首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
结合观测的海表温度距平(SSTA)对925hPa NCEP/NCAR再分析风应力距平(以下简称NCEP风应力距平)资料与FSU风应力距平资料进行了比较分析。对比分析了分别以NCEP、FSU风应力距平作为初始强迫风场时的Zebiak-Cane海气耦合模式(简称ZC耦合模式)的预报能力。结果表明:1980、1990年代NCEP风应力距平较FSU风应力距平与观测SSTA匹配更为合理。NCEP风应力距平不仅较FSU风应力距平对ZC海洋模式初始化效果好,尤其在1990年代更为显著,而且在1980、1990年代以NCEP风应力距平替代FSU风应力距平作为ZC耦合模式的初始强迫风场,都提高了该耦合模式预报能力,尤其是可提前6-8个月成功地预报出1997/1998年EI Nifio事件。进一步分析表明,在1997/1998年EI Nifio事件前兆、爆发阶段,NCEP风应力距平驱动海洋模式产生的SSTA比FSU风应力距平驱动海洋模式产生的SSTA更接近观测SSTA的水平冷、暖分布特征,这为ZC耦合模式提供了更为合理的预报初始强迫场,从而有利于提高其预报能力。  相似文献   

2.
对改进初始强迫风场后的Zebiak-Cane海气耦合模式预报性能进行了全面评估。结果表明:1)耦合模式在20世纪90年代预报能力小于80年代;提前0~5个月的耦合模式预报能力小于同期持续预报能力,之后则相反;耦合模式对Nino3区指数预报能力最强。2)在1997/1998年El Nino事件期间,耦合模式对东太平洋SSTA场预报能力大于其对中西太平洋SSTA场的预报能力,且提前0~2个月之后的耦合模式对东太平洋SSTA场预报能力远远大于持续预报。  相似文献   

3.
使用一个动力海洋与统计大气耦合的热带太平洋模式,对20 世纪90 年代的厄尔尼诺事件进行了数值模拟和预报。结果表明,模式能较好地再现3 次暖事件的发展和演化过程,也能模拟1995/1996 年的冷海温过程。预报试验的结果指出,20 世纪 90 年代发生的厄尔尼诺事件具有其特殊性,很难在发展阶段作出准确预报,而一旦形成后,模式仍可对这类事件的成熟位相阶段作出大致提前 6 个月的有效预报。文中还用该模式对 1997 年的热带太平洋海表温度作了预报试验,预测 1997 年年底可能发生一次新的厄尔尼诺事件。关键词:20 世纪90 年代厄尔尼诺,简单海气耦合模式,预报试验。  相似文献   

4.
The numerical simulations,hindcasts and verifications of the tropical Pacific sea surface temperature anomaly(SSTA) have been conducted by using a dynamical tropical Pacific ocean-atmosphere coupled model named NCCo.The results showed that the model had performed reasonable simulations of the major El Nino episodes in the history,and the model forecast skill in 1990s had been significantly improved.NCCo model has been used to predict the tropical Pacific SSTA since January 1997.The comparisons between predictions and observations indicated that the occurrence,evolution and ending of the 1997-1998 El Nino episode have been predicted fairly well by using this model.Also,the La Nina episode that began in the autumn of 1998 and the developing tendency of the tropical Pacific SSTA during the year 1999 have been predictedsuccessfully.The forecast skills of NCCo model during the 1997-1999 El Nino and La Nina events are above 0.5 at 0-14 lead months.  相似文献   

