可由基于拉格朗日观点的有限时间李亚普诺夫指数(Finite Time Lyapunov Exponents, FTLE)定量计算。文章利用卫星高度计资料统计分析了2002~2011年间南海地转流场的FTLE时空变化特征。结果显示, FTLE在越南东南海域强度最大,对应水平搅拌作用最强；而在南海西北、东南区域其值偏低。近10年的南海水平搅拌呈缓慢增强趋势,且存在明显的季节变化,夏季较强而冬季偏弱。FTLE 的空间分布与基于欧拉观点的涡动能和应变速率相似,强搅拌的区域,其涡动能和应变速率亦较高。与Okubo-Weiss参数的比较则显示,构成流场拉格朗日拟序结构(Lagrangian Coherent Structures, LCS)的FTLE脊线与流场中涡旋联系紧密, FTLE低值集中在旋转主导的涡旋内部,而高值多在涡旋周围应变主导区域。
교반시해수혼합적중요조성,기강도가유기우랍격랑일관점적유한시간리아보낙부지수(Finite Time Lyapunov Exponents, FTLE)정량계산。문장이용위성고도계자료통계분석료2002~2011년간남해지전류장적FTLE시공변화특정。결과현시, FTLE재월남동남해역강도최대,대응수평교반작용최강；이재남해서북、동남구역기치편저。근10년적남해수평교반정완만증강추세,차존재명현적계절변화,하계교강이동계편약。FTLE 적공간분포여기우구랍관점적와동능화응변속솔상사,강교반적구역,기와동능화응변속솔역교고。여Okubo-Weiss삼수적비교칙현시,구성류장랍격랑일의서결구(Lagrangian Coherent Structures, LCS)적FTLE척선여류장중와선련계긴밀, FTLE저치집중재선전주도적와선내부,이고치다재와선주위응변주도구역。
Stirring is an important part of mixing, which can be quantified using Finite Time Lyapunov Exponents (FTLE) based on Lagrangian view. In this paper, we calculated the FTLE of surface ocean derived from satellite altimeter from 2002 to 2011, and then analyzed spatial and temporal variation of horizontal stirring in the South China Sea (SCS). Results show that FTLE in the SCS is not uniform, with high values southeast of Vietnam indicating strong stirring, and low values in the northwest and southeast of the SCS. A slowly increasing trend of stirring in the SCS is observed during the 10 year period. FTLE also displays a seasonal fluctuation, strong in summer but weak in winter. Furthermore, we found that FTLE has a similar spatial distribution with Euler-based eddy kinetic energy (EKE) and strain rate, with high and low values of these three quantities locating roughly in the same areas. A comparison with Okubo-Weiss parameter reveals a strong relationship between vortices and FTLE ridges, referred to as Lagrangian Coherent Structures (LCS). Low values of FTLE are mainly present inside rotation-dominated vortices, while high values occur in strain-dominated regions surrounding the vortices.