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利用近50年华北地区26个站逐月降水观测资料和全球大气海洋分析资料,分析了华北降水的年代际变化特征及其和全球海气系统年代际变化的关系.对华北降水距平指数变化分析表明,近50年来华北降水具有减少的总体趋势,叠加在该趋势之上的是年代际变化,其中1965年和1980年发生了两次跃变,使得20世纪80年代干旱尤为严重.在对华北地区降水年代际变化特征分析的基础上,揭示了与华北降水年代际异常相伴随的大气环流和上层海洋热力异常型.结果表明,华北降水年代际异常与太平洋上层海洋热力状况异常有显著关系,主要表现为太平洋年代际振荡（PDO）与华北降水异常的相关.在年代际时间尺度上,华北干旱与上层海洋热力及大气环流异常的配置关系如下：当华北地区干旱时,则热带中东太平洋海温偏高,北太平洋中部海温偏低,即太平洋上主要表现为PDO暖位相,全球大部分地区（包括华北地区）气温偏高,青藏高原地区气温偏低,日本北部及东西伯利亚气压异常偏低,华北及其以南大片地区气压偏高,华北地区由异常西北风控制,不利于水汽向华北地区输送. 相似文献
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采用政府间气候变化委员会资料中心的模式预测结果,本文分析了SRES A2温室气体和气溶胶排放情景下中国大陆21世纪前30年的10年际气候变化趋势. 研究揭示：大陆冬季和夏季表面温度、表面最高温度和最低温度分别升高0.3～2.3℃、0.1～2.0℃、0.5～2.7℃,增幅大体上呈现东西向带状分布,由南至北升温逐渐加强,且增幅随时间加大. 此外,上述三气候要素冬季升温幅度要大于同期夏季、表面最低温度升幅要强于同期表面最高温度,冬季和夏季表面温度的季节内变化范围减小. 冬季东亚地区海平面气压异常幅度在-1.0hPa至0.4hPa之间变化,呈东西向带状分布,表现为南正北负、随时间推进异常幅度有所加大,正负交界面向南扩展;同时,东北、华北和西部海平面气压负异常较大. 夏季海平面气压异常空间分布与冬季相似. 2001～2030年,青藏高原大部、大陆东南部和河套大部分地区降水量增加0.1～0.8mm/d. 相似文献
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2015年3月30日至5月15日,巴布亚新几内亚-新不列颠地区发生了一系列地震.为研究该地区的构造应力环境及孕震背景,本文基于Global CMT目录,对新不列颠区域浅部进行构造应力场反演,拟得到高精度的应力图像.反演结果显示：（1）沿着南、北俾斯麦块体边界的区域构造应力场呈走滑体系,最大主压应力轴方位呈SWW-NEE向.（2）所罗门海的NW和NE走向的海沟处于压缩状态,所罗门海块体向新不列颠和所罗门群岛俯冲的板块弯曲部分是局部拉张.（3）受俯冲带的北向推挤,南俾斯麦板块顺时针旋转的挤压,太平洋板块向西部运动汇聚作用,新不列颠岛东北部与新爱尔兰岛南部交汇区域呈现明显非均匀应力状态.（4）此次地震序列的大多数走滑型和逆冲型地震,可能是所罗门海块体俯冲运动,和南俾斯麦块体与太平洋板块的近EW向挤压作用共同引发. 相似文献
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《中国科学:地球科学》2015,(7)
土壤干旱能够引起土壤-植被-大气系统的物质和能量循环异常,对生态环境和天气气候具有重要的影响,土壤干旱的检测和特征认识,有助于理解陆气相互作用及其评估和减缓影响.本文以观测气候资料驱动陆面模式CLM3.5模拟中国区域的土壤湿度,引入土壤孔隙度参数校正土壤湿度模拟的湿偏差,并检测了历史土壤干旱,分析不同时间尺度干旱的空间分布和变化趋势:1951~2008年40%的月份发生了月尺度的干旱,平均影响面积占我国陆地总面积的54.6%;年内干旱月数的变化呈干旱区显著减少,半干旱、半湿润区显著增加趋势,而湿润区减少但趋势不显著.1951~2008年月尺度干旱呈减少和增加趋势的面积之比为77.3%,总体上中国呈干旱加剧的趋势;平均来看月尺度干旱冬季影响范围最广,夏季最小,分别影响了我国54.3%和8.4%的陆地总面积.持续3个月以上的干旱主要发生在半干旱和半湿润区,发生概率51.7%,部分地区甚至77.6%;持续6和12个月以上的干旱主要发生在半干旱和干旱区,概率较小. 相似文献
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陕西地区地震目录完整性分析 总被引：3，自引：2，他引：1
《地震地磁观测与研究》2015,(4)
应用完整性震级范围法(EMR)、稳定b值法(MBS)、R—S检验法,对陕西中部、南部地区1970年以来地震目录完整性进行分析,认为:研究区内1970—1997年2.3级以上、1998—2008年1.8级以上、2009年至今1.4级以上地震目录基本完整。应用最大曲率法(MAXC),分析完整性震级的时空分布,结果显示,随着时间的推移,最小完整性震级呈下降趋势,且陕西地震台网监测能力在各区域间存在差异。 相似文献
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半干旱内陆地区的湖泊湿地是一种特殊的生态系统,季节和年际时间尺度上的湖泊水文变化对湖泊湿地生态结构和功能有着重要影响.近20年来,月亮泡湖泊湿地经历了自然和人为因素共同作用下的水文波动过程.为了实现大尺度地表生态年内/年际变化检测,更好地了解湖泊年际水淹范围及其水淹频次对内陆湖滨湿地生态的影响,基于1994—2018年Landsat TM/OLI影像数据(30 m),首先,计算提取月亮泡的年际水体信息和水淹频次,进而获取湖泊年际淹没范围.其次,采用综合生态指数变化检测法提取生态信息,选取3个标准观测年(1995、2006、2016年),从年内变化和年际变化视角分级评价了研究区生态变化,并分析了水淹频次与湿地生态变化的关系.最终,现有研究表明:湖泊年际水淹区主要分布在月亮泡的北侧与西侧尾闾,月亮泡湖泊湿地北侧的年际水淹频次更为显著.湖泊面积的扩展与自然湿地的减少是月亮泡水淹区域的主要变化类型.在这种变化情况下,研究区水体指数累积量的增加与植被指数累积量的衰减成为显著的生态变化特点.月亮泡湖泊年际水淹频次在一定时间和空间上影响着水淹区域的植被生产能力,水淹的低频波动是研究区植被累积量增加的关键因子.因此,在湿地生态恢复与管理过程中,维持合理的水文波动,恢复月亮泡北侧与西侧沼泽湿地是该区域内生态保护的核心措施. 相似文献
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《中国科学:地球科学》2015,(5)
利用卫星遥感和现场观测资料,结合线性Rossby波诊断解,研究了近20年热带太平洋和印度洋暖池区海面高度的快速升高趋势.结果表明,两大洋热带区域同步的海面上升趋势通过印度尼西亚海的海洋波导通道联系在一起,其动力关联主要发生在温跃层深度,表现为热带太平洋的海面高度低频波动信号通过印度尼西亚海传至印度洋,并影响到南印度洋的东部海区,而南印度洋西部的海面变化主要受印度洋内区局地风场的调制.超前-滞后相关分析的结果表明,东南印度洋海面高度的年际和年代际变化信号分别源自太平洋赤道和近赤道海区,分别受到了太平洋赤道风应力异常和近赤道风应力旋度异常的调控,并且分别与ENSO的年际过程和PDO的年代际过程密切相关. 相似文献
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A climatological northern boundary index for the East Asian summer monsoon and its interannual variability 总被引：1，自引：0，他引：1