5.
为了分析ElNio事件发生和消亡中热带太平洋纬向风应力的动力作用,建立一个类似于Zebiak的简单热带海洋数值模式,在观测到的风应力异常的强迫下,模拟赤道太平洋地区1971年1月至1998年8月海表温度异常的变化。结果表明,模式对观测的Nio3区海表温度异常(SSTA)有很好的模拟能力。模拟和观测Nio3区SSTA之间的相关系数可达0.90。模式对ElNio事件期间赤道太平洋海表温度异常随时间变化也有较好的模拟能力。为了分析ElNio期间SSTA的空间分布及其随时间变化的动力学机制,还对19861989年ENSO循环期间赤道太平洋地区观测的SSTA的传播特征及其形成机制进行了分析。模式较好地模拟出了观测到的赤道太平洋地区SSTA的传播特征,即从1986年底至1987年4月,SSTA具有向东传播的特征,从1987年6月至1988年2月具有向西传播的特征。动力学分析的结果表明,赤道中西太平洋地区的纬向风应力异常对ElNio事件的发生和消亡具有重要作用。赤道中西太平洋地区的西风异常可强迫出东传的Kelvin波,这个东传的Kelvin波对正SSTA的东传起主要作用,当这个东传的Kelvin波到达东边界,由于东边界的反射作用,在东边界产生西传的Rossby波,这个西传的Rossby波对赤道中东太平洋地区正SSTA的西传起主要作用。东传Kelvin波和反射的Rossby波对ElNio期间赤道东太平洋正SSTA二次峰值的形成具有重要作用。  相似文献   

6.
将 1 960~ 1 991年的月平均 FSU风应力资料分解为旋转部分和辐散辐合部分 ,分别用以强迫模式海洋。所用的模式为一个 2层热带太平洋区域海洋模式。结果表明 ,就季节变化而言 ,不论是用旋转分量还是散合分量强迫海洋 ,都不能产生合理的冷舌 ,哪怕将旋转或散合分量放大一倍或缩小二分之一 ,也不能使冷舌的强度和分布得到合理的改善。若采用气候平均的含有季节变化的风应力 (未对旋转和辐散分量进行分离 ) ,则可产生与实际相符的海表温度分布。在此基础上 ,分别叠加旋转和辐散分量的年际异常部分 ,通过对海洋的强迫 ,可产生海表温度异常。在年际异常旋转分量的强迫下 ,可产生较强的 SSTA振荡且具有明显的 ENSO周期 ;而在辐散辐合年际异常风应力的强迫下 ,则产生较弱的 SSTA,且振荡频率较高 ,ENSO周期不很明显。这些结果说明 ,风应力的涡旋和辐散辐合分量在海温季节变化和年际变化的形成中具有不同的作用 ,即合理的冷舌分布需要风应力旋转分量和散合分量同时作用于海洋方可产生 ,而仅有异常风应力的旋转强迫就可产生合理的 EL Nino/ La Nina现象。同时 ,风应力的辐散辐合分量在海洋平均状态的形成过程中是重要的 ,但在 EN-SO过程中就对海洋的作用而言则不如旋转分量重要。  相似文献   

7.
基于NCEP、SODA等再分析资料,采用合成分析和2.5层简化海洋模型数值模拟等方法,分析了El Ni?o和正印度洋偶极子(IOD)事件不同配置情形下印度洋海温异常的演变特征,并重点探讨了联合IOD和独立IOD事件中,关键海区海温异常的发展演变及其可能机制。对于联合IOD事件,初期马里沿岸的增暖可能对其发生起主要的激发作用;而对于独立IOD事件的发生,则可能是赤道东南印度洋的降温起主导作用。不同类型IOD事件中,热带印度洋海表温度异常(SSTA)和海面高度异常(SSHA)的演变特征有明显差别,孟加拉湾上空降水异常所起的作用也不一样,印度洋不同海区混合层温度异常的演变机制也有显著不同。基于2.5层简化海洋模式结果的分析表明,各个海区的热力、动力过程在不同IOD事件有着不同的作用。例如在索马里沿岸海区:对于联合IOD事件,西印度洋赤道东风异常和索马里沿岸东北风异常,有利于该海区出现纬向平流热输送和海表热通量正异常,从而增暖。而对于独立IOD事件,阿拉伯海上空的强西南风异常,加强了索马里沿岸底层冷水的上翻和海表的热通量损失,导致前期纬向平流和夹卷混合的负异常以及后期海表热通量的负异常,使得该海区变冷。   相似文献   

