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991.
High resolution δ18O and methane records over the last 2ka have been reconstructed from Dasuopu ice core recovered from the Himalayas. Analysis
shows that the δ18O record correlates well with the Northern Hemispheric temperature, Dunde ice core record, and with temperature record in
eastern China. The warming trend detected in δ18O record from the last century is similar to that during the Medieval warm period. There is a dramatic increasing in methane
concentration in the Dasuopu ice core, which reached 1031 nmol ⋅ mol-1 in 1997. Moreover, methane concentration in the Dasuopu ice core is about 15%-20% higher than that in Antarctica and Greenland.
There is a positive correlation between methane concentration and δ18O in Dasuopu ice core. 相似文献
992.
从大尺度环流形势场、西风环流指数、阻塞高压、副热带高压和南亚高压等方面 ,对 2 0 0 1年汛期强降水多发时段的中期天气特征进行了分析 ,结果表明 :①极涡由一个中心分裂为多个中心 ,北半球极涡呈偶极型或多极型 ,其中有一较强中心位于东半球偏于亚洲一侧 ;②亚欧中高纬环流形势为两脊一槽型 ,亚洲中部为一低压槽 ;③连续性强降水发生在西风环流指数由峰值向谷点过度的过程中 ;④鄂霍次克海阻塞高压的建立是造成我省连续性强降水的关键 ;⑤西太平洋副热带高压在短时间内迅速西伸北跳 ,14 0°E副高脊线位置位于 30°N附近并稳定 ;⑥10 0hPa南亚高压脊线北跳至 33°N以北 ,且中心位置自西向东震荡并稳定于 90°E以东地区 相似文献
993.
Based on the investigation and analysis of characteristics of precipitation, natural environment, socio-economic factors and
soil erosion, this paper indicates that the precipitation is the main driving force for the soil erosion in the sediment-rich
area, its variability determines the characteristics of soil and water loss; the natural conditions such as the drainage systems,
geological and topographic features, the composition of soil and land surface materials, vegetation and climate determine
the seriousness of soil and water loss; irrational socio-economic activities of human beings usually accelerated soil and
water loss; meanwhile, the low preservation rate and inferiority of soil and water conservation measures made it impossible
to make rapid progress on soil and water loss control. Furthermore, the characteristics of erosion environment endowed this
area with more sediment that is the main reason for the flooding disasters by the Yellow River. Therefore, more emphasis should
be placed on the enhancement of soil and water conservation. The soil loss prediction models will provide scientific basis
for the planning of soil and water conservation, the designing of soil and water conservation measures and the valuation of
effects of soil and water loss control. According to the analysis of the previous studies on soil loss prediction, and the
water-sediment variation features, it is thought that study on soil loss prediction under various rainfall conditions and
soil-water conservation measures should be carried out. 相似文献
994.
Tandong Yao L. G. Thompson Yafeng Shi Dahe Qin Keqin Jiao Zhihong Yang Lide Tian E. M. Thompson 《中国科学D辑(英文版)》1997,40(6):662-668
The climatic and environmental variations since the Last Interglaciation are reconstructed based on the study of the upper
268 m of the 309-m-long Guliya ice core. Five stages can be distinguished since the Last Interglaciation from the δ18O record in the Guliya ice core: Stage 1 (Deglaciation), Stage2 (the Last Glacial Maximum), Stage 3 (interstadial), Stage
4 (interstadial in the early glacial maximum) and Stage 5 (the Last Interglaciation). Stage 5 can be divided further into
5 substages; a, b, c, d, e. The δ18O record in the Guliya ice core indicates clearly the close correlation between the temperature variation on the Tibetan Plateau
and the solar activities. The study indicates that the solar activity is a main forcing to the climatic variation on the Tibetan
Plateau. Through a comparison of the ice core record in Guliya with that in the Greenland and the Antarctic, it can be found
that the variation of large temperature variation events in different parts of the world is generally the same, but the variation
amplitude of temperature is different.
Project supported by thc Climbing Program of the State Eighth Five-Year Plan and the National Natural Science Foundation of
China. 相似文献
995.
