两类厄尔尼诺对次年夏季中国东部降水的可能影响

发布时间：2018-04-20 00:03

本文选题：东部型厄尔尼诺 + 中部型厄尔尼诺　；参考：《中国气象科学研究院》2014年硕士论文

【摘要】：增暖中心位于赤道东部太平洋和赤道中部太平洋的厄尔尼诺事件分别称为东部型和中部型厄尔尼诺，研究其衰亡年夏季中国东部降水分布的差异有很重要的意义。因此，本文首先根据东部型ENSO和中部型ENSO热带太平洋海温分布特点，构建了两个用于区别这两类ENSO事件的新指数；其次从大尺度波动能量传播以及西太平洋副热带高压角度利用新指数研究两类厄尔尼诺次年夏季东亚环流与中国降水的异常；最后利用模式模拟前期两类厄尔尼诺对次年夏季中国环流与降水的影响，以此补充和验证之前的诊断分析工作。研究工作分为以下三个部分：一．采用联合回归—EOF方法得到东部型ENSO和中部型ENSO的热带太平洋海温分布特点，进而定义了计算相对简单的东部型ENSO指数（IEP）和中部型ENSO指数（ICP）来分别描述两类ENSO。研究结果如下：首先，构建的ICP和IEP的相关性很小，接近正交，而且IEP和ICP能够反映两类ENSO不一致的偏度和周期，因此，这对指数能够清楚地区分两类ENSO。其次，IEP和ICP这两个指数可以描述厄尔尼诺和拉尼娜事件成熟期主要海表温度异常区的位置。再次，应用IEP和ICP从随机事件概率统计的角度给出两类厄尔尼诺和拉尼娜事件较为严格的定义，以便实时有效地监测两类ENSO。最后，利用新指数对两类ENSO的特征进行研究发现，强厄尔尼诺事件一般属于东部型，而强拉尼娜事件则为中部型，并且中部型拉尼娜事件发生的前期是东部型厄尔尼诺，另外，ENSO的发生演变机制在1976/1977年左右发生了改变。二．重点分析中部型厄尔尼诺和东部型厄尔尼诺事件的海温演变特征及其对应的热带大气响应情况，并进一步探讨了这两类厄尔尼诺对次年夏季中国降水的可能影响。结果表明：首先，两类厄尔尼诺事件海温演变表现出较为明显的差异，，对应的热带太平洋上空的沃克环流异常也表现出明显的不同。其次，东部型厄尔尼诺次年6、7月北半球中高纬度呈现OKJ型波列（鄂霍次克海—日本东部—日期变更线以西副热带高压北部的波列）明显，鄂霍次克海异常高压阻碍梅雨锋和西北太平洋副热带高压北移，西北太平洋副热带高压明显偏南、偏西，大量水汽输送到长江以南地区，江南降水偏多；而中部型厄尔尼诺次年6、7月鄂霍次克海是异常低压，6月西北太平洋副热带高压偏东，大量水汽输送到华南，中国长江以南地区的降水无明显异常，7月西北太平洋副热带高压偏北，大量水汽输送到华北。最后，两类冷暖事件对次年梅雨期中国江南降水的影响均为非对称的，东部型暖事件对其是显著的正贡献，即次年梅雨期长江以南降水的增加主要体现在暖事件上；而中部型冷暖事件对此范围降水的影响均较弱。三．使用NCAR CAM3.0模式，设计多组不同海温异常的敏感性试验，讨论次年夏季中国长江以南地区降水对前期两类厄尔尼诺的响应。分析模拟结果如下：首先，模式中分别加入两类厄尔尼诺从发展年9月到衰亡年8月实测的海温异常，此结果能够很好地再现两类厄尔尼诺次年夏季东亚环流与中国南方降水的差异，证实了前期诊断分析的结论。其次，使5月的海温异常持续到6、7、8月，此试验的模拟结果与观测的较为相似，再一次证明前期两类厄尔尼诺事件对东亚环流和中国降水的滞后影响。最后，改变加入模式的海温异常强度，发现对东部型厄尔尼诺来说，随着海温异常强迫的增强，次年6、7月长江以南降水会近似地增加，而且当海温异常足够强时，长江以南的降水为正距平且其范围与实际情况接近；而对中部型厄尔尼诺来说，海温异常强度与次年夏季各月中国长江以南降水之间没有稳定的关系。
[Abstract]:The El Nio events , which are located in the Pacific and Central Pacific of the eastern equatorial Pacific and Central Pacific , are called Eastern and Central El Nio , respectively . It is very important to study the difference of precipitation distribution in the eastern part of China in summer .
Secondly , from the large scale wave energy propagation and the western Pacific subtropical high pressure angle , we use the new index to study the anomalies of the East Asian circulation and China ' s precipitation in the next summer of El Nio .
Finally , the effects of two kinds of El Nio on China ' s circulation and precipitation in summer of the next summer are simulated by using the model simulation , so as to supplement and verify the previous diagnosis and analysis work . The research is divided into three parts :

I . In this paper , the characteristics of the tropical Pacific ocean temperature distribution in the east and the central type are obtained by using the combination of the combination of the regression method and the method . The results are as follows : Firstly , the correlation between the ICP and IEP is very small and close to the orthogonality , and the IEP and ICP can reflect the two types of events of El Nio and La Nina events .

II . The effects of these two kinds of El Nio events on China ' s precipitation in the next summer are analyzed . The results show that the two types of El Nino events show distinct differences in SST evolution , and the Walker circulation anomalies over the corresponding tropical Pacific show distinct differences .
At last , two kinds of cold and warm events are asymmetric in the south of the Yangtze River . In the end , there are two types of cold and warm events which are asymmetric in the south of the Yangtze River in July , and the east type warm events are significant positive contribution to the precipitation in the second year of the Meiyu period , that is , the increase of the precipitation in the south of the Yangtze River in the second year is mainly reflected in the warm events ;
The effect of the central cold and warm events on the precipitation in this range is weak .

III . The results are as follows : First , two kinds of El Nino events in the south of the Yangtze River from September to August are analyzed . The results are as follows : First , the anomalous intensity of the two kinds of El Nino events from September to August can be reproduced . The results show that the precipitation in the south of the Yangtze River will increase approximately the next year and the precipitation in the south of the Yangtze River is close to the actual situation when the SST is strong enough .
For the middle - type El Nio , there is no stable relationship between the abnormal intensity of SST and the precipitation in the south of the Yangtze River in the summer of the next year .

【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】：2014
【分类号】：P732;P426.6

【参考文献】