共查询到20条相似文献，搜索用时 62 毫秒
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基于长时间序列的大气资料,计算了西北太平洋地区的水汽输送通量,分析了水汽输送通量场的时空变化特征,并给出了西北太平洋水汽输送通量与中国夏季降水异常的耦合模态.结果显示:西北太平洋水汽输送通量场具有显著的经向型、辐散型和纬向型3个主要的空间型,这三种模态的年循环特征都很显著.夏季,西北太平洋水汽输送通量异常以辐散型为主,且具有显著的准两年周期振荡特征和明显的年代际变率;在西北太平洋水汽输送通量与中国夏季降水异常前三类主要的耦合模态中,水汽输送通量异常以纬向型和辐散型为主.分析表明,西北太平洋水汽输送通量变化是影响中国东部降水异常的重要因素之一,而西太平洋暖池区、黑潮流域和中国近海尤其是南海海域则是向中国输送水汽的关键区域.这可为西北太平洋海气相互作用过程及其对中国气候的影响研究提供了必要的科学依据. 相似文献
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利用1957-2010年中国东部（105°E以东）355个站点的温度、降水观测资料和Hadley中心的HadISST海温再分析资料以及EOF等分析方法,分析了中国东部地表气温和邻近海域海表温度的时空变化特征,构建了一个用于表征夏季中国东部与邻近海域纬向海陆热力差异的温差序列,探讨了该序列的变化特征及其与中国东部夏季降水的关系.结果表明：（1）夏季海陆表面温度变化的强信号区分别位于中国黄海、东海北部及邻近海域和长江中下游地区;（2）夏季强信号区的海陆温差序列有明显的年际和年代际变化特征,约为4-6、8和15a的变化周期.此外,在2000年前后7月海陆温差发生明显转折,在1957-2000年期间,海陆温差幅度有下降的趋势,2000年之后则有上升的特点,并且与中国东部降水相关关系也不同;（3）6月份的海陆温差与中国东北大部分地区的降水有明显的正相关关系,7月份则与中国长江中下游及南部地区的降水有显著的负相关关系.这表明夏季中国东部纬向海陆热力差异的变化可能对中国东部的降水有重要的影响. 相似文献
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南海夏季风爆发与南海热含量异常特征的相关分析 总被引：2，自引：0，他引：2
通过利用1958—2007年SODA月平均海温资料、1958—2008年NCEP/NCAR再分析资料以及1974—2008年NOAA卫星月平均OLR资料,分析了南海季风与南海上层海洋热含量之间的可能关系,发现南海夏季风爆发早晚与前冬南海上层海洋热含量存在显著的负相关,即当冬季南海上层海洋热含量偏高(低)时,次年南海夏季风爆发早(晚)。进一步对南海夏季风爆发异常年前期及前冬南海东部热含量异常年的相关大气环流特征分析后发现,南海夏季风爆发偏早和偏晚年前期的OLR特征、对流层环流特征及位势高度场分别与前冬南海东部热含量异常偏高和偏低年相一致。得出冬季南海东部热含量偏高(低)时,OLR在赤道东印度洋至我国南海及菲律宾以东为负(正)距平,南海地区对流加强(减弱);在纬向方向上,大气环流特征表现为正(负)的Walker距平环流,低纬Walker环流发展(减弱);在经向方向上,南海地区南北向局地Hadley环流加强(减弱);次年初春(3—4月)500hPa位势高度场在西太平洋副热带高压区总体为负(正)距平,副热带高压偏弱(强)。因此有(不)利于南海夏季风的早爆发。南海和西太平洋暖池区热含量异常都通过对流作用影响其上空大尺度... 相似文献
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The occurrence of gas hydrate has been inferred from the presence of Bottom-Simulating Reflectors (BSRs) along the western
continental margin of India. In this paper, we assess the spatial and vertical distribution of gas hydrates by analyzing the
interval velocities and Amplitude Versus Offset (AVO) responses obtained from multi-channel seismics (MCSs). The hydrate cements
the grains of the host sediment, thereby increasing its velocity, whereas the free gas below the base of hydrate stability
zone decreases the interval velocity. Conventionally, velocities are obtained from the semblance analysis on the Common Mid-Point
(CMP) gathers. Here, we used wave-equation datuming to remove the effect of the water column before the velocity analysis.
