| 末次冰消期以来兰州地区冬季风变化研究 |
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| 引用本文： | 陈发虎, 吴海斌, 张家武, 江海斌. 末次冰消期以来兰州地区冬季风变化研究[J]. 第四纪研究, 1999, 19(4): 306-313. |
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| 作者姓名： | 陈发虎 吴海斌 张家武 江海斌 |
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| 作者单位： | 兰州大学地理科学系, 兰州 730000 |
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| 基金项目： | 国家自然科学基金!49871072 |
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| 摘 要： | 研究发现,本次冰消期以来兰州地区大气风力发生了显著变化,全新世早中期大气风力最弱,随后大气风力回返到接近冰期的状况,约1300aB．P．开始大气风力再次减弱,现代是大气风力又一次增强时期；近地面风向有由西北向东北变化的趋势,是大气环流位置变化的结果。在总的变化背景下,大气风力具有约1500a的准周期。我们认为,间冰期季风中国的短尺度气候变化与冰期有差异,前者与低纬度地区联系更密切。
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| 关 键 词： | 末次冰消期 风力与风向变化 千年周期 间冰期季风变化机制 |
| 收稿时间： | 1999-05-04 |
| 修稿时间： | 1999-05-10 |
STUDY ON THE WINTER MONSOON VARIATIONS INLANZHOU AREA SINCE THE LAST DEGLACIATION |
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| Chen Fahu, Wu Haibin, Zhang Jiawu, Wang Haibin. STUDY ON THE WINTER MONSOON VARIATIONS INLANZHOU AREA SINCE THE LAST DEGLACIATION[J]. Quaternary Sciences, 1999, 19(4): 306-313. |
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| Authors: | Chen Fahu Wu Haibin Zhang Jiawu Wang Haibin |
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| Affiliation: | Department of Geography, Lanzhou University Lanzhou 730000 |
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| Abstract: | Monsoon climate, one of the main climate types in the world, strongly influencesmany parts of the world. China is one of the most strongly effected countries bymonsoon climate. The winter monsoon connected with dust transportation anddeposition especially influences the environment of China. Winter monsoon is a vectorsystem. It consists of not only intensity but also direction. The study on thevariations of the East Asian winter monsoon since the last deglacial is a hot topic inthe palaeo-environmental research realm. The high deposition rate with weakpedogenesis process in Lanzhou area provides high chance to reconstruct the historyof the winter monsoon variations using the loess record. The loess deposited since thelast deglacial is about sin thick in the Longxi Loess Plateau, the western LoessPlateau of China. The Holocene soil consists of one to three pedogenic layers in theregion. A weak pedogenic layer formed in the last deglacial could even bedistinguished in Linxia area, south of Lanzhou. The Holocene soil at Jiuzhoutai loesssection consists of four pans including two paleosol layers. The section were sampledat 2 cm interval for grain size analysis and about 10cm interval for the anisotropy ofmagnetic susceptibility (AMS) at the top sin of the section. The grain size samplesare measured using the pipette method. The AMS samples are measured in HKB-1.The average result of the ten AMS samples is used in this study. The whole organicmatter of the seven samples taken in the section is used to measure the radiocarbonages. It is shown by the dates that the top sin loess at the section formed since thelast deglacial although the accurate chronology sequence could not beestablished because of the possibly large errors of the whole organic radiocarbon agesof the Holocene soil.It has been proved that the grain size of the atmospheric dust increases with thedust wind intensity. Its grain size can be used to reconstruct the atmospheric wind intensity. In this study, The medial and mean diameters, clay and coarser than 30μmgrain size contentS are used to indicate the dust wind intensity, while the long axisdirection of the AMS is employed to indicate the dust wind direction. The intensitywas the weakest during early and middle Holocene (ca 9 000-3 000 14C years),which was weaker than at present. After quickly increasing to the state of the lastdeglacial between about 3 000 and 1 500 14C years, it decreased again since ca 1 50014C years but never recovered to the states like the early and middle Holocene. Thepresent day is at the state of the strong wind. It is shown that wind intensitygradually changed from the last deglacial to Holocene. However, the end of theHolocene climate optimum was abrupt. The climate change during the last interglacialhas the same feature. This may indicate the character of the climate change in themonsoon domain. It is also found that the wind intensity has periodical increase anddecrease overlying on the trend. The shout-period variation has a quasi-cycle ofabout 1 500 yeaxs, which has global significance. This variation possibly indicatesnonlinear self-feedback to the solar radiation change. The Younger Dryas (YD) eventwas only one of the strong dust deposition events since the last deglacial. The winddirection has also changed from northwest to north and then to northeast indicatingthat both wind intensity and wind directions changed with the global temperaturesince the last deglacial in the study area. We suggest that the wind direction changeshould reflect the variation of the Mongolian-High and Westerly Jet locations. It isfound that the general trend of the winter monsoon variations is very similar to theclimate changes in the low latitude. We suggest that there had different forcingfactors between glacial and interglacial in monsoon China under millennial climatevariahons. During lacial period, the climate changes in the monsoon China are closelyteleconnected with the high latitude regions of the north hemisphere as suggested,while during interglacial period, it may closely teleconnected w |
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| Keywords: | last deglacial wind intensity and direction variations millennialchanges forcing factors during interglacial |
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