8.
Using the sea surface temperature and wind anomalies(SSTA and SSWA for short) of the tropical Pacific from January 1970 to December 1989,main spatial patterns of tropical Pacific SSTA and SSWA coupling features in the transform course from the warm phase to the cold phase of El Nino-southern Oscillation(ENSO) cycles are discussed.The main conclusions are as follows:(1)air-sea coupling patterns at the mature stage of El Nino(La Nina) are main spatial ones of tropical Pacific SSWA and SSTA coupling:(2)at the mature stage of El Nino,the interaction of the anticyclonic anomaly wind,generated by the forcing of distinct meridional SSTA gradient in the Northern Hemisphere tropical central Pacific.with the California cold current and SSTA is mainly responsible for weakening of El Nino;(3)the second sea temperature increase along the South American coast in the decaying course of El Nino results from the eastward movement of the weakened positive SSTA in the tropical central-eastern Pacific forced by anomalous west wind stress:(4)La Nina results from the joint effect of Walker circulation,Ekman drift and negative SSTA in the tropical central-eastern Pacific.  相似文献   

9.
Using the sea surface temperature and wind anomalies(SSTA and SSWA for short)of thetropical Pacific from January 1970 to December 1989,main spatial patterns of tropical PacificSSTA and SSWA coupling features in the transform course from the warm phase to the cold phaseof El Nino-southern Oscillation(ENSO)cycles are discussed.The main conclusions are as follows:(1)air-sea coupling patterns at the mature stage of ElNino(La Nina)are main spatial ones of tropical Pacific SSWA and SSTA coupling:(2)at themature stage of El Nino,the interaction of the anticyclonic anomaly wind,generated by the forcingof distinct meridional SSTA gradient in the Northern Hemisphere tropical central Pacific.with theCalifornia cold current and SSTA is mainly responsible for weakening of El Nino;(3)the secondsea temperature increase along the South American coast in the decaying course of El Nino resultsfrom the eastward movement of the weakened positive SSTA in the tropical central-eastern Pacificforced by anomalous west wind stress:(4)La Nina results from the joint effect of Walkercirculation,Ekman drift and negative SSTA in the tropical central-eastern Pacific.  相似文献   

10.
探讨了夏季(6—8月)西北太平洋(Western North Pacific,WNP)热带气旋生成频次(Tropical Cyclone Genesis Frequency,TCGF)与热带海温关系的年代际变化,发现影响WNP TCGF的热带海温型在1991/1992年发生了年代际变化。在1990年代初之前,TCGF正异常对应的热带海温异常(Sea Surface Temperature Anomaly,SSTA)呈现东部型La Ni?a衰减位相,前冬至春季WNP局地暖SSTA在其西北侧激发气旋异常,夏季时由热带印度洋冷SSTA继续维持。在1990年代初之后,TCGF正异常对应的热带SSTA呈现东部型La Ni?a向中部型El Ni?o快速转换的位相,夏季中太平洋暖SSTA在其西北侧激发气旋异常,同时热带东印度洋至海洋性大陆以及热带大西洋的冷SSTA通过垂直环流圈加强中太平洋的辐合上升运动,进一步维持其西北侧气旋异常。由于激发气旋异常的暖SSTA在第二个年代相较第一个年代明显偏南偏东,气旋异常和TCGF正异常在第二个年代也整体偏南且向东扩展至更远的区域。WNP TCGF与热带海温关系的年代际变化与1990年代初之后厄尔尼诺-南方涛动演变速率加快有关。   相似文献   

11.
A hybrid coupled ocean-atmosphere model is designed,which consists of a global atmosphericgeneral circulation model(L9R15 AGCM)and a simple ocean model(ZC ocean model over tropicalPacific).Using the model,experimental predictions are performed for the 1986/87 El Nino eventand the 1988/89 La Nina event with and without the Tibetan Plateau respectively(called TPFORC and NTP FORC hereinafter).It is found as follows:(1)The coupled system cansuccessfully predict the El Nino or La Nina event even if the Tibetan Plateau orography is notincluded in the model.The patterns of SSTA and wind anomalies in the model without the TibetanPlateau are similar to those with the Tibetan Plateau,which further verifies the fact that ENSOprocess is mainly caused by the air-sea interaction in tropical Pacific.(2)However.the existenceof the Tibetan Plateau exerts its influences on the intensity and duration of El Nino(or La Nina).It is unfavorable to the development and maintenance of westerly anomalies,so to some extent,restrains the development of El Nino,but favors the development of La Nina.(3)Effects of theTibetan Plateau orography on the wind anomalies in the coupled system are different from those inuncoupled AGCM simulation.  相似文献   

