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21.
With the observational wind data and the Zebiak-Cane model, the impact of Madden-Julian Oscillation (MJO) as external forcing on El Ni(n)o–Southern Oscillation (ENSO) predictability is studied. The obs...  相似文献   
22.
A correlation analysis is performed to investigate the relationship between El Nino-Southern Oscillation (ENSO) and the Antarctic oscillation (AAO) at the quasi-quadrennial (QQ) timescale.It is found that the cold tongue index (CTI) and the AAO index (AAOI) are negatively correlated with about a 7-month lead-time,while they are positively correlated with about a 15-month lag-time.To further explore this relationship,complex empirical orthogonal function analysis is employed in the QQ sea level pressure (SLP) anomalies from 1951 to 2002.The results indicate that,during the ENSO cycle,there exists one kind of global tropical wave of wavenumber 1 (GTW1) propagating eastward.With the traveling of GTW1,the tropical SLP anomaly tends to intrude into the southern mid-latitudes.Accordingly,three strong signals travel synchronously along the circumSouth-Pacific path,and a relatively weak signal extends eastward and poleward over the South Ocean in the Atlantic-Indian Ocean sector.Following the propagation of these signals,the AAO phase tends to be reversed progressively.As a result,there exists an evident lead-lag correlation between CTI and AAOI.It can be concluded that ENSO plays a key role in the phase transition of AAO at the QQ timescale.It is also noticed that this regular relationship is only evident in the canonical ENSO events,for which sea surface temperature (SST) anomalies extend westward from the tropical eastern Pacific.On the other hand,the similar relationships are not found among those atypical ENSO events for which SST anomalies spread eastward from the central Pacific,such as the 1982-1983 ENSO event.  相似文献   
23.
Having recognized that it is the tropospheric temperature (TT) gradient rather than the land–ocean surface temperature gradient that drives the Indian monsoon, a new mechanism of El Niño/Southern Oscillation (ENSO) monsoon teleconnection has been unveiled in which the ENSO influences the Indian monsoon by modifying the TT gradient over the region. Here we show that equatorial Pacific coralline oxygen isotopes reflect TT gradient variability over the Indian monsoon region and are strongly correlated to monsoon precipitation as well as to the length of the rainy season. Using these relationships we have been able to reconstruct past Indian monsoon rainfall variability of the first half of the 20th century in agreement with the instrumental record. Additionally, an older coral oxygen isotope record has been used to reconstruct seasonally resolved summer monsoon rainfall variability of the latter half of the 17th century, indicating that the average annual rainfall during this period was similar to that during the 20th century. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
24.
The last 2014‐16 El Niño event was among the three strongest episodes on record. El Niño considerably changes annual and seasonal precipitation across the tropics. Here, we present a unique stable isotope data set of daily precipitation collected in Costa Rica prior to, during, and after El Niño 2014‐16, in combination with Lagrangian moisture source and precipitation anomaly diagnostics. δ2H composition ranged from ‐129.4 to +18.1 (‰) while δ18O ranged from ‐17.3 to +1.0 (‰). No significant difference was observed among δ18O (P=0.186) and δ2H (P=0.664) mean annual compositions. However, mean annual d‐excess showed a significant decreasing trend (from +13.3 to +8.7 ‰) (P<0.001) with values ranging from +26.6 to ‐13.9 ‰ prior to and during the El Niño evolution. The latter decrease in d‐excess can be partly explained by an enhanced moisture flux convergence across the southeastern Caribbean Sea coupled with moisture transport from northern South America by means of an increased Caribbean Low Level Jet regime. During 2014‐15, precipitation deficit across the Pacific domain averaged 46% resulting in a very severe drought; while a 94% precipitation surplus was observed in the Caribbean domain. Understanding these regional moisture transport mechanisms during a strong El Niño event may contribute to a) better understanding of precipitation anomalies in the tropics and b) re‐evaluate past stable isotope interpretations of ENSO events in paleoclimatic archives within the Central America region.  相似文献   
25.
