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The Pacific Decadal Oscillation 总被引：60，自引：1，他引：60
The Pacific Decadal Oscillation (PDO) has been described by some as a long-lived El Niño-like pattern of Pacific climate variability, and by others as a blend of two sometimes independent modes having distinct spatial and temporal characteristics of North Pacific sea surface temperature (SST) variability. A growing body of evidence highlights a strong tendency for PDO impacts in the Southern Hemisphere, with important surface climate anomalies over the mid-latitude South Pacific Ocean, Australia and South America. Several independent studies find evidence for just two full PDO cycles in the past century: “cool” PDO regimes prevailed from 1890–1924 and again from 1947–1976, while “warm” PDO regimes dominated from 1925–1946 and from 1977 through (at least) the mid-1990's. Interdecadal changes in Pacific climate have widespread impacts on natural systems, including water resources in the Americas and many marine fisheries in the North Pacific. Tree-ring and Pacific coral based climate reconstructions suggest that PDO variations—at a range of varying time scales—can be traced back to at least 1600, although there are important differences between different proxy reconstructions. While 20th Century PDO fluctuations were most energetic in two general periodicities—one from 15-to-25 years, and the other from 50-to-70 years—the mechanisms causing PDO variability remain unclear. To date, there is little in the way of observational evidence to support a mid-latitude coupled air-sea interaction for PDO, though there are several well-understood mechanisms that promote multi-year persistence in North Pacific upper ocean temperature anomalies. 相似文献
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作者研究差分方程Δnx (t) + p (t)Δn-1x(t) + H (t,x(g(t) ) ) =0 ,其中 P∶ D→ R,H∶ D×R→ R,0≤ p (t)≤ 1,g∶ D→ D,limt→∞t∈ Dg(t) =∞ ,D={ t0 ,t0 + 1,t0 + 2 ,… } .得到保证这个方程的一切解都振动的若干充分条件 相似文献
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We studied the relationship between the dominant patterns of sea surface temperature (SST) variability in the North Pacific
and the North Atlantic. The patterns are known as the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation
(AMO). In the analysis we used two different observational data sets for SST. Due to the high degree of serial correlation
in the PDO and AMO time series, various tests were carried out to assess the significance of the correlations. The results
demonstrated that the correlations are significant when the PDO leads the AMO by 1 year and when the AMO leads the PDO by
11–12 years. The possible physical processes involved are discussed, along with their potential implication for decadal prediction. 相似文献
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黑潮入侵南海的强弱与太平洋年代际变化及厄尔尼诺-南方涛动现象的关系 总被引：2，自引：1，他引：1
在黑潮入侵南海强弱的问题上,到底是太平洋年代际变化(Pacific Decadal Oscillation,PDO)还是厄尔尼诺-南方涛动(El Nio-Southern Oscillation,ENSO)现象在起关键作用,目前还存在着较大争议。本文先以高盐水作为黑潮入侵强弱的示踪物,用120°E断面的高盐水数据和北赤道流分叉点(North Equator Current Bifurcation,NEC-Y)的南北变动进行相关分析,接着,进一步用学者所用的黑潮入侵指数(KI指数,Kuroshio intrusion index和NEC指数,North Equatorial Current index)与北赤道流分叉点南北变动进行相关分析。最后,用EMD(Empirical Mode Decomposition)方法和相关关系分析法分别分析了PDO指数、Nio3.4指数与北赤道流分叉点南北变动的关系并用NECP风场数据探讨其影响机制。结果表明:(1)通过对120°E断面的高盐水的KI指数、NEC指数与NEC-Y的相关分析,表明了北赤道流分叉点的南北变动能够很好地指代黑潮入侵南海的强弱;(2)通过PDO指数和Nio3.4指数与北赤道流分叉点的南北变动的相关性分析,发现PDO指数、Nio3.4指数与北赤道流分叉点的南北变动都具有较好的相关性,都在0.5水平。这些良好的相关性表明了PDO和ENSO对黑潮入侵南海的强弱都具有重要的影响;(3)当处于厄尔尼诺年(拉尼娜)时,赤道太平洋发生西(东)风异常,使得北赤道流分叉点偏北(南),使吕宋岛东侧的黑潮流速减弱(加强),黑潮入侵南海增强(减弱);当PDO处于暖(冷)阶段时,会加强热带太平洋的西(东)风异常,使得黑潮入侵南海增强(减弱)。 相似文献
