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1.
应用NCAR CAM3全球大气环流模式以及NCEP/NCAR再分析资料,研究了不同海域(全球、热带外、热带、热带印度洋—太平洋、热带印度洋及热带太平洋)的海表温度异常对夏季南压高压年代际变化的影响。结果表明,全球、热带、热带印度洋—太平洋和热带太平洋这些海域的海表温度异常都对南亚高压强度、面积、南界、西伸脊点和东伸脊点的1970s中后期年代际变化有重要影响:热带太平洋是关键海区,其海表温度第三模态(“三明治”式异常分布型)的变化与南亚高压的这些特征指数的年代际变化关系密切;热带印度洋的海表温度异常,主要是其第一模态(热带印度洋全区一致变化型)的变化与南亚高压强度、面积、南界和西伸脊点的年代际变化关系较密切,热带印度洋也是影响南亚高压年代际变化的关键海区;这两个关键海区的海表温度异常对南亚高压年代际变化影响的主要差异在于:热带太平洋海表温度异常能对南亚高压的东伸脊点的年代际变化有重要影响,而热带印度洋的海表温度异常对其影响小;热带太平洋和热带印度洋这两个海区的海表温度异常均可通过影响热带对流层大气温度的变化进而使南亚高压发生变化;热带外的海表温度异常对南亚高压的年代际变化影响小。 相似文献
2.
采用1950-2000年逐月观测的不同海域(全球、热带外、热带、热带印度洋-太平洋、热带印度洋及热带太平洋)海表温度分别驱动NCAR CAM3全球大气环流模式,进行了多组长时间积分试验,对比ERA-40和NCEP/NCAR再分析资料,讨论了这些海域海表温度异常对东亚夏季风年代际变化的影响。数值试验结果表明:全球、热带、热带印度洋-太平洋和热带太平洋海表温度变化对东亚夏季风的年代际变化具有重要作用,均模拟出了东亚夏季风在20世纪70年代中后期发生的年代际减弱现象,以及强、弱夏季风年代夏季大气环流异常分布的显著不同,这与观测结果较一致,表明热带太平洋是影响东亚夏季风此次年代际变化的关键海区;利用热带印度洋海表温度驱动模式模拟出的东亚夏季风在20世纪70年代中后期发生年代际增强现象,即当热带印度洋海表温度年代际偏暖(冷)时,东亚夏季风年代际增强(减弱),与热带太平洋海表温度变化对东亚夏季风年代际变化的影响相反;热带太平洋海表温度年代际背景的变化对东亚夏季风在20世纪70年代中后期的年代际减弱有重要作用。 相似文献
3.
不同海域SSTA对东半球越赤道气流年代际变化影响的数值模拟研究 总被引：1，自引：0，他引：1
采用1950—2000年逐月观测的不同海域（全球、热带外、热带、热带印度洋-太平洋及热带太平洋）海表温度,分别驱动NCAR CAM3全球大气环流模式,进行了多组长时间积分试验,对比ERA-40再分析资料,讨论了这些海域海表温度异常（SSTA）对东半球越赤道气流年代际变化的影响。数值试验结果表明,全球、热带、热带印度洋-太平洋及热带太平洋海表温度变化分别驱动NCAR CAM3全球大气环流模式,均能模拟出索马里、120 ?E和150 ?E越赤道气流在1970年代中后期由弱变强的年代际变化特征,其中模拟的索马里越赤道气流年代际变化特征及其与东亚夏季风年代际变化关系均与观测结果较一致,而热带外海表温度驱动全球大气环流模式未能模拟出此年代际变化现象,表明全球、热带、热带印度洋-太平洋及热带太平洋海表温度变化均对索马里越赤道气流在1970年代中后期的年代际变化具有重要作用,热带太平洋是关键海区;索马里越赤道气流的年代际变化与热带太平洋海温年代际背景变化密切相关,当热带太平洋处于暖（冷）背景年代,热带东太平洋海温异常从北到南呈“＋、－、＋”（“－、＋、－”）“三明治”式距平分布,有利于赤道东太平洋南北两侧产生一对距平反气旋（气旋）,然后可能通过“大气桥”的作用,与热带印度洋赤道南北两侧的一对距平气旋（反气旋）联系起来,从而引起索马里越赤道气流强度的增强（减弱）。 相似文献
4.
