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21.
Using a set of numerical experiments from 39 CMIP5 climate models, we project the emergence time for 4°C global warming with respect to pre-industrial levels and associated climate changes under the RCP8.5 greenhouse gas concentration scenario. Results show that, according to the 39 models, the median year in which 4°C global warming will occur is 2084. Based on the median results of models that project a 4°C global warming by 2100, land areas will generally exhibit stronger warming than the oceans annually and seasonally, and the strongest enhancement occurs in the Arctic, with the exception of the summer season. Change signals for temperature go outside its natural internal variabilities globally, and the signal-to-noise ratio averages 9.6 for the annual mean and ranges from 6.3 to 7.2 for the seasonal mean over the globe, with the greatest values appearing at low latitudes because of low noise. Decreased precipitation generally occurs in the subtropics, whilst increased precipitation mainly appears at high latitudes. The precipitation changes in most of the high latitudes are greater than the background variability, and the global mean signal-to-noise ratio is 0.5 and ranges from 0.2 to 0.4 for the annual and seasonal means, respectively. Attention should be paid to limiting global warming to 1.5°C, in which case temperature and precipitation will experience a far more moderate change than the natural internal variability. Large inter-model disagreement appears at high latitudes for temperature changes and at mid and low latitudes for precipitation changes. Overall, the inter-model consistency is better for temperature than for precipitation.  相似文献   
22.
Abstract. A total of 1789 fish belonging to 38 families and 73 species were collected at depths between 18 and 1102 m during 216 bottom longline operations off Lanzarote and Fuerteventura, Canary Islands, between February 1994 and December 1995. For each species the depth distribution is provided. Length-weight and depth-size relationships are reported for three shelf-dwelling species. The bigger-deeper relationship found in two of them contrasts with the bigger-shallower pattern of the deeper living trichiurid Lepidopus caudatus . In November 1997, nine additional bottom longline operations were carried out off eastern Fuerteventura at depths between 805 and 1217 m. In this area, after earlier studies in October 1995, a spawning aggregation of the morid Mora moro was encountered for the second time. The catches of 1997 revealed a strongly male-biased sex ratio. Also, the males showed a significantly lower gonadosomal index than two years earlier. These findings indicate slight interannual variations in reproductive timing and an earlier arrival of male Mora moro at the spawning grounds. Clear variations in the number of fish collected at adjacent sites possibly reflect a preference for distinct microhabitats. Preliminary evidence of local upwelling of cold water above the spawning grounds is provided by satellite imagery.  相似文献   
23.
哈达门沟金矿床地质特征及其形成时代研究   总被引:6,自引:0,他引:6       下载免费PDF全文
哈达门沟金矿床位于华北地台北缘西段,产于太古代乌拉山岩群变质碉系中,矿床以发育一系列含金钾长石-石英脉为特征,这些钾长石-石英脉沿近东西向的韧、脆性叠加断裂成 出。钾长石化是最发的近矿围为。采用离子探针(SHRIMP)对矿体边部的钾长石化蚀变岩锆石U-Pb定年结果表明:矿化钾长石化蚀变岩的年龄为132±2Ma。由于钾长石化夺本身被金矿化,因此金矿化年龄小于或接近于132±2Ma,为燕山晚期成矿。  相似文献   
24.
系统整理河北省1992-2014年流动重力资料,利用LGADJ数据处理软件,对每期重力数据进行单期平差、多期整体平差计算,改正历史遗留问题,利用差分结果绘制145幅流动重力等值线差分图,通过具体异常点位及重力变化分析,得出:①地震前重力场变化强度与震级大小存在相关性;②流动重力观测资料地震前具有较为明显的前兆异常反应;③地震均发生在重力变化的“0”等值线附近地区。  相似文献   
25.
Timing, Displacement and Growth Pattern of the Altyn Tagh Fault: A Review   总被引:1,自引:0,他引:1  
The Altyn Tagh Fault (ATF) is the longest, lithospheric scale and strike-slip fault in East Asia. In the last three decades, multidisciplinary studies focusing on the timing, displacement of strike-slip and growth mechanics of the ATF have made great progresses. Most studies revealed that the ATF is a sinistral strike-slip and thrust fault, which underwent multiple episodes of activation. The fault is oriented NEE with a length of 1600 km, but the direction, timing of activity and magnitude of its extension eastward are still unclear. The AFT was predominately active during the Mesozoic and Cenozoic, in relation to the Mesozoic collision of the Cimmerian continent (Qiangtang and Lhasa block) and Cenozoic collision of India with Asia. The AFT strike-slipped with a left-lateral displacement of ca. 400 km during the Cenozoic and the displacement were bigger in the western segment and stronger in the early stage of fault activation. The slip-rates in the Quaternary were bigger in the middle segment than in the western and eastern segment. We roughly estimated the Mesozoic displacement as ca. 150-300 km. The latest paleomagnetic data showed that the clockwise vertical-axis rotation did not take place in the huge basins (the Tarim and Qaidam) at both side of ATF during the Cenozoic, but the rotation happened in the small basins along the ATF. This rotation may play an important role on accommodating the tectonic deformation and displacement of the ATF. Even if we have achieved consensus for many issues related to the ATF, some issues still need to be study deeply; such as: (a) the temporal and spatial coupling relationship between the collision of Cimmerian continent with Asia and the history of AFT in the Mesozoic and (b) the tectonic deformation history which records by the sediments of the basins within and at both side of AFT and was constrained by a high-resolution and accurate chronology such as magnetostratigraphy and paleomagnetic data.  相似文献   
26.