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作者研究差分方程Δ 相似文献
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V. A. Bezverkhny 《Izvestiya Atmospheric and Oceanic Physics》2007,43(3):317-322
Characteristics of the Arctic Oscillation and El Niño-Southern Oscillation effects manifested on interannual scales in the equatorial stratosphere are determined. Wavelet analysis of local phase shifts, coherence, and correlation is used to obtain correlation portraits of the largest factors of climate variability against the background of coherent variations in the equatorial stratospheric wind speed at the 50- and 15-hPa pressure levels. It is shown that the Arctic Oscillation and El Niño-Southern Oscillation signals may reach the tropical stratosphere. The signals are easily identified in a wide range of scales, including quasi-biennial, 3-to 5-year, and 10-to 11-year periods. The results obtained reflect a coherent pattern of the manifestation of these signals at the selected stratospheric levels. It is found that the El Niño-Southern Oscillation effect at periods close to 10–11 years reaches the stratospheric level rather rapidly, in the same or next month, while the effects of the Arctic Oscillation index are delayed by nine months. The estimates obtained show that a phase shift of almost 180° in the Arctic Oscillation index relative to the equatorial stratospheric wind occurred in almost all of the range of interannual periods in 1978 and 1992. For the El Niño-Southern Oscillation, an increase in local correlations on a scale of 3-to 5-year variations was observed in 1980–1990, a 180° phase shift occurred in 1992, and the correlation with stratospheric wind increased in 1992–2004. The estimates obtained are indicative of a change in the atmospheric circulation pattern that took place in the Northern Hemisphere in 1978–1991. 相似文献
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Using the Comprehensive Ocean-Atmosphere Data Set (COADS), wind, surface pressure and SST fields in the Equatorial Eastern Pacific and the Equatorial South Indian Ocean were analysed comprehensively.lt is pointed out that the seesaw between surface pressure in the Equatorial South Indian Ocean and the Equatorial Southeast Pacific causes the seesaw between the wind fields in the two areas, and the seesaw of wind fields results in the seesaw of SST between Indonesia and the Equatorial Eastern Pacific. El Nino is the response of ocean to the forcing of monsoon system in the Indian Ocean and the trade system in the Pacific. 相似文献
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A class of coupled system of the El Niño/La Niña-Southern Oscillation (ENSO) mechanism is studied. Using the perturbed theory, the asymptotic expansions of the solution for ENSO model are obtained and the asymptotic behavior of solution for corresponding problem is considered. 相似文献
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线性时滞微分方程解的振动准则 总被引：1，自引：0，他引：1
武冬 《中国海洋大学学报(自然科学版)》2002,32(6):1023-1029
建立线性时滞微分方程x (t) ∑ni=1 pi(t) x(t- τi(t) ) =0 , t≥ to的所有解振动的新准则。当 pi(t) ,τi(t) (i=1 ,2 ,… ,n)均为常数时 ,条件是充分必要的。 相似文献
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该文利用 [2 ]的方法讨论了一阶超前型微分方程 x′(t) =p(t) x(τ(t) ) ,t≥ 0 ,τ(t) >t的振动性 ,建立了几个新的振动准则 ,改进了 [1]中的相应结果 相似文献
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ＳｏｕｔｈｅｒｎＯｓｃｉｌｌａｔｉｏｎｆｏｒｃｅｄｂｙｈｅａｔｓｏｕｒｃｅａｎｄｔｏｐｏｇｒａｐｈｙＱｉａｎＷｅｉｈｏｎｇ,ＹｏｕＸｉｎｔｉａｎ（ＲｅｃｅｉｖｅｄＪｕｎｅ５,１９９６,ａｃｃｅｐｔｅｄＤｅｃｅｍｂｅｒ９,１９９６）Ａｂｓｔｒａｃｔ──... 相似文献