12.
A hybrid coupled ocean-atmosphere model is designed,which consists of a global atmospheric general circulation model(L9R15 AGCM)and a simple ocean model(ZC ocean model over tropical Pacific).Using the model,experimental predictions are performed for the 1986/87 El Nino event and the 1988/89 La Nina event with and without the Tibetan Plateau respectively(called TP FORC and NTP FORC hereinafter).It is found as follows:(1)The coupled system can successfully predict the El Nino or La Nina event even if the Tibetan Plateau orography is not included in the model.The patterns of SSTA and wind anomalies in the model without the Tibetan Plateau are similar to those with the Tibetan Plateau,which further verifies the fact that ENSO process is mainly caused by the air-sea interaction in tropical Pacific.(2)However.the existence of the Tibetan Plateau exerts its influences on the intensity and duration of El Nino(or La Nina).It is unfavorable to the development and maintenance of westerly anomalies,so to some extent,restrains the development of El Nino,but favors the development of La Nina.(3)Effects of the Tibetan Plateau orography on the wind anomalies in the coupled system are different from those inuncoupled AGCM simulation.  相似文献   

13.
The 1960-1991 monthly mean FSU (Florida State University)wind stress data aredecomposed into a vortical and a divergent component with each of which to force the model oceanin the context of a two-layer tropical Pacific model.Evidence suggests that for the seasonalvariation the ocean forcing does not produce a realistic cold tongue using either of the componentsand the tongue will not be effectively improved in its intensity and pattern even if the componentsare doubled or halved:the utilization of climatic mean wind stress(no decomposition is done of thewind stress)that contains its seasonal variation will lead to a realistic SST distribution on which isimposed,separately,the interannual anomalies of each of the components so as to get the SSTApattern:under the action of the interannual anomaly of the vortical(divergent)component therearises qnite intense SSTA oscillation marked by noticeable ENSO periods(feeble SSTA withhigher oscillation frequency for obscure ENSO periods),thereby illustrating that the roles of thetwo components differ from each other in the genesis of SST variation on a seasonal and aninterannual basis such that a realistic cold tongue pattern follows under the joint effects on themodel ocean of the two components of wind stress while rational E1 Nino/La Nina phenomenaresult under the forcing of an anomalous wind stress vortical component.Moreover,the divergentcomponent is innegligible in generating a mean climatic condition of the ocean sector but of lessimportance compared to the vortical component in ENSO development.  相似文献   

14.
为了分析 EI Nio事件发生和消亡中热带太平洋纬向风应力的动力作用,建立一个类似于Zebiak的简单热带海洋数值模式,在观测到的风应力异常的强迫下,模拟赤道太平洋地区 1971年1月至 1998年8月海表温度异常的变化。结果表明,模式对观测的Nio3区海表温度异常(SSTA)有很好的模拟能力。模拟和观测Ni区SSTA之间的相关系数可达 0.90。模式对 El Nio事件期间赤道太平洋海表温度异常随时间变化也有较好的模拟能力。为了分析El Nio期间SSTA的空间分布及其随时间变化的动力学机制,还对1986~1989年 ENSO循环期间赤道太平洋地区观测的 SSTA的传播特征及其形成机制进行了分析。模式较好地模拟出了观测到的赤道太平洋地区SSTA的传播特征,即从1986年底至1987年 4月, SSTA具有向东传播的特征,从 1987年 6月至 1988年 2月具有向西传播的特征。动力学分析的结果表明,赤道中西太平洋地区的缔向风应力异常对 El Nio事件的发生和消亡具有重要作用。赤道中西太平洋地区的西风异常可强迫出东传的Kelvin波,这个东传的 Kelvin波对正 SSTA的东传起主要作用,当这个东传的 Kelv  相似文献   

