塔里木盆地绿洲形成与演变   总被引：62，自引：3，他引：62  

樊自立 《地理学报》1993,48(5):421-427

塔里木盆地的绿洲按形成历史可划分为古绿洲、旧绿洲和新绿洲,它们分别代表绿洲发展演变的三个阶段。本文对绿洲未来演变趋势作了预测,探讨了盆地古绿洲衰亡原因、认为除了风沙、盐碱及河流改道等自然原因外,人类活动引起的地表水资源时空分配发生变化是主要原因。  相似文献   

二红洼镁铁-超镁铁杂岩体特征及成因   总被引：1，自引：0，他引：1  

仲勇 《新疆地质》1991,(2)

新疆哈密二红洼镁铁-超镁铁杂岩体地表分南北两个岩体,深部可能连为一体,可划分为两个侵入期、四个岩相.第一侵入期构成岩体的主体部分,分异良好,由重力结晶分异形成自橄揽岩相、橄榄辉长岩相向含石英苏长辉长岩相的分异趋势,基性程度依次降低.岩浆多次贯入使得纵向上橄榄岩相和橄榄辉长岩相重复出现.第二侵入期辉长苏长岩相分异程度低,岩性稳定,为岩浆快速冷凝的产物.岩浆属于拉斑玄武岩系列,发生过金属硫化物熔离,有利于铜镍硫化物成矿.  相似文献   

中国东部的降水区划及备区旱涝变化的特征   总被引：2，自引：0，他引：2  

陈烈庭  吴仁广 《大气科学》1994,(5)

为了研究我国旱涝发生的规律、成因和预测，事先掌握降水的气候型区和各区降水变化的气候特征是十分必要的。本文利用１９５１—１９８６年中国东部１４０个站的月降水资料，分析了下半年降水相对系数、月际和年际标准差等参量时空变化的特征，并综合应用逐级归并法和成批调整法，对中国东部地区进行了降水气候区的划分。在此基础上，进一步探讨了各区旱涝的频数和长期变化的趋势。  相似文献   

川滇交界地区构造应力场及强震趋势的统计预测     

李桂芳  程万正 《四川地震》1994,(4):1-7

本文对川滇地区中、强震震源机制解和中小地震平均节面解分析，指出川滇地区现今构造应力场在北西－北西西向压应力作用下，以水平剪切错动为主。同时，采用极值理论、最大信息熵、线性预测和灰色理论等方法综合分析，预测川滇地区未来强震的趋势。  相似文献   

则木河与小江断裂交汇区地震危险性的概率预测     

程万正 《四川地震》1994,(4):8-12

本文针对则木河与小江断裂交汇区的强震趋势问题，给出了地震危险性的分析方法，结果及问题讨论。  相似文献   

青藏高原雪盖异常对我国环流和降水的影响   总被引：34，自引：4，他引：34       下载免费PDF全文

徐国昌  李珊 《应用气象学报》1994,5(1):62-67

利用美国NOAA NESDIS提供的1975—1986年青藏高原地区卫星雪盖资料，作出了各月冬季青藏高原雪盖频率图。发现1—3月是高原雪盖面积最大的月份，在此期间高原雪盖面积有明显的持续性，并与欧亚雪盖面积有较高的一致性。根据3月高原雪盖异常与中国环流和降水的关系，发现高原雪盖异常的后延冷却效应较弱，大约不足一个月；3月高原多雪以后，5月东亚北风加大，南岭以北降水偏少，少雪年则相反。  相似文献   

水分不足地区降水资源供需平衡模式   总被引：3，自引：0，他引：3       下载免费PDF全文

张家诚 《应用气象学报》1994,5(4):496-500

在自然界与人类系统水分平衡概念的基础上，提出了作降水评价的供需平衡模式。该模式对全面发挥由降水所形成的各种主要水资源成分的潜力是有用的。用此模式作了个例试验，并提出在水分不足地区缓解水分欠缺的途径。  相似文献   

