The Heat Balance in the Western Equatorial Pacific Warm Pool during the Westerly Wind Bursts: A Case Study

The responses of sea surface temperature (SST) in the western equatorial Pacific warm pool to the westerly wind bursts (WWBs) play an important role in the relationship between WWB and ENSO. By using data collected from eight buoys of TOGA (Tropical Ocean-Global Atmosphere)- COARE (Coupled Ocean-Atmosphere Response Experiment), the heat balances of the upper ocean in the western equatorial Pacific around 0 degrees, 156 degreesE during two WWB events were calculated according to Stevenson and Niiler's (1983) method. In both events, SST increased before and after the WWBs, while decreased within the WWBs. The SST amplitudes approximated to 1 degreesC. Although sometimes the horizontal heat advections may become the biggest term in the heat balance, the variation of SST was dominated by the surface heat flux. On the other aspect, some different features of the two events are also revealed. The two cases have different variation of mixed layer depth. The depth of mixed layer is almost double in the first case (35 in to 70 m), which is caused by Ekman convergence, while only 10m increments due to entrainment in the second one, There are also differences in the currents structure. The different variations of thermal and currents structure in the mixing layers accounted for the different variation of the heat balance during the two events, especially the advection and residue terms. The seasonal variation of SST in this area is also investigated simply. The first WWB event happened just during the seasonal transition. So we considered that it is a normal season transition rather than a so-called anomaly. That also suggested that the seasonal distinction of the WWB is worthy of more attention in the researches of its relationship to ENSO.

Research on the Propagation Acting of the Equatorial Planetary Waves on the Western Equatorial Pacific Warm Pool Heat

Based on the long-term buoy data from the Tropical Atmosphere Ocean ( TAO ) —array during the TOGA ( Tropical Ocean and Global Atmosphere ) Program (19801996), the propagation acting of the Equatorial planetary waves on the Western Equatorial Pacific warm pool heat is analyzed. Results show that the zonal heat transmission in the Western Equatorial Pacific takes palace mainly in the subsurface water and spreads eastwards along the thermocline; while the seasonal westward-spreading heat change structure occurs in the mixed layers in the middle and western Pacific. The standing-form transmission in the western Pacific appears in the thermocline layer, while in the eastern pacific, it exists in the mixed layer as well as in the thermocline layer. The standing-form and eastward-spreading sign of zonal heat transmitting in the upper water is predominant and strong, and the westward sign is weak.The component force of Kelvin Equatorial wave pressure runs through the western and eastern Equatorial pacific, and transmits heat energy eastwards. And the heat transmitted by zonal current component occurs mostly in the western Pacific; The heat transmitted by the component force of Rossby wave pressure mainly appears in the eastern and middle areas of the Pacific, while the zonal current component transmitting occurs mainly in the western Pacific; Mixed-Rossby gravity wave’s action on the zonal current is stronger than that of the thermocline layer. In the mean state, the standing wave model of Equatorial Pacific up layer ocean temperature confines the transport of western Pacific warm pool heat to the eastern Pacific. Under abnormal conditions, the standing wave model of Equatorial Pacific up layer ocean temperature weakens, the eastwardly transmitting model enhances, and subsequently n^the El Ni o event occurs.

西风爆发时赤道西太平洋热量平衡的诊断分析

西风爆发（ＷＷＢ）对赤道西太平洋暖池ＳＳＴ的影响是ＷＷＢ与ＥＮＳＯ相互作用的一个重要环节。作者运用 ＴＯＧＡ（Ｔｒｏｐｉｃａｌ Ｏｃｅａｎ－Ｇｌｏｂａｌ Ａｔｍｏｓｐｈｅｒｅ）－ＣＯＡＲＥ（Ｃｏｕｐｌｅ Ｏｃｅａｎ－Ａｔｍｏｓｐｈｅｒｅ Ｒｅｓｐｏｎｓｅ Ｅｘｐｅｒｉｍｅｎｔ）期间暖池海区 ８个浮标的观测资料，根据Ｓｔｅｎｖｅｎ和Ｎｉｉｌｅｒ的热量平衡诊断方法，从能量平衡角度分析了赤道１５６°Ｅ附近ＳＳＴ对１９９２年 ９月到 １９９３年 １月期间两次 ＷＷＢ事件的响应。两次 ＷＷＢ期间， ＳＳＴ都是在ＷＷＢ之前和其后升温，而在ＷＷＢ期间降温，升温和降温的幅度均为ｌ℃左右。热量平衡分析结果表明，季节内时间尺度上海表热通量是导致赤道西太平洋暖池混合层温度变化的主要因素。在海表热通量中，短波辐射和潜热是变化量最大的两项，决定着净通量的正负，其他项的变化则相对较小。水平平流项有时可以超过海表热通量的作用，其作用不可忽略、两次ＷＷＢ的过程中，季节变化造成的混合层的温盐结构和流场结构的差异是导致两次ＷＷＢ事件时上层海洋热量平衡差别的主要因素。另外，混合层的厚度也有明显的变化。

