首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 171 毫秒
1.
评估了耦合气候系统模式FGOALS海洋同化试验对西北太平洋夏季降水和SST相关关系的模拟技巧,并对比了相应的观测海温强迫试验(AMIP)和历史气候模拟试验结果。结果显示,FGOALS海洋同化试验对亚洲季风区大部分海域夏季SST年际变化有较高的模拟技巧,但其对菲律宾以东海域模拟技巧较低。在西北太平洋夏季降水-SST相关关系方面,同化试验部分地再现了南海和菲律宾以东海域降水超前SST变化1个月和同时二者的负相关关系,优于AMIP试验但逊于自由耦合模拟试验。同化试验对SST倾向-降水相关关系的模拟技巧亦介于AMIP试验和自由耦合试验之间。观测中,西北太平洋夏季降水与环流异常受日界线附近和赤道东印度洋海洋大陆地区海温异常的遥强迫,并通过改变到达海表的净短波辐射通量影响局地SST异常,导致局地海温-降水和局地海温倾向-降水的负相关关系。在AMIP试验中,遥强迫导致的西北太平洋地区环流异常较之观测偏弱,由于缺少局地海气耦合过程,在西北太平洋多数地区表现为海温对大气的强迫作用,即SST-降水正相关关系。FGOALS同化试验和自由耦合试验考虑了局地海气耦合过程,虽然低估了遥强迫对西北太平洋地区夏季环流异常的影响,依然部分模拟出局地降水-SST负相关关系但较之观测偏弱。同时,自由耦合试验高估了西北太平洋20°N以南地区海温异常对大气环流异常的强迫,使得其对中国南海和日本岛以南海域SST-降水负相关关系的模拟稍优于同化试验。  相似文献   

2.
江洁  周天军  吴波  邹立维 《大气科学》2019,43(3):467-482
观测发现,西北太平洋区域夏季降水—SST存在显著的负相关,主要是由于El Ni?o衰减年西北太平洋异常反气旋持续至夏季,该过程是检验耦合模式性能的重要参照标准。本文利用中国科学院大气物理研究所近期气候预测系统IAP-DecPreS,通过海洋同化试验、大气模式AMIP试验与观测结果的比较,评估海洋同化试验对西北太平洋夏季局地海气相互作用特征的模拟影响。结果表明,海洋同化试验能够模拟出西北太平洋区域夏季降水—SST负相关,但负相关区域范围偏小。其与观测之间的最大差异出现在8月,西北太平洋负降水异常及异常反气旋位置偏东,强度偏弱。这是由于其模拟的El Ni?o衰减年夏季赤道东印度洋正降水异常偏弱且移动至赤道南侧,对流层增温偏弱,对西太平洋的遥相关作用偏弱。AMIP试验未考虑大气对海洋的反馈作用,不能再现西北太平洋降水—SST负相关,无法模拟出El Ni?o衰减年夏季西北太平洋异常反气旋。研究表明,海洋同化试验对西北太平洋区域局地海气相互作用特征的模拟能力较AMIP试验有所提升,其对8月西北太平洋降水与环流场的模拟偏差与东赤道印度洋降水模拟偏差有关。  相似文献   

3.
东亚-太平洋遥相关型形成过程与ENSO盛期   总被引:2,自引:1,他引:1       下载免费PDF全文
利用1961~2000年NCEP/NCAR再分析资料、扩展重建的海表温度资料 (ERSST) 和中国730个站旬降水资料, 采用SVD和扩展SVD (ESVD) 分析、合成分析、相关分析等方法, 在分析中国梅雨期降水与同期大气环流和前期冬季海温之间关系的基础上, 研究了ENSO盛期海温异常导致与长江流域梅雨期降水密切相关的东亚/太平洋 (EAP) 遥相关型形成的过程, 及与ENSO相关的海温和大气环流异常的持续性问题.结果表明, 梅雨期EAP遥相关型的出现与ENSO遥强迫作用有密切关系.联系冬季ENSO和梅雨期EAP遥相关型的关键过程主要有三个: (1) 西北太平洋低纬地区异常反气旋环流的形成和维持, 它在冬季形成后一直可维持到夏季, 使得夏季西北太平洋副热带高压偏南偏强; (2) 东亚大槽持续偏弱, 冷空气活动路径偏北偏东, 使西北太平洋海温呈亲潮区偏冷、黑潮区偏暖的海温分布; (3) PNA遥相关型的持续发展, 使北冰洋地区高度增高.后二者通过局地海气相互作用和大气内部调整过程对初夏鄂霍次克海阻塞形势的形成起重要作用.另外, 持续性分析表明, ENSO年大气环流和海温距平型的持续性要比非ENSO年大得多.在ENSO年大气环流和海温之间存在很强的相互作用耦合关系, ENSO引起的大气环流异常可导致太平洋海温异常, 而海温异常一旦形成反过来又可导致大气环流异常的稳定和维持, 对后期初夏东亚季风和我国天气气候产生明显滞后效应.  相似文献   