中国北方秋雨与热带中太平洋海表冷却的关系 总被引：7，自引：1，他引：6
本文利用1951～2011年中国160站降水、NCEP/NCAR再分析资料和NOAA延长重建海表温度 (NOAA extended reconstructed SST) 资料,研究了中国9月北方秋雨的年际变化特征及其成因,并用ECHAM5大气环流模式开展了数值试验,最后对2011年9月历史罕见秋雨进行了分析。研究发现,中国北方秋雨有明显的年际和年代际变化,19世纪60年代到1980年代中期,北方秋雨偏多,1950年代、1980年代后期和1990年代秋雨偏少。北方秋雨与西太平洋副热带高压的西伸有密切联系,北方秋雨偏多时,副热带高压偏西偏强,有利于偏南风向北输送水汽并在中国北方辐合。西太平洋副热带高压的加强西伸与热带中太平洋的海表冷却密切有关,偏低的热带中太平洋海表温度(CTSSTI)使其上的对流活动受到抑制,热带西太平洋对流异常旺盛,在西北太平洋出现异常反气旋,加强东亚—西北太平洋的EAP波列,引起西太平洋副热带高压明显西伸,导致秋雨偏多。反之,热带中太平洋海表偏暖,副热带高压偏弱偏南,秋雨偏少。2011年9月北方秋雨的环流异常及成因与统计分析和数值模拟结果基本一致。 相似文献
5.
利用1957-2002年ERA-40月平均再分析资料以及不同海域(全球、热带外、热带、热带印度洋—太平洋、热带印度洋和热带太平洋等)1950-2000年逐月观测海表温度,驱动NCARCAM3全球大气环流模式,根据模拟结果,分析讨论了冬季东亚副热带西风急流的变化特征及其与海表温度异常的关系.表明:1957-2001年冬季东亚副热带西风急流有增强的趋势,且具有准3 a的显著周期.热带海表温度异常,特别是热带太平洋海表温度异常对东亚副热带西风急流变化有重要影响,即当热带太平洋海表温度升高时,东亚副热带西风急流增强. 相似文献
6.
夏季北印度洋海温异常对西北太平洋低层反气旋异常的影响 总被引：7，自引：0，他引：7
采用1957—2002年850 hPa风场的ERA-40再分析资料,分析得知西北太平洋低层环流存在着明显的年际变化。这种年际变化表征了西北太平洋夏季风的年际变化,并且会影响东亚夏季风的变化。用Hadley海表面气压以及海表温度资料诊断得到,这种夏季西北太平洋反气旋异常（WPAC,northwest Pacific anomalous anticyclone）的年际变化与北印度洋同期海表温度变化存在很好的相关。用偏相关方法消除N ino3.4信号的同期线性影响,这种同期相关更加显著,而西南热带印度洋的同期海温与WPAC的相关并不显著。数值试验结果表明,北印度洋存在正海温异常时,北印度洋降水偏多,同时伴随着西北太平洋反气旋异常。当只有西南热带印度洋有正海温异常时,北印度洋会出现东风异常且降水减少,而西北太平洋有弱的气旋异常。数值模式结果与观测数据的诊断结果相吻合,说明当夏季北印度洋海表温度为正异常时,可能会产生西北太平洋反气旋异常。 相似文献
7.
