Interdecadal variation of precipitation days in August in the Korean Peninsula     

《Dynamics of Atmospheres and Oceans》2017

The present study examines a climate regime shift in the time series of the number of rainy days during August in the Korean Peninsula. The statistical change-point analysis indicates that a significant shift occurred in the time series around 1998, providing a rationale to divide it into two parts: 1975–1997 for the shorter rainy-day period and 1998–2012 for the longer rainy-day period. To examine the cause of recent rapid increases in the number of days with precipitation in August in the Korean Peninsula, differences in the averages of large-scale environments between the 1998–2012 period and the 1975–1997 period were analyzed.The differences in stream flows showed that anomalous cyclones were reinforced in the East Asian continent while anomalous anticyclones were reinforced in the western North Pacific at all layers of the troposphere. The anomalous anticyclones reinforced in the western North Pacific were associated with the western North Pacific subtropical high (WNPSH) developed a little more toward the Korean Peninsula recently. Consequently, the Korean Peninsula has been affected by anomalous south westerlies that supplied warm and humid airs from low tropical regions to the Korean Peninsula. The vertical thermal instability (warm anomaly at lower-level and cold anomaly at middle and upper-level) developed near the Korean Peninsula. In addition, upper tropospheric jets were reinforced further recently near the Korean Peninsula to provide good environments for development of upward flows. The frequency of TCs that affect the Korean Peninsula in August also increased rapidly since 1998.  相似文献   

类星体光度函数     

覃一平 《天文研究与技术》1999,(1)

对前人在类星体光度函数研究中的工作作了详细的介绍。在前人工作的基础上,提出两个新的研究方法和一个新的统计方法。第一为分类研究法。将类星体分作若干子类,每一子类的光度演化形式可以通过相关分析求出,而数密度则可由简单计数求得。第二为平均星等法,定义平均星等Ｍ。研究表明,对于纯密度演化模型,Ｍ与红移ｚ无关;而对于纯光度演化模型,Ｍ与光度演化形式（Ｍｚ－Ｍ）成线性关系。提出的新的统计方法为ｎ／ｎｍａｘ检验法,它是传统的Ｖ／Ｖｍａｘ和Ｖ′／Ｖ′ｍａｘ检验法的推广。与传统方法不同,它能适用于任何光度函数模型。若所采用的光度函数正确,则样品的ｎ／ｎｍａｘ值应均匀分布于数域［０,１］  相似文献   

阿拉善左旗雷暴活动特征分析     

多福学  刘志宁  马文超  张思莲 《内蒙古气象》2011,(3):51-52

利用阿拉善左旗气象局1971—2000年30年的雷暴资料,对阿拉善左旗雷暴的年、月、日变化及产生和消失的方位进行了统计分析,得到了阿拉善左旗雷暴的变化规律。  相似文献   

The statistics of particle velocities and accelerations under waves with directional spread     

M.J Tucker 《Ocean Engineering》1998,25(6):481-496

The statistics of the horizontal component of the water particle velocity vector under random waves are considered. A spread in the directions of travel of the component wave trains does not affect the rms value of the modulus r but it affects the shape of its probability distribution in such a way that the pr3bability of extreme values is reduced. For small and moderate directional spreads the modulus for a given probability of exceedance is reduced by a factor which tends to F_s as the probability of exceedance tends to zero, where F_s is the spread factor (which is typically 0.9 in temperate storms). However, the convergence on this asymptote is not complete for probabilities of engineering importance, particularly for wide directional spreads. The standard deviation of the probability distribution of the direction of the vector is reduced roughly in inverse proportion to r. The same conclusions apply to particle accelerations.  相似文献   

Biogeographic characterization of Mediterranean and Black Seas faunal provinces using GIS procedures     

L. Garibaldi  J. F. Caddy 《Ocean & Coastal Management》1998,39(3):211-227

To identify Mediterranean and Black Seas areas where similar marine faunal provinces occur, geographical distribution maps of 536 species of actual or potential interest to fisheries have been digitized, using GIS software, and three different ecological areas have been delimited by depth, separated by the 200 and 1000 m isobaths. Information on the species ranges was taken mainly from the maps and the texts of the FAO Species Identification Sheets covering the region, and complemented by other sources when necessary. All the distribution maps have then been overlaid by a grid of points at regular intervals every half degree of latitude and longitude. This allowed creation of a matrix of presence or absence of the species at each point from which species richness maps have been generated. The species richness in the Mediterranean proper shows the same negative gradient eastwards that has been observed for nutrients, while the low number of species in the Black Sea could be linked to the fragility and recent fast degradation of this ecosystem. Through the calculation of 65 dissimilarity indices from 50 contiguous points along the coastline and the species richness maps, the region has been divided into nine faunal provinces. These faunal provinces have then been compared with the ten Mediterranean and Black Seas divisions used by the GFCM for statistical purposes, revealing few differences between the two classifications. The definition of faunal provinces in a region when deciding upon Natural Management Areas, and the appropriate GIS approach to be followed, are discussed.  相似文献   

