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781.
The time variation of the wind-induced flow in a homogeneous unbounded sea region has been analytically investigated. The time-dependent Ekman solution in a homogeneous, shallow open sea has been further extended by taking into account the time variation in water depth which might be caused by either tidal motion or change in the mixed layer thickness. The solution approach taken in this study is based on the Galerkin-eigenfunction method originally developed by Heaps [1972. On the numerical solution of three-dimensional hydrodynamical equations for tides and storm surges. Memoires de la Societe Royale des Sciences de Liege Serie 6(2), 143–180]. A series of calculations have been made with emphasis on the influence of the time variation in water depth upon the build-up of Ekman spirals in the presence of oscillatory variations in water depth. It has been found that two oscillations contribute to the wind drift current, the inertial oscillation and the depth-variation-induced oscillation; the inertial oscillation decays with time, but the depth-variation-induced oscillation remains undamped despite the presence of bottom friction. The presence of time-harmonic variation produces peculiar forms of hodograph with a curled or circular pattern according to the angular frequency of the water depth variation. 相似文献
782.
Prediction of surface horizontal displacements, and gravity and tilt changes caused by filling the Three Gorges Reservoir 总被引:11,自引:0,他引:11
Horizontal displacements, and gravity and tilt changes induced by filling the Three Gorges Reservoir are modeled using elastic
loading Green functions. When the water surface reaches its highest level, the effects become maximum on the reservoir banks.
The longitudinal and latitudinal components of the horizontal displacements reach −8.2 and 7.7 mm respectively, gravity is
increased by up to 3.4 mGal, and the prime vertical and meridian components of the tilt changes are −7.8 and −17.5 arcseconds
respectively. Accordingly, the filling of the reservoir will influence values observed from global positioning system (GPS),
gravimetry and tilt measurements in the area. The results given can be used to provide important corrections for extracting
earthquake-related signals from observed data.
Received: 19 January 2001 / Accepted: 3 September 2001 相似文献
783.
青藏高原北羌塘新生代高钾钙碱岩系火山岩角闪石类型有痕量元素地球化学 总被引:12,自引:2,他引:12
利用电子探针和激光探针剥蚀系统(LA-ICP-MS)对北羌塘新第三纪高钾钙碱岩系英安岩中角闪石的主元素和微量、角闪石强烈富集Sc、Ti、V、Cr、Co、Ni等不相容亲铁元素,而相对亏损Th、U、Pb、Rb等强不相容的大离子亲石元素。稀土元素丰度高,且无Eu异常,批示北羌塘这套高钾钙碱岩系火山岩可能是青藏高原加厚的相当于榴辉岩相物质组成的下部陆壳脱水熔融的产物。 相似文献
784.
Based on the Bayesian principle and the fact that GPS carrier-phase ambiguities are integers, the posterior distribution
of the ambiguities and the position parameters is derived. This is then used to derive the maximum posterior likelihood solution
of the ambiguities. The accuracy of the integer ambiguity solution and the position parameters is also studied according to
the posterior distribution. It is found that the accuracy of the integer solution depends not only on the variance of the
corresponding float ambiguity solution but also on its values.
Received: 27 July 1999 / Accepted: 22 November 2000 相似文献
785.
Developing a bivariate spatial association measure: An integration of Pearson's r and Moran's I 总被引:1,自引:0,他引:1
Sang-Il Lee 《Journal of Geographical Systems》2001,3(4):369-385
This research is concerned with developing a bivariate spatial association measure or spatial correlation coefficient, which
is intended to capture spatial association among observations in terms of their point-to-point relationships across two spatial
patterns. The need for parameterization of the bivariate spatial dependence is precipitated by the realization that aspatial bivariate association measures, such as Pearson's correlation coefficient,
do not recognize spatial distributional aspects of data sets. This study devises an L statistic by integrating Pearson's r as an aspatial bivariate association measure and Moran's I as a univariate spatial association measure. The concept of a spatial smoothing scalar (SSS) plays a pivotal role in this task.
Received: 07 November 2000 / Accepted: 02 August 2001 相似文献
786.
787.
Condensation heating of the Asian summer monsoon and the subtropical anticyclone in the Eastern Hemisphere 总被引:27,自引:0,他引:27
The effects of condensation heating on the formation of the subtropical anticyclone in the Eastern Hemisphere (EH) are studied
by means of theoretical analysis and numerical simulation. The complete vorticity equation is employed for the analysis. It
is found that, due to the vertical gradient of strong condensation heating, the distribution of cyclone and anticyclone in
the upper troposphere is out of phase with that in the middle and lower troposphere. This is confirmed by a series of numerical
experiments. The horizontal gradient of the condensation heating also affects the configuration of the subtropical anticyclone.
It is concluded that condensation heating is a key factor for the formation and location of the summer subtropical anticyclone
in the EH. The latent heating released by the Asian monsoon rainfall contributes to the formation of the 200 hPa South Asian
anticyclone on the western side of the heating center and the 500 hPa western Pacific subtropical anticyclone on the eastern
side of the center. Such configurations are modified to some extent by surface sensible heating and orography. The circulation
in mid-latitudes is also affected by the latent heating in the subtropical area through the propagation of Rossby waves.
Received: 10 September 1999 / Accepted: 5 June 2000 相似文献
788.
Y. Shao M. Sogalla M. Kerschgens W. Brücher 《Meteorology and Atmospheric Physics》2001,78(3-4):157-181
Summary
In this paper, we examine the effects of land-surface heterogeneity on the calculation of surface-energy and momentum fluxes
in a meso-scale atmospheric model. A series of numerical experiments has been carried out with a combination of different
resolutions for the atmosphere and the land surface, which allows an examination of the aggregation and dynamic effects associated
with land-surface heterogeneity. The numerical results show that for a given atmospheric model resolution, increased land-surface
resolution leads to better estimates of surface-energy and momentum fluxes, and for a given land-surface resolution, increased
atmospheric model resolution also improves the estimates of these fluxes. This latter result contradicts the prevailing view
that subgrid variation in atmospheric data plays only a minor role in estimating the fluxes. It is also shown that subgrid
land-surface heterogeneity leads to increased turbulent fluctuations. The responsible mechanisms of this effect are both the
subgrid variation of surface-energy fluxes and their impact upon the development of convective cells. It is suggested that
subgrid atmospheric motions induced by surface heterogeneity may be an important factor which needs to be considered in subgrid
closure schemes for atmospheric models.
Received August 28, 2000/Revised June 1, 2001 相似文献
789.
790.
利用Fourier Bessel级数展开法,给出了表面具有覆盖层的圆弧形凹陷地形对入射平面SV波散射问题的一个解析解,并利用该解分析了不同深宽比凹陷地形表面覆盖层刚度和厚度对入射SV波的影响.结果表明,凹陷地形表面覆盖层的存在,即使厚度很薄,也会显著增加对入射SV波的放大作用,该放大作用可达到单一凹陷地形的2.5倍以上.覆盖层刚度和厚度的变化对入射平面SV波也具有很大影响. 相似文献