Longitudinal variation in E- and F-region ionospheric trends   总被引：1，自引：0，他引：1  

M.J. Jarvis   《Journal of Atmospheric and Solar》2009,71(13):1415-1429

A novel technique is used to examine northern hemisphere midlatitude longitudinal variations in ionospheric long-term trends. Differences in hour-by-hour monthly median ionospheric parameters between equilatitudinal observatory pairs are analysed for long-term trends, thus eliminating at source the large solar cycle and geomagnetic variability that normally hinders ionospheric trend calculations. The results confirm the finding of Bremer [1998. Trends in the ionsopheric E- and F-regions over Europe. Annales Geophysicae 16, 698–996] that there are longitudinal variations in the F-region altitude trend across Europe, but suggest the influence of a stationary wave-like feature between 3°W and 104°E. Possible causes such as scaling errors, insufficient account of changes in ionisation underlying the F-region, varying gravity wave fluxes, and secular change in the geomagnetic field are ruled out. The data suggest that the longitudinal variation may reflect long-term changes in a large-scale stationary feature induced via non-migrating tides induced by latent heat release in the troposphere.Significant differences in the long-term trend of E-region peak plasma frequency between observatories were also found. These E-region differential trends varied with solar zenith angle reaching over 0.3 MHz per decade between Juliusruh and Moscow at midday in summer.  相似文献   

辽河盆地地下流体异常与岫岩M_S5.6地震   总被引：2，自引：0，他引：2       下载免费PDF全文

刘元生  刘贵和  佟凤兰 《地震工程学报》2000,22(3):241-246,257

分析了１９９９年１１月２９日岫岩Ｍｓ５．６地震前,辽河油田６口观测井的前兆异常特征,观测项目有水位、采液量、采气量及套管压力等。该次地震前６口井的观测资料均出现明显的趋势异常和短临前兆异常,辐且具有较好的同步性,异常形态表现为升－降－升型,抽水、注水、气压、温度等干扰因素对观测资料没有影响,异常是可信的。  相似文献   

1954年山丹地震破裂带初步考证   总被引：2，自引：1，他引：1       下载免费PDF全文

董治平  何文贵  戴华光 《地震工程学报》2000,22(1):47-47

计算和分析了云南地区 5次ML ≥ 6 .5强震前的应变扰动εi 值 .结果表明 ,地震前 5 ～ 8年 ,归一化为 4级的地震的εi出现明显的高值异常 ;未来震中区域εi值变小 ,周围地区增大 ,形成空区 ;εi 值有由零星分布逐渐向震中区收缩、集中并增强的趋势 .  相似文献   

Resolving controls on epeiric sedimentation using trend surface analysis     

W. L. Watney 《Mathematical Geology》1985,17(4):427-454

An understanding of patterns of regional sedimentation is crucial to identifying trends of perspective petroleum reservoirs. The Upper Pennsylvanian, Missourian Kansas City Group consists of repetitions of widespread carbonate rock and shale. Each of four cyclothems chosen for subsurface study of western Kansas contains transgressive and regressive lithofacies with evidence of extensive subaerial exposure across the entire paleoshelf. Distribution of carbonate facies on the 350+ km-wide shelf was affected strongly by slight changes in structural configuration of the shelf and variations in sea level. Polynomial trend surface models prepared from selected wireline log information for four successive cyclothems assist in resolving regional and local patterns of sedimentation and help to access the effect of subtle structural deformation on sedimentation. Isopachs of marine portions of four cyclothems were fit by fourth-order trend surfaces, optimizing fit by comparing goodness-of-fit and minimizing skewness of residuals using the smallest order surface. Several cyclothems showed simple patterns of regional, basinward thickening with local, strike-elongated anomalies where goodness-of-fit was maximized with increasing order. One cyclothem did not converge to a good fit at small orders nor did distribution of residuals indicate convergence toward zero. Both anomalies reflected a more complex surface. Rather than thickening regionally, the pattern created by this anomalous cyclothem was more irregular. Mapped patterns resemble those of the present-day structural configuration of these horizons suggesting a general persistence in similar epeirogenic deformation.  相似文献   

Trend analysis and its tectonic implications using digital bathymetric data     

Takeshi Matsumoto 《Marine Geodesy》2013,36(3-4):265-272

Abstract

Quantitative and objective trend analysis of bottom topography in order to detect the tectonic structures has become available by use of the processed Seabeam data. The following two procedures of trend analysis are introduced.

(1) Edge detection procedures in digital image processing are applicable to the analysis of topography for extraction of the lineament of tectonic structures and prediction of the existence of faults based on the digital bathymetric data.

(2) Automatic calculation of water flow using the topographic grid data is used for estimation of not only water flow pattern and volume but also the construction of the ridge or trough axis by calculating the accumulated water volume. This method was also applied to the Seabeam bathymetric data. This is quite useful for detection of offset structures and hidden faults.