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By using archival monthly data for 100 yr, we analyze the statistical structure of time series characterizing the variability of the Azores High and Iceland Low. We show that there exists a long-term tendency towards approach of the centers of action of the atmosphere (CAA) in the North Atlantic and their strengthening. At the same time, quasiperiodic decadal intensification of the CAA is accompanied by an increase in the distance between them. In the spectra of sea-level pressure in the Azores High and Iceland Low, significant peaks for periods of 2–5 and 10 yr are strongly pronounced. Furthermore, oscillations with a period 50 yr are clearly seen. The main contribution to the interannual changes in the index of the North-Atlantic Oscillation (NAO) is made by pressure variability in the Iceland Low. Different ways of behavior are characteristic of the CAA for time scales of 2–7, 7–15, and more than 15 yr. Each of these variability intervals is analyzed separately. We established a significant correlation between the index of the Southern Oscillation (SO) and characteristics of the CAA of the North Atlantic only for time scales of 7–15 yr. It demonstrates that, as the SO index increases in autumn, the pressure at the center of the Azores High grows and the latitudinal distance between the Azores High and Iceland Low decreases, i.e., the zonal circulation in the North Atlantic becomes more intense. We also discuss possible mechanisms of the obtained statistical relations. 相似文献
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一类非线性中立型时滞微分方程的振动性 总被引：3，自引：0，他引：3
研究了一类非线性中立型时滞微分方程(x(t)-P(t)g(x(t-τ)))′ Q(t)h(x(t-δ))=0解的振动性,其中P,Q∈C([t0,∞),R),g,h∈C(R,R),τ>0,δ≥0。通过建立这个方程与某个线性中立型微分方程的联系导出了1个较简单的振动准则。 相似文献
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地形与热源强迫下的南方涛动 总被引：1，自引：0，他引：1
用El Nino和La Nina位相时的海温异常和地形作为大气下垫面的异常强迫,引入IAP的两层原始方程大气环流模式,模拟出了南方涛动的典型结构.当去掉地形后,仅仅由海温异常也能模拟出太平洋东西部的气压异常振荡,但太平洋东部振荡中心的位置并不与观测的一致.由此可见,观测到的南方涛动是在实际地形下对全球海温异常的响应. 相似文献
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On the basis of more than 200-year control run, the performance of the climate system model of Chinese Academy of Sciences(CAS-ESM-C) in simulating the El Ni?o-Southern Oscillation(ENSO) cycle is evaluated, including the onset, development and decay of the ENSO. It is shown that, the model can reasonably simulate the annual cycle and interannual variability of sea surface temperature(SST) in the tropical Pacific, as well as the seasonal phase-locking of the ENSO. The model also captures two prerequisites for the El Ni?o onset, i.e., a westerly anomaly and a warm SST anomaly in the equatorial western Pacific. Owing to too strong forcing from an extratropical meridional wind, however, the westerly anomaly in this region is largely overestimated. Moreover, the simulated thermocline is much shallower with a weaker slope. As a result, the warm SST anomaly from the western Pacific propagates eastward more quickly, leading to a faster development of an El Ni?o. During the decay stage, owing to a stronger El Ni?o in the model, the secondary Gill-type response of the tropical atmosphere to the eastern Pacific warming is much stronger, thereby resulting in a persistent easterly anomaly in the western Pacific. Meanwhile, a cold anomaly in the warm pool appears as a result of a lifted thermocline via Ekman pumping. Finally, an El Ni?o decays into a La Ni?a through their interactions. In addition, the shorter period and larger amplitude of the ENSO in the model can be attributed to a shallower thermocline in the equatorial Pacific, which speeds up the zonal redistribution of a heat content in the upper ocean. 相似文献