差巴嘎蒿繁殖若干问题的探讨   总被引：9，自引：0，他引：9  

李进 《中国沙漠》1994,14(3):60-65

差巴嘎蒿（Ａｒｔｅｍａｓｉａｈａｌｏｄｅｎｄｒｏｎ）营养繁殖的最佳材料是当年生带根基部营养枝；降水量是影响营养繁殖成活率的主导因子，栽植后５日内降水之和（ｘ）与成活率（ｙ）的相关系数为０．９７０１，回归方程为：ｙ＝３４．０２３６＋４１．０４６７１ｇｘ。营养繁殖应在有一定降水的条件下及时进行，最佳时间在６月中旬。不宜利用种子繁殖建立人工植被。  相似文献   

Tropospheric methane in the mid-latitudes of the Southern Hemisphere     

P. J. Fraser  M. A. K. Khalil  R. A. Rasmussen  L. P. Steele 《Journal of Atmospheric Chemistry》1984,1(2):125-135

Results of more than 800 new measurements of methane (CH₄) concentrations in the Southern Hemisphere troposphere (34–41° S, 130–150° E) are reported. These were obtained between September 1980 and March 1983 from the surface at Cape Grim, Tasmania, through the middle (3.5–5.5 km) to the upper troposphere (7–10 km). The concentration of CH₄ increased throughout the entire troposphere over the measurement period, adding further support to the view that CH₄ concentrations are currently increasing on a global scale. For data averaged vertically through the troposphere the rate of increase found was 20 ppbv/yr or 1.3%/yr at December 1981. In the surface CH₄ data a seasonal cycle with a peak to peak amplitude of approximately 28 ppbv is seen, with the minimum concentration occurring in March and the maximum in September–October. A cycle with the same phase as that seen at the surface, but with a significantly decreased amplitude, is apparent in the mid troposphere but no cycle is detected in the upper tropospheric data. The phase and amplitude of the cycle are qualitatively in agreement with the concept that the major sink for methane is oxidation by hydroxyl radicals. Also presented is evidence of a positive vertical gradient in methane, with a suggestion that the magnitude of this gradient has changed over the period of measurements.  相似文献   

The global distribution of methane in the troposphere   总被引：6，自引：0，他引：6  

L. P. Steele  P. J. Fraser  R. A. Rasmussen  M. A. K. Khalil  T. J. Conway  A. J. Crawford  R. H. Gammon  K. A. Masarie  K. W. Thoning 《Journal of Atmospheric Chemistry》1987,5(2):125-171

Methane has been measured in air samples collected at approximately weekly intervals at 23 globally distributed sites in the NOAA/GMCC cooperative flask sampling network. Sites range in latitude from 90° S to 76° N, and at most of these we report 2 years of data beginning in early 1983. All measurements have been made by gas chromatography with a flame ionization detector at the NOAA/GMCC laboratory in Boulder, Colorado. All air samples have been referenced to a single secondary standard of methane-in-air, ensuring a high degree of internal consistency in the data. The precision of measurements is estimated from replicate determinations on each sample as 0.2%. The latitudinal distribution of methane and the seasonal variation of this distribution in the marine boundary layer has been defined in great detail, including a remarkable uniformity in background levels of methane in the Southern Hemisphere. We report for the first time the observation of a complete seasonal cycle of methane at the South Pole. A significant vertical gradient is observed between a sea level and a high altitude site in Hawaii. Globally averaged background concentrations in the marine boundary layer have been calculated for the 2 year-period May 1983–April 1985 inclusive, from which we find an average increase of 12.8 ppb per year, or 0.78% per year when referenced to the globally averaged concentration (1625 ppb) at the mid-point of this period. We present evidence that there has been a slowing down in the methane growth rate.Presented at the Conference on the Scientific Application of Baseline Observations of Atmospheric Composition (SABOAC), Aspendale, Australia, 7–9 November 1984.  相似文献