改进BP算法在风暴潮极值水位预报中的应用

提出1种基于改进BP算法的风暴潮极值水位预报方法。首先针对现有人工神经网络BP算法存在的缺陷,引入Cauchy训练方法计算连接权的调整,解决BP算法的局部极小点和网络瘫痪的问题。然后结合山东海区水文观测站每年的台风风暴潮资料,应用该改进算法建立台风强度、风速和台风移速与风暴潮极值水位的非线性网络预报模型,对该站极值水位进行预报。实验结果表明,该算法具有很好的稳定性和准确性,为风暴潮预报分析提供了1种可靠的技术手段。     

Surface circulation derived from drifting buoys in mid- and low-latitude Pacific

1 INTRODUCTION Measuring the velocity of ocean currents is one of the most important tasks in physical oceanography research. Many centuries ago, mariners had begun to obtain the sea surface cur- rents from vessel drift records. As early as in 1870s instr…     

Interpretation of sea surface wind interannual vector EOFs over the China seas

Using interpolation and averaging methods, we analyzed the sea surface wind data obtained from December 1992 to November 2008 by the scatterometers ERS-1, ERS-2, and QuikSCAT in the area of 2°N–39 °N, 105°E–130°E, and we reported the monthly mean distributions of the sea surface wind field. A vector empirical orthogonal function (VEOF) method was employed to study the data and three temporal and spatial patterns were obtained. The first interannual VEOF accounts for 26% of the interannual variance and displays the interannual variability of the East Asian monsoon. The second interannual VEOF accounts for 21% of the variance and reflects the response of China sea winds to El Niño events. The temporal mode of VEOF-2 is in good agreement with the curve of the Niño 3.4 index with a four-month lag. The spatial mode of VEOF-2 indicates that four months after an El Niño event, the southwesterly anomalous winds over the northern South China Sea, the East China Sea, the Yellow Sea, and the Bohai Sea can weaken the prevailing winds in winter, and can strengthen the prevailing winds in summer. The third interannual VEOF accounts for 10% of the variance and also reflects the influence of the ENSO events to China Sea winds. The temporal mode of VEOF-3 is similar to the curve of the Southern Oscillation Index. The spatial mode of VEOF-3 shows that the northeasterly anomalous winds over the South China Sea and the southern part of the East China Sea can weaken the prevailing winds, and southwesterly anomalous winds over the northern part of the East China Sea, the Yellow Sea, and the Bohai Sea can strengthen the prevailing winds when El Niño occurs in winter. If El Niño happens in summer, the reverse is true.     

非线性随机海浪的波高分布

利用水波动力学中的Stokes波理论建立了随机波统计模式, 并由此导出了非线性海浪的波高概率分布函数. 结果表明, 水波波陡既可作为控制波高分布函数变化的参量, 又能通过它的大小体现波高分布偏离瑞利分布的程度.含有波陡参量的波高统计分布克服了瑞利分布大波预报过高, 而众值预报过低的不足之处; 同时也使得小概率对应的波高值比瑞利分布预报的为低.资料验证表明, 新提出的波高分布在应用中更为合理.     

Effect of wave spectrum width on the probability density distribution of wind-wave heights

The probability distribution of wave heights under the assumption of narrowband linear wave theory follows the Rayleigh distribution and the statistical relationships between some characteristic wave heights,derived from this distribution,are widely used for the treatment of realistic wind waves. However,the bandwidth of wave frequency influences the probability distribution of wave heights. In this paper,a wave-spectrum-width parameter B was introduced into the JONSWAP spectrum. This facilitated the construction of a wind-wave spectrum and the reconstruction of wind-wave time series for various growth stages,based on which the probability density distributions of the wind-wave heights were studied statistically. The distribution curves deviated slightly from the theoretical Rayleigh distribution with increasing B. The probability that a wave height exceeded a certain value was clearly smaller than the theoretical value for B ≥0.3,and the difference between them increased with the threshold value. The relation between the H s /σ ratio and B was investigated statistically,which revealed that the H s / σ ratio deviated from 4.005 and declined with B. When B reached 0.698 1,the H s / σ ratio was 3.825,which is about 95.5% of its original value. This indicates an overestimation in the prediction of H s from H s =4.005 σ,and provides a potential method for improving the accuracy of the H s remote sensing retrieval algorithm,critical for extremely large waves under severe sea states.     