太平洋中低纬度海表温差与副热带高压异常的数值模拟 总被引：1，自引：0，他引：1
中国夏季天气变化与太平洋副热带高压关系密切,而中低纬度热力差异可能是副热带高压的强度和位置发生变化的莺要原因,文中利用NCAR/NCEP再分析位势高度、垂商速度和海表温度场资料,在对太平洋海表温度合理分区的基础上.根据海表温度EOF分解的第一模态时间系数与副热带高压的相关关系,定义了太平洋中、低纬度海表温差指数,并通过统计分析和数值模拟方法分析了温差的年代际变化特征及其对副热带高压的影响.结果表明:副热带高压的变化分别与中纬度太平洋的(30°-40°N,180°-140°W)和低纬度太平洋的(10°S-10°N,140°～100°W)两块区域海温关系密切,对由此两区域定义的温差指数分析发现,1976年前后温差指数出现一次显著的由弱变强的年代际突变,且温差的年代际变化特征与副热带高压异常有很好的对应关系,温差大值年,副热带高压偏强,面积增大,西伸尤其明显;温差小值年,副热带高压偏弱,面积减小,东撤明显.进一步的统计分析和NCAR/CAM3.0模式数值模拟都发现,夏季中低纬海表温差增大将引起哈得来环流加强,副热带的下沉速度加大,使副热带高压增强;夏季中低纬海表温差减小将引起哈得来环流减弱,副热带的下沉速度减小,使副热带高压减弱.冈此夏季中低纬海表温差的变化是导致副热带高压强度和位置异常的重要原因之一. 相似文献
8.
太平洋—印度洋海温与我国东部旱涝型年代际变化的关系 总被引：4，自引：2，他引：2
对我国东部各区域的夏季降水的正交小波分解表明,其大于28年的分量可以很好地表示华北和长江中下游地区在20世纪70年代前后旱涝相反的年代际变化特征。合成分析表明,北太平洋、热带印度洋海温和东亚高空急流与我国东部夏季旱涝型的年代际变化密切相关。东亚高空急流和西太平洋副热带高压在70年代前后的年代际差异对旱涝型发生年代际变化起到重要作用;北太平洋和热带印度洋海温的年代际变化近百年来是协同一致的,二者有可能共同对旱涝型的变化产生影响。进一步分析指出,北太平洋—热带印度洋海温的变化与急流和副高的南北位置在年际和年代际尺度上都密切相关。可见,北太平洋-热带印度洋海表温度异常(SSTA)对于我国东部旱型涝的年代际变化确实具有重要的预示作用。 相似文献
9.
采用1961—2014年逐月全球标准化降水蒸散指数(Standardized Precipitation Evapotranspiration Index,SPEI)数据集、ORA-S4海温资料及NCEP/NCAR再分析资料,对华南地区秋季干旱的年代际转折及其与热带印度洋热含量的关系进行了研究。结果表明:华南秋季SPEI主要表现为全区一致变化型,且具有明显的年代际变化特征,在1988年发生了年代际转折,转折后(前)为偏旱(涝)期。进一步分析表明,华南秋季SPEI与同期热带西印度洋海洋热含量变化呈显著的正相关关系,即当秋季热带西印度洋热含量偏低时,华南地区SPEI偏小,易发生干旱。热带西印度洋热含量异常影响华南秋季干旱的可能机制为:秋季热带印度洋热含量变化表现为""型的东西向偶极子分布,即当热带西印度洋热含量偏低时,热带东印度洋热含量将会偏高;而热带东印度洋热含量偏高将会使热带东印度洋—西太平洋海表温度偏高、外逸长波辐射偏小、降水增多,凝结潜热释放增强,产生偏强的东亚Hadley环流,使华南地区存在异常下沉运动,不利于产生降水;热带东印度洋—西太平洋海表温度偏高,还会使西北太平洋副热带高压位置偏西、面积偏大,西北太平洋存在气旋性环流异常,使华南地区受偏北气流异常控制,从而削弱了向华南地区的水汽输送。热带东印度洋—西太平洋海表温度年代际变化是热带西印度洋热含量异常影响华南秋旱年代际变化的重要环节,因此用NCAR CAM5.1全球大气环流模式进行了热带东印度洋—西太平洋海表温度年代际变化的敏感性试验,证实该区海表温度年代际升高对华南秋季年代际干旱具有重要作用。 相似文献
10.
