福建沿海精细化台风风暴潮集合数值预报技术研究及应用

该文首先基于高级环流模型(ADCIRC)建立了一个适合台湾海峡及福建沿海区域的精细化台风风暴潮数值预报模式。利用所建立的精细化数值预报模式对影响台湾海峡及福建沿海的8次台风风暴潮个例进行了模拟,对模拟的24个站次的风暴潮增水峰值与实测值进行了对比,平均绝对误差小于15 cm;其次,为了尽可能减小由于台风路径预报误差而造成的风暴潮增减水误差,本文采用了集合数值预报技术,试报证明此方法可以在一定程度上减小风暴潮增减水误差。     

一个高分辨率的长江口台风风暴潮数值预报模式及其应用

利用河口海岸海洋模式(ECOM-Si)建立了一个适用于长江口区风暴潮的数值预报模式.该模式采用对岸线有较好拟合能力的自然正交水平坐标系统和能分辨较复杂海底地形的垂直σ坐标系统.模式考虑了长江口径流量对风暴潮的影响,部分地考虑了天文潮和风暴潮非线性相互作用对风暴增水的影响.风暴潮预报的大气强迫场用模型气压场和模型风场.利用所建立的模式对长江口区台风风暴潮进行了8个个例模拟,模拟增水与实测增水的峰值相比较,平均绝对误差不足10cm.利用本研究建立的模式,就气象因子对风暴潮位的敏感性进行了数值试验.试验结果表明,台风中心气压降低(升高)20hPa可导致约100cm的风暴潮位升高(或降低).台风最大风速半径误差对台风增水的变化影响也较显著.试验还表明,长江径流量增加1倍(减半),可以造成风暴潮的平均增加25cm(减小13cm).天文潮位相变化对风暴增水的影响数值试验表明,当台风暴潮与天文潮在不同位相相互作用,可使风暴潮位最大增加达70cm或减小90cm.     

港湾台风暴潮嵌套数值模型的初步研究

本文提出一套可适用港湾台风暴潮的二维嵌套数值模型,经大亚湾的具体应用试验,结果显示:在有实测台风增水资料可对比的47站次台风增水过程数值模拟中,过程最大增水的计算值与实测值偏差在15cm以内者占83%,二者的增水曲线变化趋势较为吻合,良好的试验结果证明了本文的嵌套数值模型及其处理方法是有效的和可行的.     

“威马逊”台风暴潮增水及水动力响应数值模拟

基于河口海岸水动力三维数值计算模型,建立浙江沿海天文潮与风暴潮耦合预报模式。利用该模式,对经过浙江沿海海域的台风"威马逊"进行数值计算,风暴潮增水计算结果与实测值符合较好,误差基本在±20 cm以内。计算增水值与传统的调和分析法所得的增水结果相比,也较为一致。进一步对局部水动力响应的研究发现,风暴潮期间,局部地区从底到表各层水流流速均急剧增大或减小,其值达到了与天文潮流同等的数量级。当水流流向与风向相同或相近时,流速增大,相反时,则流速减小。且台风期间,各层水流流向也随风向发生改变,流态变得更加复杂。     

南海东北部台风潮的数值后报及极值增水估计

本研究对近40年来影响南海东北部陆架海区的28次台风引起的风暴潮进行了数值后报,其中8个过程的沿岸后报增水值与实测值进行了比较,表明后报值与实测值符合良好,90%以上的最大增水值偏差在30厘米以下。为了得出本海区多年一遇的台风增水极值,在后报台风路径密集处选择了9个不同水深点,对每点取出各次台风下的最大增水值,然后用Weibull分布进行拟合,得出了各点的极值分布。     

珠江口外海风暴潮的数值模型

采用二维全流浅水波动方程和Leendertse的交替方向隐格式,对珠江口外海发生较大增水的7次台风进行了数值模拟。 经多次试验,选定拖曳系数与空气密度之积为一常数pa·CD=2.5×10~(-6)g/cm~3。同时,在一般情况下,取台风半径R=95km,但对影响范围较小的8309次台风,取R=60km。模拟所得增水过程与实测值符合得较好。在所有模拟结果中,最高增水偏差小于10cm的占65％,小于20cm的占71％,小于30cm的占94％,     

