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基于振幅的东亚大槽强度指数及其与东亚冬季气候的联系
Alternative TitleIntensity Index of the East Asian Trough Based on Amplitude and its relationship with winter climate in East Asia
王一璞
Subtype硕士
Thesis Advisor左洪超
2020-06-15
Degree Grantor兰州大学
Place of Conferral兰州
Degree Discipline气象学
Keyword东亚大槽 振幅 强度指数 演变过程 东亚冬季气候
Abstract~东亚大槽是东亚冬季风的主要子系统之一,作为东亚冬季风对流层中层的重要活动中心,东亚大槽的强度变化对东亚地区的天气气候有着显著的影响。本文利用NECP/NCAR月平均500 hPa位势高度数据,定义了东亚大槽振幅强度指数,分析了东亚大槽的长期变化特征。之后通过与其它东亚大槽特征指数对比,讨论了不同东亚大槽特征之间的联系和区别。进一步研究了东亚大槽在10月至次年4月的发展演变过程;通过相关分析、合成分析等方法研究和讨论了东亚大槽对于东亚冬季气候的影响和可能机制。研究主要结论如下: (1)东亚大槽振幅强度指数可以用来表征东亚大槽的强度。当东亚大槽振幅强度指数偏大时,东亚大槽强度偏强,相反当东亚大槽振幅强度指数偏小时,东亚大槽强度偏弱。在1948至2018年期间,东亚大槽强度总体有微弱的增强趋势。 (2)不同东亚大槽特征指数之间具有较好的相关性,表明从不同特征出发定义的东亚大槽指数对东亚大槽长期变化的描述基本一致,有着一定的相似性。但不同的东亚大槽指数有不同的变化特征,当东亚大槽发生变化时,各种特征的变化之间存在较好的联系,但并不完全一致。表明东亚大槽的不同特征具有相对独立性。 (3)从10月份开始,东亚大槽区域的500 hPa位势高度值不断降低,并在次年1月份达到了最小值,东亚大槽强度持续增强,东亚大槽特征指数不断增大;从次年3月份开始,东亚大槽区域的500 hPa位势高度值明显升高,东亚大槽强度开始明显减弱,东亚大槽特征指数减小,直至东亚地区没有明显的低压槽结构出现。 (4)冬季东亚大槽与东亚冬季地面气温之间有密切的联系。当东亚大槽振幅强度指数偏大时,在500 hPa位势高度场上,东亚大槽和欧洲浅槽加深;在海平面气压场上,西伯利亚高压增强;对流层低层850 hPa风场上,西伯利亚地区存在异常反气旋,60°N以北地区西风增强,冷空气最终沿东亚沿岸南下入侵,造成东亚沿岸地区冬季地面气温偏低,当东亚大槽振幅强度指数偏小时,情况相反。 (5)冬季东亚大槽对东亚地区冬季降水存在显著的影响。当东亚大槽振幅强度指数偏大时,20°N以北地区为水汽辐散区,并处于东亚大槽槽后下沉气流控制下,不利于降水的产生,易造成中国东部地区以及朝鲜半岛地区冬季降水偏少;而20°N以南地区,偏强的北风引导冷空气南下入侵到热带地区,引发了强烈的上升运动,有利于降水的产生,易造成菲律宾、马来西亚等东亚低纬度地区冬季降水偏多。
Other Abstract~The East Asian Trough is one of subsystems of the East Asian Winter Monsoon. As an important activity center in the middle troposphere of the East Asian Winter Monsoon, the intensity of the East Asian Trough has a significant impact on the weather and climate in East Asia. This paper had defined the Amplitude Intensity Index of East Asia Trough by using the 500 hPa geopotential height data from the NECP / NCAR monthly mean reanalysis dataset, and the long-term variation characteristics of the East Asian Trough has been analyzed. By comparing with other indexes of the East Asian Trough, the relationship and difference between the characteristics of the East Asian Trough have been discussed. The development and evolution of the East Asian trough during the period from October to April had been studied. The influence and possible mechanism of the East Asian trough on the winter climate of East Asia have been studied and discussed by using correlation analysis and synthetic analysis. The main conclusions are as follows: (1) The Amplitude Intensity Index of East Asia Trough can be used to characterize the str英语th of the East Asian Trough. When Amplitude Intensity Index of East Asia Trough is larger, the str英语th of the East Asia Trough is stronger. On the contrary, when Amplitude Intensity Index of East Asia Trough is smaller, the str英语th of the East Asia Trough is weaker. From 1948 to 2018, the intensity of the East Asian Trough showed a weak increase trend. (2) There was a good correlation between the different characteristic indexes of East Asian Trough, which meant that different East Asian Trough indexes both could describe the long-term variation characteristics of East Asian Trough and have similarities. But the differences between East Asian Trough indexes have indicated that the East Asian Trough has many characteristics. When the East Asian Trough changes, there was a good relationship between the changes of various characteristics. But the different characteristics of the East Asian Trough were not identical, which meant that they have relative independence. (3) From October, the 500 hPa geopotential height in the area of the East Asia Trough has been decreasing, and reached the minimum value in January. The intensity of the East Asia Trough and the characteristic index of the East Asia Trough have been increasing. From March, the 500 hPa geopotential height in the area of the East Asia Trough has been increasing, the intensity of the East Asia trough and the characteristic index of the East Asia trough have been decreasing until there was no obvious trough structure in East Asia. (4) There was a close relationship between the East Asian Trough and the surface temperature of East Asia in winter. When the Amplitude Intensity Index of the East Asian Trough was larger, the 500 hPa geopotential height field showed that the intensity of the East Asian Trough and the European Trough both became stronger. In the sea level pressure field, the Siberian High pressure enhanced. The anomalous anticyclone over the Siberian region caused a significant increase in westerly winds of area north of 60°N. The cold air eventually invaded the East Asian coast, resulting in a significant decrease in the surface temperature of the East Asian coast area in winter. When the Amplitude Intensity Index of East Asian Trough was smaller, the situation is reversed. (5) The East Asian Trough has influence on the winter precipitation in East Asia. When the Amplitude Intensity Index of the East Asian Trough is larger, the area north of 20°N is the water vapor divergence area, and it is under the control of the downdraft caused by the East Asian Trough, which is not conducive to precipitation in eastern 中文na and the Korean Peninsula. However, in the area south of 20°N, strong north wind anomaly causes the cold air invade the tropical region, triggering a strong upward movement, which is beneficial to the precipitation in the low latitudes of East Asia such as the Philippines and Malaysia.
Pages64
URL查看原文
Language中文
Document Type学位论文
Identifierhttp://ir.lzu.edu.cn/handle/262010/448092
Collection兰州大学
Affiliation大气科学学院
First Author AffilicationCollege of Atmospheric Sciences
Recommended Citation
GB/T 7714
王一璞. 基于振幅的东亚大槽强度指数及其与东亚冬季气候的联系[D]. 兰州. 兰州大学,2020.
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