Bases on the NCEP / NCAR reanalysis products, HadISST dataset, and data of tropical cyclone (TC)landfalling in the Chinese mainland during 1960-2019, the possible impacts of Indian Ocean Dipole (IOD) mode andIndian Ocean basin (IOB) mode on the last-TC-landfall date (LLD) and first-TC-landfall date (FLD), respectively, areinvestigated in this study. The LLD is in significantly negative correlation with autumn IOD on the interannual time-scale and their association is independent of El Ni?o-Southern Oscillation (ENSO). The LLD tends to be earlier when theIOD is positive while becomes later when the IOD is negative. An anomalous lower-level anticyclone is located aroundthe Philippines during October-November, resulting from the change of Walker circulation over the tropical Indo-westPacific Ocean forced by sea surface temperature (SST) anomalies related to a positive IOD event. The Philippinesanticyclone anomaly suppresses TCs formation there and prevents TCs from landfalling in the Chinese mainland due tothe anomalous westerly steering flows over southeast China during October-November, agreeing well with the earlierLLD. However, the robust connection between spring IOB and FLD depends on ENSO episodes in preceding winter.There is an anticyclonic anomaly around the Philippines caused by the tropical SST anomalies through modulating theWalker circulation during May-June when the IOB is warming in the El Ni?o decaying phase. Correspondingly, the TCsgenesis is less frequent near the Philippines and the mid-level steering flows associated with the expanded westernPacific subtropical high are disadvantageous for TCs moving towards southeast China and making landfall during May-June, in accordance with the later FLD. By contrast, cooling IOB condition in spring of a La Ni?a decaying year andnegative IOD cases during autumn could produce a completely reversed atmospheric circulation response, leading to anearlier FLD and a later LLD over the Chinese mainland, respectively.  相似文献   
26.
This study reveals that the interannual variability of the western edge of the western North Pacific (WNP) subtropical high (WNPSH) in early summer experienced an interdecadal decrease around 1990. Correspondingly, the zonal movement of the WNPSH and the zonal extension of the high-pressure anomaly over the WNP (WNPHA) in abnormal years possess smaller ranges after 1990. The different influences of the tropical SSTAs are important for this interdecadal change, which exhibit slow El Ni?o decaying pattern before 1990 while rapid transformation from El Ni?o to La Ni?a after 1990. The early summer tropical SSTAs and the relevant atmospheric circulation anomalies present obvious interdecadal differences. Before 1990, the warm SSTAs over the northern Indian Ocean and southern South China Sea favor the WNPHA through eastward-propagating Kelvin wave and meridional-vertical circulation, respectively. Meanwhile, the warm SSTA over the tropical central Pacific induces anomalous ascent to its northwest through the Gill response, which could strengthen the anomalous descent over the WNP through meridional-vertical circulation and further favor the eastward extension of the WNPHA to central Pacific. After 1990, the warm SSTAs over the Maritime Continent and northern Indian Ocean cause the WNPHA through meridional-vertical and zonal-vertical circulation, respectively. Overall, the anomalous warm SSTs and ascent and the resultant anomalous descent over the WNP are located more westward and southward after 1990 than before 1990. Consequently, the WNPHA features narrower zonal range and less eastward extension after 1990, corresponding to the interdecadal decease in the interannual variability of the western edge of the WNPSH. On the other hand, the dominant oscillation period of ENSO experienced an interdecadal reduction around 1990, contributing to the change of the El Ni?o SSTA associated with the anomalous WNPSH from slow decaying type to rapid transformation type.  相似文献   
27.
