涌浪对风浪能量影响的实验研究

在实验室风浪水槽中进行纯风浪和混合浪波面位移观测,研究波长较长的规则波对风浪能量的影响.本文用混合浪和纯风浪中的风浪显著波的零阶谱矩之比代表混合浪中的风浪与纯风浪能量之比,并以此表征涌浪对风浪能量的影响.研究了该能量比随涌浪波陡S、风区x、波龄倒数u/C、涌浪频率与纯风浪谱峰频率之比fs/fwp的变化规律.结果表明,涌浪对风浪能量的抑制作用随涌浪波陡的增加、波龄倒数的增大及涌浪频率与纯风浪谱峰频率之比的增大而增强.发现该能量比依赖于无因次量R=(1+80(πS)2)1.9(fs/fwp)0.9(u/C)0.27,并拟合得到2者的经验关系.此外,本文实验还发现,在某些情况下,涌浪的存在使风浪能量增加.     

一种自适应匹配子空间亚像元目标探测方法

为了克服基于线性混合模型的高光谱遥感影像亚像元目标探测方法的缺陷, 提出了一种基于全限制性线性分解的自适应匹配子空间探测方法。首先利用交叉相关光谱匹配技术求得各个像元所含端元类别信息, 然后根据端元类别信息和全限制性分解的结果构造自适应匹配子空间探测算子, 利用端元类别信息在探测中动态选择端元, 降低端元数目估计偏差对探测结果的影响, 提高探测器对目标与背景的可分性。实验证明, 该方法与其他基于线性混合模型的亚像元目标探测方法相比, 可以更好地克服端元数目估计偏差对探测结果的影响, 无论是端元个数低估还是     

Compass系统与GPS系统L1频段信号干扰仿真分析

全球导航卫星系统间的频率兼容性研究已经成为一个热点问题。首先介绍了国际电联建议的卫星导航系统间干扰分析方法;然后根据该方法对Compass系统和GPS系统在L1频段的信号进行了干扰仿真分析,并比较了系统间互干扰和系统自干扰的影响。仿真计算结果表明,除了互用信号L1C和B1C外,其余信号间的自干扰在总干扰中占主导,互干扰的影响相对较小。     

Argo floats revealing bimodality of large-scale mid-depth circulation in the North Atlantic

Analysis of Argo float trajectories at 1 000 m and temperature at 950 m in the North Atlantic between November 2003 and January 2005 demonstrates the existence of two different circulation modes with fast transition between them. Each mode has a pair of cyclonic - anticyclonic gyres. The difference is the location of the cyclonic gyre. The cyclonic gyre stretches from southeast to northwest in the first mode and from the southwest to the northeast in the second mode. The observed modes strongly affect the heat and salt transport in the North Atlantic. In particular, the second mode slows down the westward transport of the warm and saline water from the Mediterranean Sea.     

方向分布对三维聚焦波浪波面特性影响研究

波浪聚焦被认为是产生极限波浪的重要机理之一,近年来受到普遍重视。通过高阶谱方法,引入造波边界建立数值计算模型,模拟聚焦波浪在不同方向分布时的产生和聚焦过程,研究波浪的方向分布对聚焦波浪的波面、波峰最大值、聚焦点的偏移、波面参数及频谱的影响。研究结果表明波浪方向分布越窄,波浪的非线性影响越强、波面越陡,波峰值、聚焦点的偏移和波面特征参数都越大;同时方向分布对波浪聚焦前后的能量具有很大的影响。     

Cadmium and phosphorus cycling in the water column of the South China Sea: The roles of biotic and abiotic particles