These two methods are applied to the topographic data obtained in the North Fiji Basin, which is characterized by active spreading ridges. The regional tectonic structure of the North Fiji Basin was found to be expressed by the topographic trend of the central axis.  相似文献   

溴化锂的生产工艺综述          下载免费PDF全文

魏述彬  邓小川 《盐湖研究》2006,14(3):58-62

综述了国内外溴化锂生产方法,并指出了每种方法的优缺点,同时展望了今后溴化锂生产方法的发展方向。  相似文献   

Long-term variability in Arctic sea surface temperatures     

Rajkumar Kamaljit Singh  Megha Maheshwari  Sandip R. Oza  Raj Kumar 《Polar Science》2013,7(3-4):233-240

In this study, we used 30 years of an operational sea surface temperature (SST) product, the NOAA Optimum Interpolation (OI) SST Version 2 dataset, to examine variations in Arctic SSTs during the period December 1981–October 2011. We computed annual SST anomalies and interannual trends in SST variations for the period 1982–2010; during this period, marginal (though statistically significant) increases in SSTs were observed in oceanic regions poleward of 60°N. A warming trend is evident over most of the Arctic region, the Beaufort Sea, the Chuckchi Sea, Hudson Bay, the Labrador Sea, the Iceland Sea, the Norwegian Sea, Bering Strait, etc.; Labrador Sea experienced higher temperature anomalies than those observed in other regions. However, cooling trends were observed in the central Arctic, some parts of Baffin Bay, the Kara Sea (south of Novaya Zemlya), the Laptev Sea, the Siberian Sea, and Fram Strait. The central Arctic region experienced a cooling trend only during 1992–2001; warming trends were observed during 1982–1991 and 2002–2010. We also examined a 30-yr (1982–2011) record of summer season (June–July–August) SST variations and a 29-yr (1982–2010) record of September SST variations, the results of which are discussed.  相似文献   

2013年芦山MS7.0地震前甘孜台地电阻率变化分析   总被引：1，自引：0，他引：1  

解滔  卢军  任越霞  赵民渊 《震灾防御技术》2013,8(4):377-388

甘孜台地电阻率N30°E测道观测资料自2011年7月开始出现趋势上升变化,N60°W测道地电阻率则从2012年出现趋势上升变化.2011年测区原317国道实施扩建工程,N30°E测道测量电极分别向供电极方向移动10m.采用甘孜台电测深曲线以水平层状模型反演了测区的电性结构,理论计算表明,测量电极的移动将会引起N30°E测道4Ω·m的上升变化,扣除这部分变化后,甘孜台两测道观测值于2012年同步上升.以水平层状模型计算了甘孜台两测道各层介质的影响系数,两测道浅层两层介质影响系数均为负,能合理地解释甘孜台地电阻率在雨季降水量增加时观测值上升、旱季降水量减少时观测值下降这一“夏高冬低”的年变现象.建立三维有限元模型计算了317国道拓宽部分对观测的影响,计算结果表明,拓宽部分仅能引起N60°W测道约0.15Ω·m的下降变化和N30°E测道约0.1Ω ·m的上升变化,其对观测的影响非常小.同时2013年1月甘孜台两测道年变低值显著高于2008年以来各年的年变低值,在芦山地震前呈同步的上升变化,但是与汶川地震前的下降变化相反,因此甘孜台自2012年的趋势上升变化是不是芦山地震的前兆异常还难以确定.  相似文献   

近50年中国北方不同地区降水周期趋势的比较分析     

刘扬  韦志刚 《地球科学进展》2012,27(3):337-346

对中国北方243个站点1958—2009年逐月降水资料,采用小波分析和奇异谱分析(SSA)方法,在分4区基础上,对北方不同地区降水的周期和趋势进行分析,并进行比较。结果表明,西北地区(青海区、干旱区)降水的趋势性比北方中、东部区的明显。北方中、东部区在20世纪50年代末到60年代相对多雨,而青海区、干旱区在20世纪50年代末到70年代末或80年代中相对少雨。在20世纪80年代,北方中部区降水由偏多转为偏少,而其余3个区域(北方东部区、青海区、干旱区)的降水由偏少转为偏多,发生和持续时间各不相同。近几年,北方东部区、北方中部区、青海区的降水增加,而干旱区降水下降。北方东部区、中部区、干旱区存在10年以上的长周期,北方东部区为准22年,北方中部区为准15年,干旱区为准11年,这种长周期在20世纪80年代之后变得规则且稳定。北方降水普遍存在准2～3年周期和准5年周期,其振幅有明显的年际、年代际变化,具有一定的周期性。  相似文献   

我国西南山区降雨侵蚀力时空变化趋势研究   总被引：14，自引：0，他引：14  

刘斌涛  陶和平  宋春风  郭兵  史展 《地球科学进展》2012,27(5):499-509

降雨是我国西南山区土壤侵蚀的主要动力因素,降雨侵蚀力反映了降雨对土壤侵蚀的潜在能力,研究降雨侵蚀力的时空变化趋势对我国西南山区土壤侵蚀的监测、评估、预报和治理具有重要意义。利用1960—2009年129个气象站逐日降雨量资料,计算出西南山区各气象站逐年降雨侵蚀力。采用趋势系数、气候倾向率和克吕格插值等方法对西南山区降雨侵蚀力50年来的时空变化趋势进行了探讨。结果表明:西南山区降雨侵蚀力空间分布特征与年降水量的空间分布特征一致;西南山区西北部的青藏高原区域降雨侵蚀力年际变化明显,变差系数Cv一般高于0.40;西南山区大部地区降雨侵蚀力呈上升趋势,说明由降雨侵蚀力引起的土壤侵蚀风险在增加,但在成都平原附近降雨侵蚀力在明显下降;降雨侵蚀力变化趋势系数随海拔高度升高而不断增加,在海拔2 500 m以上地区尤为明显,西南山区西北部的高海拔地区海拔高度对降雨侵蚀力增加具有放大效应。  相似文献