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1.
Two onboard observation campaigns were carried out in the western boundary region of the Philippine Sea in December 2006 and January 2008 during the 2006/07 El Niño and the 2007/08 La Niña to observe the North Equatorial Current (NEC), Mindanao Current (MC), and Kuroshio current system. The NEC and MC measured in late 2006 under El Niño conditions were stronger than those measured during early 2008 under La Niña conditions. The opposite was true for the current speed of the Kuroshio, which was stronger in early 2008 than in late 2006. The increase in dynamic height around 8°N, 130°E from December 2006 to January 2008 resulted in a weakening of the NEC and MC. Local wind variability in this region did not appear to contribute to changes in the current system.  相似文献   

2.
V. N. Stepanov 《Oceanology》2009,49(3):310-319
In this paper, we present the results of modeling of El Niño events using a simple model of a classical oscillator with decay under external forcing. The sea surface temperature in the East Pacific and the mean thermocline depth in the Equatorial Pacific correspond to the roles of the momentum and position, respectively. The external forcing of the system is determined by two factors: the short-period meridional mass fluctuations in the Pacific sector of the Southern Ocean due to the joint effect of the atmospheric variability over the Antarctic Circumpolar Current, bottom topography, and coastlines; and the variability of western winds in the tropics. Under such conditions, oscillations of El Niño type arise in the model as a result of propagation of signals generated in the Southern Ocean (due to the fluctuations of meridional transport fluxes and the variability of western winds in the tropics). These signals propagate over the Equatorial Pacific as fast wave processes. It is shown that external forcing is the main factor in establishing the oscillation pattern of the model characteristics variability.  相似文献   

3.
On the basis of the statistical analysis of the global fields of outgoing long-wave radiation, surface temperature of the ocean, and components of the wind velocity, we analyze five El Niño events observed in 1963–1983. We study the dependence of the global circulation in the lower atmosphere on the behaviour of the temperature of the surface waters and outgoing long-wave radiation in the west part of the tropical zone of the Pacific Ocean. General regularities and specific features of different El Niño events are also analyzed.  相似文献   

4.
The coastal waters of Peru and Chile are among the most productive of the world's oceans. A striking source of interannual variability in this upwelling ecosystem, El Niño, results in large population and community variations. During El Niño the seasonal upwelling ceases and warm, clear oceanic waters occur close inshore, setting a unique oceanographic scenario in which the performance of populations and communities can be studied. While most attention has been focused on the pelagic components of such systems, numerous changes occur in inshore, benthic populations. Likewise, little attention has been paid to the critical role of humans as predators or active users of inshore, benthic resources. Humans as components of the ecosystem can impose significant alterations on population and community structure. In this paper the fishery statistics of three economically important inshore, benthic resources (the gastropod Concholepas concholepas, the cephalopod Octopus vulgaris and the kelp Lessonia nigrescens) are analysed in relation to the strong 1982/83 El Niño event. In particular, trends are described for landings in the far northern regions of Chile, where the marked effect of El Niño was concurrent with high levels of exploitation of C. concholepas and L. nigrescens.  相似文献   

5.
The article deals with the influence of wind and atmospheric pressure on the barotropic variability of the Antarctic Circumpolar Current (ACC). This effect is studied using a global barotropic model under idealized and realistic atmospheric forcings. The results of barotropic modeling demonstrate that variations in the wind forcing over the ACC, together with the effects of the topography and coastline, lead to the variability in the meridional water flux in the Southern Ocean. The variability of these fluxes is negatively correlated with the wind strength over the ACC. A possible link between the short-period variability of the water flux in the Pacific sector of the Southern Ocean and El Niño is demonstrated using 3D ocean modeling and correlation analysis. It is shown that the variability of the meridional water flux caused by atmospheric perturbations over the ACC can lead to short-period density anomalies in the Southern Ocean north of 47°S, which later can be transferred to low latitudes by means of the wave mechanism described in [15] and strongly influence the tropical region.  相似文献   