西北太平洋副热带高压(西太副高)是影响东亚夏季气候的主要环流系统,其年际变率受热带多个海区的海-气相互作用过程的调控。为明确影响夏季西太副高的关键海区及其影响机制,在总结最近十余年来相关研究进展的基础上,归纳出影响夏季西太副高年际变率的5个关键海区,包括赤道中东太平洋、热带印度洋、副热带西北太平洋、海洋大陆附近海区以及热带大西洋。阐述了这5个关键海区的海温异常影响西太副高年际变率的机制,并探讨了5个关键海区海温异常的形成机制。围绕夏季西太副高的年际变率,回顾了当前气候模式的模拟和预测研究的现状。最后,提出了本领域亟待解决的关键科学问题,展望未来可能的研究热点。 相似文献
11.
NUMERICAL SIMULATION OF SSTA IMPACTS UPON THE INTERDECADAL VARIATION OF THE CROSS-EQUATORIAL FLOWS IN EASTERN HEMISPHERE 总被引：1，自引：0，他引：1
Impacts of regional sea surface temperature(SST)anomalies on the interdecadal variation of the cross-equatorial flows(CEFs)in Eastern Hemisphere are studied using numerical simulations with a global atmospheric circulation model(NCAR CAM3)driven with 1950-2000 monthly SSTs in different marine areas(the globe,extratropics,tropics,tropical Indian Ocean-Pacific,and tropical Pacific)and ERA-40reanalysis data.Results show that all simulations,except the one driven with extratropical SSTs,can simulate the interdecadal strengthening of CEFs around Somali,120oE,and 150oE that occurred in the midand late-1970s.Among those simulated CEFs,the interdecadal variability in Somali and its interdecadal relationship with the East Asian summer monsoon are in better agreement with the observations,suggesting that changes in the SSTs of tropical oceans,especially the tropical Pacific,play a crucial role in the interdecadal variability of CEFs in Somali.The interdecadal change of CEFs in Somali is highly associated with the interdecadal variation of tropical Pacific SST.As the interdecadal warmer(colder)SST happens in the tropical Pacific,a"sandwich"pattern of SST anomalies,i.e."+,-,+"("-,+,-"),will occur in the eastern tropical Pacific from north to south with a pair of anomalous anticyclone(cyclone)at the lower troposphere;the pair links to another pair of anomalous cyclone(anticyclone)in the tropical Indian Ocean through an atmospheric bridge,and thus strengthens(weakens)the CEFs in Somali. 相似文献
12.
Intensification of decadal and multi-decadal sea level variability in the western tropical Pacific during recent decades 总被引：1，自引：0，他引：1
Weiqing Han Gerald A. Meehl Aixue Hu Michael A. Alexander Toshio Yamagata Dongliang Yuan Masayoshi Ishii Philip Pegion Jian Zheng Benjamin D. Hamlington Xiao-Wei Quan Robert R. Leben 《Climate Dynamics》2014,43(5-6):1357-1379
Previous studies have linked the rapid sea level rise (SLR) in the western tropical Pacific (WTP) since the early 1990s to the Pacific decadal climate modes, notably the Pacific Decadal Oscillation in the north Pacific or Interdecadal Pacific Oscillation (IPO) considering its basin wide signature. Here, the authors investigate the changing patterns of decadal (10–20 years) and multidecadal (>20 years) sea level variability (global mean SLR removed) in the Pacific associated with the IPO, by analyzing satellite and in situ observations, together with reconstructed and reanalysis products, and performing ocean and atmosphere model experiments. Robust intensification is detected for both decadal and multidecadal sea level variability in the WTP since the early 1990s. The IPO intensity, however, did not increase and thus cannot explain the faster SLR. The observed, accelerated WTP SLR results from the combined effects of Indian Ocean and WTP warming and central-eastern tropical Pacific cooling associated with the IPO cold transition. The warm Indian Ocean acts in concert with the warm WTP and cold central-eastern tropical Pacific to drive intensified easterlies and negative Ekman pumping velocity in western-central tropical Pacific, thereby enhancing the western tropical Pacific SLR. On decadal timescales, the intensified sea level variability since the late 1980s or early 1990s results from the “out of phase” relationship of sea surface temperature anomalies between the Indian and central-eastern tropical Pacific since 1985, which produces “in phase” effects on the WTP sea level variability. 相似文献
13.
