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1.
用赤道太平洋长达21a的温度资料以及经验正交函数(EOF)分析方法,讨论了在5°S-5°N平均纬向垂直剖面上赤道太平洋垂向温度梯度距平的时空变化,得到了一些有意义的结果。赤道太平洋垂向温度梯度距平EOF分析第1模态的正/负位相反映了El Nino/La Nina发生前赤道太平洋温跃层的分布,第2模态的正/负位相反映了El Nino/La Nina鼎盛以及开始衰减时赤道太平洋温跃层的分布。根据我们对赤道太平洋温跃层核心位置的定义,在El Nino向LaNina转换的过程中,赤道东太平洋温跃层上升了30-40m,而赤道中太平洋温跃层先是上升了40-50m,然后又下降了40-50m,赤道西太平洋温跃层下降了90m;随着赤道西太平洋暖水的堆积以及东移,温跃层首先在赤道西太平洋加深,El Nino发生前赤道中东太平洋温跃层开始加深,El Nino达到鼎盛时赤道西太平洋温跃层抬升,而赤道中东太平洋温跃层加深;赤道太平洋垂向温度梯度距平EOF分析第1特征向量的时间系数与Nino3区的SST距平有非常好的相关,并且超前于Nino3区的SST距平,超前3个月的相关系数高达0.7017,超前6个月的相关系数高达0.6467,因此可以用该量来预测Nino3区的SST距平。 相似文献
2.
内蒙古准格尔旗树轮年表的建立及其气候意义 总被引：2，自引：0，他引：2
通过在内蒙古准格尔旗建立树轮宽度年表、早材宽度年表和晚材宽度年表，并和邻近呼和浩特气象站的资料进行相关分析，结果表明各年表和2—6月的降水量之和呈正相关关系。在准格尔旗西南方向、相距约500km的贺兰山树木生长主要受到5—7月降水量的支配。从这两个区域气象站资料的对比中发现，月降水量、月平均温度的多年平均值在年内表现出非常好的一致性，对应单月月降水量、月平均温度序列显著相关，反映了其受共同的气候驱动因子支配。从两个区域年表对各自气象站气候因子的响应可以看出，树木的生长都主要受到生长季前期和生长季早期降水量的支配。 相似文献
3.
ENSO对天目山柳杉树轮同位素的影响 总被引：8，自引：0，他引：8
在Nin↑～o3,4区SST序列和Jones等的SOI序列基础上，通过主分量分析方法建立了一个ENSO指数序列。并与根据天目山柳杉树轮碳，氢同位素组成比所建立的树轮指数序列进行相关分析。结果表明，天目山树轮指数与ENSO指数有很好的相关性，尤其与前2年的ENSO指数相关显著。说明ENSO对该地区树木的生长和同位素的分馏有影响，也说明天目山地区的树木年轮对于ENSO事件具有一定的记录能力。 相似文献
4.
热带太平洋-印度洋上层热含量年际变化的主模态 总被引：3，自引：0，他引：3
利用多种海洋资料,采用经验正交函数分解(EOF)与合成分析等方法研究了热带太平洋-印度洋热含量年际变化的主要模态及其对应的转换过程。结果表明其第一模态对应El Nino事件成熟位相时的空间分布,即热带西太平洋和东印度洋为一冷中心,西南印度洋和赤道东太平洋为暖中心;第二模态对应着El Nino事件过渡期的空间分布,太平洋10°N附近以及赤道带为变化中心,而印度洋的变化中心主要在苏门答腊岛西部的赤道东印度洋海区。这2个模态基本刻画了ENSO循环过程中热带两大洋热含量变化的关键海区。利用合成分析结果与EOF分解结果的相似性,探讨了EOF分解前两个模态之间的转换过程,发现第一模态可能主要是通过海洋波动的传播过程调整到第二模态的,而第二模态还可以作为El Nino或La Nina事件的预报因子。此外,分析结果还表明,El Nino事件与La Nina事件对应的热含量变化并不是反对称的。 相似文献
5.
本文用最近 20 年赤道太平洋温度、流场资料,诊断了绝热不可压缩热平衡方程中纬向对流项,并且利用 EOF 分析方法,讨论了纬向对流距平变化及其与 El Nino/La Nina 的关系。分析发现:赤道太平洋温度纬向对流距平 EOF 分析第一模态反映了在经向的振荡,第二模态反映了在纬向的振动,它们都与 El Nino/LaNina 有密切的联系。这两个模态占了总量的 70%左右。纬向温度对流距平在 3°S~3°N、3°S 以南和 3°N 以北分为正负相间的三个不同的区域,当 3°S 以南和 3°N 以北的区域温度纬向对流正/负距平沿着斜温层向西太平洋移动时,赤道区域的温度纬向对流负/正距平则穿越斜温层向东太平洋移动,形成以赤道为对称的南北两个回路。对应赤道,在 3°S 以南和 3°N 以北区域的纬向温度对流距平并不是对称的,它们在位相、中心强度和中心强度位置上都是不同的,其中 3°N 以北与赤道区域形成一个比较明显的回路,而赤道以南的回路就不是那么明显。在赤道西太平洋暖池,温度的纬向对流有很大的贡献。在 El Nino 发生前一年,赤道西太平洋暖池,主要暖的对流发生在赤道和其以南地区。 相似文献
6.