近2000年来气候环境变化的冰芯记录研究 总被引:18,自引:0,他引:18
文章通过对古里雅冰芯中δ18O、冰川积累量和Ca等指标的研究,恢复了过去近2000a来气候环境的变化。作为温度指标的δ18O反映了过去近2000a来气候在冷暖波动中逐渐变暖的趋势。作为降水指标的冰川积累量反映出降水变化具有和温度变化相似的特征,即降水在增减波动中显示出逐渐增大的趋势。与温度升高和降水增大的趋势相反,冰芯中的Ca含量呈现明显的减少趋势,说明大气中尘埃含量随气候的变暖逐渐减少。这和我们研究中所得出的冷期时大气尘埃增加,暖期时大气尘埃减少的结论是一致的 相似文献
996.
全球石炭纪-二叠纪植物群的演化和分布特征 总被引:8,自引:0,他引:8
在全球范围内,石炭纪和二叠纪植物群可以划分为五个植物群,即早石炭世(杜内期、维宪期和纳缪尔A期)的全球性拟鳞木植物群(Lepidodendropsisflora)和晚石炭世(纳缪尔B—C期、威斯发期和斯蒂芬期)至二叠纪的华夏植物群、欧美植物群、安加拉植物群和冈瓦纳植物群。早石炭世拟鳞木植物群广泛分布于世界许多地区,具有全球一致性,以Lepidodendropsis,Sub lepidodendron,Archaeosigilaria,Archaeocalamites,Cardiopteridium,Rhodeopteridium,Rha copteris,Adiantites,Triphylopteris等为特征。拟鳞木植物群逐渐从泥盆纪植物群分离出来,繁盛于早石炭世早期,绝灭于早石炭世末期。在早石炭世和晚石炭世的转换期,全球性气候变化和构造运动导致早石炭世拟鳞木植物群典型分子的绝灭和晚石炭世植物群先驱分子的出现。因此,华夏植物群、欧美植物群、安加拉植物群和冈瓦纳植物群衍生于早石炭世全球一致性拟鳞木植物群,但它们各自发展在不同的环境中。 相似文献
997.
台湾附近地形对台风影响的数值模拟 总被引:6,自引:0,他引:6
利用TCM-90资料分析并用数值方法成功地模拟了9017号台风经过台湾时发生复杂变化的过程,包括环流场副中心和高度场副中心形成及与其主中心的合并过程,环流中心合并时路径跳跃过程,台湾西侧低压中心异常北移过程,台湾海峡低层急流变化过程以及上下层高度中心与环流中心明显偏离的现象,并详细分析了模拟中每隔3小时的演变过程,给出了台风经过台湾前后的结构及详细的路径变化,这种详细的演变图像不可能从间隔6小时的 相似文献
998.
Geomorphology of the Urümqi River Valley and the uplift of the Tianshan Mountains in Quaternary 总被引:1,自引:0,他引:1
The Shaerqiaoke Gravel, more than 400 m in thickness, on the north piedmont of the Tianshan Mountains, is located at the exit of the Urümqi River Valley and belongs to the Molasse construction of the Tianshan Mountains. Another uplift event with the tectonic boundary expansion ended the deposition of the Shaerqiaoke Gravel, and resulted in folding, faulting and down-erosion in the frontier of the deposit. The ESR dating indicates that the top of the Shaerqiaoke Gravel accumulated before 1148 kaBP, probably responding to the Kunlun-Huanghe movement of the Qinghai-Tibetan plateau. After that time, erosion-deposition cycle occurred and 9 terraces developed. The TL and ESR dating techniques were employed to date these terraces, and the results indicate that Terrace 3 was formed at MIS 6. Terrace 2 at Houxia also developed simultaneously. Terraces 5 and 6 were accumulated in 338 kaBP and 562-591 kaBP, respectively. The oldest glaciation, named Gao Wangfeng, correlates to MIS 12. 相似文献
999.
1000.
采用1992年、2005年、2019年上海市存续航运服务企业(组织)数据,运用加权核密度、最近邻指数以及关键词共现网络,研究其空间分布及功能演变,结果表明:上海市航运服务业的空间分布总体趋于集聚,早期沿城市内河形成连片分布,后向工业园、港口及城市CBD等多区位、多核心转变。从功能演变来看,重要功能元构成长期稳定,仓储保持首位。新兴功能元发展持续性不足,电子商务、集装箱运输、船舶技术突变强度高。已形成7个功能元聚类,呈价值链攀升态势。传统港航业、金融业及信息业是功能元聚类形成的关键行业。功能多元化对资源组合需求异质化,而资源在空间分布不均衡,两者动态调整匹配是空间分布及功能形成演变的根本原因。 相似文献