| 东亚季风期极端降水事件与亚洲夏季风活动的关系研究 | |
| Alternative Title | Extreme Precipitation Events during Monsoon Period over Eastern Asia and its Relationship with Asian Summer Monsoon Activities |
| 崔丹阳 | |
| Thesis Advisor | 王澄海 |
| 2019-05-20 | |
| Degree Grantor | 兰州大学 |
| Place of Conferral | 兰州 |
| Degree Name | 硕士 |
| Degree Discipline | 气象学 |
| Keyword | 极端降水 亚洲夏季风 CMIP5 未来预估 |
| Abstract | 近年来，全球极端天气气候事件频发，研究指出，极端天气气候事件和大气环流及季风活动异常有着密切关系。东亚地区是典型的季风活动区，在全球变暖背景下，东亚季风区季风期（5-9月）极端降水的时空分布、未来变化及其与亚洲夏季风活动具有怎样的关系是一个基本的科学问题（本文与季风相关的内容均指夏季风）。本文利用1986-2015年近30年的逐日降水观测资料，分析了东亚季风区季风期极端降水的时空分布特征和年际变化规律；讨论了极端降水的时空变化与亚洲夏季风活动的关系；在综合评估29个CMIP5(Coupled Model Inter-comparison Project Phase 5)模式对东亚季风期极端降水和季风范围模拟能力的基础上，优选模式并进行集合平均，预估了未来（21世纪）东亚季风区季风期极端降水和季风范围的变化特征；分析了东亚季风区夏季风期极端降水变化、季风范围对全球升温的响应。得到以下主要结论：（1）东亚季风区季风期的极端降水是年总降水的主要部分。1986-2015年，东亚季风区季风期的极端降水量和频次存在明显的区域性差异，年际变化较大的区域位于华南及东南亚、长江流域和华北东北地区。东亚季风区各分区季风期的极端降水事件具有显著的年际变化特征，东南亚及华南地区，华北东北地区的极端降水趋于增多，而长江流域的极端降水则趋于减少。（2）东亚季风区极端降水事件是亚洲夏季风的产物。极端降水事件主要发生于亚洲夏季风活动期，季风期极端降水时空变化的特征与东亚地区夏季风的南撤和北进相对应；极端降水事件主要发生在亚洲夏季风前沿附近。亚洲夏季风强度和极端降水的相关也存在空间和时间上的差异，亚洲夏季风偏强时，华中西部7、8月的极端降水量减少，华南地区7月的极端降水量增多。（3）模式能够较好再现东亚季风期极端降水指数的空间分布特征，但仍存在一定偏差，模式对总降水量的模拟效果最好，对极端降水频次有高估。相对于1986-2005年，未来100年内东亚季风期极端降水量将增多，在21世纪后期RCP8.5情景下增加更加显著，其中华南、华中及马来群岛的增多幅度将达40%以上。 （4）随着温室气体（典型排放浓度、辐射强迫）的增加，21世纪，东亚季风区季风期极端降水发生时对应的温度也将升高，升温也会引起极端降水的增加。通过对一次强降水个例的模拟，WRF模式较好的再现了这一结论。也即，气温升高会使极端降水增加并使极端降水过程更加集中。全球升温1.5℃和2℃时，相对于1986-2005年，极端降水量增多的区域主要分布在华北东北东部、长江流域、华东地区及热带地区，其中增多幅度可达40%；中国东部季风期极端降水量将加剧增多，江南地区季风期极端降水频次将显著减少。（5）随着温室气体的排放，东亚季风区范围也会发生变化。相对于1986-2004年，21世纪东亚夏季风范围在RCP2.6, RCP4.5和RCP8.5排放情景下，将分别扩大2.66%，2.58%和3.02%。东亚夏季风区的北边界有较小的向西北扩张的趋势；RCP8.5情景下，季风范围的增大更为显著，且增幅更大。季风区面积扩大的同时也对应着降水中强降水比例的增加。 |
| Other Abstract | In recent years, global extreme climate events occur frequently in the world. Studies have shown that extreme climate events are closely related to the abnormal atmospheric circulation and monsoon activities. Eastern Asia (EA) is one of the most sensitive areas to global climate change. Therefore, under the global warming scenario, the spatial and temporal distribution characteristics and future changes of extreme precipitation during monsoon period (May - September) in EA and its relationship with Asian summer monsoon (ASM) activities are the basic scientific issues that deserve to be further investigated. Based on the in-situ daily precipitation observation data of the last 30 years, the spatial and temporal distribution characteristics and the inter-annual variation of four extreme precipitation indexes during the monsoon period in EA are analyzed and the relationship between them and the ASM are discussed. Combined with the reanalysis data, the simulation performances of 29 CMIP5 models on extreme precipitation indexes and the change of monsoon area in EA are comprehensively evaluated. On this basis, the averaged results of the selected models are used to project the relative change of extreme precipitation and monsoon area over EA in the 21st century. The responses of extreme precipitation during monsoon period over EA to global warming as well as its relationship with monsoon area are also analyzed. The main conclusions are as follows:(1)Extreme precipitation during monsoon period is the main component of annual total precipitation in EA. From 1986 to 2015, there are obvious regional differences in the extreme precipitation and frequency during monsoon period in EA, and the regions with evident changes are located in south China and Southeast Asia, the Yangtze River basin and northeast China. In addition, the regional extreme precipitation events during monsoon period in eastern Asia have significant inter-annual variability. There is a gradual increase trend in Southeast Asia, south China and northeast China, while the Yangtze River basin has a decreasing trend.