共查询到20条相似文献，搜索用时 672 毫秒
1.
本文研究了前期冬季北极海冰与中国东部春季极端降水频次的联系及其可能机制,并进一步探讨了海冰异常信号对极端降水的预测价值。结果表明,前冬戴维斯海峡—巴芬湾区域海冰异常与中国东部春季极端降水频次经验正交分解第一模态(EOF1)之间存在密切联系。当前冬戴维斯海峡—巴芬湾区域海冰异常偏多时,冬季大气环流呈现出类北大西洋涛动(NAO)正位相的异常分布,并伴随经向的北大西洋三极型海温异常。该海温异常可以从冬季持续到春季,进而激发出从北大西洋到欧亚中纬度的纬向遥相关波列,在东亚地区引起气旋型环流异常。该气旋型环流异常会引起中国东部地区湿度显著增加,上升运动增强,从而为该地区极端降水的发生提供了有利的背景条件。相反,当前冬戴维斯海峡—巴芬湾区域海冰异常偏少时,其滞后引起的春季环流异常则不利于中国东部地区极端降水的发生。进一步的交叉检验结果表明,前冬戴维斯海峡—巴芬湾区域海冰异常信号对中国东部春季极端降水具有重要的预测价值。 相似文献
2.
基于NOAA OISST.V2月平均SST资料和FSU月平均风应力资料对南海的SST和风场异常进行了分析,发现：南海对1997/1998年El Nio事件响应最为强烈,并在1997/1998年冬季和次年的夏季SST存在2个异常高峰值,风速存在2个异常减小的极值。为研究南海环流在1997/1998年的异常变化,利用ECOM水动力模型计算了1995—2000年的南海环流场,分析了1998年1月和8月南海水位和环流的异常分布,二者均存在显著的异常：①1月,整个南海海盆为正的水位异常,流场为反气旋异常环流,冬季控制整个南海海盆的气旋式环流减弱;②8月,南海海盆水位为正异常,特别是越南东部海区出现较强的正水位异常,南海南部的高水位中心扩大北移;异常流场表现为南部为气旋式异常环流,北部为反气旋的异常环流,且在越南东部海区形成非常强的反气旋异常环流中心,使得控制南海南部的反气旋环流和北部的气旋环流均减弱。风应力的分析表明,风应力旋度的异常变化是南海环流年际异常变化的主要因素。 相似文献
3.
Unusual circulation pattern during Indian summer monsoon failure in July 2002 and June 2009 总被引：1，自引：0，他引：1
The circulation patterns over the Indian Ocean and the surrounding continents have been studied during June 2009 and July 2002 to explain the failure of Indian summer monsoon (ISM) rainfall. This study presents evidences that the failure of the ISM during these 2?months was probably due to the development of cyclonic circulation anomaly over the Western Asia and anticyclonic circulation anomalies downstream of Eastern Asia. These circulation anomalies were associated with the equatorward advection of cold air up to 10°N. This may be due to the equatorward intrusion of midlatitude Rossby waves. We hypothesize that the intrusion of midlatitude Rossby wave is responsible for breaking the east?Cwest circulation cell over the Indian region into two cells and weakening it. The weak east?Cwest cell reduces the strength of the easterly wind field usually present over the monsoonal region, thus reducing the cross-equatorial moisture transport into the Indian subcontinent and decreasing monsoon rainfall. 相似文献
4.
根据气候模拟的夏季降水量及古气候湿润度代用资料,指出全新世中国夏季降水量变化存在两种模态。模态1：降水量异常的中心为一个东北－西南向的带; 从东北、内蒙东部、经华北、河套到青藏高原为一正异常中心。模拟结果的EOF分析表明这种模态占模拟的全新世中国夏季降水量变化总方差的75.8%。全新世降水量变化的模拟主要考虑地球轨道要素,其中岁差起着重要作用。因此,这个模态可以称为岁差模。岁差模主要反映近万年全新世降水变化的趋势。模态2：降水量异常分布在中国东部(100°E以东)自北向南表现为负－正－负分布。负异常在内蒙中部到华北,正异常在黄河中游、淮河、到长江流域,江南部分地区又有负异常。这与模拟的大西洋热盐环流减弱所造成的中国夏季降水量异常分布一致。因此,这个模态可能与全新世的气候突变有关,称为气候突变模。覆盖中国的80个代用资料序列给出的9kaB.P.和4kaB.P.干湿分布,证明早全新世气候湿润,晚全新世气候干旱。这种变化趋势主要反映了岁差的影响。同时,4kaB.P.虽然干旱分布广泛,但是长江流域、关中地区到高原东部则有若干气候湿润的指示。这表明4kaB.P.同时受岁差及气候突变的影响。 相似文献
5.
