| 我国气候变化将比模式预期的小吗？谁驱动了亚洲季风的演化：一个瞬变模拟试验的启示 |
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| 引用本文： | 石正国,刘晓东.我国气候变化将比模式预期的小吗？谁驱动了亚洲季风的演化：一个瞬变模拟试验的启示[J].第四纪研究,2009,29(6):1025-1032. |
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| 作者姓名： | 石正国 刘晓东 |
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| 作者单位： | 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,西安,710075;中国科学院研究生院,北京,100049
2. 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,西安,710075 |
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| 基金项目： | 国家杰出青年科学基金项目，国家重点基础研究发展规划项目(973项目)，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课题 |
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| 摘 要： | 亚洲季风演化受到地球轨道参数强迫，尤其是岁差所引起日射变化的显著影响，但关于其驱动机制的争议仍然存在，且集中在“零相位”和“南半球潜热”两种假说上。两个假说都得到了部分地质证据的支持，因此亟需相应的数值模拟，尤其是长期瞬变试验的检验。长期瞬变模拟试验可以对气候的连续演变进行模拟，并能与地质证据进行对比，有助于深入认识亚洲季风系统演化的内在物理机制。但由于计算能力的匮乏，过去的古季风数值模拟多为“时间片”模拟，这使得季风变迁机理研究受到限制。文章通过一个海－气耦合模式的长期瞬变试验，讨论了轨道日射的变化特征，证明过去280ka亚洲夏季风降水对日射有十分显著的响应，且与北半球初夏日射变化相位接近，部分支持了“零相位”假说。同时，模拟结果还揭示了随意选取日射参考标尺会导致缺乏内在物理机制的位相关系，合理选择日射参考以及明确地质记录的气候学意义在古季风强迫－响应机制研究中十分重要。
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| 关 键 词： | 亚洲夏季风 瞬变模拟 轨道强迫 相位差 |
WHAT IS DRIVING THE ASIAN MONSOON EVOLUTION: INSPIRATIONS FROM A TRANSIENT SIMULATION |
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| Shi Zhengguo,Liu Xiaodong.WHAT IS DRIVING THE ASIAN MONSOON EVOLUTION: INSPIRATIONS FROM A TRANSIENT SIMULATION[J].Quaternary Sciences,2009,29(6):1025-1032. |
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| Authors: | Shi Zhengguo Liu Xiaodong |
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| Institution: | State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment|Chinese Academy of Sciences|Xi'an 710075|Graduate University of Chinese Academy of Sciences|Beijing 100049 |
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| Abstract: | How the orbital-scale Asian monsoon has developed during the Quaternary is still an open question up to now. Geological records and numerical simulations have demonstrated that the evolution of the Asian monsoon system is significantly influenced by the insolation variation induced by the Earth's orbital parameters. In the low-latitude region, owing to the dominance of precession in the variability of solar radiation, most researches have focused on the evolution of monsoonal climate with quasi-2Oka precession cycles. However, debates still exist on the mechanism how precession affects the Asian monsoon. At present,there are two hypotheses on this question: "Zero phase" and "Sothem Hemispheric latent heat", proposed by John Kutzbach and Steven Clemens, respectively, which are both supported by several geological proxies. The main attention is paid to whether the Asian monsoon evolution is controlled by local northern insolation or remote southern insolation. So, numerical experiments, especially the long-term transient ones, are eagerly required to better understand the internal dynamic mechanism in the monsoon development. Owing to the lack of computing resources, nevertheless, most of previous numerical experiments were usually limited to some specific "time-slice" simulations,which fail to provide continuous sequence of climate evolution to compare with geological climatic proxies and therefore restrict our paleo-monsoons studies. In this paper,a 280ka-long transient simulation is conducted with an ocean-atmosphere coupled model and an acceleration technique of orbital forcing to explore the response of Asian monsoon to continuous insolation forcing. The results show that the South Asian summer precipitation, as an indicator of summer monsoon intensity, strongly responds to precession change and is nearly consistent with the phase of northern solar radiation in early summer. Hence,although our experiment fails to simulate such significant effect from Southern Hemisphere as Clemens proposed and partly supports the "Zero phase" hypothesis. Further,the results appeal that because of the thermal inertia, the response of climate system often lags the solar forcing some time in the annual cycle. For example, the June ～ August rainfall is actually controlled by the April～ Juny insolation. This phase lag could lead to a mismatch between the monsoon response and the synchronous insolation forcing on the orbital scale, which means that choosing the referenced insolation arbitrarily when comparing with geological proxies might lead to the uncertain phase relation lacking of effectual physical mechanisms. Therefore, it is of great importance for the paleo-monsoon "forcing-response" studies to select the valid reference frame of insolation and clarify the climatic significance of the geological proxies. |
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| Keywords: | Asian summer monsoon transient simulation orbital forcing phase difference |
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