摘要
本文首先指出北太平洋副热带中部模态水(简称中部模态水)的形成具有显著的"局地"特征,其形成海区在(165°E^160°W,38°N^42°N)区间.海气通量分析表明单纯的外部大气强迫场(太阳短波辐射、净热通量和风应力旋度)不能解释中部模态水形成海区的"局地"性;进一步对上层海洋层结季节变化特征的分析发现秋季(9~10月)在北太平洋中部上层海洋(<75m)(165°E^160°W,38°N^42°N)区间存在特殊的浮力频率低值区——层结稳定性"豁口".该层结稳定性"豁口"作为"预条件(Precondition Mechanism)"机制对中部模态水形成的"局地"特征给出了合理的解释.在上述研究的基础上,基于一个上层海洋混合层热平衡方程,通过诊断分析揭示该层结稳定性"豁口"是由海表热力强迫、垂向挟卷、Ekman平流和地转平流效应共同导致的,"豁口"东、西边界的确定直接或间接地取决于海表热力强迫、Ekman冷平流和地转暖平流的纬向分布差异.
local feature of the formation region （ 165°E -160°W, 38°N - 42°N） of the North Pacific Central Mode Water （NPCMW） is first put forward from data analysis, and for which, the external atmospheric forcing （solar shortwave radiation, net heat flux and wind stress curl） could not give acceptable explanation. Further analysis on the seasonal variability of the upper ocean stratification shows that a special weak zone of the ocean stratification in the upper ocean （ 〈 75 m）-the ＂stability gap＂ is detected in （165°E- 160°W, 38°N -42°N） in autumn （September-October）. As ＂Precondition Mechanism＂, the ＂stability gap＂ provides a reliable answer for the ＂local feature＂ of the formation of the NPCMW. Based on a heat balance equation of the upper ocean mixed layer, diagnostic analysis suggests that the formation of the ＂stability gap＂ is the cooperative product of the surface heat flux forcing, vertical entrainment, Ekman advection and geostrophic advction. Among which, the latitudinal differences of the surface heat flux forcing, the cold Ekman advection and the warm geostrophic advection play the crucial roles on determining the critical eastern and western bound of the ＂stability gap＂.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2008年第1期77-87,共11页
Chinese Journal of Geophysics
基金
国家重点基础研究发展计划项目(第二课题2007CB816002)
国家自然科学基金(40333030,40406005)
基本科研业务费专项资金(海三科2007018)
国家海洋局青年海洋科学基金(2006206,2007208)资助