6.
The relations between the processes occurring in the equatorial latitudes of the Pacific and Atlantic oceans were studied on the basis of the Granger causality analysis and a simulation of phase dynamics using the indices of the El Niño-Southern Oscillation (ENSO) and the equatorial Atlantic mode (EAM). Data on the monthly means of the sea-surface temperature over the period 1870–2006 for the Niño 3 (5° S-5° N, 150° W-90° W) and Niño 3.4 (5° S-5° N, 170° W-120° W) regions in the Pacific and the Atlantic 3 region (20° W-0, 3° S-3° N) in the Atlantic Ocean were used as the ENSO and EAM indices. The statistically significant influence of the EAM on the ENSO is noted. The lag time of this influence is estimated at two months. No significant reverse effect is revealed. An increase in the EAM’s influence on the ENSO was observed in the second half of the 20th century.  相似文献   

7.
Sea‐level data from two sites in northern New Zealand, along with the Southern Oscillation Index (SOI), are analysed for interannual and decadal variability using wavelets. The analysis shows, using statistically significant wavelet power, there is a significant relationship between mean sea level (MSL) and SOI. However, the relationship is highly variable, both in magnitude and in the range of time‐scales over which it occurs. This non‐stationarity necessitates the use of techniques such as wavelets for analysis. An interdecadal response in MSL around northern New Zealand has been isolated, with shifts occurring in 1950 and the late 1970s. This behaviour in MSL appears to coincide with shifts in the Pacific Decadal Oscillation, thought previously to be largely centred in the North Pacific. A strong correlation between SOI and sea surface temperature (SST) is also demonstrated. This relationship appears to be stable in magnitude (a large change in SOI produces a large change in SST) and to occur over the same range of time‐scales. More SST and MSL data are required for other parts of New Zealand to determine whether these findings apply elsewhere.  相似文献   

8.
Izvestiya, Atmospheric and Oceanic Physics - Regional anomalies in the frequency of atmospheric blockings in the Northern Hemisphere detected on the basis of reanalysis data since 1979 during...  相似文献   

9.
The statistical analysis of the secular hydrometeorological data sets revealed a particular El Niño impact on the climatic system of the Indian Ocean domain. The spatial distribution of the sequent anomalies showed prominent local effects depending on the climatic season as well. The El Niño signal turned out to be better visible within the considered fields during the transitional phases of the Indian monsoon, when its activity is rather weak, unstable, or even almost absent. The hints of certain phase shifts found to appear in the monsoon cycle coincided timely with the El Niño event. First of all, this concerns the hamper effect, which being applied to the wind stress field in the spring season leads to the later onset of the wet southwest monsoon, which is accompanied by a precipitation shortage over huge inhabited territories. During the northeast monsoon, the equatorial-tropic part of the domain is affected by El Niño in such a way that the eastern near surface air transport arises and after this the Winter Monsoon Equatorial Current notably increases its speed. Quantitative estimations showed that the El Niño signal’s relative energy in the Indian Ocean area is nearly an order of magnitude lower when compared to the total monsoon energy. This implies that the total impact of El Niño upon the Indian Ocean domain’s climate system could not lead to a fundamental change of its regime, as, for example, a reversal of the monsoon circulation.  相似文献   

10.
Many infaunal sandy-bottom communities in shallow waters of the Peruvian upwelling system are inhabited by large coexisting populations of the surf clams Mesodesma donacium and Donax peruvianus as well as by the anomuran mole crab Emerita analoga. Under normal conditions, equilibrium states are possible with any one of these species dominating. A Mesodesma community south of Lima in Peru was investigated over 2,5 years, covering periods prior to, during and after the El Niño (EN) of 1982–83. It was revisited several times later. Growth, recruitment and mortality and, therefore, production of Mesodesma and Donax varied to some extent before EN. However, during the event Mesodesma became locally extinct and had not recolonized the area by July 1986, three years after the return of normal temperatures. Donax, which took over immediately after EN, never reached the densities of the former dominant Mesodesma. Emerita remained a rare species as well, whereas spionid polychaetes increased in importance. The medium-term effect of the exceptionally strong EN of 1982–83 appears to have been very marked on Peruvian sandy beaches. A comparison is made with other shallow-water communities of the upwelling system, and the importance of EN in terms of oscillations of clam stocks off Peru and Chile is discussed.  相似文献   