4.
利用1961~2000年NCEP/NCAR再分析资料、扩展重建的海表温度资料(ERSST)和中国730个站旬降水资料,采用SVD和扩展SVD(ESVD)分析、合成分析、相关分析等方法,在分析中国梅雨期降水与同期大气环流和前期冬季海温之间关系的基础上,研究了ENSO盛期海温异常导致与长江流域梅雨期降水密切相关的东亚/太平洋(EAP)遥相关型形成的过程,及与ENSO相关的海温和大气环流异常的持续性问题。结果表明,梅雨期EAP遥相关型的出现与ENSO遥强迫作用有密切关系。联系冬季ENSO和梅雨期EAP遥相关型的关键过程主要有三个:(1)西北太平洋低纬地区异常反气旋环流的形成和维持, 它在冬季形成后一直可维持到夏季,使得夏季西北太平洋副热带高压偏南偏强;(2)东亚大槽持续偏弱,冷空气活动路径偏北偏东,使西北太平洋海温呈亲潮区偏冷、黑潮区偏暖的海温分布; (3)PNA遥相关型的持续发展,使北冰洋地区高度增高。后二者通过局地海气相互作用和大气内部调整过程对初夏鄂霍次克海阻塞形势的形成起重要作用。另外,持续性分析表明,ENSO年大气环流和海温距平型的持续性要比非ENSO年大得多。在ENSO年大气环流和海温之间存在很强的相互作用耦合关系,ENSO引起的大气环流异常可导致太平洋海温异常,而海温异常一旦形成反过来又可导致大气环流异常的稳定和维持,对后期初夏东亚季风和我国天气气候产生明显滞后效应。  相似文献   

5.
应用1979—2010年MRI-CGCM模式回报、NCEP/NCAR再分析数据和中国东部降水观测资料检验了模式对东亚夏季风的模拟能力,并利用模式500 hPa高度场回报资料建立了中国东部夏季降水的奇异值分解(SVD)降尺度模型。模式较好地模拟了亚洲季风区夏季降水的气候态,但模拟的季风环流偏弱、偏南,导致降水偏弱。模拟降水的方差明显偏小,且模拟降水的外部、内部方差比值低,模拟降水受模式初值影响较大。模式对长江雨型的模拟能力最高,华南雨型次之,华北雨型最低。模式对东亚夏季风第1模态的模拟能力明显高于第2模态。对于东亚夏季风第1模态,模式模拟出了西太平洋异常反气旋,但强度偏弱,且未模拟出中高纬度的日本海气旋、鄂霍次克海反气旋,导致长江中下游至日本南部降水偏弱。各时次模拟环流均能反映但低估了ENSO衰减、印度洋偏暖对西太平洋反气旋的增强作用。对于东亚夏季风第2模态,模式对西太平洋的“气旋-反气旋”结构有一定的模拟能力,但未模拟出贝加尔湖异常反气旋和东亚沿海异常气旋,导致中国东部“北少南多”雨型在模拟中完全遗漏。仅超前时间小于4个月的模拟降水能够反映ENSO发展对降水分布的作用。通过交叉检验选取左场时间系数可以提高降尺度模型的预测技巧,SVD降尺度模型在华南、江南、淮河、华北4个区域平均距平相关系数分别为0.20、0.23、0.18、0.02,明显高于模式直接输出。   相似文献   

