2000—2015 年伊犁河谷植被覆盖时空变化特征   总被引：1，自引：0，他引：1       下载免费PDF全文

孙国军  李卫红  朱成刚  崔东  刘海军 《干旱区地理》2020,43(6):1551-1558

利用 2000—2015 年的 EOS／MODIS 数据，采用趋势分析、Hurst 指数、变异系数法对伊犁河 谷植被时空变化及未来趋势进行分析，结果显示：空间分布上，伊犁河谷植被覆盖度呈北部、南部、 东部偏高，西部、中部偏低的分布特征；时间变化上，2000—2015 年，伊犁河谷植被覆盖度波动减 小，减速为 6.25%·(10 a)^-1；区域分布上，伊犁河谷植被表现为低波动变化，波动程度中等以及下占 73.16%，波动程度高的区域占 26.84%。未来预测表明，伊犁河谷植被覆盖呈退化趋势，其中，持续 退化的面积占 57.55%，持续改善的面积占 13.51%。  相似文献   

巢湖杭埠河流域湖相沉积物多指标揭示的全新世以来环境演变     

周慧  吴立  马春梅  管后春  孙小玲  路曙光  尚广春  汪勇  徐仪红  徐军  陈晔  鲍远航 《湖泊科学》2020,32(6):1869-1881

在巢湖杭埠河流域中的古湖盆中心——三河圩区获取28.6 m长的湖相岩芯（SZK1507孔），利用AMS¹⁴C测年技术建立可靠的地层年代序列，通过对SZK1507孔738 cm以上段湖相沉积物平均粒径、磁化率、总氮（TN）、总有机碳（TOC）及C/N的综合分析，高分辨率重建了巢湖杭埠河流域全新世以来的古环境演变过程.结果表明，本区域的环境变化过程可以分为4个阶段，阶段Ⅰ（约10050—9700 cal.a B.P.）与阶段Ⅲ（约9250—5300 cal.a B.P.）气候较为湿润，巢湖水位较高，平均粒径、磁化率值较低，TN、TOC、C/N也偏低；阶段Ⅱ（约9700—9250 cal.a B.P.）与阶段Ⅳ（约5300 cal.a B.P.以来）气候干燥，巢湖水量减少，水位降低，平均粒径、磁化率值、TN、TOC、C/N均较高.一些全球范围内显著发生的气候突变事件在SZK1507孔沉积记录中也有体现，如9.3、8.2和4.2 ka B.P.事件等.将巢湖杭埠河流域10000 cal.a B.P.以来的平均粒径、磁化率、TN、TOC、C/N沉积记录与全新世以来的北纬30°夏季太阳辐射量、太阳黑子数、火山喷发对大气中硫酸盐含量贡献率等进行对比，发现巢湖杭埠河流域全新世气候突变事件主要受控于北半球夏季太阳辐射量变化、太阳活动以及火山活动等因素，并与它们之间复杂的响应机制有关.  相似文献   

Snow cover area change and its relations with climatic variability in Kashmir Himalayas,India     

Mifta ul Shafiq  Zahoor ul Islam  P. K. Joshi  Waseem A. Bhat 《国际地球制图》2019,34(6):688-702

Snowmelt makes an essential component of the hydrological system of Kashmir Himalayas. The present study was carried out to examine the status of Snow Cover Area (SCA) using Moderate Resolution Imaging Spectroradiometer (MODIS) 8-day Snow Cover Product between 2000 and 2016. The intra- and inter-annual variability in SCA and in meteorological parameters was observed and various statistical tests were used to study the interrelationship. Results of statistical analysis indicate decrease in maximum temperature (?0.05 °C/year) and minimum temperatures (?0.02 °C/year) while rise in precipitation (19.13 mm/year). It also showed an increase in annual mean SCA (43.5 sq km) during the study period. The analysis was also carried out on a seasonal basis. The results revealed that in Kashmir Himalayas, climate plays a dominating role in controlling the SCA. The results depict the short-term fluctuations in SCA and show the magnitude of change between two successive values being very large in SCA.  相似文献   

Synergistic contribution of precipitation anomalies over northwestern India and the South China Sea to high temperature over the Yangtze River Valley   总被引：1，自引：0，他引：1  

