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391.
William P. O'Connor Benjamin Fong Chao Dawei Zheng & Andrew Y. Au 《Geophysical Journal International》2000,142(2):620-630
We conduct numerical simulations of the wind forcing of sea level variations in the North Sea using a barotropic ocean model with realistic geography and bathymetry to examine the forcing of the 14 month 'pole tide', which is known to be anomalously large along the Denmark–Netherlands coast. The simulation input is the monthly mean surface wind stress field from the National Centers for Environmental Prediction (NCEP) reanalysis for the 40 year period 1958–1997. The ocean model output sea level response is then compared with 10 coastal tide gauge records from the Permanent Service for Mean Sea Level (PSMSL) over the same period of time. Besides the strong seasonal variations, several prominent quasi-periodicities exist near 7 years, 3 years, 14 months, 9 months and 6.5 months. Correlations and spectral analyses show remarkable agreement between the model output and the observations, particularly in the 14 month, or Chandler, period band. The latter indicates that the enhanced pole tide found in the North Sea along the Denmark–Netherlands coast is actually the coastal set-up response to wind stress forcing with a periodicity of around 14 months. We find no need to invoke a geophysical explanation involving resonance enhancement of the pole tide in the North Sea to explain the observations. 相似文献
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J. C. A. Miller-Jones M. P. Rupen R. P. Fender A. Rushton G. G. Pooley R. E. Spencer 《Monthly notices of the Royal Astronomical Society》2007,375(3):1087-1098
There is currently a clear discrepancy in the proper motions measured on different angular scales in the approaching radio jets of the black hole X-ray binary GRS 1915+105. Lower velocities were measured with the Very Large Array (VLA) prior to 1996 than were subsequently found from higher resolution observations made with the Very Long Baseline Array and the Multi-Element Radio Linked Interferometer Network. We initiated an observing campaign to use all three arrays to attempt to track the motion of the jet knots from the 2006 February outburst of the source, giving us unprecedented simultaneous coverage of all angular scales, from milliarcsecond scales out to arcsecond scales. The derived proper motion, which was dominated by the VLA measurements, was found to be 17.0 mas d−1 , demonstrating that there has been no significant permanent change in the properties of the jets since 1994. We find no conclusive evidence for deceleration of the jet knots, unless this occurs within 70 mas of the core. We discuss possible causes for the varying proper motions recorded in the literature. 相似文献
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Y. Z. Fan Bing Zhang D. M. Wei 《Monthly notices of the Royal Astronomical Society》2005,361(3):965-970
We discuss the high-energy afterglow emission (including high-energy photons, neutrinos and cosmic rays) following the 2004 December 27 giant flare from the soft gamma-ray repeater (SGR) 1806−20. If the initial outflow is relativistic with a bulk Lorentz factor Γ0 ∼ tens, the high-energy tail of the synchrotron emission from electrons in the forward shock region gives rise to a prominent sub-GeV emission, if the electron spectrum is hard enough and if the initial Lorentz factor is high enough. This signal could serve as a diagnosis of the initial Lorentz factor of the giant flare outflow. This component is potentially detectable by the Gamma-Ray Large Area Telescope ( GLAST ) if a similar giant flare occurs in the GLAST era. With the available 10-MeV data, we constrain that Γ0 < 50 if the electron distribution is a single power law. For a broken power-law distribution of electrons, a higher Γ0 is allowed. At energies higher than 1 GeV, the flux is lower because of a high-energy cut-off of the synchrotron emission component. The synchrotron self-Compton emission component and the inverse Compton scattering component off the photons in the giant flare oscillation tail are also considered, but they are found not significant given a moderate Γ0 (e.g. ≤ 10). The forward shock also accelerates cosmic rays to the maximum energy 1017 eV, and generates neutrinos with a typical energy 1014 eV through photomeson interaction with the X-ray tail photons. However, they are too weak to be detectable. 相似文献
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In this paper a statistical forecasting model designed for bounded areas of near-surface ocean wind speeds is implemented.Dimension reduction is achieved by decomposing the covariance structure into one large-scale and one small-scale component using empirical orthogonal functions. The large-scale component is modelled with an AR process and forecasts are calculated by applying a Kalman filter.The model is suited for stable weather situations as for unsteady situations it requires more frequent wind information. From the prediction variance fields it is possible to identify where unexpected weather usually enters the area. 相似文献
399.
利用修改的一层原始方程模式(Danard模式),对台湾海峡地区地面风场进行了数值试验和数值模拟。首先在一些理想情况下,研究了地面气压场、地形、摩擦和加热对地面风场的影响。指出:地面气压场决定了地面风场的基本分布;摩擦对海陆风速差异有重要作用;地形作用表现为弱的分流和阻流作用,加热作用使风场趋于紊乱。并在东北气流控制下的实际风场进行了数值模拟,效果良好。 相似文献
400.
A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions 总被引:2,自引:0,他引:2