陇南山区农业气候资源特征与开发利用     

余优森  尹东  费晓玲  任三学 《山地学报》1997,(4)

分析了甘肃陇南山区农业气候资源的分布特征及其水平、垂直差异,提出了合理开发利用的农业决策建议,指出应利用资源优势建立名特优小商品生产基地。  相似文献   

The Sahelian desertification debate: a view from the American south-west     

Charles F. Hutchinson 《Journal of Arid Environments》1996,33(4):519-524

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中国西北部“4.5”沙尘暴过程中尺度低压的数值模拟   总被引：3，自引：9，他引：3  

陈伟民  王强  牛志敏  徐建芬  高风荣 《中国沙漠》1996,16(2):140-144

利用改进型ＰＳＵ／ＮＣＡＲ中尺度数值模式（ＭＭ４标准版），取模式水平格距４０ｋｍ，４６×６１网格，垂直方向ａ取１５层，即从地面到模式顶（１００ｈＰａ），σ＝０．０、０．１、０．２、０．３、０．４、０．５、０．６、０．７、０．７８、０．８４、０．８９、０．９３、０．９６、０．９８、０．９９、１．００，采用ＮＣＡＲ的３０＇×３０＇地形资料，以常规观测资料作为初始场，较好地模拟了此次沙尘暴过程的海平面气压的演变和分布，特别是张掖、柴达本盆地以及敦煌附近的三个中低压。同时，模拟了张掖中低压与蒙古冷高压之间的甘肃河西沙尘暴东大风。敏感性试验表明，沙尘暴中低压的形成发展主要是受于物理过程制约；沙尘暴中尺度系统的研究与暴雨中尺度系统的研究是有区别的，积云对流参数化并不是特别重要，在设计研究沙尘暴的数值模式中，应当合理地处理其他的热力、动力过程及大气外强迫源的作用。模式水平格距、地形真实程度对模拟中低压的位置、中心强度有重要贡献；下垫面变化中低压强度有一定影响。张掖热低压的形成发展主要是在有利的环境形势下，特殊地势起了重要作用，表现为直接动力强迫和间接热力强迫。  相似文献   

祁连山地区1310年以来湿润指数及其年际变幅的变化与突变分析   总被引：23，自引：0，他引：23  

张志华  吴祥定 《第四纪研究》1996,16(4):368-378

本文通过用树木年轮资料重建的祁连山地区5～7月份1310年以来的湿润指数序列，建立了一个反映该地区湿润指数年际变幅序列，对这两个序列分别进行了等级分类和干湿、强弱的时段分析，并用最大熵谱分析法对这两个序列的不同时段分别进行了周期分析。采用HK突变检验方法对这两个序列分别进行了突变分析，发现祁连山地区的湿润指数及其年际变幅存在明显的突变年份。  相似文献   

中国东部6区域近1000年干湿序列的重建和气候跃变分析   总被引：54，自引：6，他引：54       下载免费PDF全文

张德二  刘传志  江剑民 《第四纪研究》1997,17(1):1-11

本文利用我国的历史气候记载，为东部6区域重建了最近1033年的时间分辨率为1年的区域于湿气候序列，讨论其可靠性，并分析其变化的准周期性和跃变特征。跃变分析采用移动t检验方法，分析各区域干湿气候的世纪尺度和10～20年尺度的跃变现象，辨识跃变信号的参考年代，指出北方各区域的跃变趋势相同，但有时与长江下游地区相反，以及跃变信号在寒冷气候背景下较多出现等特点。  相似文献   

Solar modulation of cosmogenic nuclide production over the last millennium: comparison between C and Be records     

Edouard Bard  Grant M. Raisbeck  Franoise Yiou  Jean Jouzel 《Earth and Planetary Science Letters》1997,150(3-4):453-462