1 Introduction Alunite [KAl3(SO4)2(OH)6] is a very important non-ferrous metal resource, so many countries throughout the world have made great investments in research on the mechanism of its formation, its geological characteristics and applications. O… 相似文献
6.
A large, roughly circular structural basin is recognised on the Falkland (Malvinas) Plateau to the NW of West Falkland (Gran Malvina) Island (S 51°00′, W 62°00′). The basin, seen in seismic‐reflection profiles and evident as a large negative gravity anomaly, has a diameter of ~250 km. The age of the basin is estimated to be Late Palaeozoic. It is completely buried by younger sediments and has no topographic expression on the sea floor. We propose that the basin and geophysical anomalies, especially the combination of a large circular negative gravity anomaly with a rim of positive anomalies, and a marked circular series of positive magnetic anomalies in the same area, may be best explained by the presence of a large buried impact structure. 相似文献
7.
青藏高原初春积雪的多尺度变化与北大西洋海温的关系 总被引：3，自引：3，他引：0
青藏高原冬、春季积雪变化影响东亚甚至全球春、夏季的环流及气候异常。利用中国西部环境与生态科学数据中心提供的中国雪深长时间序列数据集,美国大气海洋局提供的全球逐月扩展重建海表温度,以及欧洲中期天气预报中心提供的逐月再分析数据,对青藏高原初春（3、4月）积雪的多尺度变化与北大西洋海表温度的关系进行了研究。结果表明,初春青藏高原雪深异常与初春北大西洋关键区海温异常有显著的负相关关系。当初春关键区海温正（负）异常时,初春高原中部偏北腹地地区、东南部地区积雪深度减少（增加）;初春北大西洋关键区海温异常通过激发下游青藏高原上空大气波列以及波作用通量异常来影响高原局地区域的温度和垂直运动,从而影响降雪的产生和积雪的累积。该结果为青藏高原初春积雪的多尺度变化及其影响提供了依据。 相似文献
8.
多重分形模型在区域地球化学异常分析中的应用探讨 总被引：8，自引：2，他引：6
地球化学异常分析是地球化学勘查中的重要环节, 对有效发现异常至关重要。但是, 在以往研究中, 研究者们多重视对成矿元素及其伴生元素正异常的研究, 忽视对由元素贫化而形成的负异常的研究。元素的负异常在地球化学勘查中具有与正异常同等重要的作用, 以往没有重视负异常的原因之一是缺乏有效发现此类异常的方法, 尤其是确定负异常上限的方法。本文以北山地区1: 20万峡东幅水系沉积物测量Ba数据为基础, 探讨了应用多重分形模型确定贫化元素负异常上限的可行性。结果发现, 利用含量-面积法、含量-求和法确定的Ba的异常上限, 有效圈定了辉铜山矿床产出地段Ba的负异常, 取得了预期成果。 相似文献
9.
V. N. Eremeev A. N. Zhukov M. A. Krasheninnikova A. A. Sizov A. E. Chekhlan 《Doklady Earth Sciences》2012,443(1):357-360
Based on the conception of the cyclic (wave) nature of the changes in the circulation of the atmosphere of the Atlantic-European
sector (index of the North Atlantic oscillations) and surface temperature of the Black Sea on scales smaller or equal to the
century scale, anomalies of the winter surface temperature are analyzed. It is shown that in the phase of the maximum of the
presumably 60-year cycle of changes in the NAO index a negative anomaly of surface temperature forms and in the phase of minimum
of this scale of changes of NAO, there is a positive anomaly. Estimates of the possible thermal state of the surface of the
Black Sea during the phase of the expected minimum in 2011–2020 of the 60-year cycle (60-year wave) of the NAO index are made.
The possibility of a phase shift between changes in solar activity, the NAO index, and anomalies of temperature of the Black
Sea on the scales of cyclic (wave) processes larger than 100 years is considered. 相似文献
10.