11.
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12.
Thirty La Niña events have been selected from monthly mean sea surface temperature (SST) data of the Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) and Centennial Observation-Based Estimates (COBE SST2) datasets from 1870 to 2013 based on a criterion of –0.5°С for a cold anomaly in the Niño 3.4 region (5° N–5° S, 170°–120° W) and its minimum duration of 5 months. The selected events are classified by hierarchical clustering analysis according to two characteristics: geographic coordinates and SST anomalies during the mature phase of La Niña. The objective classification method identifies two types of La Niña differing by the evolution of negative SST anomalies in the equatorial Pacific and by the Southern Oscillation Index.  相似文献   

13.
A set of spatially nested circulation models is used to explore interannual change in the northeast Pacific (NEP) during 1997–2002, and remote vs. local influence of the 1997–1998 El Niño on this region. Our nested set is based on the primitive equations of motion, and includes a basin-scale model of the north Pacific at ∼40-km resolution (NPac), and a regional model of the Northeast Pacific at ∼10-km resolution. The NEP model spans an area from Baja California through the Bering Sea, from the coast to ∼2000-km offshore. In this context, “remote influence” refers to effects driven by changes in ocean velocity and temperature outside of the NEP domain; “local influence” refers to direct forcing by winds and runoff within the NEP domain. A base run of this model using hindcast winds and runoff for 1996–2002 replicates the dominant spatial modes of sea-surface height anomalies from satellite data, and coastal sea level from tide gauges. We have performed a series of sensitivity runs with the NEP model for 1997–1998, which analyze the response of coastal sea level to: (1) hindcast winds and coastal runoff, as compared to their monthly climatologies and (2) hindcast boundary conditions (from the NPac model), as compared to their monthly climatologies. Results indicate penetration of sea-surface height (SSH) from the basin-scale model into the NEP domain (e.g., remote influence), with propagation as coastal trapped waves from Baja up through Alaska. Most of the coastal sea-level anomaly off Alaska in El Niño years appears due to direct forcing by local winds and runoff (local influence), and such anomalies are much stronger than those produced off California. We quantify these effects as a function of distance along the coastline, and consider how they might impact the coastal ecosystems of the NEP.  相似文献   

14.
文中综述了El Ni(?)o现象的调整、监测及研究的进展,同时指出了尚待进一步研究的问题。此外,还简介了根据“中美热带西太平洋海气相互作用联合研究”四个航次的考察资料并结合美国NOAA提供的SST和夏威夷大学Wyrtkl博士赠送的水位资料对1986—1987El Ni(?)o期间的海洋事件的研究结果。  相似文献   

15.
Ecological data for the Atlantic humpback dolphin Sousa teuszii are scant. Six on-effort Sousa teuszii sightings were recorded during 817.6?km of boat-based effort in the Río Nuñez region of Guinea during October and November 2013. Two incidental sightings were also reported. Groups comprised 1–25 animals. Photo-identification produced a minimum population estimate of 47 animals. Most sightings (n = 5) were located close (<1?km) to shore along a 5.7?km stretch of coast on the west side of Île de Taïdi, primarily over shallow, sand–mud habitat. Two very distinctive individuals were present in all four Taïdi photo-identification encounters, suggesting high site fidelity and stable associations. Two sightings occurred in the outer Río Nuñez Estuary much farther from the coast (5–12?km) but in relatively shallow water (≤15?m) over sand–mud sediment. Focal follows (n = 5: 0.2–3.8?h duration) produced 9.02?h of behavioural data. Travel (51%), foraging (39%) and feeding (9.2%) dominated, with Taïdi dolphins spending more time foraging and feeding than the outer estuary groups. Three individuals had linear-severed dorsal fins consistent with injuries from fishing line. Some management implications of variation in habitat, site fidelity and movements of Sousa teuszii groups are discussed.  相似文献   

