兰州大学机构库 >资源环境学院
基于现代类比法的全新世千年尺度东亚冬夏季风变化及其驱动机制研究
Alternative TitleA study of the millennial-scale Holocene East Asian summer and winter monsoon variability and mechanism based on modern analogue methods
刘媛
Thesis Advisor李育
2018-04-20
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword东亚季风 季风机制 不同时间尺度 季风敏感区 中国
Abstract

东亚季风系统是气候系统和北半球环流系统的重要组成部分,在季风气候条件下,东亚夏季温暖潮湿,冬季寒冷干燥,对东亚地区人类生活环境产生深远的影响。东亚夏季风和冬季风是东亚季风系统的两个主要分支,季风强弱、爆发的早晚以及向北推进的快慢与全球气候系统密切相关,会引起洪涝、干旱、冰冻、雨雪等自然灾害,影响东亚国家和地区的经济、工农业生产和人民生活。长时间尺度季风动力学研究可以帮助我们更好地理解季风气候系统,对于预测和评估未来全球季风变化具有重要的意义。前人做了大量研究探讨东亚冬夏季风变化及其驱动机制,青藏高原的抬升、轨道驱动、太阳辐射、赤道辐合带(Inter Tropical Convergence Zone, ITCZ)、海冰、海表温度(sea surface temperature, SST)、厄尔尼诺—南方涛动(El Niño-Southern Oscillation, ENSO)以及全球冷事件等被认为是亚洲季风的驱动因素。然而,从年际变化尺度到千年变化尺度,不同时间尺度东亚季风驱动因子存在差异,且多时间尺度之间的季风动力学关系尚不明确。
本文基于NCEP/NCAR再分析数据、海表温度数据、海冰数据、月平均温度数据、月平均降水数据、月平均太阳黑子数据、Niño-3.4 SST指数和古季风代用指标等资料,以及场分析、空间分析、敏感性分析、空间检验和季风模拟等方法,探讨了不同时间尺度季风的演化过程和各驱动机制之间的联系。首先,分析了1964—2013年50年东亚夏季风与冬季风的年际变化规律,以及东亚夏季风与夏季降水、冬季风与冬季温度的关系。继而,探讨年际变化尺度东亚冬夏季风变化及其驱动机制。其次,为对比千年尺度东亚季风与年际尺度东亚季风驱动机制的异同,根据现代气候学方法,在全国范围内挑选出对东亚夏季风和冬季风均响应的季风敏感区。利用季风敏感区内古季风代用指标,重建全新世千年尺度东亚冬夏季风的演化历史,同时利用季风模拟方法模拟全新世东亚冬夏季风变化过程,并探讨千年尺度季风变化的驱动机制。最后,通过分析千年尺度古季风和年际尺度现代季风变化与太阳辐射、北极海冰以及气候环流的关系,探讨不同时间尺度东亚季风变化的驱动机制。得到如下主要结论:
(1)根据现代观测数据,计算了1964—2013年50年的东亚夏季风指数和冬季风指数,结果显示:东亚夏季风和冬季风存在明显的年际和年代际变化特征。虽然东亚冬夏季风指数出现了一些极端值,但东亚夏季风和冬季风整体上呈平缓的减弱趋势。
(2)东亚夏季风与夏季降雨相关性区域和东亚冬季风与冬季温度相关性区域存在一定的空间分布规律。东亚夏季风与夏季降雨在长江流域和淮河流域以北地区为明显的正相关关系,而在长江流域和淮河流域以南大部分地区为负相关关系。东亚冬季风整体上与东亚地区冬季温度呈负相关关系,在中国西北地区、东部沿海区域、朝鲜半岛、日本海附近区域相关性达到95%的信度检验水平。
(3)基于现代气候学方法,本文挑选出对东亚夏季风和冬季风均响应的季风敏感区——青藏高原北缘区域。在季风敏感区内,东亚夏季风和夏季降水呈显著的正相关关系,而东亚冬季风和冬季温度呈显著的负相关关系。这表明,东亚夏季风强时,青藏高原北缘地区季风降水将相应增加,而东亚冬季风强时,青藏高原北缘地区气温相应降低。
(4)东亚夏季风重建和模拟结果显示:早全新世,东亚夏季风强度较强,季风降水较多,在10000~6000 cal yr BP之间保持相对较高的水平。中全新世开始,东亚夏季风强度减弱,季风降水减少。晚全新世,东亚夏季风强度最弱,季风降水最少。东亚冬季风重建和模拟结果显示:末次冰消期和早全新世,东亚冬季风强度较强,中全新世东亚冬季风开始减弱。
(5)通过探讨古季风和现代季风变化驱动机制,发现不同时间尺度东亚季风的主要驱动因子具有明显的差异。从早全新世到晚全新世,东亚夏季风和东亚冬季风呈逐渐减弱的趋势,东亚夏季风减弱趋势与低纬度夏季太阳辐射减弱有关,而东亚冬季风减弱趋势与中纬度冬季太阳辐射增强有关。在年际和年代际尺度上,东亚季风变化与全球大气环流系统、北极海冰和海表温度变化紧密相关。北极海冰异常与北太平洋海温异常可能导致大气环流异常,而大气环流异常也可能导致北极海冰和北太平洋海温异常。

