浙江省几种灾害性大风近地面阵风系数特征   总被引：1，自引：1，他引：0       下载免费PDF全文

周福  蒋璐璐  涂小萍  申华羽  郑铮 《应用气象学报》2017,28(1):119-128

阵风特性研究是大风预报和服务的基础。基于2011-2013年浙江省自动气象站逐日逐10 min测风资料,分析了浙江省陆地和近海海面冷空气、热带气旋和强对流大风的阵风系数特征。结果表明:冷空气和热带气旋大风阵风系数空间分布基本相同,大风主要发生在近海海面和沿海地区,海面阵风系数一般小于1.5,等值线平行于海岸线且自西向东逐渐减小,陆地阵风系数一般大于2.0,山区可超过3.0,表现出地形对阵风系数的增强作用。强对流大风阵风系数明显高于业务规范平均值,发生地点遍及浙江省各地,但发生概率超过10%的站点主要位于沿海地区和近海海面。风向基本不影响阵风系数空间分布。冷空气和热带气旋站点阵风系数与海拔高度有较高正相关性。模糊聚类分析发现:浙江省400 m以上山区站与70 m以下的低海拔站点在阵风系数特征上分属不同空间类型;基于逐步回归建立站点阵风系数预报模型,检验表明:模糊聚类可帮助提高模型阵风系数预报能力。  相似文献   

Hydrography of the eastern tropical Pacific: A review   总被引：3，自引：10，他引：3  

Paul C. Fiedler  Lynne D. Talley 《Progress in Oceanography》2006,69(2-4):143

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Capelin in Faroese waters-a messenger of harsh times?     

Jakupsstovu  Stein Hjalti i; Reinert  Jakup 《ICES Journal of Marine Science》2002,59(5):884-889

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The circulation in the southern Huanghai Sea and northern East China Sea in June 1999   总被引：1，自引：0，他引：1  

Yaochu Yuan  Yonggang Liu  Mingyu Zhou  Arata Kaneko  Zhou Yuan  Noriaki Gohda 《海洋学报(英文版)》2003,22(3):321-332

On the basis of hydrographic data and current measurement (the mooring system, vessel-mounted ADCP and toward ADCP) data obtained in June 1999, the circulations in the southern Huang-hai Sea (HS) and northern East China Sea (ECS) are computed by using the modified inverse method. The Kuroshio flows northeastward through eastern part of the investigated region and has the main core at Section PN, a northward flow at the easternmost part of Section PN, a weaker anti-cyclonic eddy between these two northward flows, and a weak cyclonic eddy at the western part of Section PN. The above current structure is one type of the current structures at Section PN in ECS. The net northward volume transport (VT) of the Kuroshio and the offshore branch of Taiwan Warm Current (TWCOB) through Section PN is about 26.2×106m3/s in June 1999. The VT of the inshore branch of Taiwan Warm Current (TWCIB) through the investigated region is about 0.4×106m3/s. The Taiwan Warm Current (TWC) has much effect on the currents over the  相似文献   

The accuracy of supermassive black hole masses determined by the single-epoch spectrum (Dibai) method     

N. G. Bochkarev  C. M. Gaskell 《Astronomy Letters》2009,35(5):287-293

The first set of supermassive black hole mass estimates, published from 1977 to 1984 by E.A. Dibai, are shown to be in excellent agreement with recent reverberation-mapping estimates. Comparison of the masses of 17 AGNs covering a mass range from about 10⁶ to 10⁹ M _⊙ shows that the Dibai mass estimates agree with reverberation-mapping mass estimates to significantly better than ±0.3 dex and were, on average, only 0.14 dex (∼40%) systematically lower than masses obtained from reverberation mapping. This surprising agreement with the results of over a quarter of a century ago has important implication for the structure and kinematics of AGNs and implies that type-1 AGNs are very similar. Our results give strong support to the use of the single-epoch-spectrum (Dibai) method for investigating the co-evolution of supermassive black holes and their host galaxies. The article was translated by the authors.  相似文献   

An anisotropic strength criterion for jointed rock masses and its application in wellbore stability analyses     

X. Chen  Q. Yang  K. B. Qiu  J. L. Feng 《国际地质力学数值与分析法杂志》2008,32(6):607-631

In this paper, an anisotropic strength criterion is established for jointed rock masses. An orientation distribution function (ODF) of joint connectivity, is introduced to characterize the anisotropic strength of jointed rock masses related to directional distributed joint sets. Coulomb failure condition is formulated for each plane of jointed rock masses by joint connectivity, where the friction coefficient and cohesion of the jointed rock mass are related to those of the intact rock and joint and become orientation dependent. When approximating joint connectivity by its second‐order fabric tensor, an anisotropic strength criterion is derived through an approximate analytical solution to the critical plane problem. To demonstrate the effects of joint distribution on the anisotropic strength of jointed rock masses, the failure envelopes are worked out for different relative orientations of material anisotropy and principal stress axes. The anisotropic strength criterion is also applied to wellbore stability analyses. It is shown that a borehole drilled in the direction of the maximum principal in situ stress is not always the safest due to the anisotropic strength of the jointed rock mass. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

The Cretaceous sedimentary history of the Pindos Basin (Greece)     