利用TRMM降水和ERA-Interim温度、比湿、环流场等再分析资料, 探讨了在1998-2018年冬季年际尺度海温变化对MJO的强度、结构和传播特征的影响。主要结论如下: 通过一种追踪MJO的方法在研究时间范围内共可挑选出50个MJO事件, 其中有14个MJO事件发生在El Ni?o期间, 25个发生在La Ni?a期间, 11个发生在ENSO正常年。El Ni?o年MJO会传播至更远的中东太平洋附近, 而La Ni?a年MJO事件趋于在西太平洋地区消亡, 这主要与东太平洋地区持续的季节内尺度的经向水汽输送有关。此外, 在印度洋和太平洋地区, El Ni?o年的MJO活动更强, 而在海洋性大陆附近, La Ni?a年的MJO活动略强一些。ENSO对MJO强度的影响主要通过影响MJO对流中心东侧水汽的输送, 水汽在异常东风气流的输送下穿过对流中心东边界进入对流中心, 进而造成MJO活动强度的差异。   相似文献   
28.
厄尔尼诺-南方涛动(El Niño-Southern Oscillation, ENSO)是地球气候系统中最强的年际变率信号, 起源于热带太平洋海气相互作用过程, 并对全球的天气和气候等产生显著的影响。过去几十年来, 广泛、深入而细致的海气相互作用研究致力于发展和改进海气耦合模式以用于ENSO模拟和预测, 各种类型的海气耦合模式应运而生。经过半个多世纪的努力, ENSO数值模式及其应用已经取得了巨大进展, 包括已发展了一些高度理想化的概念(concept)模型来解释ENSO准周期性循环(包括正负反馈机制等); 同时也已发展了几类复杂程度不同的海气耦合模式并用于对ENSO的真实模拟和实时预测等研究, 尤其是已能提前6个月或更长时间对ENSO事件的发生和发展等进行有效的实时预测。其中最为复杂的模式是基于原始方程组的大气环流模式(Atmospheric General Circulation Models, AGCMs)与海洋环流模式(Oceanic General Circulation Models, OGCMs)等所组成的环流型耦合模式(Coupled General Circulation Models, CGCMs), 这类模式变量取为完全变量的形式(如总的海表温度场, 其可以分解为气候态部分和年际异常部分), 还考虑了尽可能详尽的物理过程及其参数化方案。中间型耦合模式(Intermediate Coupled Models, ICMs)是一类介于高度理想化概念模型与复杂的环流型耦合模式之间的简化模式, 其对应的控制方程组采用距平形式, 直接取大气和海洋年际异常场作为预报变量(如海表温度年际异常), 而相应的气候平均态部分则由对应的观测资料来给定; 大气与海洋模式间的耦合采用异常耦合(anomaly coupling)。混合型耦合模式(Hybrid Coupled Models, HCMs)是另一类简化的海气耦合模式, 其中海洋或大气模式有一个分量模式采用了简化的距平类模式(类似于ICMs),而另一个分量模式则采用环流型模式(General Circulation Models, GCMs); 如可采用统计的大气风应力年际异常模式与OGCM间的耦合而构建一种HCMOGCM,也可采用简化的海洋距平类模式(如ICM中的海洋分量模式)与AGCM间的耦合而构建另一种HCMAGCM。历史上, ICMs、HCMs和CGCMs等这几类耦合模式都在ENSO理论体系的发展、数值模拟和实时预测等方面都起到了重要作用。本文主要回顾作者与合作者所研发的ICMs和HCMs的构建、特点和应用例子等。  相似文献   
29.
On the basis of the data of the partial pressure of CO2 (PCO2)and the concentration of the total dissolved CO2(TCO2) in surface water during the expeditions in Nov.-Dec. 1991, the world ocean circulation experiment (WOCE) and Oct. 1992-Mar. 1993, the tropical ocean-global atmosphere coupled ocean-atmosphere response experiment (TOGA COARE) in the western tropical Pacific and of the comparison with data from 1986 to 1990 TOGA expeditions and that from Japan Meteorological Agency, the response of CO2 in surface water to ENSO event is proved. The CO2 signals indicated that the air-sea system in the western and central tropical Pacific from 1991 to 1993, except for a short period in autumn of 1992, was in a strong state of ENSO.
The change of CO2 in the floating stations near 2°S, 155°E from Nov. 1992 to Mar. 1993 reflected the change of currents, water mass and its thermal and salt content during the forming and developing of ENSO.  相似文献   
30.
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