A long-term perspective on the spatial variation of the northern boundary of the East Asian summer monsoon(EASM) and the related physical mechanisms is important for understanding past climate change in Asia and for predicting future changes. However, most of the meteorological definitions of the EASM northern boundary do not correspond well to the actual geographical environment, which is problematic for paleoclimatic research. Here, we use monthly CMAP and GPCP precipitation data to define a new EASM northern boundary index by using the concept of the global monsoon, which is readily applicable to paleoclimatic research. The results show that the distribution of the 2 mm day~(-1) precipitation isoline(i.e., 300 mm precipitation)has a good relationship with the spatial distribution of modern land cover types, the transitional climate zone and the potential natural vegetation types, in China. The locations of the precipitation isolines also correspond well to the locations of major shifts in wind direction. These results suggest that the 2 mm day~(-1) isoline has a clear physical significance since the climatic, ecological,and geographical boundary can be used as the northern boundary index of the EASM(which we call the climatological northern boundary index). The index depicts the northeast-southwest orientation of the climatological(1981-2010) EASM northern boundary, along the eastern part of the Qilian Mountains-southern foothills of the Helan Mountains-Daqing Mountains-western margin of the Greater Khingan Range, from west to east across Northwest and Northeast China. The interannual change of the EASM northern boundary from 1980 to 2015 covers the central part of Gansu, the northern part of Ningxia, the eastern part of Inner Mongolia and the northeastern region in China. It can extend northward to the border between China and Mongolia and retreat southward to Shangdong-central Henan. There is a 200-700 km fluctuation range of the interannual EASM northern boundaries around the locations of the climatological northern boundary. In addition, the spatial variation of the interannual EASM northern boundaries gradually increases from west to east, whereas the trend of north-south fluctuations maintains a roughly consistent location in different regions. 相似文献
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ABSTRACT This paper presents an analysis of trends in six drought variables at 566 stations across India over the period 1901–2002. Six drought variables were computed using standardized precipitation index (SPI). The Mann-Kendall (MK) trend test and Sen’s slope estimator were used for trend analysis of drought variables. Discrete wavelet transform (DWT) was used to identify the dominant periodic components in trends, whereas the significance of periodic components was examined using continuous wavelet transform (CWT) based global wavelet spectrum (GWS). Our results show an increasing trend in droughts in eastern, northeastern and extreme southern regions, and a decreasing trend in the northern and southern regions of the country. The periodic component influencing the trend was 2–4 years in south, 4–8 years in west, east and northeast, 8–64 years in central parts and 32–128 years in the north; however, most of the periodic components were not statistically significant. 相似文献