山东招远界河金矿床地球化学元素统计分析特征研究   总被引：1，自引：0，他引：1       下载免费PDF全文

曹新志  高秋斌  徐伯骏  王来峰 《地质找矿论丛》1999,14(2):30-35

通过对地化元素量值的统计分析可以推测地化元素在成矿过程中的演化特征,进而为预测找矿提供有用的深层次信息。本文通过有关元素的聚类分析、因子分析研究揭示界河矿区内Ａｕ与Ｂｉ以外的其他元素基本不具相关性、Ａｕ的成矿经历了长期、多次的地质演化过程,揭示了矿区内仅Ａｕ独立成矿的内在原因。文中据元素的共生组合及相关性特征认为矿区内Ｂｉ可作为找金的近程指示元素,Ａｓ可作为找金的远程指示元素。  相似文献   

精密补偿器水准仪受地球磁场影响的检测统计分析     

杨辉  任道胜  陈如丽 《测绘学报》1999,28(1):71-75

根据精密补偿器水准仪受地球磁场影响的检测统计,证实了磁场对不同型号的补偿器水准仪有不同程度的影响。分析了受磁影响的主要原因,并提出防磁措施及应注意的一些问题。  相似文献   

体应变地震波最大振幅与地震震级和震中距的统计关系探讨     

姜佳宁  吴利军 《中国地震研究》2017,31(1):107-115

Based on the body strain record of Tiantanghe station from 2008 to 2014,we make a statistical analysis of the relationship between the maximum amplitude of the body strain record and the surface-wave magnitude,epicenter distance of the earthquakes,which occurred in the Chinese mainland and its surrounding areas with MS≥6. 0 and the rest of the world with MS≥7. 0. According to statistical results,we propose a statistical formula between the surface-wave magnitude of earthquake and the maximum amplitude of the body strain record,the epicenter distance: M_S~*= 0. 37 ln A_max+ 0. 57 ln D + 0. 07. We can also derive a theoretical estimation formula for the maximum amplitude: A_max=e~(2. 7(M_S~*-0. 07))D~(-1. 54). This demonstrates that the maximum amplitude of the body strain record increases exponentially with the increase of the surface-wave magnitude, and decreases with the increase of the epicenter distance,and shows a negative correlation with their product. We further discuss the necessity of adding instruments with high frequency sampling to earthquake monitoring, and dicuss the prospects for precise earthquake prediction in future.  相似文献   

Statistical facies classification from multiple seismic attributes: comparison between Bayesian classification and expectation–maximization method and application in petrophysical inversion          下载免费PDF全文

Dario Grana  Xiaozheng Lang  Wenting Wu 《Geophysical Prospecting》2017,65(2):544-562

We present here a comparison between two statistical methods for facies classifications: Bayesian classification and expectation–maximization method. The classification can be performed using multiple seismic attributes and can be extended from well logs to three‐dimensional volumes. In this work, we propose, for both methods, a sensitivity study to investigate the impact of the choice of seismic attributes used to condition the classification. In the second part, we integrate the facies classification in a Bayesian inversion setting for the estimation of continuous rock properties, such as porosity and lithological fractions, from the same set of seismic attributes. The advantage of the expectation–maximization method is that this algorithm does not require a training dataset, which is instead required in a traditional Bayesian classifier and still provides similar results. We show the application, comparison, and analysis of these methods in a real case study in the North Sea, where eight sedimentological facies have been defined. The facies classification is computed at the well location and compared with the sedimentological profile and then extended to the 3D reservoir model using up to 14 seismic attributes.  相似文献   

基于OH全天空气辉成像仪观测的中国低纬地区的重力波传播统计特征   总被引：2，自引：2，他引：2       下载免费PDF全文

王翠梅  李钦增  徐寄遥  袁韡  刘伟军  孙龙昌  陈金松  燕春晓 《地球物理学报》2014,57(11):3659-3667

利用位于海南富克(19.5°N,109.1°E)和广西桂平(23.4°N,110.1°E)两个台站两年多的OH全天空气辉成像仪观测数据,对中国低纬地区的重力波传播统计特征进行了研究.从富克和桂平的气辉成像观测中, 分别提取了65和86个重力波事件.研究结果表明,观测水平波长,观测周期和水平相速度分别集中分布在10~35 km, 4~14 min和20~90 m·s^-1范围.重力波传播方向,在夏季表现出很强的东北方向传播.然而,在冬季主要沿东南和西南方向传播. 同时,结合流星雷达风场观测和TIMED/SABER卫星的温度数据,也发现在中层-低热层中传播的大多数重力波表现为耗散传播.且低层-中层大气中背景风场的滤波作用和多普勒频移可能对纬向方向传播的重力波产生的各向异性起到重要的调制作用.然而,经向方向传播的重力波产生的各向异性可能同时被低层大气中波源的非均匀分布以及潮汐变化所影响.  相似文献