黑潮延伸体海区海洋锋与北太平洋风暴轴的关系及其气候效应

发布时间：2018-01-15 08:22

本文关键词：黑潮延伸体海区海洋锋与北太平洋风暴轴的关系及其气候效应　出处：《中国气象科学研究院》2017年硕士论文　论文类型：学位论文

【摘要】：黑潮延伸体海区存在着明显的海表温度锋,已有研究证明海洋锋对大气边界层乃至对流层高层都有一定影响。在此基础上,本文首先利用英国Hadley中心海温资料分析了黑潮延伸体海区海温经向梯度的分布特征和季节变化,同时将黑潮延伸体海区海温经向梯度大值区域的平均值定义为黑潮延伸体海区海洋锋强度指数(KEFI),并研究了KEFI的年际和年代际变化。北太平洋中纬度对流层中高层主要表现为瞬变扰动,与黑潮延伸体海区海洋锋变化存在着一定的耦合关系。通过研究发现冬季北太平洋瞬时扰动与KEFI存在显著正相关,显著区域位于北太平洋风暴轴主体位置,即当冬季黑潮延伸体海区海洋锋强度增强时,北太平洋风暴轴也偏强,并且这种相关性在KEFI超前风暴轴一个月时就有所显现。之后分析了这种影响的可能机制,发现在冬季KEFI高值年,由于海洋锋两侧的热量输送差异更加明显,导致海洋锋附近的近表面气温经向梯度增强,维持了近表面的斜压性,促进涡动热量向极输送和海洋锋南侧的涡动热量向上输送,有利于瞬时涡旋的发展。同时海洋锋变化与大尺度背景环流场也有一定关系,具体表现为在冬季海洋锋偏强时,阿留申低压加深,副热带高压略有加强,对应的对流层中层位势高度场在40oN以北有负变高,以南有正变高,同时高空极锋急流加强,副热带西风急流减弱加宽北抬,海洋锋偏弱年的变化相反。黑潮延伸体海区海洋锋强度的变化对北美气温变化存在一定影响。当秋季海洋锋增强(减弱)时,北美西部气温升高(降低),东部气温降低(升高);当冬季海洋锋增强(减弱)时,北美大部分地区气温升高(降低),南部低纬度小范围地区气温降低(升高)。通过分析发现,这种影响主要是通过大气环流对海洋锋变化的响应所产生。另外,海洋锋强度在冬春季节对东亚气温也有影响,并且这种影响可以持续到下一个季节。当冬季海洋锋偏强时,同期冬季东亚东部及南部沿海地区气温升高,春季我国华北及东北地区气温升高,分析发现这是由于当海洋锋偏强时对应北部高空急流增强,不利于冷空气向南爆发;春季的海洋锋增强同样使东亚东南部气温升高,并且使我国夏季的西北及华北地区气温升高,产生这种影响的主要原因是东亚气温对上游黑潮的同期异常变化产生的邻域响应,并且这种影响可以持续至夏季。
[Abstract]:There are obvious sea surface temperature fronts in the Kuroshio extensional sea area. It has been proved that the ocean front has a certain influence on the atmospheric boundary layer and even the upper troposphere. In this paper, the distribution characteristics and seasonal variation of the meridional gradient of sea surface temperature in the Kuroshio extension area are analyzed by using the SST data of the Hadley Center in the United Kingdom. At the same time, the mean value of the high value area of sea surface temperature in the Kuroshio extension area is defined as the sea front intensity index (KEFI) in the Kuroshio extension area. The interannual and Interdecadal variations of KEFI are studied. The middle and upper troposphere in the mid-latitude of the North Pacific Ocean is characterized by transient disturbances. There is a coupling relationship with the oceanic front variation in the Kuroshio extensional area. It is found that there is a significant positive correlation between the North Pacific transient disturbance and the KEFI in winter. The significant area is located in the main part of the North Pacific storm track, that is, when the strength of the oceanic front in the Kuroshio extension area increases in winter, the North Pacific storm track is also stronger. And this correlation appeared one month before the storm track of KEFI. Then the possible mechanism of this effect was analyzed and found in the high value year of KEFI in winter. Because the difference of heat transfer between the two sides of the ocean front is more obvious, the near surface temperature near the ocean front increases along the gradient, maintaining the baroclinic near the surface. It is beneficial to the development of instantaneous vortices to promote the vortex heat transfer to the pole and the vortex heat to the south of the oceanic front. At the same time, the variation of the ocean front is also related to the large-scale background circulation field. When the oceanic front is strong in winter, the Aleutian low pressure deepens and the subtropical high is slightly strengthened. The corresponding mid-tropospheric geopotential height field is negative higher to the north of 40oN and positive to the south. At the same time, the upper polar front jet strengthened and the subtropical westerly jet weakened and widened to the north. The variation of ocean front intensity in the Kuroshio extensional sea area has a certain effect on the temperature change in North America. When the ocean front intensifies (weakens) in autumn, the temperature in western North America increases (decreases). Lower temperature in the east; When the winter oceanic front strengthens (weakens), the temperature in most parts of North America increases (decrease), and in the small area of southern low latitude, the temperature decreases (increases). This effect is mainly caused by the response of the atmospheric circulation to the variation of the oceanic front. In addition, the intensity of the oceanic front also affects the temperature in East Asia during the winter and spring seasons. When the winter oceanic front is strong, the temperature in the eastern and southern coastal areas of East Asia rises in the same period, and the temperature in North and Northeast China rises in spring. It is found that this is due to the enhancement of the upper air jet corresponding to the north when the ocean front is strong, which is not conducive to the onset of cold air to the south. The strengthening of the spring ocean front also increases the temperature in the southeast of East Asia and the temperature in the northwest and north China in summer. The main reason for this effect is the neighborhood response of East Asian temperature to the synchronous anomaly of the upper Kuroshio and the effect can last into summer.
【学位授予单位】：中国气象科学研究院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P731.2;P732

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