长江口区可能最高潮位估算研究

利用《西北太平洋热带气旋年鉴》资料,简要分析了影响上海地区可能最高潮位的台风路径、强度变化特征.分析表明,造成上海地区严重风暴潮的台风路径有3种类型,它们分别是登陆浙江沿海西行类、近海北上类和正面袭击上海类.上海及其近海区域台风强度随纬度增加而减弱的变化特征明显,在东海北部,近50a内尚未出现过中心气压低于920hPa的台风.利用特定的统计模式,根据假想台风路径、强度变化给出的可能最大增水只有210cm,其值明显偏小,认为用统计方法进行上海地区最大可能增水的估算似乎不合适.在考虑可能变化的台风路径、强度、移动速度以及天文大潮汛等综合因素后,利用高分辨率ECOM-Si的数值模式计算出的上海地区(吴淞)可能最大增水是由5612台风以10km/h速度北抬纬度2°并取所在位置的历史最低气压值造成的,其可能最大增水为367cm,如以长江口区天文可能高潮值420cm计算,则获得长江口的最大可能水位为787cm.     

台风“圣帕”登陆福建前后的风暴潮特征分析

通过普查台风影响和登陆前后的气象和水文资料,分析总结了2007年登陆福建的第9号台风"圣帕"风暴增水特征及其与气象要素的相互关系."圣帕"引起的福建沿海风暴增水明显 ( 50 cm 以上 ) 且持续时间长 (52 h );风暴增水最大峰值出现在台风位于台湾海峡时,次峰值分别出现在台风登陆台湾岛前 1～2 h 和台风登陆福建沿海前 4 h."圣帕"风暴增水幅度与各验潮站的海平面气压关系密切,6h变压值对于风暴增水幅度的预报有一定的提前预报价值.     

对台风潮单站极值预报方法的改进

前 言 近年来以相关统计方法建立的台风潮单站极值预报公式进入预报业务并取得较好的效果。为了进一步提高预报精度,本文以汕头测站为例,在原有预报公式的基础上对局地风场在增水中的贡献又作了一些探讨和计算,供预报参考。 一、现行台风潮预报公式 现行预报公式为: △H_(max)=a+b△P_0(1-e~(-r)o/r) 式中△H_(max)为最大增水。△P_0=1008—P_0为气压下降量,外围气压取1008hPa,P_0为台风中心气压,采用最大增水时刻前24小时(即四个正点资料)实测资料的平均值。r_0为大风半径,取常数0.64。r为最大增水时刻台风中心至测站距离,从台风路径图中量取(以纬距为单位)。a、b为待定系数。     

博鳌风暴潮研究

利用与博鳌相邻的有关站位验潮资料,结合台风风暴潮数值预报模式(FbM模式)对该区的风暴潮进行了论证。结果显示,当登陆台风(或经海南省南部海上西进的台风)位于博鳌、清澜向海右侧登陆时,同一台风在博鳌引发的风暴潮过程与清澜相似。通过考察1949年以来登陆海南省的台风,以1973年的7314号台风的强度最大,经对其作模式计算,当台风以最有利于博鳌港增水的路径移动时,所引起的该港最大风暴潮是201cm。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.     

A Tidal Flow Model for the Gulf of Kachchh, India

A vertically integrated model has been used to study the tidal circulation and currents in the Gulf of Kachchh along the west coast of India. The model is fully nonlinear and uses a semiexplicit finite difference scheme to solve the basic hydrodynamic equations on a staggered grid. The model is forced by prescribing the tides along the open boundary of the model domain. The flow is simulated both with and without the presence of the proposed tidal barrage across the Hansthal Creek in the Gulf of Kachchh. The results show a considerable change in the behavior of the tidal flow in the presence of the barrage.