摘要:西北太平洋纬向扰动海温经验正交函数（EOF）分解第一和第三模态、第二和第四模态分别代表同期黑潮延伸体和亲潮强弱的配置关系，将两者的典型位相合成，可以分别得到延伸体收缩和扩张状态时的典型模态海温，本文以此及气候态海温作为初始海温强迫场，利用CESM1.2.0模式，讨论了延伸体的系统变异对北太平洋风暴轴的影响及其在不同能量转换过程的主要影响机制，结果表明，延伸体收缩状态下，北太平洋风暴轴强度整体加强，而扩张模态下强度减弱。空间分布上，收缩模态下，风暴轴主要体现为经向方向的变化，中心及其以北强度加强，中心以南减弱；扩张状态下，则主要表现为纬向方向的差异，中心及以西强度减弱明显，中心以东有所增强。对能量转换的诊断分析表明，正压能量转换过程对涡动动能的变化贡献很小，且在风暴轴中心附近，其作用主要为消耗涡动动能，延伸体收缩状态下其消耗作用增强，而扩张状态下消耗作用减弱，这一差异主要是由于不同海温异常强迫下瞬变涡旋的形变不同造成；斜压有效位能释放比正压能量转换大一个量级以上，该过程几乎全部通过基流的经向温度梯度和经向涡动热量输送的相互作用完成，在这一过程中大气斜压性（经向温度梯度）起了关键性作用，大气斜压性异常、基流经向温度梯度异常、斜压有效位能释放异常与风暴轴异常的空间分布均具有较好的对应关系，该过程可能也是延伸体海温异常影响北太平洋风暴轴的主要物理过程；涡动有效位能需要进一步转换为涡动动能才能产生瞬变涡旋运动，涡动有效位能释放的量级与斜压有效位能的释放相当，但数值要小，这一过程通过冷暖空气的上升下沉运动完成，延伸体异常模态下，扰动垂直速度和扰动温度的负相关性的变化与涡动有效位能向涡动动能转换的变化也有较好的对应关系。
关键词:北太平洋风暴轴/
黑潮延伸体系统变异/
能量转换/
大气斜压性
Abstract:The first and third modes, and the second and fourth modes of the empirical orthogonal function (EOF) decomposition of the zonal sea surface temperatures (SST) perturbations (ZSSTP) in the Northwest Pacific are in good synchronous correlations, respectively. By synthetizing the typical phases of the two separately, the typical SST modes of the Kuroshio Extension (KE) in contraction and elongation states can be obtained. The influences of the variability of KE on the North Pacific storm track and the main mechanisms in different energy conversion processes are discussed based on the CESM1.2.0 model simulations, which are initialized with SST forcing fields in contraction and elongation modes and with climatological SST, respectively. It is found that under the KE's contraction mode, the intensity of the North Pacific storm track basically enhances, but the vortex activities weaken to the south of the center; under the KE's elongation mode, the intensity of the storm track decreases to the west of the center but the vortex activities increase to the east of the center. Diagnostic analysis of energy conversion shows that the barotropic energy conversion process makes little contribution to the change of the eddy kinetic energy (EKE). Near the center of the storm track, its major effect is to consume EKE. Under the contraction mode of the KE, the EKE consumption in the barotropic energy conversion process weakens, while it enhances under the elongation state of KE. The above differences are mainly due to different deformations of the transient eddies under different SST anomalies. The baroclinic potential energy release is one order of magnitude higher than the barotropic energy conversion. It is completed through the interaction between the meridional temperature gradients of the base flow and the meridional vortex heat transport. The atmospheric baroclinicity (meridional temperature gradient) plays a key role in this process, while the spatial distribution of the atmospheric baroclinic anomalies, the meridional temperature gradient anomalies of base flows, the baroclinic effective potential energy release anomalies and the storm tracks anomalies all have a good correspondence. This process may also be the main physical process for SST anomalies of the KE to affect the North Pacific storm track. Eddy effective potential energy needs to convert to EKE to produce transient vortex motions. The magnitude of the release of the eddy effective potential energy is approximately the same as that of the baroclinic effective potential energy, but the value is relatively small. This process is accomplished by the warm air rising and cold air falling. The changes in the negative correlation between perturbed vertical velocity and perturbed temperature also agree well with the variations of the conversion from the eddy effective potential energy to the eddy kinetic energy.
Key words:North Pacific storm track/
Systematic variations of the Kuroshio extension/
Energy conversion/
Atmospheric baroclinic property
PDF全文下载地址:
http://www.iapjournals.ac.cn/qhhj/article/exportPdf?id=20180606