For about the last 30 years it has been recognized that the high frequency component of the tree rings ¹⁴C/¹²C record is dominated by the modulation of the cosmic ray flux by the solar wind. In particular, it has been demonstrated that the three most recent periods of low sunspot occurrence were characterized by high values of atmospheric ¹⁴C/¹²C. During the last millennium other periods of high ¹⁴C/¹²C values were observed but their solar origin is still debatable. In the present work we compare these fluctuations with an independent record of cosmogenic ¹⁰Be measured in ice from the South Pole to check the solar origin of the observed ¹⁴C/¹²C variations. In order to compare quantitatively the results obtained on ¹⁰Be and ¹⁴C, it is necessary to take into account the different behaviour of these two cosmogenic isotopes, and especially the damping effect of the carbon cycle in the case of ¹⁴C. As an input to a 12-box numerical model we used the relative fluctuations of the ¹⁰Be concentrations record measured in South Pole ice and converted it into a synthetic ¹⁴C record. We took into account the fact that ¹⁰Be modulation is enhanced in polar regions due to the orientation of the geomagnetic field. As expected, the fluctuations of the modelled ¹⁴C record are much smaller (a factor of 20) than those observed for the raw ¹⁰Be record. In addition, the variations are smoother and shifted in time by a few decades. The ¹⁰Be-based ¹⁴C variations closely resemble the ¹⁴C measurements obtained on tree rings (R = 0.81). In particular, it is easy to identify periods of maximal ¹⁴C/¹²C which correspond to solar activity minima centred at about 1060, 1320 (Wolf), 1500 (Spörer), 1690 (Maunder) and 1820 (Dalton) yr A.D. Cross-correlation calculations suggest that there is no significant lag between the ¹⁰Be-based ¹⁴C and the tree-ring ¹⁴C records. Our study strongly suggests the dominance of the solar modulation on the cosmonuclide production variations during the last millennium.  相似文献   

Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau   总被引：5，自引：0，他引：5  

Donghuai Sun  Dongsheng Liu  Mingyang Chen  Zhisheng An  Shaw John 《中国科学D辑(英文版)》1997,40(4):337-343

Two Red Clay profiles near Xi’an and Xifeng were investigated in an attempt to determine magnetostratigraphic and palaeoclimatic records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma, and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5–2.5 Ma. Stepwise increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan Plateau, solar radiation, global ice volume, etc. Project supported by the National Natural Science Foundation of China and the Foundation of Xi’an Laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences.  相似文献   

古里雅冰帽8米浅冰芯的化学成分组成特征及其来源   总被引：10，自引：3，他引：10  

李月芳  姚檀栋 《冰川冻土》1997,19(2):173-179

对古里雅冰帽８ｍ浅冰芯的８０个雪冰样品化学分析结果表明，化学成分主要来自陆源物质，陆源冰芯样品叶弱碱性，明显不同于一般的大气降水及南北极冰雪样品。  相似文献   

从天山乌鲁木齐河源1号冰川变化估计近百年来该地区夏季升温   总被引：6，自引：6，他引：6  

王宁练  刘时银 《冰川冻土》1997,19(3):207-213

通过冰川波动历史来揭示气候变化是一种重要的方法。然而，以往有关这一方面的研究大都是一些定性的。文章试图依据冰种变化来定量的研究气候变化，并且通过近百年来天山乌鲁木齐河源１号冰川的变化，揭示出本世纪以来该河源地区夏季气温上升约０．２３￣０．２５℃，同时，对于该冰川不同长度规模时的气候敏感性也进行了讨论。  相似文献   

湖相沉积物与全球变化的研究     

ＤｏｕｇｌａｓＦ．Ｗｉｌｉａｍｓ 《地学前缘》1997,(Z1)

为预测未来全球的气候变化，必须了解在过去水圈、气圈与生物圈的各自作用以及它们是如何相互影响的。为此，ＩＧＢＰ（国际地圈－生物圈计划）组织了过去全球变化项目（ＰＡＧＥＳ）。湖相沉积物保存着与ＰＡＧＥＳ有关的不同时空尺度的丰富的地球系统历史信息，特别是湖相沉积物包含着可以说明全球气候变化的水圈与生物圈的陆源组分的反应。这种信息对了解影响气候变化的流域是如何发展的至关重要。笔者应用西伯利亚贝加尔湖与中国西北部青海湖作为两个实例，叙述了多学科研究湖相沉积物物理与化学参数，并利用这些参数测定了晚更新世湖区及其流域对过去气圈的变化以及日幅射分布的影响  相似文献