15.
The 1960-1991 monthly mean FSU (Florida State University)wind stress data are decomposed into a vortical and a divergent component with each of which to force the model ocean in the context of a two-layer tropical Pacific model.Evidence suggests that for the seasonal variation the ocean forcing does not produce a realistic cold tongue using either of the components and the tongue will not be effectively improved in its intensity and pattern even if the components are doubled or halved:the utilization of climatic mean wind stress(no decomposition is done of the wind stress)that contains its seasonal variation will lead to a realistic SST distribution on which is imposed,separately,the interannual anomalies of each of the components so as to get the SSTA pattern:under the action of the interannual anomaly of the vortical(divergent)component there arises qnite intense SSTA oscillation marked by noticeable ENSO periods(feeble SSTA with higher oscillation frequency for obscure ENSO periods),thereby illustrating that the roles of the two components differ from each other in the genesis of SST variation on a seasonal and an interannual basis such that a realistic cold tongue pattern follows under the joint effects on the model ocean of the two components of wind stress while rational E1 Nino/La Nina phenomena result under the forcing of an anomalous wind stress vortical component.Moreover,the divergent component is innegligible in generating a mean climatic condition of the ocean sector but of less importance compared to the vortical component in ENSO development.  相似文献   

16.
The importance of initializing atmospheric intra-seasonal (stochastic) variations for prediction of the onset of the 1997/1998 El Ni?o is examined using the Australian Bureau of Meteorology coupled seasonal forecast model. A suite of 9-month forecasts was initialized on the 1st December 1996. Observed ocean initial conditions were used together with five different atmospheric initial conditions that sample a range of possible initial states of intra-seasonal (stochastic) variability, especially the Madden-Julian Oscillation (MJO), which is considered the primary stochastic variability of relevance to El Ni?o evolution. The atmospheric initial states were generated from a suite of atmosphere-only integrations forced by observed sea surface temperatures (SST). To the extent that low frequency variability of the tropical atmosphere is forced by slow variations in SST, these atmospheric states should all represent realistic low frequency atmospheric variability that was present in December 1996. However, to the extent that intra-seasonal variability is not constrained by SST, they should capture a range of intra-seasonal states, especially variations in the activity, phase and amplitude of the MJO. For each of these five states, a 20-member ensemble of coupled model forecasts was generated by the addition of small random perturbations to the SST field at the initial time. The ensemble mean from all five sets of forecasts resulted in El Ni?o but three of the sets produced substantially greater warming by months 4?C5 in the NINO3.4 region compared to the other two. The warmer group stemmed from stronger intra-seasonal westerly wind anomalies associated with the MJO that propagated eastward into the central Pacific during the first 1?C2?months of the forecast. These were largely absent in the colder group; the weakest of the colder group developed strong easterly wind anomalies, relative to the grand ensemble mean, that propagated into the central Pacific early in the forecast, thereby generating significantly weaker downwelling Kelvin waves in comparison to the warmer group. The strong reduction in downwelling Kelvin waves in the weakest case acted to limit the warming in the eastern Pacific, resulting in a ??Modoki?? type El Ni?o that is more focused in the central Pacific. Our results suggest that the intra-seasonal stochastic component of the atmospheric initial condition has an important and potentially predictable impact on the forecasts of the initial warming and flavour of the 1997/1998 El Ni?o. However, to the extent that atmospheric intra-seasonal variability is not predictable beyond a month or two, these results imply a limit to the accuracy with which the strength and perhaps the spatial distribution of an El Ni?o can ultimately be predicted. These results do not preclude a predictable role of the MJO and other intra-seasonal stochastic variability at longer lead times if some aspects of the stochastic variability are preconditioned by the evolving state of El Ni?o or other low frequency boundary forcing.  相似文献   

