| 中国全新世气候适宜期东亚夏季风时空变迁 |
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| 引用本文： | 吴锡浩,安芷生,王苏民,刘晓东,李小强,周卫健,刘俊峰,陆济军,S.C. Porter,J.E. Kutzbach.中国全新世气候适宜期东亚夏季风时空变迁[J].第四纪研究,1994,14(1):24-37. |
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| 作者姓名： | 吴锡浩 安芷生 王苏民 刘晓东 李小强 周卫健 刘俊峰 陆济军 S.C. Porter J.E. Kutzbach |
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| 作者单位： | 地质矿产部地质力学研究所，中国科学院黄土与第四纪地质国家重点实验室，中国科学院南京地理与湖泊研究所，中国科学院兰州高原大气物理研究所 |
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| 基金项目： | 中国和美国国家自然科学基金 |
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| 摘 要： | 本文据湖面、花粉和风成堆积等地质资料，分析１２０００年以来主要由夏季风决定的降水或湿度状况的时空分布，并运用数值模拟结果计算夏季(７月)降水增量、有效降水和季风强度指数。两者的结果一致表明，全新世适宜期有效降水增量的峰值在中国中、东部具有明显的穿时性，即以东亚夏季风降水或有效湿度为标志的全新世气候适宜期盛期在各地的出现时间并不相同，东北、西北和华北三区偏早，长江中下游区稍晚，华南区最晚，而西南区又偏早。作者对导致这种穿时性的轨道驱动力和季风锋面移动的机理进行了初步分析，对于尚待深入研究的问题也有简要讨论。
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| 关 键 词： | 季风区 全新世 气候适宜期 夏季风降水 数值模拟 穿时性 |
THE TEMPORAL AND SPATIAL VARIATION OF EASTASIAN SUMMER MONSOON IN HOLOCENE OPTIMUM IN CHINA |
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| Abstract: | For studing and understanding Holocene Optimum in Chinese monsoon area,the precipitation or effective humidity(precipitation minus evaporation) seems much more important than temperature alone to the environment within the East-Asia monsoon influencing zone, i.e. the central and eastern China. In this paper, the Chinese monsoon area is subdivided into 6 regions, that is Northeast region(A), Northwest region(B), North China region(C), the region of middle-lower reaches of Yangtze River(D), South China region(E) and Southwest region(F), according to the physiographic environment and the horizontal resolution of numeric modelling. The geological data in each region, such as the lake-level fluctuations, the pollen sequences, the eolian deposits and the loess paleosol sequences with its magnetic susceptibility curves, are utilized to analyse the status of the precipitation or humidity during the past 12 000a. Then a numeric modelling of Summer(July) precipitation increment, effective precipitation and monsoon strength index has been made for the last 15 000 a using the CCM0(Community Climate Model of the National Center for Atmosphere Research, USA). The results of both geological data and numeric modelling are unanimously indicating that the Holocene full-Optimum as identified by the precipitation-increment peak is obviously diachronic in the central and eastern China.If we look into the results in some detail, one can find some discrepancies.Firstly, the maximum effective precipitation recorded by lake-level fluctuations appeared earier than that by pollen data. This is probably because the lake-level recorded the precipitation rather directly while the vegetation evolution took a little time to respond the variation of the climate, so the later should be lagged a little behind. Secondly, the ages of maximum effective precipitation calculated by the results of numeric modelling is younger than that recorded by geological data, this may be caused either by the 3 000 a interval in the modelling being a bit too coarse or more probably, by the values fixed to the model, such as the climate background and soil humidity in the different physiographic regions, being not consistent with the variable in reality. East-Asian monsoon precipitation is dependent upon the convergence of the cold, dry high-latitude air mass with the warm, moist air mass from tropic ocean along the monsoon front. Today the frontal precipitation belt is located south of the Naming at the end of Spring; it shifts rapidly to the middle-lower reaches of Yangtze river to generate the so-called plum-rains there in June and then shifts northwards to North China, Northeast China and part of Northwest China and stays there in July and August. The seasonal cycle of the East-Asia monsoon and the advance or retreat or staggering of its front is caused by the seasonal cycle of the solar insolation, so the cycle in much larger scale of the solar insolation caused by the variation of the orbital forcing since Last Glaciation might be reflected in the similar pattern of the monsoon's variation. When the Holocene full-Optimum is defined by the maximum effective precipitation, then it appeared diachronically across the central and eastern China, i.e. at 12 000 a B.P. in Northeast, at 9 000 a B.P. in Northwest and in North China, at 6 000 a B.P. in middle-lower reaches of Yangtze River and at 3 000 a B.P. in South China. Thus, the diachronism is related to the variation of the East-Asian Monsoon front caused by the changing orbital parameters. Besides, the appearance of the precipitation summit in Southwest at about 12 000 a B.P. is not necessarily related directly to the East-Asian Monsoon strengthening, but it is probably related to the tropical india Monsoon which reached its maximum at about 12 000 a B.P. We also notice, however, that the orbital forcing is not the factor which alone determine the climatic change in Chinese monsoon area. |
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