Generation Mechanism of the South Pacific Subtropical Dipole
Generation Mechanism of the South Pacific Subtropical Dipole
复制标题
DOI：
10.1175/jcli-d-12-00648.1
复制
发表时间：
2013-08-01
影响因子：
4.9
通讯作者：
Masumoto, Yukio
中科院分区：
文献类型：
--
作者：
Morioka, Yushi;Ratnam, J. V.;Masumoto, Yukio
使用耦合大气环流模型的输出来检查南太平洋海面温度（SST）[即南太平洋副热带偶极子（SPSD）]年际变化的独特模式。 SPSD表现为南太平洋海温异常的第二经验正交函数(EOF)模式，并与中部盆地正负海温异常的东北-西南方向的偶极子相关。海温正、负异常极在南半球春季开始发展，在南半球夏季达到高峰，之后逐渐衰减。对混合层热平衡的仔细检查表明，海温异常极点的形成主要是因为短波辐射对混合层的变暖是由异常混合层厚度调制的。在正极（负极）极上，混合层变得比正常情况更薄（更厚），并通过气候短波辐射增强（减少）混合层的变暖。这种较薄（较厚）的混合层可能与上覆海平面压力（SLP）异常相关的蒸发抑制（增强）有关。在正极的情况下，比正常情况弱的表面风也会导致混合层变薄。此外，海平面气压异常与对流层上部的位势高度异常相关，并与中纬度地区沿西风急流的静止罗斯贝波模式相关。这表明产生 SPSD 的 SLP 异常不是本地激发的，而是远程感应的信号。
Distinct pattern of interannual variability in sea surface temperature (SST) in the South Pacific [i.e., the South Pacific subtropical dipole (SPSD)] is examined using outputs from a coupled general circulation model. The SPSD appears as the second empirical orthogonal function (EOF) mode of the SST anomalies in the South Pacific and is associated with a northeast-southwest-oriented dipole of positive and negative SST anomalies in the central basin. The positive and negative SST anomaly poles start to develop during austral spring, reach their peak during austral summer, and gradually decay afterward. Close examination of mixed-layer heat balance yields that the SST anomaly poles develop mainly because warming of the mixed layer by shortwave radiation is modulated by the anomalous mixed-layer thickness. Over the positive (negative) pole, the mixed layer becomes thinner (thicker) than normal and acts to enhance (reduce) the warming of the mixed layer by climatological shortwave radiation. This thinner (thicker) mixed layer may be related to the suppressed (enhanced) evaporation associated with the overlying sea level pressure (SLP) anomalies. Weaker-than-normal surface wind also contributes to the thinner mixed layer in the case of the positive pole. Furthermore, the SLP anomalies are linked with the geopotential height anomalies in the upper troposphere and are associated with a stationary Rossby wave pattern along the westerly jet in the midlatitudes. This suggests that the SLP anomalies that generate the SPSD are not locally excited but remotely induced signals.