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Geochemical characterization of major elements in desert sediments and implications for the Chinese loess source 总被引：2，自引：0，他引：2
Mineral dust released from the desert is one of the important components of atmospheric aerosols. Arid and semi-arid deserts, sandy lands in northern China and their adjacent Gobi Desert lands in northern China and neighboring Mongolia(hereinafter referred to as Gobi) are potential sources of mineral dust in Asia. However, there is currently a lack of systematic studies on the characteristics of major elements in the potential mineral dust source area. This study investigates the major elements of 310 surficial sand samples in the stabilized and semi-stabilized dune fields from 12 deserts/sandy land and Gobi in northern China and southern Mongolian Gobi and compiles published data. We identify four regions with distinct geochemical characteristics:(1) Taklimakan, Kumtag and Qaidam deserts in western China;(2) Badain Jaran, Tengger, Hobq, and Mu Us deserts in the central and western regions of northern China;(3) Hulun Buir, Onqin Daga and Horqin sandy lands in northeast China; and(4) Gobi and Gurbantunggut deserts. The spatial distributions of the SiO_2 and CaO contents in Chinese deserts are highly variable. The average content of SiO_2 generally reflects an increasing trend from west to east, while the average content of CaO shows a decreasing trend from west to east. We demonstrate that the spatial variation of major elements is likely controlled by two key scenarios: the composition of source rocks and the mineral maturity caused by the supply of fresh materials. The SiO_2/(Al_2O_3+K_2O+Na_2O) ratio of desert sediments is relatively lower in western China and may be caused by high ferricmagnesia and high carbonate minerals; this ratio is relatively higher in the northeast sandy lands and may be linked to a lack of fresh material supply and the presence of high K-feldspar minerals in source rocks. The deserts can be further distinguished by ternary diagrams with SiO_2/10-CaO-Al_2O_3,(K_2O+Na_2O)-CaO-Fe_2O_3 and CaO-Na_2O-K_2O. The comparison of major elements between desert sediments and loess suggests that the western and/or central deserts in China may be the potential provenances of loess on the Loess Plateau. 相似文献
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秦岭-大别造山带横贯中国大陆中部,并将我国东部分为南北两部;即华北克拉通和扬子克拉通.在南、北相向运动力系驱动下构成了一个极为复杂的复合、叠加构造带、成矿带和地震活动带.同时导致了该地域异常变化的沉积建造和强烈起伏的结晶基底.然而对它们形成的地球物理边界场响应,岩相和结构的异常变化尚不清晰,特别对盆山之间的耦合响应更缺乏深层动力过程的理解.为此本文通过该区榆林-铜川-涪陵长1000 km剖面的地震探测和研究结果提出：（1）沉积建造厚度变化为4~10 km,结晶基底起伏强烈,幅度可达4~6 km;（2）一系列基底断裂将该区切割为南鄂尔多斯盆地和秦岭北缘前陆盆地、秦岭-大巴造山带和南缘前陆盆地与东北四川盆地,其中前陆盆地为秦岭北渭河盆地和秦岭南通江-万源盆地;（3）秦岭造山带是北部华北克拉通向南推挤、南部扬子克拉通向北推挤下隆升的陆内山体,并构筑了其南、北前陆盆地;（4）秦岭造山带的南、北边界并非是一条边界断层,而应是包括前陆盆地在内的组合界带;（5）秦岭与大巴弧形山系源于同一深部结晶基底,即同根生.这一系列的新认识对深化理解秦岭-大巴造山带形成的深层动力过程和演化机理及厘定扬子克拉通的真实北界具有极为重要的意义. 相似文献
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南北地震带是以青藏高原地壳为主体和兼并了扬子地块西部而成的新生构造实体,具弥漫性边界。构成其基本格架的巨型反S形或缓弧形构造带,分布在中部的弧顶朝南的弧形构造以及发育在东界附近的旋卷构造,成为南北地震带的三大构造特色,它们都是塑性伸展流动的产物。据弧形构造形态实际数据分析表明,地壳物质向南移动的规模,由北往南逐渐加大,从西到东渐逐减小;自北纬31.5°往南,青藏高原物质东移量逐渐加大。 相似文献
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Study of spatial distribution of sandy desertification in North China in recent 10 years 总被引：2，自引：0，他引：2