We show that the interval velocities obtained in this fashion are more stable than those computed from the conventional semblance
analysis. The initial velocity model thus obtained is updated using the tomographic velocity analysis to account for lateral
heterogeneity. The resultant interval velocity model shows large lateral velocity variations in the hydrate layer and some
low velocity zones associated with free gas at the location of structural traps. The reflection from the base of the gas layer
is also visible in the stacked seismic data. Vertical variation in hydrate distribution is assessed by analyzing the AVO response
at selected locations. AVO analysis is carried out after applying true amplitude processing. The average amplitudes of BSRs
are almost constant with offset, suggesting a fluid expulsion model for hydrate formation. In such a model, the hydrate concentrations
are gradational with maxima occurring at the base of hydrate stability zone. 相似文献
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Sampling effort required to recover the main gradients in marine benthic species composition 
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下载免费PDF全文 Marine benthic surveys and monitoring programs may have several goals. When the aim of such studies is to reveal and describe gradients in species composition, the gain in ecological insight achieved by the study depends on how well the spatial variability of species’ occurrence and abundance within the study area is covered by the sampling design. The common practice in such programs is to collect four or five grab samples from each visited site to capture the site's species composition. The rationale for this practice is based on the aim of capturing a large proportion of species at a specific site (i.e. point). We argue that this practice has been established without taking Iterative approaches into account, such as decreasing the sampling effort at each site and instead increase the number of sites visited. The collection and processing of data from marine sediment ecosystems are time‐consuming and, thus, expensive. Therefore, finding the optimal trade‐off between the number of sites visited and the number of samples per site is important. We examined this trade‐off by exploring how reduction of sampling effort per site affects the stability and recovery of gradients in species composition of marine benthic macrofauna. Our full data set consisted of four grab samples from each of 28 sites from the inner part of the Oslofjord, SE Norway. Procrustes analysis and calculation of Kendall's rank correlation coefficients showed that the main gradient in species composition extracted by detrended correspondence analysis of data sets with reduced per‐site sampling effort closely resembled the main gradient extracted for the full data set. Our results therefore suggest that marine benthic surveys that aim to identify the main gradient structure of species composition and relate this structure to main environmental complex gradients are likely to benefit from reducing the sampling effort at each site and, instead, increasing the number of visited sites. We argue that coverage of both the variation in species composition and the environment in the study area will then be improved. Monitoring programs with other aims than to identify the main gradients in species composition may also benefit from the adoption of a many‐sites, one‐sample sampling strategy. This may be particularly true if additional sampled sites are based on a stratified sampling strategy that ensures that the spatial variability in the study area is accounted for. 相似文献
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Cloning and sequence analysis of the partial sequence of the rbcL from Bryopsis hypnoides 总被引：1，自引：0，他引：1
TIAN Chao WANG Guangce YE Naihao ZHANG Baoyu FAN Xiaolei ZENG Chengkui 《海洋学报(英文版)》2005,24(5):150-161
1 IntroductionRibulose-1,5-bisphosphatecarboxylase/oxygenase(EC 4.1.1.39;Rubisco) plays an important role in photo-synthetic carbon fixation by controlling the initial stageof the Calvin cycle and possessing the functions of bothCO2 fixation and ribulose-1, 5-bisphosphate (RuBP)oxygenation. Rubisco is composed of eight large andeight small subunits in higher plants and green algae,and the large subunit is encoded by chloroplast genomeand the small subunit by nuclear genome. The gene en-cod… 相似文献
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北太平洋副热带逆流区海流的准90天振荡 总被引：1，自引：1，他引：1
根据 POCM模式输出的流场资料 (1993年 1月 1日～ 1998年 12月 31日 ) ,运用小波分析方法分析北太平洋副热带逆流区海流的季节内振荡特征 ,并用功率谱方法作了验证。结果表明 :在以 19.81°N为中心 ,18～ 2 2°N,16 0°E以西的西太平洋海域 ,海流具有显著的准 90 d振荡特征 ;该振荡对应的波长约为 86 5 km,沿 19.81°N该振荡信号自东向西传播的相速度约为 0 .0 9m/ s。从能量角度看 ,该振荡信号主要存在于 15 0 m以内的海洋次表层 ,2 2 2 .5 m深度能量是 6 2 .5 m能量的13%。 相似文献
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桩腿耦合装置(简称LMU)在平台浮托安装过程中上部组块插尖与导管架桩管对接期间起缓冲作用,是海上浮装的最重要装置之一。运用非线性有限元软件ABAQUS,对相同尺寸、受相同垂向载荷作用的有沙箱和无沙箱的LMU分别进行了显式准静态和动态数值模拟,并将计算结果进行对比,以考察沙箱对LMU力学特性的影响。结果表明,与无沙箱的LMU相比,有沙箱的LMU能够承受较大的外载荷作用,可提升外套筒钢材的使用效率,较迅速地降低载荷转移作业过程中整个平台的运动速度,提高平台浮托安装过程中能量吸收速率,并且能减小LMU在动态过程中的最大应力。 相似文献
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《Marine Policy》2014
The Marine Strategy Framework Directive, adopted by the EU, and several other initiatives to improve marine environmental management emphasize the need to integrate environmental and social analyses. This article proposes and tests a general Behavior-Pressure-State-Impact-Response (BPSIR) framework for identifying and structuring environmentally relevant social data. The framework is compatible with the widely applied Driver-Pressure-State-Impact-Response (DPSIR) framework, but emphasizes actors and their behavior and defines ‘impact’ more specifically. In particular, it distinguishes between: (i) actors directly involved in activities causing physical, chemical, and biological disturbances, and (ii) actors who indirectly affect marine resource use and the pressures on marine ecosystems. Three case studies of chemical and biological disturbances in the Swedish parts of the North and Baltic seas demonstrate the need to balance current ecosystem monitoring with systematically collected and organized data on social factors, i.e., both direct and indirect actors and stakeholders, their adaptation to policy measures, and the role of general trends in consumption and production. 相似文献
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GMRES方法在大型离岸结构水弹性分析中的应用 总被引：1，自引：1，他引：1
使用GMRES方法求解了大型离岸结构水弹性分析所获得的复系数线性方程组，并按照向后误差分析的方法，给出了它的终止准则。数值试验表明对于所考虑的问题，GMRES方法优于直接方法。 相似文献
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Optimization of the indophenol blue method for the automated determination of ammonia in estuarine waters 总被引：1，自引：0，他引：1
Existing automated methods for the determination of ammonia in natural waters suffer from serious ‘salt error’ in estuaries because of changes in pH, ionic strength and optical properties with salinity. A modified automated indophenol blue method is described which minimizes the ‘salt error’ to less than 8% over the entire salinity of estuaries. 相似文献