Other Abstract

The East Asian monsoon system, which is an important part of the climate system and the circulation system in the Northern Hemisphere, results in warm, humid summer monsoon and cold, dry winter monsoon over the East Asia continent and exerts a profound influence on living environments in the most Asian regions. East Asian summer monsoon and East Asian winter monsoon are two major branches of the East Asian monsoon system. Significant variabilities of East Asian monsoon, especially the monsoon′s advancing, retreating and conversion are closely related to the global climate system, resulting flood, drought, freezing, rain and snow disasters and may cause great damage to agriculture and industrial production, transportation, and daily life of people in many East Asian countries. Research on long-term monsoon dynamics is directed toward understanding the monsoon climate change and it is of great significance for the prediction and assessment of future global monsoon changes. Scientists have studied East Asian monsoon variability and its mechanism and various levels of factors have been hypothesized as the dominant Asian monsoon forcing, such as the uplift of the Qinghai-Tibet Plateau, orbital forcing, solar activities, high-latitude ice volume, the Inter Tropical Convergence Zone (ITCZ), sea surface temperature (SST), El Niño-Southern Oscillation (ENSO) and global cold events. However, the dominant monsoon forcing can change from interannual to millennial time scales and it is still unclear the links of monsoon forcing between different time scales.
Varieties of data and calculating methods were used to discuss the variability and mechanism of the Asian monsoon between different time scales. Varieties of data included NCEP/NCAR reanalysis data, SST, sea ice, the monthly air temperature and precipitation, monthly mean total sunspot number, Niño-3.4 SST index, as well as the paleo-climatic proxies. Calculating methods included the definition of monsoon index, field analysis, spatial correlation, sensitivity analysis, space check and monsoon simulation methods. Firstly, we discussed the annual variation of East Asian summer and winter monsoon during 1964—2013 and the correlation between East Asian summer monsoon and summer precipitation, East Asian winter monsoon and winter temperature. Further, we researched variability and mechanism of the Asian monsoon on interannual to interdecadal time scales. Secondly, with regards to a comparison between the modern and millennial-scale monsoon change, the monsoon sensitive zone, which is both sensitive to summer and winter monsoon, was selected. The paleo-climatic proxies from the monsoon sensitive zone were used to reconstruct millennial-scale summer and winter monsoon variations. Monsoon simulation data were used to analyze Holocene Asian summer and winter monsoon variations, as well as to explore the paleo-monsoon mechanism. Lastly, by analyzing the relationship between the monsoon and the solar radiation, the Arctic sea ice, atmospheric circulation, we discussed the variability and mechanism of the Asian monsoon between different time scales. We get the following conclusions:
(1) According to the modern observation data, the time series of the East Asian summer monsoon and winter monsoon index from the 1964 to 2013 were calculated. The East Asian summer monsoon and East Asian winter monsoon from the 1964 to 2013 show a strong interannual and interdecadal variation. While there are several extreme values in monsoon indices, the East Asian summer monsoon and winter monsoon show a slight weakening trend.
(2) The correlation area between East Asian summer monsoon and summer precipitation, East Asian winter monsoon and winter temperature has a certain spatial pattern. East Asian summer monsoon and the summer precipitation in the north of the Yangtze river and the Huaihe river basin have a positive correlation, while in the south of the Yangtze river and the Huaihe river basin have a negative correlation. On the whole, East Asian winter monsoon is negatively related with winter temperature over East Asia, and the highly correlated area of more than 95% significance covers Northwest China, East China, the Korean peninsula and the area near the Japan sea.
 (3) Based on the modern climatology, the monsoon sensitive region which is both sensitive to summer and winter monsoon is located in the northeast of the Qinghai-Tibet Plateau region. In the monsoon sensitive area, East Asian summer monsoon and summer precipitation have an obviously positive correlation, while East Asian winter monsoon and winter temperature have an obviously negative correlation. This suggests when the East Asian summer monsoon is strong, the summer precipitation in the northeast of the Qinghai-Tibet Plateau region tends to be more than normal, and when the East Asian winter monsoon is strong, the winter surface temperature in the northeast of the Qinghai-Tibet Plateau region tends to be low than normal.
 (4) The reconstructed and simulated Holocene summer monsoon indicator reveals a significant increase since the Last Deglaciation, and maintains at a relatively high level during 10000-6000 cal yr BP. In the early Holocene, the East Asian summer monsoon is stronger, and the monsoon precipitation is more, and then the East Asian summer monsoon shows a weakening trend and the monsoon precipitation is least. As a whole, the East Asian summer monsoon in East Asia is gradually weakening from the early Holocene to the late Holocene. The reconstructed and simulated Holocene winter monsoon indicator generally shows that the East Asian winter monsoon is relatively strong during the Last Deglaciation and early Holocene and weakens since the mid-Holocene.
(5) By studying the variability and mechanism of East Asian summer and winter monsoon on different time scales, it can be found that the main driving factor of the East Asian monsoon has significant differences on various time scales. The Holocene East Asian summer and winter monsoon intensity showed a weakening trend that was consistent with the low-latitude summer insolation change for summer monsoon and mid-latitude winter insolation for winter monsoon. On interannual to interdecadal time scales, the Arctic sea ice anomalies and SST anomalies in North Pacific can cause atmospheric circulation anomalies, meanwhile, the atmospheric circulation anomalies can also cause the Arctic sea ice anomalies and SST anomalies.

URL查看原文
Language中文
Document Type学位论文
Identifierhttp://ir.lzu.edu.cn/handle/262010/240634
Collection资源环境学院
Recommended Citation
GB/T 7714
刘媛. 基于现代类比法的全新世千年尺度东亚冬夏季风变化及其驱动机制研究[D]. 兰州. 兰州大学,2018.
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