龙门山均衡重力异常及其对青藏高原东缘山脉地壳隆升的约束 总被引：16，自引：0，他引：16
青藏高原东缘处于不均衡状态，自西而东可分为青藏高原弱负均衡重力异常区、龙门山正均衡重力异常区和四川盆地负均衡重力异常区，表明该区的不均衡状态并未导致Airy均衡运动的产生，即龙门山没有均衡下降，而处于不断的隆升状态，显示该地区反均衡运动的构造抬升是导致龙门山隆升的主因。本次采用似三度体重力异常计算方法对该区的正均衡重力异常进行模拟和反演，研究了大尺度地貌分异与均衡重力异常分区之间的相互关系，结果表明，龙门山的下地壳顶面抬升了11．2～12．6km，造成了龙门山的正均衡异常，揭示了构造抬升和剥蚀作用在相似的时间尺度上和空间尺度上控制着龙门山地貌的形成，龙门山的表面隆升是构造隆升和剥蚀作用相叠加的产物。 相似文献
11.
SHI Changyi ZHANG Jinhua China University of Geosciences Beijing Institute of Geophysical Geochemical Exploration Langfang Hebei 《《地质学报》英文版》2003,77(1):72-80
Regional stream sediment surveys at a 1:200,000 scale reveal positive and negative regional multi-element geochemical anomalies over medium to large copper-polymetallic orefields of different genetic types in China. Regional geochemical anomalies of orefield refer to those geochemical anomalies that are related to metallogenesis of an orefield in a certain area. The anomaly area is typically 10 to 100 km2. The regional multi-element anomalies related to mineralization can be divided into three groups, that is, the ore-element anomaly association, indicator element anomaly association, and metallogenic environmental element anomaly association. Their common spatial distributions over ore deposits or orefields possess unique structures.The model of spatial structure of regional multi-element geochemical anomalies (RAGSS) of an orefield delineates structural feature possessed by orderly spatial distributions of different groups of multi-element anomaly associations related to orefield metallogenesis. It is 相似文献
12.
The present study explored the effect of assimilation of Advanced TIROS Vertical Sounder (ATOVS) temperature and humidity
profiles and Spectral sensor microwave imager (SSM/I) total precipitable water (TPW) on the simulation of a monsoon depression
which formed over the Arabian Sea during September 2005 using the Weather Research and Forecast model. The three-dimensional
variational (3DVAR) data assimilation technique has been employed for the purpose of assimilation of satellite observations.
Statistical scores like “equitable threat score,” “bias score,” “forecast impact,” and “improvement parameter” have been used
to examine the impact of the above-mentioned satellite observations on the numerical simulation of a monsoon depression. The
diagnostics of this study include verification of the vertical structure of depression, in terms of temperature anomaly profiles
and relative vorticity profiles with observations/analysis. Additional diagnostics of the study include the analysis of the
heat budget and moisture budget. Such budget studies have been performed to provide information on the role of cumulus convection
associated with the depression. The results of this study show direct and good evidence of the impact of the assimilation
of the satellite observations using 3DVAR on the dynamical and thermodynamical features of a monsoon depression along with
the effect of inclusion of satellite observation on the spatial pattern of the simulated precipitation associated with the
depression. The “forecast impact” parameter calculated for the wind speed provides good evidence of the positive impact of
the assimilation of ATOVS temperature and humidity profiles and SSM/I TPW on the model simulation, with the assimilation of
the ATOVS profiles showing better impact in terms of a more positive value of the “forecast impact” parameter. The results
of the study also indicate the improvement of the forecast skill in terms of “equitable threat score” and “bias score” due
to the assimilation of satellite observation. 相似文献
13.
《International Geology Review》2012,54(14):1744-1762
The European Cenozoic Rift System hosts major temperature anomalies in Central Europe. In its central segment, the Upper Rhine Graben (URG), temperatures range from 75°C to nearly 150°C at a depth of 2000 m. Different hypotheses have been suggested to explain the localization of these anomalies. Our review and comprehensive interpretation of gravimetric and magnetic data, as well as neotectonic activity patterns, suggests that low-density, mostly magnetic and fractured granitic basement is systematically associated with major temperature anomalies. Further analyses provide insight into different heat transport processes contributing to the localization of these anomalies. Magnetic and gravity anomalies are known to represent lithological variations associated with the pre-Permian. We show their spatial relationship with positive temperature anomalies in the URG. Correlation between magnetics and temperature reveal a mean contribution of heat production to the temperature anomaly of about 10–15°C. A slightly higher mean value is obtained from correlation between gravity and temperature, which may be attributed to effects resulting from fracture porosity. The spatial relationship between temperature anomalies and neotectonic patterns indicates compressional shear and uplift regime for the major anomalies of the central segment of the URG. This is in agreement with different numerical models indicating free convection on fracture zones linked to faults. Our findings show that about 15–25% of the temperature anomaly can be attributed to variation in heat production. Hydrothermal circulation convection along faults, activated by the tectonic context, may explain the remaining 75–85% of the temperature anomalies. 相似文献
14.