吕宋海峡水交换季节变化的数值研究

提要利用POM(Princeton Ocean Model)对吕宋海峡附近的环流情况进行数值模拟,结果表明,吕宋海峡净流量季节变化明显,除5月和6月为东向净流外,全年自7月至翌年4月皆为西向净流。7月至11月净流量由1.6Sv(1Sv=1×106m3/s)持续增加至14Sv,12月至翌年4月净流量从13.8Sv持续减小至3.1Sv。年平均值为5.7Sv。500m以上,秋、冬季有明显的黑潮分支进入南海,而在春、夏季黑潮南海分支消失或者较弱。在500m以下,黑潮位置由于北赤道流分岔位置的变化而发生南北移动,从而影响黑潮深层入侵南海。作者以保持与表层流速方向相一致的最大深度为界将流场分为上下两层,上层西向(入)流区域占据吕宋海峡南部、中部,秋、冬季范围最大,夏季向中部收缩,其深度空间分布呈东浅西深结构,在吕宋海峡入口处,入流深度呈南北浅中间深的结构。上层东向(出)流主要分布在海峡北部,夏季向南部扩展,范围最大。120.75°E断面除9月和10月外,下层净输运量与上层反方向。9月和10月上、下层净输运量皆为西向。上层年平均净流量为?7.6Sv(这里"?"表示净流量向西,下同),下层为1.8Sv。上层出入流深度随季节上下浮动范围可达数百米,海峡中部入、出流最深可达1800m。     

阿德雷企鹅声信号特征初步研究

企鹅是南极生物的代表，约有1.2亿只，其中阿德雷企鹅的种群最大，约占其总数量的1/3，主要分布在南极大陆东部和南极半岛及其沿岸岛屿。 南极鸟类发出的声信号是它们集群、行动、繁殖、辨认配偶及幼子、抚育后代和防御外来侵害保卫自己的重要功能之一。中外学者分别对南极某些鸟类的生态行为和发声信号进行了研究，并取得较好的研究成果(Taylor et al.，1990；张春光等，1991；程明华等，1992，1993；Kerry et al.，1993)。但有关企鹅在不同生态行为下发声信号的研究却较少，除Speirs等(1991)对企鹅发声识别能力进行研究外，迄今尚未见有关其他报道。因此，本文作者利用范振刚同志20世纪80年代从南极现场对企鹅录音磁带作为原始资料，采用日本产7T08信号处理器，对阿德雷企鹅伴随生态行为发出的声信号的波形结构、声频范围及频谱特征等有关物理参数进行了初步研究，为更好地保护企鹅、维持南极的生态平衡提供了科学依据。     

青岛冷水团强度的变化特征

青岛冷水团盘踞于山东半岛东南部近海的深底层。它是南黄海西部海域中的一个突出而重要的水文现象。青岛冷水团的存在和变动不仅使南黄海西部的环流结构和水文状况趋于复杂,而且还影响山东近海渔场春汛渔期的早晚和鱼群的集散程度(郑东等,1983;张元奎等,1989)。     

阿德雷企鹅声信号特征初步研究

企鹅是南极生物的代表,约有1.2亿只,其中阿德雷企鹅的种群最大,约占其总数量的1／3,主要分布在南极大陆东部和南极半岛及其沿岸岛屿。 南极鸟类发出的声信号是它们集群、行动、繁殖、辨认配偶及幼子、抚育后代和防御外来侵害保卫自己的重要功能之一。中外学者分别对南极某些鸟类的生态行为和发声信号进行了研究,并取得较好的研究成果(Taylor et al.,1990;张春光等,1991;程明华等,1992,1993;Kerry et al,1993)。但有关企鹅在不同生态行为下发声信号的研究却较     

辐射应力在黄河三角洲近岸波浪和潮汐风暴潮相互作用中的影响

基于考虑辐射应力机制的近岸高分辨率的波浪和潮汐风暴潮相互作用耦合数值模式 ,研究了辐射应力在黄河三角洲胜利油田近岸海域波浪和潮汐风暴潮相互作用过程中对水位的影响 ,并与两个中等强度天气过程引发的实测水位过程进行比较。结果表明 ,考虑辐射应力机制的波浪和潮汐风暴潮相互作用耦合模式模拟的结果与实测更接近 ,特别在极值增水位处吻合很好。对本研究的中等强度天气过程 ,辐射应力可增水 40cm ,在黄河三角洲近岸区有 2 0cm以上最大增水区域 ,这在工程上非常重要。可以预见 ,对引发黄河三角洲沿岸强增水的台风及强寒潮过程 ,辐射应力对增水的影响会更明显。本研究结果表明 ,在实际工程应用中 ,应采用波浪和潮汐风暴潮相互作用耦合数值模式。