The concentrations of cadmium, phosphorus, and aluminum in size-fractionated phytoplankton, zooplankton, and sinking particles are determined using ICPMS to evaluate the roles of biotic and abiotic particles on the cycling and ratios of Cd and P in the water column. Plankton were collected with a filtration apparatus equipped with 10-, 60-, and 150-μm aperture plankton nets on two occasions (2002 and 2006), and sinking particles were sampled by moored sediment traps deployed at depths of 120, 600, and 3500 m from 2004 to 2005. In contrast to what our previous study revealed, i.e., that most of the other bioactive trace metals in plankton were strongly correlated with abiotic Al and adsorbed on phytoplankton [Ho, T.Y., Wen, L.S., You, C.F., Lee, D.C., 2007. The trace metal composition of size-fractionated plankton in the South China Sea: biotic versus abiotic sources. Limnol Oceanogr 52, 1776–88.], Cd/P ratios, ranging from 0.12 to 0.34 mmol/mol P, did not vary with Al and exhibited fairly consistent values among different sizes of plankton, showing that Cd was mostly incorporated on an intracellular basis. In terms of the sinking particles, fluxes in Cd and P as well as in Cd/P ratios were strongly influenced by both biotic and abiotic particles. Overall, the Cd/P ratios in the sinking particles ranged from 0.03 to 1.2 mmol/mol, with the highest value observed in traps at 120 m during the productive season. The lowest value was observed in deep water during high flux periods for lithogenic particles. At surface depth, flux and Cd/P ratios were elevated during the most productive season in the region. The elevated ratios in the traps at 120 m were most likely related to preferential uptake of Cd for the dominant species (coccolithophores) during the productive period. Relatively, Cd/P ratios sharply decreased with increasing Al flux in deep water and ratios were much lower than the expected Cd/P ratios obtained from the relative portion of lithogenic and biogenic particles, indicating that the adsorption of soluble P into lithogenic particles was significant in the deep water during high lithogenic particle flux periods. Using averaged annual fluxes and standing stock in the water column, the residence time of biogenic Cd and P are 0.10 and 0.20, 250 and 100, and 9100 and 5000 years respectively in the top 120 m, 600 m, and water column as a whole, also showing preferential removal for Cd in the euphotic zone but relatively higher removal rates for P in the deep water. Our study suggests that the shift in microalgal community structure along with input of lithogenic minerals are both potentially important factors in influencing Cd/P ratios in oceanic water on a geological time scale.     

高光谱遥感的物质组分和物质成分反演的应用分析

高光谱遥感的最大特点是可以提取和重建像元光谱,从而依据光谱特征直接识别地物类型、地物组成,乃至地物的成分,反演地物的物理、化学参量。本文阐述了高光谱的光谱识别方法所能探测的岩石、土壤、植被和人工建筑物的物质组分或成分;另外,与多光谱相比较的角度,讨论了高光谱图像地物特征识别和物质成分反演等技术方法的应用。     

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小球藻和铜绿微囊藻的高浓度Chl-a高光谱定量模型

本研究将地物高光谱遥感技术应用于室内实验,从而得到小球藻和铜绿微囊藻的高光谱特征.通过多种半经验方法,如单波段、波段比值和微分法,建立了两藻种最优的Chl-a高光谱定量模型,并与室外情况进行了对比.结果表明:小球藻的最优定量模型为Chl-a=174.6 1138292(R703) 2.3(109[(R703)]2(p＜0.01),相应的方法适宜性为:一阶微分法＞单波段法＞波段比值法;铜绿微囊藻的最优定量模型为Chl-a=5299164(R757)1.9773(p＜0.01),相应的方法适宜性为:单波段法＞波段比值法＞一阶微分法;从高光谱特征来看,小球藻在540 nm和700 nm附近存在明显的特征波峰,其位置随Chl-a浓度增大而向长波方向偏离,铜绿微囊藻在530 nm、660 nm和700 nm附近存在3个较强的特征波峰,在610 nm和680 nm附近存在明显的波谷;与以往室外研究不同的是铜绿微囊藻的反射率在400-500 nm之间的R值并不低,是因为没有非藻类颗粒物的影响,总吸收明显降低.     

北极孔斯峡湾表层沉积物中溶解有机质的来源与转化历史

在北极地区孔斯峡湾采集28个表层沉积物样品,测定了其中水溶性有机质(也称溶解有机质,DOM)的分子量分布、紫外/可见吸收光谱和三维荧光光谱特征,并利用平行因子分析(PARAFAC)模型对DOM的荧光组分和来源进行了解析。结果表明:孔斯峡湾表层沉积物中有色溶解有机质(CDOM)及其中的荧光溶解有机质(FDOM)含量均从内湾向外湾方向呈逐渐累积的趋势,但CDOM中的FDOM所占比例逐渐减小,与DOM趋于老龄化密切相关。沉积作用减弱以及长期的光化学降解和微生物降解作用对此起主要贡献,并导致腐殖质和小分子组分在沉积物DOM中所占的比例呈逐渐递增的趋势。沉积物DOM包含陆源类腐殖质、自生源类腐殖质和类蛋白等三个荧光组分,但是其组成比例空间差异很大。吸收光谱斜率比(S_R)随自生源所占百分比增加而减小,随DOM腐殖质组分中陆源与自生源的比值增加而增加;腐殖化指数(HIX)随类腐殖质与类蛋白质比值和水深的增加而增加,生物源指数(BIX)随自生源比例增加而增加。峡湾沉积物DOM的组成和来源存在着高度的空间差异,在冰川湾区由水体颗粒有机质(POM)的近期转化和迁移而来,而在峡湾中央及口门附近以较老的腐殖质为优势,主要源于水体DOM长期迁移和转化。研究表明,FDOM/CDOM,S_R,HIX和BIX等构成的CDOM光谱指纹信息可以作为揭露沉积物溶解有机质来源及迁移转化历史的工具,对探索海洋与冰川相互作用影响下的峡湾环境演变有着重要意义。