一个大洋环流模式中赤道西太平洋暖池海面温度对西风爆发的响应

用逐日的欧洲中期数值预报中心再分析（ＥＲＡ）风应力，和由Ｈａｎｅｙ公式结合ＥＲＡ海表资料与预报海温计算出的热通量强迫一个全球大洋环流模式。并用逐日的模拟结果与ＴＯＧＡ－ＣＯＡＲＥ（Ｔｒｏｐｉｃａｌ Ｏｃｅａｎ－Ｇｌｏｂａｌ Ａｔｍｏｓｐｈｅｒｅ－Ｃｏｕｐｌｅｄ Ｏｃｅａｎ—ＡｔｍｏｓｐｈｅｒｅＲｅｓｐｏｎｓｅ Ｅｘｐｅｒｉｍｅｎｔ）浮标观测资料对比，分析模拟结果中暖池海区上层海洋热量平衡对西风爆发（ＷＷＢ）的响应。在第一次ＷＷＢ过程中，模拟与观测的主要差异在ＷＷＢ期间，而造成差异的原因主要是模式中由下沉运动引起的增温和由强的纬向温度梯度引起的暖平流。初步认为下沉增温可能是差分格式本身和模式分辨率不足造成的。从热量平衡的结果看，第二次ＷＷＢ事件的模拟比第一次更成功，两次差异可能与两次ＷＷＢ事件的季节背景不同有关。

赤道行星波对西赤道太平洋暖池热传播的作用

利用热带海洋和全球大气试验(TOGA)期间(1980～1996年)热带大气海洋观测阵(TAO)的长期浮标资料,分析了赤道行星波对西赤道太平洋暖池热传播的作用。结果表明,西赤道太平洋暖池纬向热传播主要出现在次表层水体中,并沿温跃层向东传播;而向西传播的季节热结构变化主要出现在中、西赤道太平洋的混合层中;驻波型传播在西赤道太平洋主要出现于温跃层,在中赤道太平洋主要出现于混合层和温跃层,在东赤道太平洋主要出现于混合层。在平均条件下,赤道太平洋上层水温纬向热传播信号以驻波型和东传型较强,西传型较弱。赤道Kelvin波压力分量贯穿西、东赤道太平洋并向东输送暖池热能,纬向流分量的热输送主要出现在西赤道太平洋;Rossby波压力分量的热输送主要出现在东、中赤道太平洋;混合Rossby重力波激发纬向流的热输送作用比相应温跃层扰动强。在平均条件下,赤道太平洋上层水温的驻波型变化制约了西赤道太平洋暖池热量的持续向东输送,因此形成了赤道太平洋水温的正常季节变化形态。当水温的驻波型变化减弱而东传型变化加强时,随后将形成厄尔尼诺现象。

西太平洋暖池热含量与南海夏季风强度的关系

为了进一步明确西太平洋暖池热含量对南海夏季风强度的影响,利用1948～2012年日本气象厅（japan meteorological agency,JMA）逐月的海温资料、Hadley中心的海表面温度（Sea Surface Temperature,SST）资料以及NCEP/NCAR再分析资料,分析比较了南海夏季风强度与热带太平洋上层海洋热含量和SST的关系;探讨了海洋热含量影响南海夏季风强度的机制。结果表明：（1）相比于西太暖池SST,西太暖池上层海洋热含量是南海夏季风强度更好的预测因子;（2）前期冬春季的西太平洋暖池热含量与南海夏季风强度呈现显著的正相关,尤其在3月,二者相关系数最大;当暖池热含量偏高（低）时,西太平洋副热带高压偏弱（强）,赤道印度洋出现异常反气旋（气旋）,印度洋上空的Walker环流分支偏强（弱）,南海越赤道气流增强（减弱）,最终使得南海夏季风强度偏强（弱）。