The relationship between the East Asian winter monsoon(EAWM) and East Asian summer monsoon(EASM) during the Holocene is complicated and remains controversial.In this study,analysis of grain size and benthic foraminife...The relationship between the East Asian winter monsoon(EAWM) and East Asian summer monsoon(EASM) during the Holocene is complicated and remains controversial.In this study,analysis of grain size and benthic foraminiferal oxygen isotope,as well as accelerator mass spectrometry ^(14)C dating was performed on a sediment core retrieved from the newly revealed muddy deposit on the northern South China Sea continental shelf.The history of the EAWM and EASM were reconstructed for the last 8200 a BP.Further analysis in conjunction with previously published paleo-climate proxies revealed that the relationship between the EAWM and EASM during the Holocene is more complex than a simple and strict anti-phase one-both negative and positive correlations were identified.The EAWM and EASM are negatively correlated around 7500,4800,4200,3200,and 300 a BP(cooling periods),while positively correlated around 7100,3700,and 2100 a BP(warm periods).In particular,both the EAWM and EASM intensified during the three positive correlation periods.However,we also found that the relationship between these two sub-monsoons is anti-phase during the final phase of particularly hot periods like Holocene Optimum and Medieval warm period.The possible impact from variations of solar irradiance on the relationship between the EAWM and EASM was also discussed.展开更多
利用长时间的逐日再分析资料和澳大利亚气象局提供的MJO指数,研究了MJO对我国南海冬季风异常的影响和过程。结果表明,随着MJO的对流中心从西印度洋进入西太平洋,南海海面风场出现偏南风-东北风-偏南风异常的振荡现象,表明南海冬季风阶...利用长时间的逐日再分析资料和澳大利亚气象局提供的MJO指数,研究了MJO对我国南海冬季风异常的影响和过程。结果表明,随着MJO的对流中心从西印度洋进入西太平洋,南海海面风场出现偏南风-东北风-偏南风异常的振荡现象,表明南海冬季风阶段性的间断和活跃,最明显的偏南风异常和东北风异常分别位于MJO第8—2位相和第5—6位相。通过合成MJO各位相下500 h Pa东亚大槽异常和200 h Pa东亚急流异常,我们进一步证实南海冬季风活跃期(MJO第5—6位相),东亚大槽加深,高空急流加强,我国华南沿海上空的反气旋式环流异常,东南边缘的引导气流利于冷空气南下直达南海。相反,在南海冬季风间断期(MJO第8—2位相),东亚大槽和高空急流均减弱,不利于冷空气的南下。对200 h Pa垂直速度的分析表明,MJO深对流活动的东移,调整东亚局地Hadley环流异常,在高空表现为反气旋/气旋式环流异常交替发展东移,最终消失在北太平洋地区。一方面通过科氏力的作用,引起东亚高空急流的异常,进而影响东亚大槽的位置和强度,从而影响冷空气的南下;另一方面直接加剧南海海面风场异常的南北向振荡。因此,在做南海冬季风季内变化特别是大风天气过程的延伸期预报时,热带MJO活动可以作为一个重要因子考虑在内。展开更多
基金supported by the National Programme on Global Change and Air-Sea Interaction(Nos.GASI-GEOGE-03 and GASI-GEOGE-06-02)the National Natural Science Foundation of China(Nos.41476047,41106045,41506012 and 41206045)the School of Geographic and Oceanographic Sciences,Nanjing University,China,State Key Laboratory of Marine Geology,Tongji University,China and Beta Analytic Inc.,USA for their technical assistance in the laboratory
文摘The relationship between the East Asian winter monsoon(EAWM) and East Asian summer monsoon(EASM) during the Holocene is complicated and remains controversial.In this study,analysis of grain size and benthic foraminiferal oxygen isotope,as well as accelerator mass spectrometry ^(14)C dating was performed on a sediment core retrieved from the newly revealed muddy deposit on the northern South China Sea continental shelf.The history of the EAWM and EASM were reconstructed for the last 8200 a BP.Further analysis in conjunction with previously published paleo-climate proxies revealed that the relationship between the EAWM and EASM during the Holocene is more complex than a simple and strict anti-phase one-both negative and positive correlations were identified.The EAWM and EASM are negatively correlated around 7500,4800,4200,3200,and 300 a BP(cooling periods),while positively correlated around 7100,3700,and 2100 a BP(warm periods).In particular,both the EAWM and EASM intensified during the three positive correlation periods.However,we also found that the relationship between these two sub-monsoons is anti-phase during the final phase of particularly hot periods like Holocene Optimum and Medieval warm period.The possible impact from variations of solar irradiance on the relationship between the EAWM and EASM was also discussed.
文摘利用长时间的逐日再分析资料和澳大利亚气象局提供的MJO指数,研究了MJO对我国南海冬季风异常的影响和过程。结果表明,随着MJO的对流中心从西印度洋进入西太平洋,南海海面风场出现偏南风-东北风-偏南风异常的振荡现象,表明南海冬季风阶段性的间断和活跃,最明显的偏南风异常和东北风异常分别位于MJO第8—2位相和第5—6位相。通过合成MJO各位相下500 h Pa东亚大槽异常和200 h Pa东亚急流异常,我们进一步证实南海冬季风活跃期(MJO第5—6位相),东亚大槽加深,高空急流加强,我国华南沿海上空的反气旋式环流异常,东南边缘的引导气流利于冷空气南下直达南海。相反,在南海冬季风间断期(MJO第8—2位相),东亚大槽和高空急流均减弱,不利于冷空气的南下。对200 h Pa垂直速度的分析表明,MJO深对流活动的东移,调整东亚局地Hadley环流异常,在高空表现为反气旋/气旋式环流异常交替发展东移,最终消失在北太平洋地区。一方面通过科氏力的作用,引起东亚高空急流的异常,进而影响东亚大槽的位置和强度,从而影响冷空气的南下;另一方面直接加剧南海海面风场异常的南北向振荡。因此,在做南海冬季风季内变化特别是大风天气过程的延伸期预报时,热带MJO活动可以作为一个重要因子考虑在内。