Ge Liu  Renguang Wu  Shuqing Sun  Huimei Wang 《大气科学进展》2015,32(9):1255-1265

This study explores the characteristics of high temperature anomalies over eastern China and associated influencing factors using observations and model outputs. Results show that more long-duration (over 8 days) high temperature events occur over the middle and lower reaches of the Yangtze River Valley (YRV) than over the surrounding regions, and control most of the interannual variation of summer mean temperature in situ. The synergistic effect of summer precipitation over the South China Sea (SCS) region (18°-27°N, 115°-124°E) and the northwestern India and Arabian Sea (IAS) region (18°-27°N, 60°-80°E) contributes more significantly to the variation of summer YRV temperature, relative to the respective SCS or IAS precipitation anomaly. More precipitation (enhanced condensational heating) over the SCS region strengthens the western Pacific subtropical high (WPSH) and simultaneously weakens the westerly trough over the east coast of Asia, and accordingly results in associated high temperature anomalies over the YRV region through stimulating an East Asia-Pacific (EAP) pattern. More precipitation over the IAS region further adjusts the variations of the WPSH and westerly trough, and eventually reinforces high temperature anomalies over the YRV region. Furthermore, the condensational heating related to more IAS precipitation can adjust upper-tropospheric easterly anomalies over the YRV region by exciting a circumglobal teleconnection, inducing cold horizontal temperature advection and related anomalous descent, which is also conducive to the YRV high temperature anomalies. The reproduction of the above association in the model results indicates that the above results can be explained both statistically and dynamically.  相似文献   

祁连山老虎沟12号冰川冰内结构特征分析   总被引：2，自引：0，他引：2  

武震  张世强  刘时银  杜文涛 《地球科学进展》2011,26(6):631-641

利用探地雷达(Ground Penetration Radar,GPR)调查冰川冰内结构和冰层厚度是一种监测冰川变化常用手段.应用麦克斯维(Maxwell)方程的二维时域有限差分(FDTD)方法,通过将模拟图像与老虎沟12号冰川的实测图像的对比,分析了雷达剖面中的几种反射特征,如冰裂隙、融洞、暖冰等.对比结果表明,GP...  相似文献   

绰斯甲水电站野人谷泥石流发育特征分析与防治建议     

赵军  袁国庆  唐世明  蔡仁龙 《四川地质学报》2011,(4):446-449

介绍了野人谷泥石流的发育特征,利用雨洪法进行了定量分析,为在该泥石流沟内布置渣场提出了合理的建议.  相似文献   

Beryllium-10 terrestrial cosmogenic nuclide surface exposure dating of Quaternary landforms in Death Valley     

Lewis A. Owen  Kurt L. Frankel  Jeffrey R. Knott  Scott Reynhout  Robert C. Finkel  James F. Dolan  Jeffrey Lee 《Geomorphology》2011,125(4):49

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Age of the MGS5 segment of the Milanggouwan stratigraphical section and evolution of the desert environment on a kiloyear scale during the Last Interglacial in China's Salawusu River Valley: Evidence from Rb and Sr contents and ratios     

Shuhuan Du  Baosheng Li  Dongfeng Niu  David Dian Zhang  Xiaohao Wen  Deniu Chen  Yi Yang  Fengnian Wang 《Chemie der Erde / Geochemistry》2011,(1):87-95

The MGS5 segment of the Milanggouwan stratigraphical section in China's Salawusu River Valley records 8.5 sedimentary cycles consisting of dune sands alternating with fluviolacustrine facies or/and paleosols. Based on a comprehensive analysis of the distribution of Rb and Sr within the segment and paleoecological evidence (fossils), it appears that the observed sedimentation cycles mainly resulted from fluctuations between dry-cold and warm-humid climates, which indicates that the MGS5 segment experienced at least eight cold-dry and nine warm-humid climatic fluctuations. Of these, 12 cold–warm climate fluctuations correspond to DO20–DO25 and stadia 21–26 recorded by the NGRIP ice cores. Another five cold–warm climatic fluctuations that occurred during MGS5e correspond to five substages (5e1–5e5) recorded by the GRIP ice cores from Greenland. This kind of high-frequency climatic fluctuation on a kiloyear scale was mainly subject to variations in the strength of the East Asian winter and summer monsoons.  相似文献   

青藏高原河谷地区历史时期耕地格局重建方法探讨——以河湟谷地为例   总被引：4，自引：1，他引：3  

罗静  陈琼  刘峰贵  张镱锂  周强 《地理科学进展》2015,34(2)