众所周知，ENSO(El Nino/ Southern Oscillation)是发生在热带太平洋的年际时间尺度上最强的气候信号，与 El Nino (La Nina)相应的正(负)海温距平(SSTA)主要分布于赤道中东太平洋地区(Rasmusson et al.，1982)。相对于热带太平洋的年际ENSO现象，人们注意到北太平洋海平面气压(SLP)存在更长周期的年代际变化(Trenberth et al.，1994)，有人认为这与北太平洋的表层温度(SST)变化有关(Latif et al.，1994)，也有人认为与热带SST的异常关系更为密切(Jacobs et al.，1994)。20世纪80年代后的ENSO事件和20世纪60，70年代有明显的差别(Wang，1995)，20世纪90年后El Nino发生频数增加，并且在1997和1998年出现了20世纪最强的一次Nino事件(McPhaden，1999)。
因此，不论是作为大气年代际变化可能的一个驱动因子，还是作为年际ENSO的背景场，从整体上了解太平洋SST的年代际时间尺度上的时、空变化特征都是十分重要的。 相似文献
7.
陕西黄龙树轮年表的建立及其2-3月降水记录 总被引：5，自引：0，他引：5
通过两组油松树轮宽度的研究,建立了陕西黄龙地区过去近200 a来的树轮STD、RES、ARS年表,树轮宽度在20世纪20年代有过明显的下降,1929年前后达到年轮宽度最低值,与历史记载的自民国11年以来连续干旱时期相吻合(1922-1932年).经过相关函数、响应函数分析,发现树轮宽度与生长季当年2-3月降水显著正相关,在此基础上设计了转换方程,重建了过去200 年来黄龙地区早春2-3月降水历史,重建序列的解释方差为44.3%(F=16.298,p<0.001).功率谱分析检测到2-3月降水存在7.69、6.90、6.06、5.13、5.00、4.88、4.65、2.02、2.00 年的周期. 相似文献
8.
本文分析了1996－1998年逐月太平洋海面距平资料及热带太平洋海面赤道槽、脊及上层海水体积变化资料，清楚地看到20世纪最强的一次EL97／98事件，不仅基本特征明显，而且太平洋海面变化与其有密切的响应关系，受此启发，作者依据1975－2000年间赤道槽、脊、逆流槽及热带太平洋上层海水体积变化的历史资料，经年周期滑动平均数据处理和采用基于均生函数的正交化筛选建模方法，建立了各单预测因子周期外延的ENSO预测模式。结果表明，本预测模式除把单预测因子序列的历史变化趋势反映和预测出来，还揭示了历史上的El Nino事件发生了经滑动平均后的赤道脊或热带太平洋上层海水体积的峰值附近，结束于谷底附近，La Nina则出现在滑动平均后的赤道脊谷底上升至均值期间的一般规律性。根据各单预测因子周期外延曲线的峰、谷变化，预测下一次El Nino事件将于2001年下半年至2002年上半年期间形成。 相似文献
9.
珠江口近30a的SST变化特征分析 总被引：5，自引：0，他引：5
根据珠江口多个定点站近30a表层海水温度（SST）实测资料和气象站观测的气温资料，使用功率谱和小波分析方法，计算分析珠江口SST变化特点、上升趋势及其与El Nino／La Nino的响应关系．结果表明各月SST存在着1-2℃的海域差异，SST的年较差达10～11℃，SST的季节变化与全球气候变暖呈显著相关．1971-2003年SST呈显著上升趋势，其线性上升率为0．019～0．034℃／a，且珠江口外高于口内．El Nino／La Nino事件对珠江口SST变化的影响并非单一的对应关系． 相似文献
10.
北京地区近70年来白皮松树轮纤维素的碳稳定同位素与气候变化 总被引：5，自引：0，他引：5
对采自北京大学校园内的白皮松（Pinus bungeana)树轮α-纤维素的δ^13C进行了分析，结合北京气象台的气象记录，建立树轮δ^13C与气候各要素的回归方程，重建值与观测值吻合较好，表明北京地区树轮α-纤维素的碳稳定同位素与1928-1999年3-9月的平均气温及6-9月的平均降雨量显著相关，重δ^13C对应于3-9月的低温和6-9月的少雨，轻δ^13C对应于3-9月的高温和6-9月的多雨。而3-9月的温度正好是适宜树木生长的光合作用所需要的最佳温度，6-9月正好是一年中降雨最充沛的时期，由此认为；树轮δ^13C值与生长季节的降水和气温密切相关，可以考虑作为季风盛行地区的气候替代性指标。在一定程度上反映了季风盛行区白皮松树轮纤维素碳稳定同位素与气候因子的关系。 相似文献
11.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
13.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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15.
《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
16.
The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
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The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献
19.
Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
20.
Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献