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11.
Andrew J. L. Harris Anna L. Butterworth Richard W. Carlton Ian Downey Peter Miller Pedro Navarro David A. Rothery 《Bulletin of Volcanology》1997,59(1):49-64
Satellite data offer a means of supplementing ground-based monitoring during volcanic eruptions, especially at times or locations
where ground-based monitoring is difficult. Being directly and freely available several times a day, data from the advanced
very high resolution radiometer (AVHRR) offers great potential for near real-time monitoring of all volcanoes across large
(3000×3000 km) areas. Herein we describe techniques to detect and locate activity; estimate lava area, thermal flux, effusion
rates and cumulative volume; and distinguish types of activity. Application is demonstrated using data for active lavas at
Krafla, Etna, Fogo, Cerro Negro and Erebus; a pyroclastic flow at Lascar; and open vent systems at Etna and Stromboli. Automated
near real-time analysis of AVHRR data could be achieved at existing, or cheap to install, receiving stations, offering a supplement
to conventional monitoring methods.
Received: 21 January 1997 / Accepted: 3 April 1997 相似文献
12.
D. Prandle 《Estuarine, Coastal and Shelf Science》1985,20(5):615-635
An examination is made of the circulation in narrow estuaries subject to a predominant tidal forcing. Velocity structures are derived separately for residual flow components associated with (a) river flow, (b) wind stress, (c) a well-mixed longitudinal density gradient and (d) a fully stratified saline wedge. Dimensionless parameters are introduced to indicate the magnitude of each component and these parameters are evaluated for 9 major estuaries, thereby revealing their sensitivity to each component.For a channel of constant breadth and depth, formulae are deduced for the length of saline intrusion, L. Comparisons with observed data show that such formulae may be used with confidence to predict changes in L arising from variations in river flow, tidal range or channel depths.The level of stratification is shown to be related to a product of two parameters, one associated with velocity structure and a second involving the square of the ‘flow ratio’ (i.e. residual velocity/amplitude of the tidal velocity). This relationship provides a simple classification system for estuarine stratification which can be used to indicate the sensitivity of any particular estuary to changing conditions. 相似文献
13.
李新生 《地球科学与环境学报》1993,(Z2)
本文首先简述了斜坡演化过程与构造运动的关系,然后阐明了滑坡的空间分布、活动周期及活动规模与构造因素的联系。在此基础上指出:构造因素是滑坡产生的基础,对滑坡分布具宏观控制作用,并与滑坡的活动周期和活动规模密切相关,是滑坡研究及其灾害预测、预防研究工作中值得重视的重要因素。 相似文献
14.
Wing-Huen Ip 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):197-202
In the context of the survival of periodic comets of different origins, rotational breakup and tidal disruption could be important, especially of the short period comets injected from the Kuiper belt. This is because long-period comets from the distant Oort cloud tend to be subject to thermal stress and volatile 'explosion' far more severely. A simple calculation using the Öpik method of random planetary close encounters was performed to estimate the probability of tidal disruption of comets and scattered Kuiper belt objects (SKBOs) during their orbital migration. It was found that a large fraction of the short period comets and SKBOs might have been internally fragmented by single or multiple close encounters with the outer planets. 相似文献
15.
Nicolas Rascle Fabrice Ardhuin Pierre Queffeulou Denis Croiz-Fillon 《Ocean Modelling》2008,25(3-4):154-171
Ocean surface mixing and drift are influenced by the mixed layer depth, buoyancy fluxes and currents below the mixed layer. Drift and mixing are also functions of the surface Stokes drift Uss, volume Stokes transport TS, a wave breaking height scale Hswg, and the flux of energy from waves to ocean turbulence Φoc. Here we describe a global database of these parameters, estimated from a well-validated numerical wave model, that uses traditional forms of the wave generation and dissipation parameterizations, and covers the years 2003–2007. Compared to previous studies, the present work has the advantage of being consistent with the known physical processes that regulate the wave field and the air–sea fluxes, and also consistent with a very large number of in situ and satellite observations of wave parameters. Consequently, some of our estimates differ significantly from previous estimates. In particular, we find that the mean global integral of Φoc is 68 TW, and the yearly mean value of TS is typically 10–30% of the Ekman transport, except in well-defined regions where it can reach 60%. We also have refined our previous estimates of Uss by using a better treatment of the high frequency part of the wave spectrum. In the open ocean, Uss 0.013U10, where U10 is the wind speed at 10 m height. 相似文献
16.
Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyse the diffusion of suspended sediments and the change of tidal radial sand ridges in the northern part of the Changjiang River delta, the South Yellow Sea. The results showed that the diffusion of suspended sediments was controlled by the tide, net current, and submarine topography in this area. The distribution of suspended sediments had close relationship with thesubmarine topography. The old Huanghe River delta and the Changjiang River comprise the main sediment supply for the formation of radial sand ridges, whose evolution can be divided into three stages since the Huangbe River changed its course and flowed northward into the Bohai Sea. 相似文献
17.
Blazar 的X射线谱性质 总被引:1,自引:0,他引:1
从Donato文献中选择了一个含有69个Blazar的样本,样本中每个源有多个X射线辐射流量数据,用该样本研究了流量密度和谱指数之间的关系,以及研究了三类源(HBL,LBL,FSRQ)的红移和谱指数的分布。结果表明:对于HBLs,谱指数和流量密度之间有一个较好的反相关关系存在,而对于LBLs和FSRQs却没有相关。因此认为HBL的X射线是同步辐射所致,而LBL和FSRQ的X射线辐射较为复杂可能是同步自康普顿过程导致。HBL显示软X射线谱,而FSRQ显示硬X射线谱,LBL居中。在谱图中HBL位于近端,rSRQ位于远端,LBL居中。 相似文献
18.
O. Sadot K. Levy A. Yosef-Hai D. Cartoon Y. Elbaz Y. Srebro G. Ben-Dor D. Shvarts 《Astrophysics and Space Science》2005,298(1-2):305-312
The hydrodynamic instability, which develops on the contact surface between two fluids, has great importance in astrophysical
phenomena such as the inhomogeneous density distribution following a supernova event. In this event acceleration waves pass
across a material interface and initiate and enhance unstable conditions in which small perturbations grow dramatically.
In the present study, an experimental technique aimed at investigating the above-mentioned hydrodynamic instability is presented.
The experimental investigation is based on a shock-tube apparatus by which a shock wave is generated and initiates the instability
that develops on the contact surface between two gases. The flexibility of the system enables one to vary the initial shape
of the contact surface, the shock-wave Mach number, and the density ratio across the contact surface.
Three selected sets of shock-tube experiments are presented in order to demonstrate the system capabilities: (1) large-initial
amplitudes with low-Mach-number incident shock waves; (2) small-initial amplitudes with moderate-Mach-number incident shock
waves; and (3) shock bubble interaction.
In the large-amplitude experiments a reduction of the initial velocity with respect to the linear growth prediction was measured.
The results were compared to those predicted by a vorticity-deposition model and to previous experiments with moderate- and
high-Mach number incident shock waves that were conducted by others. In this case, a reduction of the initial velocity was
noted. However, at late times the growth rate had a 1/t behavior as in the small-amplitude low-Mach number case. In the small-amplitude moderate-Mach number shock experiments a
reduction from the impulsive theory was noted at the late stages.
The passage of a shock wave through a spherical bubble results in the formation of a vortex ring. Simple dimensional analysis
shows that the circulation depends linearly on the speed of sound of the surrounding material and on the initial bubble radius. 相似文献
19.
卞菊梅 《地球科学与环境学报》1995,(1)
本文主要依据地形图和航空照片解译,并经已有地质、钻孔资料验证及野外实地考察的方法来研究地形面及其变形特征,由此确定渭河盆地活断层的分布、最新活动特征及活动规律,为地震预报及地震危险性分析提供依据。 相似文献
20.