基于家庭的购物行为时、空间 决策模型及其应用   总被引:6,自引:1,他引:5  
张文佳  柴彦威 《地理研究》2010,29(2):338-350
基于家庭的购物行为决策的概念模型,利用2007年北京市活动日志调查的第一手数据,建立购物出发时间决策和购物目的地决策的条件Logit模型,并探讨其在相关政策评估和预测上的应用。结果发现:家庭内部相互作用和决策层面要素对购物时、空间决策的影响比较显著;早晚高峰出行的人群具有不同的社会经济属性和购物行为属性;居民休息日的购物活动集中在离家6km以内或者高密度的商业中心;影响购物目的地选择的因素更多是购物地距离,而非商业密度。通过模拟发现,土地混合利用的政策可能会增加高峰期的交通拥挤程度,而商业设施分散布局可能更有利于城市交通状况的改善和居民日常生活质量的提升。  相似文献   
27.
This article reports the depositional environment, provenance, and U–Pb zircon age constraints for the newly identified Zhaga Formation in northern Tibet and uses these to better understand the tectonic evolution of the Bangong–Nujiang suture. One transect across the Zhaga Formation was investigated. The Zhaga Formation is ~2 km thick, dominated by greywacke and conglomerate at the base, basalt and limestone in the middle, and greywacke and shale at the top. Greywacke in the Zhaga Formation typically contains 70–75% quartz, 5% feldspar, 3–5% rock debris, and >15% matrix, with normal grading and convolute bedding, basal flow structures, and distinct Bouma sequences interpreted as bathyal to abyssal turbidites. One rhyolite sample and one greywacke sample from the studied transect were collected for zircon U–Pb dating. The rhyolite yields a concordia age of 118 Ma, and the greywacke yields nine age peaks of 247, 330, 459, 541, 611, 941, 1590, 1871, and 2482 Ma, indicating that the Zhaga Formation formed during the late Early Cretaceous and the provenance of its detritus was the Qiangtang area. These data, combined with the Early Cretaceous ocean islands, indicates that the Bangong–Nujiang Neo-Tethys Ocean must have been open during the late Early Cretaceous. We conclude that the Bangong–Nujiang Neo-Tethys Ocean closed after the late Early Cretaceous and not during the Late Jurassic or the early Early Cretaceous as proposed by previous workers.  相似文献   
28.
李玉广  周剑  黄凤楼  张小虎 《测绘科学》2011,36(1):22-23,139
在光学摄像测量中,各种数据的同步采集在事后处理中尤为重要。目前GPS授时同步技术已经很成熟,它具有精度高,操作灵活等优点,可以很好地应用于光学摄像测量中。本文深入研究了GPS OEM板授时原理,在分析了GPS OEM板芯片中RS232时间输出与1pps输出特点的基础上,基于VC开发环境下实现了GPS OEM板与计算机串口的通信,为摄像测量设置一精确的时间起点,再利用CPU时间戳进行高精度计时,这样整个测量系统就有一高精度的时钟,任一数据的产生都被标记上精确的绝对时刻,利用这些时刻信息就间接地实现了摄像测量数据的高精度同步。实验数据表明,该方法的同步精度可以达到毫秒级,可以满足光学摄像测量的同步精度要求。  相似文献   
29.
韩伟  周建波 《岩石学报》2020,36(3):703-725
饶河杂岩作为那丹哈达增生杂岩的主体,是古太平洋板块西向俯冲的直接证据。饶河增生杂岩组成与增生过程的研究对限定古太平洋板块向欧亚大陆的俯冲与增生过程具有重要的指示意义。本文在野外地质调查和饶河大岱地区大比例尺填图基础上,明确了饶河杂岩主要由枕状玄武岩、辉长岩以及大洋板块沉积地层(OPS)组成,这些岩石均呈构造透镜体状分布在海沟沉积物中,并被中生代花岗质岩脉所穿切,因此为限定饶河增生杂岩的组成、增生和就位时代提供了关键制约。地球化学数据表明玄武岩具有洋岛玄武岩(OIB)的地球化学属性。LA-ICPMS锆石测试结果表明该地区玄武岩和辉长岩的形成时代分别为166±2Ma和214±5Ma,限定了饶河杂岩中镁铁质-超镁铁质岩石的形成时代为晚三叠世至中侏罗世。结合该区粉砂质泥岩和砂岩的沉积时代下限分别为167±3Ma和133±4Ma,表明饶河杂岩的增生时代为167~133Ma,此外样品的碎屑年龄信息表明基质的物源为邻近的佳木斯地块和中亚造山带东段,其中前寒武的碎屑年龄在中国东北的多个陆块均有出现,可能源于早前存在的前寒武纪基底。本文测得侵入饶河杂岩的2个二长花岗岩形成年龄分别为126±1Ma和105±2Ma,表明饶河杂岩中的花岗岩脉主要形成于两个阶段,其中较老的花岗岩侵入体进一步限定了饶河杂岩的最终就位时代为133Ma至126Ma,表明古太平洋板块在中侏罗世至早白垩世存在西向俯冲-增生作用,为古太平洋板块的构造演化提供了重要的制约。  相似文献   
30.
对祁漫塔格山体不同海拔高度所取的9个磷灰石样品的裂变径迹分析结果表明,东昆仑西段中新世早中期为主要的隆升期且隆升速率较高,早期隆升速率为111m/Ma,晚期隆升速率为98m/Ma,总体隆升速率为100m/Ma。样品显示出磷灰石裂变径迹长度大致分2类,一类磷灰石裂变径迹长度为(12.21±10.20)-(13.75±0.30)μm,径迹长度分布图基本上为窄而对称的正态分布,反映具有快的剥露冷却速率,未受到后期热事件的干扰。另一类磷灰石裂变径迹长度为(11.88±0.33)~(13.32±0.27)μm,较前一类具有稍慢的剥露冷却速率,并且受到了后期热事件的干扰。  相似文献   
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