Sandy desertification is a land degradation characterized by wind erosion, mainly resulted from the excessive human activities in arid, semiarid and part of sub-humid regions in North China. It is one of main kinds of desertification/land degradation as well as water-soil erosion and salinization in China. Rapid and continuous spread of sandy desertification during last 50 years has created a major environmental and socio-economic problem in North China. Remote sensing monitored results in 2000 showed that the sandy desertified land area has been 38.57×104 km2. The area of potential to slightly sandy desertified land is 13.93×104 km2, moderately land 9.977×104 km2, severely land 7.909×104 km2 and very severely land 6.756×104km2. Sandy desertification mainly occurs in the semi-arid mixed farming-grazing zone and its northern rangeland zone, semi-arid dryland rainfed cropping zone and arid oasis-desert margin zone. The average annually developmental rate of sandy desertified land increased from 2,100tion in North China is "overall deterioration, while local rehabilitation". Already achieved rehabilitation results and monitoring assessment show that about 60% of desertified land in North China can be restored under the conditions of rational land-use ways and intensity. 相似文献
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为了研究西藏中、北部壳、幔导电性结构,讨论高原中、北部岩石圈热状态,1998年和1999年（INDEPTH（Ⅲ） MT）在西藏中、北部完成了德庆—龙尾错（500线）和那曲—格尔木（600线）超宽频带大地电磁深探测剖面的研究.研究结果表明,西藏中、北部以昆仑山断裂为界,其南北壳、幔电性结构有很大差异.昆仑山断裂以北地壳和上地幔为高阻区.而昆仑山以南,地壳和上地幔的导电性有明显的分层结构：地壳上部以不连续的高阻体为主,夹有局部低阻异常体,沿南北方向上地壳的电性结构复杂,具有不连续、分块的特点;但中、下地壳为大范围的高导异常区,区内发育有大规模、不相连续、产状各异的高导体,其电阻率均小于4Ωm;在班公—怒江和金沙江缝合带之下,壳内高导体都具有向上地幔延伸的趋势,存在连通壳、幔的低阻通道.根据西藏高原中、北部壳、幔电性结构的研究推断：如同藏南一样,这里也普遍存在部分熔融体和热流体,它们的成因主要与班公—怒江和金沙江缝合带的壳-幔热交换、热活动有关,这是两期形成的壳-幔热交换通道.其中,班公—怒江缝合带的壳-幔热交换通道形成时间比金沙江缝合带早.因此,研究区壳、幔的热活动是从南边和西边开始,向北、向东扩展,导致现今西藏中、北部地壳和上地幔的热流分布由西向东、由南向北增大. 相似文献
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Global tectonics and the plate motion obtained from the ITRF97 station velocity vectors 总被引：2，自引：0，他引：2
~~Global tectonics and the plate motion obtained from the ITRF97 station velocity vectors@马宗晋
@任金卫
@张进~~ 相似文献
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本文主要根据1980年中、美联合调查南海时所获得的声纳浮标测量结果,探讨中国南海中部和北部各个地貌单元上的地壳结构、性质以及新生代的发展简史。 相似文献
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Ecological response to the climate change on the northern slope of the Tianshan Mountains in Xinjiang 总被引：7，自引：2，他引：5
CHEN Xi LUO Geping XIA Jun ZHOU Kefa LOU Shaoping & YE Minquan . Xinjiang Institute of Ecology Geography Chinese Academy of Sciences Urumqi China . Institute of Geographical Resources Sciences Chinese Academy of Sciences Beijing China . Urumqi Meteorological-satellite Land Station Urumqi China . Seismological Bureau of Xinjiang Uygur Autonomous Region Urümqi China Correspondence should be addressed to Chen Xi 《中国科学D辑(英文版)》2005,48(6):765-777
The relationship between the terrestrial ecosys-tems and the climate change is one of the importantfields in the study on global change,and the rela-tionship between vegetation and climate change is oneof the main research focuses[1―3].On the one hand,the high-amplitude global warming results in the increase of evaporation from the oceans and the waters on land and of precipitation in most parts of the oceans and theterrestrial regions,thus,the modern glaciers are seri-ously melted,the runoff … 相似文献