Peter?NeumannEmail author  Wolfgang?Zacher 《International Journal of Earth Sciences》2004,93(1):119-131

The Cretaceous sedimentary rocks of the Pindos Zone in western Greece document the evolution of a Tethyan deep-water basin. New sedimentological and micropalaeontological studies reveal a complex basin history. Siliceous sediments with abundant radiolaria and organic-rich facies prevailed up to the early Late Cretaceous. Within the sediment-starved pre-Middle Cenomanian, marked black shale levels appear that are probably linked to oceanic anoxic events. At the change from the late Early to the early Middle Cenomanian, the sedimentary regime altered abruptly. The early Late Cretaceous is characterized by major calcareous redepositional events (orbitoline horizons) and often associated siliciclastic turbidite deposition (submarine-fan environments). In the late Late Cretaceous, carbonate supply increased rapidly, resulting in the evolution of a carbonate slope and basin-plain setting. Pelagic and allodapic limestones recorded basinwide blooms in planktonic foraminifera (elevata event) and a polyphase redepositional history that is interpreted to reflect the sensitivity of the basin to the tectonic evolution of Apulia.  相似文献   

Upward-thickening patterns and lateral continuity of Permian sand-rich turbidite channel fills, Laingsburg Karoo, South Africa   总被引：1，自引：0，他引：1  

Martin Grecula  Stephen S. Flint  Henry De V. Wickens†  Stephen D. Johnson‡ 《Sedimentology》2003,50(5):831-853

Abstract Analysis of extensive exposures of the Permian Laingsburg Formation, Karoo basin, South Africa, have enabled a detailed reconstruction of the base of slope stratigraphy and palaeoenvironments in a deep-water system characterized by a very narrow grain-size range (fine sandstone). The deposits include an ≈ 4 km wide and 80 m thick channel complex, fringed by sandy sheet deposits that extend laterally for at least 6 km across depositional strike. Within the channel complex, individual channel fills are marked by shallow basal erosion surfaces draped by thin, parallel-stratified beds of very fine sandstone and siltstone, interpreted as flow tails to largely bypassing flows. These thin beds are overlain by 0·4 to 5 m thick beds of structureless, fine-grained sandstone that represent the majority of the channel fills. The basal packages may be partially to completely removed by localized scour in the axial zone of the channel complex but can be mapped laterally into overbank areas where they thicken and are dominated by rippled fine sandstones with intercalated siltstones. Axial confinement resulted from subtle topography on the basin floor, whereby the lower, dense parts of the initially erosive and bypassing flows were partially confined in the lows and the more dilute, slower moving upper parts of the flows deposited sheet-like successions across slightly elevated overbank areas. The narrow grain-size distribution prohibited the formation ofcoarse-grained residual bypass deposits during the initial phases of channel formation. With decreasing magnitude, later flows became more depositional, filling remaining axial depressions with thick-bedded structureless sandstone. The smaller volumes of late-stage sediment were more axially focused, producing local scour-and-fill features and starvation of the overbank areas. Resulting grain-size vertical profiles are complex. The basal flow tail packages and overlying massive deposits form a thickening and slightly coarsening-upward trend in the channel fills. The overbank deposits show a thinning- and fining-upward profile as a result of less bypass plus late-stage starvation of sand. Application of traditional deep-water facies models could therefore potentially lead to erroneous interpretations of the channel complex as a prograding lobe and the overbank sheets as channel-fills.  相似文献   

一个太平洋海盆尺度环流模式及其模拟结果   总被引：3，自引：2，他引：3  

徐永福  李阳春  赵亮  李荣凤  俞永强 《大气科学》2006,30(5):927-938

在中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG)发展的全球气候海洋环流模式(LICOM)的基础上构建了一个太平洋海盆环流模式,并对其模拟结果进行了深入的分析.在模拟中对中尺度示踪物输送采用了两种方案,即传统的水平扩散方案(HOR)和包括涡旋诱导速度的等密度面扩散方案(GM).对这两个试验的气候平衡态结果分析发现,该模式较好地模拟出了太平洋的环流特征,包括副热带大涡、副极地涡旋以及南极绕流(ACC)等.赤道附近的各种流系亦得到了较好的模拟,模拟的150°W赤道潜流的最大流速为40 cm/s,出现在次表层130 m左右,虽然模拟值比基于NCEP资料估计的最大流速80 cm/s小,但与其位置十分相近.两个试验均较好地模拟出了温盐的分布结构,包括北太平洋和南太平洋中层水的形成以及南极底层水的输送等.通过详细分析两个试验结果发现,总的说来在目前模式所采用的参数条件下,GM的结果稍好于HOR的结果.这些模拟结果表明,在LICOM基础上构建的太平洋环流模式从总体上是能再现许多观测特征的,可为今后进一步研究被动示踪物在北太平洋的分布等问题提供一个十分有用的工具.  相似文献   

节理岩体爆破数值模型及模拟研究   总被引：2，自引：1，他引：1  

郭文章  员永峰 《岩土力学》1998,19(3):1-9

运用多刚体系统动力学及接触冲击理论建立了节理岩体弹塑性动态本构模型。基于DYNA－2D程序原理及其框架,利用所建模型,模拟了节理岩体的爆破过程,量化了节理岩体在爆炸载荷作用下不同时刻的应力场。  相似文献