【作者】 胡瑞金；

【导师】 刘秦玉； J. Stuart Godfrey； 周发琇；

【作者基本信息】 中国海洋大学 ， 气象学， 2003， 博士

【摘要】 热带印度洋与热带太平洋或热带大西洋相比，有很多独一无二的特性。本文根据COADS、SODA等实际观测资料，较全面的分析了热带印度洋主要的气候特点，并研究了海表面温度(SST)、热收支与海洋动力、热力过程的联系；利用全球海洋环流模式较好地模拟出热带印度洋的季节和年际变化；基于热力学方程和海洋环流模式输出结果，探讨了热带印度洋SST和北印度洋热量收支的季节和年际变化机制，进一步揭示了海洋动力过程在北印度洋热平衡中的重要作用；在此基础上，利用理想化的数值试验与数值模拟结果相结合的方式，证实了风应力的季节变化和Ekman抽吸，以及水平热量扩散系数对北印度洋海洋环流和热收支的影响。 热带印度洋，尤其是7°S以北的印度洋，受亚洲季风的显著影响，与季风对应，海洋环流也有很明显的季节变化，最明显的是索马里海流的季节转向。此外，索马里-阿拉伯沿岸夏季的很强的上翻，冬季则是下翻；跨越赤道在夏季有向南的EKMAN输送，在冬季相反。不仅如此，北印度洋SST在一年有两次增暖、夏季风期间阿拉伯海中部混合层的加深，以及季风转换其间赤道急流的存在等也是季节变化尺度上引人注目的现象。夏季的风应力在一年中占有优势，在赤道上出现了西风。此外，在赤道附近风应力大致从赤道以南的向西变为赤道以北的向东，这意味着年平均意义上有跨越赤道向南的Ekman流。这些特点是印度洋与其他大洋不同之处，对北印度洋的热收支和SST有重要影响。SST与海表面高度、热含量、温跃层深度等的相关分析也表明，在某些区域，除受海洋-大气之间热交换的影响外，海洋动力过程对SST的影响也占重要地位。 根据混合层温度变化方程，利用海洋模式模拟结果进行诊断分析，估计了在SST变化中不同物理过程影响的相对重要性。就赤道以北印度洋而言，海面净热通量和混合层底的卷夹过程都有半年周期，这是SST呈现半年周期变化的主要原因。在夏季，整个阿拉伯沿岸和孟加拉湾西部混合层底的卷夹作用占优势；海面净热通量在孟加拉湾SST的变化中始终是主要的影响因子；对几个典型区域的研究表明，不同的区域的混合层温度有着非常不同的变化机制。 根据热量收支方程和海洋模式资料，定量估计了北印度洋的热量收支，重点研究了经向热输送及其影响机制。结果表明越赤道和越10oN阿拉伯海的热输送量大小具有可比性，且有相同的年循环特征，而10oN孟加拉湾纬度的经向热输送较小，且具有半年变化周期;俨S以北印度洋任一纬度上的纬向风应力异常与此纬度上的经向热输送异常以及此纬度以北印度洋总的海面净热通量异常有很好的相关关系，相关系数最大可达一0.5以上。经向热输送集中在上500米，尤其在150米以上。在总的经向热输送中，经向翻转环流的贡献起主要作用，进一步证实了风对经向翻转环流的重要性。 基于MOMZ，我们设计了一个包括赤道的理想的热带印度洋矩形海盆模式，其目的是为了研究控制跨越赤道进入北印度洋的平均流深度的基本物理过程及影响机制。利用数值试验，分别研究了水平热量扩散系数、风应力的季节变化，以及风的Ekman抽吸对海洋热收支、海洋环流的影响。研究表明，水平热量扩散系数不同对越赤道流的深度和经向热通量的影响不大;风的季节循环形成的季节扰动通量会使年平均的越赤道流加深，进入北印度洋的经向热通量减少，致使模式中SST降低，海面净热通量增加。北印度洋风场负的Ekman抽吸将使上层 (混合层)海洋温度降低，下层升高，越赤道流加深，进入北印度洋的经向热通量减少，致使模式中SST降低，海面净热通量增加。 我们还通过全球海洋环流模式，进一步证实了风应力的季节变化在北印度洋热收支、SST以及海洋环流变化中的作用:即包含风应力的季节变化将使长期平均的SST降低，海面净热通量增加。与之相联系，海洋环流也发生了相应的变化。 揭示了风的季节变化形成的经向热输送的“季节扰动通量”会使北印度洋SST降低，海面净热通量增加的机制:在夏季风作用下，北半球的索马里沿岸产生强的上翻，上翻的冷水在被加热的过程中，有较多的海面净热通量进入海洋;而冬季相反的风应力不能“抵消”夏季的上翻，因为被加热的水不能够在冬季被下翻，致使冬季海洋释放的海面净热通量小于夏季进入海洋的海面净热通量。这种“不对称”的“季节矫正(rectify)”将引起海面净热通量增加;第二种途径是季节变化的风场引起了强的穿越等密面的热通量，其方向总是向下，它的增加使得深层温度升高，而上层温度降低，也会导致海面净热通量增加。 以上研究成果为研究印度洋海洋一大气相互作用和印度洋海洋环流的数值模拟提供了新的理论依据和进一步的认识。更多还原

