不同El Nino事件对西北太平洋热带气旋活动的影响

发布时间：2018-06-09 17:33

本文选题：热带气旋 + 东太型El　；参考：《中国海洋大学》2014年硕士论文

【摘要】：本文利用JTWC热带气旋资料、HadISST以及NCEP大气资料分季节讨论了不同El Ni(?)o事件时西北太平洋热带气旋活动的差异以及引起差异的原因。文章首先分夏季和秋季讨论了东太型El Ni(?)o与中太型El Ni(?)o对热带气旋生成地和强度的影响的不同。然后，以是否同时发生正IOD事件为标准，将中太型El Ni(?)o事件分成纯中太型El Ni(?)o事件（p-CPEN）、与IOD同时发生的事件（CPEN-IOD），并比较了两类事件发生时，西北太平洋秋季热带气旋生成地的差异。东太型El Ni(?)o年夏季，热带气旋生成频数在西北太平洋西北区域减小、东南增大，正负异常呈长条状偶极子分布。西北区域SSTA呈现显著负异常、低层涡度减小、中层相对湿度较小是该区域热带气旋生成受到抑制的主要原因，东南区域热带气旋生成活跃的主因是低层涡度增大、垂直风切变减小、相对湿度增大。中太型El Ni(?)o年夏季，热带气旋生成频数增大的区域较东太型El Ni(?)o年向西北方向延伸，产生这种差异的主要原因是中太型El Ni(?)o夏季，西北区域低层涡度增大、垂直风切变减小。东太型El Ni(?)o年秋季，位于东南区域的热带气旋生成活跃区较夏季东退大约20个经度，发生这种季节变化的主要原因是秋季负涡度异常中心南移，同时垂直风切变增大的区域向东向北扩张、干空气在南侧的扩张。中太型El Ni(?)o夏季热带气旋生成向西北扩张的趋势在秋季被截断，菲律宾以东区域热带气旋生成受抑制区域扩大，造成这种季节差异的主要原因是在这些区域垂直风切变增大、相对湿度减小。热带气旋累积能量（ACE）被用来考查两类事件对热带气旋强度的影响。东太型El Ni(?)o指数Ni(?)o3以及中太型El Ni(?)o指数EMI在夏秋两季都与ACE呈正相关，但Ni(?)o3与ACE的相关性在秋季不显著。夏季时，ACE与Ni(?)o3的相关系数大于ACE与EMI的相关系数，而秋季时两者的大小关系正好相反。东太型El Ni(?)o夏季与中太型El Ni(?)o夏季相比，前者强度较大的热带气旋生成频数比后者的多，同时前者热带气旋累积持续时间更长，所以前者的ACE比后者的大。秋季，强度最强的CAT4、CAT5的生成频数在中太型El Ni(?)o时要比在东太型El Ni(?)o时多，同时，前者热带气旋累积持续时间也比后者大，最终使得中太型El Ni(?)o的ACE大于东太型El Ni(?)o的。 CPEN-IOD秋季热带气旋生成地较p-CPEN秋季东伸20°。CPEN-IOD秋季西北太平洋暖SSTA位置较p-CPEN秋季时偏东，同时西侧冷异常也更显著，从而导致CPEN-IOD秋季赤道区域西风异常场明显强于p-CPEN秋季，西风异常东伸的也更远；这进一步使得CPEN-IOD秋季季风槽明显偏东。由于大部分热带气旋都是生成于季风槽内，所以CPEN-IOD秋季热带气旋生成地也延伸的更东。同时，CPEN-IOD时期，垂直风切变的正负异常较p-CPEN都要大，且前者的正异常区较后者明显偏东，使得前者适合热带气旋生成的区域明显东移，这也是热带气旋生成地偏东的原因。
[Abstract]:Based on the JTWC tropical cyclone data HadISST and NCEP atmospheric data, the seasonal differences of tropical cyclone activities in the Northwest Pacific Ocean and the causes of the differences are discussed in this paper. In this paper, we first discuss the difference between the East Pacific type El Nianzao and the middle Pacific type El Nianzao on the ground and intensity of the tropical cyclone in summer and autumn. Then, based on the criterion of whether or not the positive IOD events occur at the same time, this paper classifies the middle and Pacific type El Niadao events into pure center-Pacific type El Nianzao events, and compares the two types of events when they occur simultaneously with the IOD events, which occur at the same time as the CPEN-IOD events. In summer, the frequency of tropical cyclone formation in the Northwest Pacific decreases in the Northwest Pacific region and increases in the southeast, and the positive and negative anomalies show a long strip dipole distribution. In the northwest region, the SSTA showed significant negative anomalies, the vorticity of the lower layer decreased, and the relative humidity of the middle layer decreased. The main reason for the suppression of tropical cyclone formation in the southeast region was the increase of the vorticity of the lower layer, the main reason for the active formation of the tropical cyclone was the increase of the vorticity of the lower layer. The vertical wind shear decreases and the relative humidity increases. The increasing frequency of tropical cyclones extends northwestward than that of east-Pacific El Nianzao in summer. The main reason for this difference is that in summer, the vorticity of the lower layer increases and the vertical wind shear decreases in the northwest region of the northwestern region, the main