刘晓东1,3
1. 中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 陕西 西安 710061
2. 国家科技资源共享服务平台——国家地球系统科学数据中心, 北京 100101
3. 中国科学院大学, 北京 100049
基金项目: 中国科学院(B类)战略性先导科技专项项目(批准号:XDB40030100)和国家自然科学基金项目(批准号:41690115和41991254)共同资助
详细信息
作者简介: 谢小训, 男, 27岁, 博士后, 古气候模拟研究, E-mail:xiexx@ieecas.cn
中图分类号: P532;P534.63+1 收稿日期:2020-06-07
修回日期:2020-09-01
刊出日期:2020-11-30
Regional differences of East Asian monsoon precipitation in response to orbital forcing and global ice-volume changes since the late Middle Pleistocene
Xie Xiaoxun1,2,,Liu Xiaodong1,3
1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shaanxi
2. National Earth System Science Data Center, National Science and Technology Infrastructure of China, Beijing 100101
3. University of Chinese Academy of Sciences, Beijing 100049
MSC: P532;P534.63+1
--> Received Date: 07 June 2020
Revised Date: 01 September 2020
Publish Date: 30 November 2020
摘要
摘要:利用通用气候系统模式CCSM3完成的3组不同气候强迫因子驱动下过去30万年的长期瞬变模拟试验，即纯轨道强迫试验（O）、轨道加温室气体强迫试验（OG）和进一步包含冰盖变化的全强迫试验（OGI），对比研究了晚中更新世以来东亚季风降水变化的区域差异及其对天文日射、温室气体和全球冰量变化的响应机制。模拟结果表明，轨道尺度东亚季风降水变化以2.3万年的岁差周期为主导，但东亚北方（35°~45°N，105°~120°E）和南方（25°~35°N，105°~120°E）季风降水在岁差波段具有不同的相位关系。东亚北方季风降水主要受岁差强迫控制，与岁差引起的北半球6月日射同相位变化；而在岁差波段上东亚南方季风降水变化直接受全球冰量变动的调制，其相位显著滞后于北半球6月日射变化约5000年，东亚南方季风降水极大（小）值与全球冰量极小（大）值相对应。岁差引起的北半球夏季日射增加通过放大东亚大陆至北太平洋之间海陆热力对比，增强东亚地区向北的水汽输送，从而使东亚北方季风降水增多；相反，当岁差引起的北半球夏季日射降低时东亚北方季风降水减少。当在岁差波段上北极冰盖减少（增大）时，冰量变化所激发的夏季对流层中层北半球环流异常能够通过北太平洋传递到东亚，导致东亚南方地区对流层低层风场辐合加强（减弱）、降水相应增多（减少）。本文的模拟结果指出，轨道尺度东亚季风降水变化存在明显的区域差异，轨道强迫和冰量变动分别主导了岁差尺度东亚北方和南方夏季降水的变化。
关键词: 东亚夏季风/
轨道尺度/
日射/
全球冰量/
瞬变模拟
Abstract:Based on the results of long-term transient simulations driven by different climatic forcings for the last 300 ka simulated by Community Climate System Model version 3(CCSM3), we comparatively studied the regional differences of East Asian monsoon(EAM) precipitation since the late Middle Pleistocene and their response mechanisms to the changes of insolation, greenhouse gases and global ice volume. Three experiments were conducted, including an orbital-forcing-only experiment (O), an orbital forcing plus greenhouse gases forcing experiment(OG) and a full-forcing experiment(OGI) with further addition of global ice-sheet forcing. The results showed that:The EAM precipitation on the orbital time scale is dominated by a 23-ka precessional period, but the phase of EAM precipitation at the precessional band is different between the northern EAM(35°~45°N, 105°~120°E) and southern EAM(25°~35°N, 105°~120°E). The northern EAM precipitation is mainly controlled by precession forcing, changing in phase with the Northern Hemisphere(NH) insolation in June, while the southern EAM precipitation is directly modulated by global ice-volume variation, lagging behind the NH insolation in June by about 5-ka, with the maximum(minimum) of the southern EAM precipitation corresponding to the minimum(maximum) of global ice volume. The increased NH summer insolation induced by the precession, can enhance the water vapor transport northward in the East Asian region by amplifying the land-sea thermal contrast between the East Asian continent and the North Pacific, thereby strengthening the summer precipitation of the northern EAM. Conversely, the deceased NH summer insolation induced by the precession can weaken the northern EAM precipitation. When the Arctic ice sheets decreases(increases) at the precessional band, the summer circulation anomalies of the middle troposphere in response to the changes in the ice volume can be transmitted to the southern East Asia through the North Pacific, resulting in enhanced(weakened) convergence of wind fields in the lower troposphere, and corresponding increase(decrease) in precipitation over southern EAM. Our simulation results suggest that there are significant regional differences in the EAM precipitation changes on the orbital time scale. Orbital forcing and ice volume changes dominate the summer precipitation changes in the northern and southern East Asia at the precessional scale, respectively.
Key words:Asian summer monsoon/
orbital scale/
insolation/
global ice volume/
transient simulation
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