【Abstract】 There are many unique features in the tropical Indian Ocean, compared with the tropical Pacific or Atlantic. Based on the observation data such as COADS and SODA, the main climatological features of the tropical Indian Ocean and relationships of sea surface temperature (SST), heat budget with ocean dynamics and thermodynamics processes are analyzed; the seasonal and interannual variability of the tropical Indian Ocean are well simulated using a ocean general circulation model; Based on the thermal equation and model output data, the variation mechanism of SST and heat budget are investigated in the tropical Indian Ocean; Besides, the effect of seasonal variation of wind stress, Ekman pumping and horizontal diffusivity on the ocean current and heat budget are studied, using both ideal model and complex model.The tropical Indian Ocean, especially for the region north of 7, is strongly influenced by Asia monsoon. In response to the seasonal reversal of wind, ocean currents also show obvious seasonal reversal with Somali current most prominent. Besides, the strong upwelling appears along the Somali-Arabian coast in summer but downwelling in winter, the southward cross-equator Ekman transport occurs in summer but opposite in winter. Further more, the SST warming twice in one year in the northern Indian Ocean, the mixed layer deepening in the central Arabian Sea during summer, as well as the equator jet occurred only in transient seasons are all noteworthy. The wind in summer dominates other seasons with annual mean westerly on the equator. In addition, the wind stress near the equator basically changes from west to east, resulting in southward Ekman transport on both sizes of the equator. Those unique dynamics have significant effects on the heat budget and SST of the northern Indian Ocean. The correlation analysis between SST and sea surface height, heat content and depth of thermocline also shows the important role of ocean dynamic processes in some regions, besides the influence of heat exchange between air and sea.Based on the equation of temperature in mixed layer, combined with the data from an ocean model, the relative important of different processes in controlling the SST variations are determined. For the northern I ndian Ocean, the net surface heat flux and entrainment through the bottom of mixed layer have semiannual period, which is the major cause of semiannual variations in SST. In boreal summer, the entrainment dominates the western part of Bay of Bengal and most part of Arabian coast; net surface heat flux is always a dominant factor controlling the SST variation in Bay of Bengal throughout a year. Difference physical processes control the temperature of the mixed layer in different regions.The quantitatively studies of the heat budget in the northern Indian Ocean are given, focusing on the heat transport and the mechanisms involved in, based on the heat budget equation and data from the ocean model. It is showed that the heat transport crossing the equator has the similar magnitude and the same period of one year, compared with that of 10°N in Arabian Sea. By contrast, the heat transport across 10°N in Bay of Bengal has a much smaller value with a prominent semiannual period; There are tight relationship between integrated zonal wind stress in one latitude of the Indian Ocean north of 7°N and the total heat transport across that latitude, as well as the total net surface heat flux north of that latitude. The maximum correlation coefficient is less than -0.5. The heat transport concentrated on upper 500m, especially upper 150m; Of the total transport, the contribution from the meridional overturning circulation is overwhelming. All these results confirm the important of wind in meridional circulation and heat transport.Based on MOM2 model, a rectangular basin model with ideal w ind stress and other ideal conditions is designed to study the main processes and dynamical mechanism in setting the depth of cross-equator flow. The effects of horizontal diffusivity, seasonal variations of更多还原