青藏高原受其特殊自然地理环境条件的限制,耕地主要分布在自然环境条件相对优越的河谷地区,人为因素对耕地分布范围的作用和影响极其微弱,尤其是在历史时期生产力水平较低的前提下,耕地的空间分布主要取决于土地的宜垦程度。本文将影响青藏高原河谷地区耕地分布的因子按其性质分为限制性因子和非限制性因子,并以此为基础排除了高原河谷地区不适宜耕作的地区,在适宜耕作的地区根据土地的宜垦程度,按"先优后劣"的原则将历史时期的耕地数据分配到空间上。选取青藏高原农业发展历史悠久的河谷地区之一河湟谷地作为实例,重建该区1726年耕地空间格局。将重建结果与已有的M模型重建结果进行对比分析,两者重建的耕地在空间分布上呈现出一致性,但重建结果在垦殖范围与垦殖强度上存在一定的差异;M模型的重建主要是以现代耕地分布格局为基础重建,忽略了现代耕地空间分布受现代农业技术的影响;而本文模型则是从低生产力水平前提下影响历史时期耕地分布的因子出发,重建结果更具合理性。  相似文献   

大兴安岭西坡比利亚谷银铅锌多金属矿床成因     

梁小龙  孙景贵  邱殿明  徐智涛  谷小丽  任泽宁 《吉林大学学报(地球科学版)》2020,50(3):781-799

比利亚谷银铅锌多金属矿床位于大兴安岭西坡的得尔布干成矿带，它是近些年来在该区新发现的一座大型银铅锌多金属矿床。该矿床矿体主要呈脉状、细脉浸染状、角砾状赋存于塔木兰沟组中—基性火山岩和满克头鄂博组酸性火山岩中的NW向断裂体系内。根据矿石的结构、构造以及矿物之间的共生组合、穿切关系，将成矿过程从早到晚划分为硅化石英+黄铁矿阶段（Ⅰ）、石英+黄铁矿+闪锌矿阶段（Ⅱ）、石英+黄铁矿+闪锌矿+方铅矿+辉银矿+黄铜矿±黝铜矿阶段（Ⅲ）、石英+黄铁矿+方解石+萤石±蛋白石阶段（Ⅳ）；详细的石英、闪锌矿流体包裹体研究揭示：成矿早阶段（Ⅰ、Ⅱ）石英中发育WL型、C型包裹体，包裹体完全均一温度为188~254℃，盐度（w（NaCl））为1.83%~4.79%，密度为0.81~0.94 g/cm³，属于中低温、低盐度的H₂O-NaCl-CO₂体系；成矿主阶段（Ⅲ）石英、闪锌矿中发育WL型包裹体，包裹体完全均一温度为160~188℃，盐度为3.69%~7.15%，密度为0.92~0.96 g/cm³，属于低温、中低盐度的H₂O-NaCl-CH₄体系；成矿晚阶段（Ⅳ）石英中发育WL型、L型包裹体，WL型包裹体完全均一温度为130~165℃，盐度为1.22%~3.53%，密度为0.93~0.95 g/cm³，属于低温、低盐度的H₂O-NaCl体系。流体包裹体H-O同位素地球化学特征揭示：早阶段流体的δ¹⁸O_H2O-SMOW值为-6.3‰~-5.9‰，δD_H2O-SMOW值为-163.4‰~-162.7‰；成矿主阶段流体的δ¹⁸O_H2O-SMOW值为-14.4‰，δD_H2O-SMOW值为-165.4‰~-162.0‰；成矿晚阶段流体的δ¹⁸O_H2O-SMOW值为-19.1‰，δD_H2O-SMOW值为-150.7‰；硫化物Pb同位素比值分别为²⁰⁶Pb/²⁰⁴Pb=18.435~18.513、²⁰⁷Pb/²⁰⁴Pb=15.579~15.675、²⁰⁸Pb/²⁰⁴Pb=38.283~38.603。这种特征揭示，该矿床成矿流体为低温、低盐度的H₂O-NaCl-CH₄体系，早期为残余岩浆水和大气降水混合、中—晚期大气降水逐渐增加；成矿物质源于壳幔混合源区；成矿过程以流体混合方式导致成矿元素聚集和沉淀，矿床成因类型为与陆相火山-次火山作用有关的低硫化型浅成热液铜（银）铅锌多金属矿床；其整体与大兴安岭西坡同类型矿床相似，成矿作用发生在早白垩世（131.3 Ma），与古太平洋板块俯冲产生的弧后伸展环境相关。  相似文献