17.
利用多年逐月海温距平和风应力距平观测资料,运用线性回归和EOF分析方法,分析了与ENSO相联系的热带太平洋典型风应力异常场结构。结果显示,与ENSO线性相关的风应力异常场在时间尺度上表现为低频变化,在水平结构上主要表现为四个典型分布。其中,分布型1主要表现为日界线以东赤道地区东风异常和赤道风应力场辐散;分布型2主要表现为日界线以东赤道地区西风异常和经向异常风应力向赤道气流;分布型3主要表现为日界线以东赤道偏南地区西风异常和风应力场辐合,日界线以西为东风异常;分布型4主要表现为160°W以东的弱东风异常和160°W以西的西风异常。与ENSO线性无关的风应力场主要表现为高频过程,在水平空间结构上其典型场主要位于赤道外地区。还用与ENSO有关的那部分回归风应力异常场强迫海洋距平模式,成功地再现了ENSO的主要信号。这表现观测揭示的典型风应力异常型对于El Nino的产生是根本性的。   相似文献   

18.
一个可供ENSO预测的海气耦合环流模式及1997/1998 ENSO的预测   总被引:33,自引:9,他引:24  
利用中国科学院大气物理研究所设计发展的具有较高分辨率的热带太平洋和全球大气耦合环流模式,设计了一个初始化方案,建立了ENSO预测系统,进行了系统性的预测试验。预测结果检验评估表明,该预测系统表现出较强的预报能力,赤道中东太平洋地区(Nino3和Nino34)海表温度距平预报相关技巧高于052的预报可持续18个月,该预测系统可应用到试验性的海温预测实践中。利用该系统对1997/1998年ENSO进行了实际预测,表明预测是成功的,预测的海温距平已提供给今年我国夏季降水预测使用,取得了良好的预测效果。  相似文献   

19.
热带印度洋海温的年际变化与ENSO   总被引:22,自引:3,他引:22  
文中讨论了热带印度洋海表温度距平空间分布的年际变化与赤道中东太平洋海温的关系。EOF分析的结果表明 ,印度洋海温的变化主要存在全区符号一致的单极型和西部与东南部符号相反的偶极型 ,它们具有显著的年际变化。小波凝聚谱揭示了单极、偶极的变化与Nino3区海表温度距平存在密切关系 ,印度洋海温距平从偶极到单极的变化对应着ElNi no事件从发展到衰减的过程。平均而言 ,印度洋偶极超前Nino3区海温距平约 4个月 ,单极滞后约 6个月。整个热带印度洋 -太平洋地区海气耦合特征的演变表明 ,与ElNino从发展到衰减相联系的热带西太平洋海气耦合相互作用在印度洋海温距平从偶极到单极的演变过程中起着非常重要的作用。  相似文献   

20.
Record-breaking heavy and persistent precipitation occurred over the Yangtze River Valley (YRV) in June-July (JJ) 2020. An observational data analysis has indicated that the strong and persistent rainfall arose from the confluence of southerly wind anomalies to the south associated with an extremely strong anomalous anticyclone over the western North Pacific (WNPAC) and northeasterly anomalies to the north associated with a high-pressure anomaly over Northeast Asia. A further observational and modeling study has shown that the extremely strong WNPAC was caused by both La Ni?a-like SST anomaly (SSTA) forcing in the equatorial Pacific and warm SSTA forcing in the tropical Indian Ocean (IO). Different from conventional central Pacific (CP) El Ni?os that decay slowly, a CP El Ni?o in early 2020 decayed quickly and became a La Ni?a by early summer. This quick transition had a critical impact on the WNPAC. Meanwhile, an unusually large area of SST warming occurred in the tropical IO because a moderate interannual SSTA over the IO associated with the CP El Ni?o was superposed by an interdecadal/long-term trend component. Numerical sensitivity experiments have demonstrated that both the heating anomaly in the IO and the heating anomaly in the tropical Pacific contributed to the formation and maintenance of the WNPAC. The persistent high-pressure anomaly in Northeast Asia was part of a stationary Rossby wave train in the midlatitudes, driven by combined heating anomalies over India, the tropical eastern Pacific, and the tropical Atlantic.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号