(2) The extreme precipitation events during monsoon period in EA mainly occur during the active period of the ASM, which may be the product of the ASM. The movement of extreme precipitation events is highly consistent with the northwards advance and southwards withdrawal of ASM. The extreme precipitation mainly occurs in the vicinity of the frontier of ASM. There are spatial and temporal differences in the correlation between the intensity of ASM and extreme precipitation. When the ASM is strong, the extreme precipitation in western central China decreases in July and August over western central China, while it increases in July over southern China.(3) The ensemble mean model results can well simulate the spatial distribution characteristics of extreme precipitation index in EA during the monsoon period, however, deviations still exist among the models. The models have the best simulation effect on the total precipitation, while overestimated the extreme precipitation frequency. Compared with 1986-2005, the extreme precipitation in monsoon period over EA would increase in the next 100 years, and the increase will be more significant in the late 21st century under RCP8.5 scenario, with the increase of South China, Central China and Malaysia more than 40%.(4) With the increase of RCPs (typical emission concentration), the temperature corresponding to extreme precipitation during monsoon period over EA would increase in the 21st century. The high temperature rise corresponds to the increase of maximum extreme precipitation. Numerical simulation of a heavy rainfall case indicates that above conclusion could be well reproduced by WRF model. In other words, the rise of temperature will increase extreme precipitation and extreme precipitation process will be more concentrated. Compared with 1986-2005, when the global temperature rises at 1.5℃ and 2℃, the areas with increased extreme precipitation are mainly distributed in the North China, Northeast China, the Yangtze River Basin, and the tropical regions, with an maximum increase up to 40%. Temperature rises from 1.5℃ to 2℃ will aggravate the increase of extreme precipitation in eastern China during monsoon period, and cause the decrease of extreme precipitation frequency in the south of the Yangtze River during monsoon period.(5) The change of EA monsoon area in the future projected by ensemble model results show that, compared with 1986-2004, the monsoon area will enlarge by 2.66%, 2.58% and 3.02% under the RCP2.6, RCP4.5 and RCP8.5 emissions scenarios, respectively. The northern boundary of the eastern Asian monsoon region has a weak northwest of extend trend. Under RCP8.5, the monsoon areas will increase more significantly. The expansion of monsoon area has a positive impact on the occurrence and development of extreme precipitation events. |
| Pages | 69 |
| URL | 查看原文 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.lzu.edu.cn/handle/262010/338304 |
| Collection | 大气科学学院 |
| Affiliation | 大气科学学院 |
| First Author Affilication | College of Atmospheric Sciences |
| Recommended Citation GB/T 7714 | 崔丹阳. 东亚季风期极端降水事件与亚洲夏季风活动的关系研究[D]. 兰州. 兰州大学,2019. |
| Files in This Item: | There are no files associated with this item. | ||||
