CAJ | 학술논문

基于正压出入流模式,利用条件非线性最优扰动(CNOP)方法研究初始异常的位置与模态对日本南部黑潮路径变异的影响。以模式模拟出的黑潮平直路径的平衡态作为参考态,计算CNOP,考察该扰动随时间的发展,并与随机扰动的发展进行对比。结果表明, CNOP能够导致黑潮弯曲路径发生,随机扰动则不能。因此, CNOP可以作为导致日本南部黑潮路径发生弯曲的一种最优前期征兆。通过分析CNOP和随机扰动的发展过程,可以得出：(1) CNOP使黑潮发展成弯曲路径的过程是一个气旋涡向下游传播并增长的过程。(2)气旋涡的向东传播都是非线性项的作用,也就是涡度平流造成的。(3) CNOP和随机扰动发展过程中所产生的气旋涡均会传播到下游区域,但是 CNOP 产生的气旋涡能够增强,最终导致弯曲路径发生,而随机扰动产生的气旋涡则会减弱,并不能导致弯曲路径发生。分析发现,在CNOP实验中,非线性作用使气旋涡增大；但在随机扰动实验中,非线性作用使气旋涡减弱,所以非线性作用对日本南部黑潮路径发生弯曲有重要影响。(4)底摩擦效应对日本南部黑潮路径变异影响较小。本文揭示的黑潮路径发生弯曲的最优前期征兆及其非线性发展机制,对提高黑潮路径变异的预报技巧具有重要意义。
기우정압출입류모식,이용조건비선성최우우동(CNOP)방법연구초시이상적위치여모태대일본남부흑조로경변이적영향。이모식모의출적흑조평직로경적평형태작위삼고태,계산CNOP,고찰해우동수시간적발전,병여수궤우동적발전진행대비。결과표명, CNOP능구도치흑조만곡로경발생,수궤우동칙불능。인차, CNOP가이작위도치일본남부흑조로경발생만곡적일충최우전기정조。통과분석CNOP화수궤우동적발전과정,가이득출：(1) CNOP사흑조발전성만곡로경적과정시일개기선와향하유전파병증장적과정。(2)기선와적향동전파도시비선성항적작용,야취시와도평류조성적。(3) CNOP화수궤우동발전과정중소산생적기선와균회전파도하유구역,단시 CNOP 산생적기선와능구증강,최종도치만곡로경발생,이수궤우동산생적기선와칙회감약,병불능도치만곡로경발생。분석발현,재CNOP실험중,비선성작용사기선와증대；단재수궤우동실험중,비선성작용사기선와감약,소이비선성작용대일본남부흑조로경발생만곡유중요영향。(4)저마찰효응대일본남부흑조로경변이영향교소。본문게시적흑조로경발생만곡적최우전기정조급기비선성발전궤제,대제고흑조로경변이적예보기교구유중요의의。
The barotropic inflow-outflow model was built to study the impacts of spatial locations and patterns of the initial anomaly on the variability of the Kuroshio path using the conditional nonlinear optimal perturbation (CNOP) method. First, the CNOP was calculated using the equilibrium of the straight path as reference state. Then the CNOP was superimposed on the reference state to investigate its development process, which was compared with the evolutions of random perturbation (RP). We found that the CNOP caused the Kuroshio path to transfer to meander path while the random perturbation did not. In this case, the CNOP could be regarded as the optimal precursor of the Kuroshio meander path. By analyzing the developing processes of the CNOP and the RP, we concluded that: 1) The formation process of the Kuroshio meander path caused by CNOP was the process of a cyclonic eddy advection downstream. 2) The cyclonic eddy was transferred to downstream due to the effect of nonlinear items, which was also the vorticity advection term. 3) The eddies both in the CNOP and RP cases would transport to the downstream, but the eddy in the CNOP case could grow up and develop into meander path while the eddy in the RP case could not. The cyclonic eddy was strengthened by the nonlinear effect in the CNOP case, while it was weakened by the nonlinear effect in the RP case. In conclusion, the nonlinear effect was very important in the processes of the formation of the Kuroshio meander path in the south of Japan. 4) The impact of bottom friction has relatively small effeots on the variability of the Kuroshio path in the south of Japan. This study has revealed the optimal precursor of the occurrence of Kuroshio meander path and its nonlinear evolution mechanism, which is very important for improving the forecast skill of the Kuroshio path variations.