Predictability of the western North Pacific summer climate demonstrated by the coupled models of ENSEMBLES 总被引：1，自引：0，他引：1
The Asian monsoon system, including the western North Pacific (WNP), East Asian, and Indian monsoons, dominates the climate of the Asia-Indian Ocean-Pacific region, and plays a significant role in the global hydrological and energy cycles. The prediction of monsoons and associated climate features is a major challenge in seasonal time scale climate forecast. In this study, a comprehensive assessment of the interannual predictability of the WNP summer climate has been performed using the 1-month lead retrospective forecasts (hindcasts) of five state-of-the-art coupled models from ENSEMBLES for the period of 1960–2005. Spatial distribution of the temporal correlation coefficients shows that the interannual variation of precipitation is well predicted around the Maritime Continent and east of the Philippines. The high skills for the lower-tropospheric circulation and sea surface temperature (SST) spread over almost the whole WNP. These results indicate that the models in general successfully predict the interannual variation of the WNP summer climate. Two typical indices, the WNP summer precipitation index and the WNP lower-tropospheric circulation index (WNPMI), have been used to quantify the forecast skill. The correlation coefficient between five models’ multi-model ensemble (MME) mean prediction and observations for the WNP summer precipitation index reaches 0.66 during 1979–2005 while it is 0.68 for the WNPMI during 1960–2005. The WNPMI-regressed anomalies of lower-tropospheric winds, SSTs and precipitation are similar between observations and MME. Further analysis suggests that prediction reliability of the WNP summer climate mainly arises from the atmosphere–ocean interaction over the tropical Indian and the tropical Pacific Ocean, implying that continuing improvement in the representation of the air–sea interaction over these regions in CGCMs is a key for long-lead seasonal forecast over the WNP and East Asia. On the other hand, the prediction of the WNP summer climate anomalies exhibits a remarkable spread resulted from uncertainty in initial conditions. The summer anomalies related to the prediction spread, including the lower-tropospheric circulation, SST and precipitation anomalies, show a Pacific-Japan or East Asia-Pacific pattern in the meridional direction over the WNP. Our further investigations suggest that the WNPMI prediction spread arises mainly from the internal dynamics in air–sea interaction over the WNP and Indian Ocean, since the local relationships among the anomalous SST, circulation, and precipitation associated with the spread are similar to those associated with the interannual variation of the WNPMI in both observations and MME. However, the magnitudes of these anomalies related to the spread are weaker, ranging from one third to a half of those anomalies associated with the interannual variation of the WNPMI in MME over the tropical Indian Ocean and subtropical WNP. These results further support that the improvement in the representation of the air–sea interaction over the tropical Indian Ocean and subtropical WNP in CGCMs is a key for reducing the prediction spread and for improving the long-lead seasonal forecast over the WNP and East Asia. 相似文献
14.
中低纬海气相互作用的耦合模态变化研究 总被引：2，自引：0，他引：2
利用1948—2003年的NCEP再分析资料和英国气象局Hadley气候预测和研究中心的海表面温度资料,从整体分析地球中低纬三大洋海气耦合系统的角度出发,使用SVD方法研究中低纬海气相互作用的耦合变化。结果表明,中低纬海气相互作用是一个有机的耦合整体,其变化不管从年际还是年代际上都存在耦合相关性,这一点给我们提出了一个新的研究全球范围海气耦合变化的思路。提取的海气耦合基本模态的正、负异常年份的海温和风场异常合成分析结果显示,当赤道东太平洋的海水偏暖时,热带印度洋和热带大西洋的海水也偏暖,热带西太平洋直至中纬度太平洋的海温总体偏冷。就印度洋而言非洲大陆以南30~50 °S的大片海区存在明显的海温负异常。北美洲大陆的东岸30 °N以北和南美洲大陆的东岸30 °S以南的海区都为明显的海温负异常。当赤道东太平洋的海水偏冷时各大海区的海温分布情况反之。 相似文献
15.