烂泥塘矿床是云南香格里拉地区典型的斑岩型铜矿床,主矿体产于在地表以下300～500米,地表矿化带仅见脉状铜矿体和铜矿化体.为研究云南香格里拉烂泥塘斑岩铜矿床的原生晕异常结构,本文以异常结构模式理论和方法为基础,对矿床地表和坑道岩矿石样品开展了元素组合、异常特征和水平分带规律研究.结果表明,烂泥塘铜矿床地球化学系统的结构... 相似文献
15.
采用改进的遥感异常提取方法,以甘肃金川地区的LandSat 8遥感影像数据为基础,结合主成份分析方法及低通滤波后期处理,得到空间规律性较强的烃基及铁染异常;进而对测区的土壤地球化学取样分析数据,利用统计学方法寻找不同元素异常(或地球化学指标)的内在关联,并建立土壤地球化学指标比值与遥感异常之间的关系模型。继续构建出基于LandSat 8遥感影像的净反射率值与地球化学因子之间的统计模型,并以此预测模型对测区进行了遥感地球化学异常的圈定。预测结果表明:建立的遥感地球化学统计模型高异常区与已知矿区范围基本吻合,通过提取的遥感地球化学异常不仅能表达化探常规异常的信息,还可以把其空间分布规律明晰出来,让某些局部弱异常得到增强。遥感地球化学异常得到了野外验证,说明利用地质资料建立的基于LandSat 8遥感地球化学预测模型比单一的遥感或化探异常有更好的预测效果。 相似文献
16.
滇西北红牛—红山铜矿床是义敦—沙鲁里岛弧上与晚白垩纪中酸性侵入体有关的典型的斑岩-矽卡岩-热液型铜矿床。本文通过对其成矿地质背景、矿床地质特征、矿化富集规律及成矿模式、矿床地球物理和地球化学特征的综合研究，建立了红牛—红山铜矿床的"大比例尺地质填图和综合研究+重力+激电和高精度磁测+土壤化探测+工程验证"组合勘查技术方法、"燕山晚期石英二长斑岩+接触带矽卡岩和层间破碎带矽卡岩+重力低异常+高磁异常+高视极化率和低视电阻率异常+Cu-Mo-Pb-Zn-Ag-Au等元素综合异常"组合勘查模型。地质调查研究确定矿床成矿地质体和找矿地质体、矿化类型及其空间分布规律，建立矿床"四位一体"的成矿模式和区域-矿区地质找矿模型。区域中小比例尺的土壤化探测量确定区域找矿靶区，大比例尺土壤化探测量进一步缩小找矿靶区，逼近矿体赋存部位。矿区处于1∶5万土壤测量圈定的Cu-Pb-Zn-Mo-Au-Ag元素综合高异常区，1∶2.5万土壤测量圈出Cu-Pb-Zn-Ag-W元素综合异常面积较大、强度高、浓集中心明显、元素套合好，与矿区铜（铁）矿体赋存区域异常相对应。区域重力低异常区和正磁异常强度高区域是重要的找矿靶区，矿区大比例尺磁异常和激电异常区确定了矿体的空间位置和产状；矿区铜（铁）矿体赋存区为低视电阻率、高视极化率异常区，高精度磁测表现为正负磁异常相伴。矿区地质-地球化学-地球物理综合勘查模型对矿区深边部找矿起到重要的指导作用。 相似文献
17.
利用1961 - 2017年青海省43站逐日最低气温观测资料, 依据区域持续性低温事件判识标准, 提取历史上61次典型事件, 对影响该类事件的环流演变和前兆信号进行分析。结果表明： 事件发展中北半球极涡经历分裂 - 收缩增强的变化过程, 中高纬自西向东逐渐发展为“正 - 负 - 正”异常波列状分布; 事件发生当日, 大西洋地区、 乌拉尔山及西伯利亚地区高度场异常偏高, 东亚大槽偏深, 利于自极地南下的冷空气在西欧上空堆积并沿纬向西风急流路径向东传播影响东亚地区。进一步分析表明, 当出现该类事件时, 中高纬地区存在三个关键影响区, 其中乌拉尔山关键区高度场正异常同此类事件的联系最紧密。 相似文献
18.
