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11.
A theoretical model for wind‐sand flow is developed by considering the coupling between wind flow and sand particle motion, the latter subject to the Magnus effect, under different atmospheric stability conditions. Using this model, the characteristics of the wind‐sand flow are discussed in detail. The results show that the atmospheric stability and the Magnus effect both have a strong influence on wind profiles and on the trajectories of sand particles. This approach produces results with characteristics that differ from those previously reported; the latter only applying to atmospheric conditions of neutral stability. The saltating sand reaches a greater height under non‐neutral stability than under neutral stability, while the maximum horizontal distance is greater under unstable conditions and is smaller under stable conditions than under conditions of neutral stability. 相似文献
12.
Tensioned foundations are common in civil engineering applications such as transmission towers, harbors, offshore structures, basement slabs under pressure, industrial equipment, etc. Procedures for the design of tensioned foundations are discussed in this paper, including specific recommendations for more common transmission tower foundations. Starting from a distinction between shallow and deep modes of failure, the paper presents the most common failure mechanisms for shallow failure in tension, including procedures for calculation of foundation tensile capacity under vertical and inclined loading. Emphasis is given to the influence of the strength of the compacted backfill compared to the strength of the natural soil, including presentation of results of full-scale loading tests. 相似文献
13.
Predictability of Interannual Variability in the Kuroshio Transport South of Japan Based on Wind Stress Data over the North Pacific 总被引:1,自引:3,他引:1
It is expected that a roughly two-year forecast of the Kuroshio transport variation can be made from a past record of wind
stress data over the ocean, since it takes nearly ten years for the first-mode baroclinic Rossby wave to traverse the entire
basin in the midlatitude North Pacific (∼30°N). We therefore investigated the predictability using an ocean general circulation
model driven by the wind stress data from the National Centers for Environmental Prediction/National Center for Atmospheric
Research (NCEP/NCAR) reanalysis. Referring to a hindcast experiment as the control run, we carried out fifteen forecast experiments,
the initial conditions of which are taken from the hindcast experiment at intervals of two years during the period from the
end of 1969 to the end of 1997. Each of the forecast experiments is driven only by wind stress in the year preceding each
experiment. The forecasted Kuroshio transport anomaly south of Japan agrees better with the hindcasted one during the first
two years of the forecast in most cases. In some cases, however, significant disagreements occur, most of which are likely
due to larger unpredictable variations caused by wind stress anomalies near Japan. At the end of forecast year 2, the anomaly
correlation coefficient is about 0.7, and rms of the forecast error is smaller than rms of the hindcasted anomaly. These results
indicate that the prediction of the interannual variability in the Kuroshio transport could be made two years in advance at
a statistically significant level.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
揭示Rankine涡风场模式和Jelesnianski风场模式之间的联系,并设计了一种台风风场分布模式,它的风速分布曲线落在Jelesnianski和Rankine涡两个风场模式的风速分布曲线之间,具有一个既优于Jelesnianski又优于Rankine涡的风速衰减速率,因此它同时克服了Rankine涡模式计算风速偏小和Jelesnianski模式计算风速偏大的缺点,以一种比较合理的变化趋势向远方衰减,成为一个比较切合实际的台风风场分布模式。同时,文中提出的移行台风风场计算方法对宫崎正卫、上野武夫和Jelesnianski模式都有一定的改进。 相似文献
15.
本文探讨东海区近海强风预报模式,首先介绍建立预报模式的思路和步骤,及使用说明,为了验证强风预报模式和判别条件,用1986、1987上日本传真天气图进行试报,准确和基本准确度为91.1%,并给出了1989、1995年随船试验预报结果,准确和基本准确率为90%以上。 相似文献
16.
本文以南麂海洋站1983~1990年风、浪的实测资料为依据,建立了南麂海城春、夏、秋、冬季定常波风浪波高与风速的经验关系式。检验结果表明,曲线回归显著,计算值与实测值吻合良好。文中还对偏NNE向和偏SSW向计算波高随风速增大的快慢,同一方向在同一风速作用下计算波高的季节变化及其机理作了初浅的讨论。 相似文献
17.
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19.
W.R. Geyer 《Estuarine, Coastal and Shelf Science》1997,44(6):713-722
Observations of two small estuaries in Cape Cod, U.S.A. indicate large variations in salinity structure that are forced by variations in along-estuary wind stress. During onshore winds, the estuarine circulation is reduced, and the along-estuary salinity gradient increases as freshwater accumulates. During offshore winds, the surface outflow is enhanced, freshwater is flushed out of the estuary, and the along-estuary salinity gradient becomes weak. Constrictions block the wind-induced flushing, resulting in strong salinity fronts across the constrictions. The residence time of one of the estuaries varies by more than a factor of three in response to variations in wind-induced flushing. The other estuary has little variation of flushing associated with winds, due to a constriction at the mouth that inhibits the wind-induced exchange. The strong influence of winds on the flushing of these estuaries is due in part to their shallow depths, which accentuates the influence of wind stress relative to the effects of the horizontal density gradient. In addition, the residence times of the estuaries are comparable to the time scale of wind forcing, allowing large changes in water properties during wind events. 相似文献
20.
两次大风过程的对比分析 总被引:1,自引:0,他引:1
文章对两次冷空气结合低气压大风过程进行了对比分析,揭示了海上低压轴向的突然向西北转变而引起的地面气压梯度的迅速加大是造成浙北沿海大风的重要原因之一。同时,揭示了两次过程由于高低层辐合辐散差异而引起的大风区上空两类不同的高低空垂直下沉速度分布特征,指出动量下传作用在地面造成风速的加大主要决定于对流层低层下沉速度(而非中层),这可能是两次大风过程地面气压梯度接近,而实际风力却差一级的原因。 相似文献