Tropical storms: representation and diagnosis in climate models and the impacts of climate change 总被引：4，自引：0，他引：4
R. E. McDonald D. G. Bleaken D. R. Cresswell V. D. Pope C. A. Senior 《Climate Dynamics》2005,25(1):19-36
Tropical storms are located and tracked in an experiment in which a high-resolution atmosphere only model is forced with observed sea surface temperatures (SSTs) and sea ice. The structure, geographic distribution and seasonal variability of the model tropical storms show some similarities with observations. The simulation of tropical storms is better in this high-resolution experiment than in a parallel standard resolution experiment. In an anomaly experiment, sea ice, SSTs and greenhouse-gas forcing are changed to mimic the changes that occur in a coupled model as greenhouse-gases are increased. There are more tropical storms in this experiment than in the control experiment in the Northeast Pacific and Indian Ocean basins and fewer in the North Atlantic, Northwest Pacific and Southwest Pacific region. The changes in the North Atlantic and Northwest Pacific can be linked to El Niño-like behaviour. A comparison of the tracking results with two empirically derived tropical storm genesis parameters is carried out. The tracking technique and a convective genesis parameter give similar results, both in the global distribution and in the changes in the individual basins. The convective genesis parameter is also applied to parallel coupled model experiments that have a lower horizontal resolution. The changes in the global distribution of tropical storms in the coupled model experiments are consistent with the changes seen at higher resolution. This indicates that the convective genesis parameter may still provide useful information about tropical storm changes in experiments carried out with models that cannot resolve tropical storms. 相似文献
16.
The monthly mean sea surface temperature data of 6 areas are used to study the El Nino/Southern Oscillation signals in the global tropical ocean. These areas are in the 5oN-5oS latitude zone at 1) eastern Pacific (110o-l40oW), 2) western Atlantic (30o-50oW), 3) eastern Atlantic (10oW-10oE), 4) western Indian Ocean (30o-50oE), 5) central Indian Ocean (70o-90oE) and 6) far western Pacific (120o-140oE), and the data cover the 120-month period of December 1968 to November 1978.A power spectrum analysts shows that the characteristic time of the El Nino/Southern Oscillation (about 3-4 years) appears not only in the eastern Pacific but also in other areas of the tropics except for the western Pa-cific, where the spectrum is of white noise. The amplitude of oscillation in the eastern Pacific is about 4 times larger than the others, making the El Nino/Southern Oscillation signal the strongest in this area. According to a cross-spectrum analysis, there is no time lag between the variation in the central Indian Ocean and that in the eastern Pacific. These two areas oscillate simultaneously and comprise the main feature of the El Nino/ Southern Oscillation. Other tropical areas are related with time lags, as shown by correlation and coherence calculations.It should be noted that the sea surface temperature in the eastern Pacific oscillates in phase with that in the Indian Ocean, while the pressure oscillations in these two areas are out of phase with each other, according to the Southern Oscillation definition. It is suggested that the Southern Oscillation cannot be explained simply by the sea surface temperature anomalies.Variations in the far western equatorial Pacific do not have the time scale of the El Nino/Southern Oscilla-tion, perhaps because it is a buffer zone between the monsoon system and the trade wind system. 相似文献
17.
热带海洋海气相互作用的区域差异 总被引：7，自引：3，他引：7
用NCEP/NCAR40年再分析1000hPa月平均风场资料及COADS月平均海表温度资料，对热带西、中、东太平洋、热带大西洋和印度洋五个区域的海气异常作了奇异值分解（SVD）。比较区域间SVD的主要参数和分析第一奇异向量及其时间系数表明，热带海气相互作用可区分为三类；热带东、中太平洋属‘单元型’，ENSO是唯一重要的过程，热带西太平洋、印度洋属‘二元型’，除了ENSO过程，还应存在唯一重要的过程；热带西太平洋，印度洋属‘二元型’，除了ENSO过程还应存在另一重要过程，热带大西洋属‘多元型’，其构成复杂，ENSO循环则不明显。 相似文献