甘肃北山白山堂铜矿外围找矿靶区地球化学评价方法示范 总被引：1，自引：0，他引：1
在甘肃北山白山堂铜矿及其外围,以1:20万营盘幅区域化探数据为基础,探讨了综合利用富集贫化两类指标形成的正、负异常圈定找矿靶区并进行靶区评价的可行性示范研究。结果表明,在1:20万区域尺度上,已知白山堂铜矿产出位置出现了成矿元素(Cu)及伴生元素(Zn、Au、Ag、As、Sb、Mo)、常量组分(Fe2O3、MgO)的正异常和亲石分散元素(Ba、Sr)、常量组分(Al2O3、Na2O)的负异常,构成白山堂铜矿整体异常结构模式。以是否出现异常结构模式为标准,利用岩石裂隙充填物测量或岩屑测量结果,对白山堂铜矿外围出现的地球化学异常成矿前景进行了评价。根据示范研究结果认为,利用异常结构模式进行找矿靶区评价是行之有效的,较单纯利用成矿元素及伴生元素异常进行靶区评价证据更系统、充分。 相似文献
19.
The structure of the lithosphere beneath the Eastern rift, East Africa, deduced from gravity studies 总被引：1，自引：0，他引：1
J.D. Fairhead 《Tectonophysics》1976,30(3-4):269-298
A compilation of all published and unpublished gravity data for the Eastern rift between latitudes 1°N and 5°S is presented. The Bouguer anomaly map reveals that the shape of the negative regional anomaly associated with the rift is approximately two-dimensional, striking east of north, of width 350 ± 50 km and amplitude500 ± 100 g.u. relative to the background value of−1300 ± 100 g.u. to the west. The regional anomaly is interpreted in terms of an upward thinning of the lithosphere and replacement by low-density asthenosphere. This model is different from previous interpretations in that major lithospheric thinning is restricted to the region of the Eastern rift affected by the domal uplift and does not extend beneath the Lake Victoria region to the west. The gravity and seismic models are compatible if the anomalous upper mantle (asthenospheric part), beneath the rift, is in a state of partial melt. A consequence of the revised regional anomaly is that it reduces previous amplitude estimates of the axial positive residual anomaly within the rift by at least 50% and generates negative anomalies over the rift shoulders in areas covered by Cenozoic volcanics. These negative anomalies are considered to be caused by the low density of the surface volcanics. Within the rift, elongated negative anomalies of amplitude 100–350 g.u. are associated with sedimentary basins and are attributed to low-density sediments up to 3 km thick. The positive residual anomaly along the axis of the rift can be interpreted in terms of either a dyke injection zone less than 15 km wide or by a dense infill body about 2.5 km thick. The positive anomaly is shown to be confined to the volcanic province of the Eastern rift and has its southern termination in the Magadi—Natron area, just north of where the Kenya rift valley changes to block faulting in N. Tanzania. This termination coincides with a change in the spatial distribution of the seismic and geothermal activity. 相似文献
20.
Paleoclimatic interpretation of proxy data is complicated sometimes by the appearance of heterogeneous patterns of climatic responses across networks of sites. Modern climate analogues for the western United States, similar to those patterns of atmospheric circulation of 18,000 and 9000 yr B.P., were examined in order to explain such patterns of spatial heterogeneity. Modern analogues were defined by comparing modern atmospheric circulation patterns with those simulated by general circulation models. Maps of temperature and precipitation anomalies of the modern analogues reveal patterns of spatial heterogeneity, which resemble the patterns of effective moisture compiled from paleoclimatic data. January 1957 was found to be a reasonable 18,000 yr B.P. analogue, and it features isolated areas of increased wetness in the northern Great Basin and increased dryness in the Northwest interior. Analogues for 9000 yr B.P. from a composite of 11 Augusts display patterns of spatial heterogeneity of effective moisture over most of the mountainous areas. The analogues suggest that spatial heterogeneity of climate is the rule rather than the exception over much of the western United States, with the climatic anomalies at any particular time representing the outcome of the mediation of large-scale atmospheric circulation controls by smaller scale topographic features. 相似文献