reason for this difference is that in the summer of the mid-Pacific type El Nianzhuo, the vertical wind shear is decreased with the increase of the vorticity of the lower layer in the northwestern region. In autumn, the active tropical cyclones in the southeastern region retreated about 20 degrees of longitude than that in summer. The main reason for this seasonal variation is the southward shift of the anomalous center of the autumn negative vorticity. At the same time, the area with vertical wind shear increases to the east and north, and the dry air expands to the south. The trend of tropical cyclones spreading northwestward in summer was cut off in autumn, and the restrained area of tropical cyclones in the east of the Philippines was enlarged. The main reason for this seasonal difference was the increase of vertical windshear in these areas. The cumulative energy of tropical cyclones (ACEE) is used to study the effects of two types of events on the intensity of tropical cyclones. The EMI of EST and EMI were positively correlated with ACE in summer and autumn, but the correlation between EMI and ACE was not significant in autumn. In summer, the correlation coefficient between ACE and Nijiao _ 3 is higher than that between ACE and EMI, but the relationship between ACE and EMI is opposite in autumn. Compared with the east-Pacific type El Nianzao in summer, the intensity of the former is higher than that of the latter, and the accumulative duration of the former is longer, so the ACE of the former is larger than that of the latter. In autumn, the most intense CAT4 / CAT5 has more frequency of formation than that of east-type El Nianzao, and the accumulative duration of the former tropical cyclone is also larger than that of the latter, and the intensity of CAT4 / CAT5 is higher than that of the east-Pacific type of El Nianzao in autumn, and the cumulative duration of the former is larger than that of the latter. As a result, the ACE of the mid-Pacific type El Nianzao is larger than that of the East Pacific type El Nianzao. The tropical cyclones of CPEN-IOD in autumn are more eastward than those of p-CPEN in autumn when the tropical cyclones extend 20 掳eastward. CPEN-IOD shows that the position of warm SSTA in the Northwest Pacific Ocean in autumn is more easterly than that in the autumn of p-CPEN, and the cold anomaly in the western side is also more significant than that in the autumn of p-CPEN. As a result, the westerly anomaly field in the equatorial region in autumn is obviously stronger than that in the p-CPEN autumn, and the westerly anomaly extends further eastward, which makes the monsoon trough of CPEN-IOD obviously eastward in autumn. Since most tropical cyclones occur in monsoon trough, CPEN-IOD also extends eastward in autumn. In the CPEN-IOD period, the positive and negative anomalies of vertical wind shear are larger than that of p-CPEN, and the positive anomalous regions of the former are obviously eastward than those of the latter, which makes the former suitable for the eastward movement of the region where the tropical cyclones are formed, which is also the reason for the eastward formation of the tropical cyclones.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P732

【参考文献】