16.
前 言 E1 Ni(?)o现象越来越引起人们的注意。因为E1 Ni(?)o现象经常伴随着出现全球大气的异常。E1 Ni(?)o年会使原来干旱的赤道东太平洋地带有强烈的降水。南美和北美沿岸也常造成洪水灾害。1982年强E1 Ni(?)o年中加利福尼亚的洪水造成了几亿美元的损失。而印度尼西亚和澳大利亚以及南非却会遭受持久的干旱。E1 Ni(?)o现象对我国的气候也有明显的影响,有人认为我国东北地区夏季的低温冷害和南方梅雨的多寡与E1 Ni(?)o现象有关。 近年来,对E1 Ni(?)o现象的研究已作了很多工作。本文试图对E1 i(?)o现象的研究概况作一简要的介绍。  相似文献   

17.
本文利用1949—1984年西北太平洋地区的台风资料,分析了近赤道的西北太平洋台风与E1Nino的关系。提出了一个利用西北太平洋近赤道台风预报E1Nino的方法,预报结果是令人满意的。  相似文献   

18.
本文通过统计分析,发现西太平洋赤道雨连续3个月出现降水量为正距平,且距平大于200mm时,则未来1—2个月内发生厄尔尼诺(E1 Nino,下同)事件的可能性十分大。由这一相关事实出发,并从动力学进行探讨。初步认为,西太平洋赤道雨是通过降水量连续偏多改变赤道太平洋上空的Walker环流形势,产生Kelvin波,使赤道太平洋表层有热量自西向东传,叠加在赤道东太平洋和秘鲁外海表面的辐射加热场上,从而引发厄尔尼诺事件的出现。  相似文献   

19.
本文拟从赤道波导作用这一侧面探讨E1 Ni(?)o(厄尔尼诺)事件发生的机制。通过求解运动方程,得到赤道Kelvin(开尔文)波动解。假定运动过程绝热,如考虑平流输送作用,可给出亦道Kelvin波引起E1 Ni(?)o事件发生前期亦道中、东太平洋SST的局地变化和海洋上层热含量变化的定性解析表达式。表达式表明SST异常及上层热含量的变化均随赤道Kelvin波向东传播。利用赤道Kelvin波还可解释1982—1983年E1 Ni(?)o事件前期风场异常的作用,前期(?)(SST)/(?)t为正时SST异常的时,空分布以及(?)(SST)/(?)t为正时SST异常之所以自西向东传播的原因。因此,有理由认为亦道Kelvin波可能是激发更E1 Ni(?)o事件发生的一种机制。  相似文献   

20.
Concentrations of dissolved sulfate and sulfur isotopic ratios of dissolved sulfide in surface sediments of the Peru shelf and upper slope indicate that the sediments can be divided into two depth intervals based on the dominant biogeochemical reactions. Although rates of bacterial sulfate reduction are high throughout Peru surface sediments, chemistry of the upper interval (<10–20 cm) is dominated by chemoautotrophic oxidation of dissolved sulfide and elemental sulfur, while the lower interval (>10–20 cm) is dominated by dissimilatory sulfate reduction. In three of the four cores examined here, pore water concentrations of sulfate in the top 10 cm of the sediment are significantly higher than those of the overlying seawater. Peak sulfate concentrations in pore water (37–53 mmol/l) are ∼1.3–1.9 times that of seawater sulfate and are located 1–6 cm below the sediment/water interface (SWI). The excess sulfate is most likely produced by oxidation of elemental sulfur coupled to reduction of nitrate, a reaction mediated by a facultative chemoautotrophic sulfide-oxidizing bacterium, Thioploca spp. Numerical simulations demonstrate that the anomalously high concentrations of dissolved sulfate can be produced by steady-state or non-steady-state processes involving high rates of bacterial oxidation of elemental sulfur. If bacterial sulfur oxidation is a transient phenomenon, then it is probably triggered by seasonal or El Niño-induced changes in water-column chemistry of the Peru undercurrent.  相似文献   

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