6.
基于1979-2016年ERA-Interim再分析资料和CAM5.3模式,研究了2016年和1998年北大西洋海温异常对中国夏季降水以及大尺度环流的可能影响及其机制。结果表明,这两年前夏(6-7月)长江中下游及其以南地区降水均异常偏多,但1998年降水异常较2016年更为显著。后夏(8月),2016年长江以南地区降水异常偏多,长江-黄河流域降水异常偏少,而1998年降水异常分布与之相反。2016年和1998年夏季中国东部降水异常的差异与西北太平洋对流层低层异常反气旋以及欧亚中高纬度环流变化的共同作用直接相关。敏感性数值试验的结果表明,北大西洋海温异常的显著差异是导致2016年和1998年夏季中国东部降水以及大尺度环流异常存在明显差异的重要原因之一。一方面,北大西洋海温异常可以通过改变欧亚中高纬度环流进而对中国夏季降水产生影响。1998年北大西洋海温异常自热带至副极地呈类似"+ - +"型分布,这种海温异常型能够在前夏欧亚中高纬度地区激发出双阻型的环流异常响应。2016年北大西洋海温异常自热带至副极地呈相对弱的"- + -"型分布,欧亚中高纬度环流异常响应总体偏弱。另一方面,北大西洋海温异常还可以通过影响热带纬向环流进而对西北太平洋对流层低层异常反气旋起调制作用。1998年北大西洋海温异常对夏季西北太平洋异常反气旋起增强作用,这与热带印度洋-太平洋海温的强迫作用相协调。然而,2016年北大西洋海温异常则有利于西北太平洋异常反气旋的减弱,这与热带印度洋-太平洋海温的强迫作用相反。因此,在这3个大洋的协同作用下,2016年和1998年前夏西北太平洋异常反气旋均偏强,但前者的振幅弱于后者。在后夏,1998年西北太平洋对流层低层仍受异常反气旋控制,2016年则为异常气旋控制。   相似文献   

7.
柳伊  范磊 《山东气象》2019,39(3):36-42
通过资料分析与数值模拟研究了西北太平洋低空环流特征及其与海面温度(SST)异常关系的季节性差异,得到如下结论:1)西北太平洋低空环流的空间尺度和位置在春季和夏季存在明显差异,从春季到夏季,异常环流范围缩小且中心位置向西北偏移;2)西北太平洋低空环流与西北太平洋局地海温的相互作用存在季节差异,春季西北太平洋冷海温与上空反气旋异常之间存在相互作用,而夏季则以大气影响海洋为主,异常的反气旋/气旋可以加热/冷却其下垫面的海温,大气超前3~4 d影响海洋;3)夏季异常反气旋环流(WNPAC)的维持主要来自非局地海温异常(北印度洋暖海温与中太平洋冷海温异常)的强迫,这两个海区对WNPAC的影响也存在季节性差异,北印度洋的影响主要体现在晚春至盛夏,而中太平洋则主要在晚夏发挥作用。  相似文献   

8.
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   

9.
本文分析了中国科学院大气物理研究所年代际气候预测系统IAP DecPreS的海洋同化试验(简称EnOI-IAU试验)在西北太平洋地区的海表面温度(SST)年循环的模拟技巧,并通过对比IAP DecPreS系统自由耦合历史气候模拟试验结果,在包含海气耦合过程的框架下讨论了耦合模式中西北太平洋夏季SST模拟差异,及其对亚洲季风区夏季季风降水模拟的影响。结果表明,EnOI-IAU试验较好地模拟出了西北太平洋各个季节的SST空间分布,并显著减小了原存在于历史气候模拟试验中持续全年的SST冷偏差。混合层热收支诊断分析表明,包含同化过程在内的海洋过程的模拟差异对西北太平洋海温的模拟提升有重要贡献。夏季,EnOI-IAU试验模拟的印度季风伴随的低层西风较观测偏东、偏强,且高估了赤道西太平洋区域的降水量值、低估了印度洋区域的降水量值。水汽收支分析显示,气旋式环流异常造成的水汽辐合异常是造成亚洲季风区降水模拟差异的主要原因。研究表明,较之历史模拟试验,EnOI-IAU试验中夏季西北太平洋地区SST增暖造成局地对流增强,进而使得局地产生异常上升运动,水汽辐合增强,造成西北太平洋地区降水模拟偏多,激发出低层西风异常及赤道外气旋式环流异常。该低层西风异常导致了北印度洋地区低层辐散异常,减小了原存在于历史试验中印度洋地区的正降水偏差。西北太平洋气旋式环流异常一方面增强了印度夏季风伴随的低层西风,使得更多的水汽从阿拉伯海输送到西太平洋暖池区域,增强了该区域的降水量;另一方面,该气旋式环流异常减小了历史模拟试验中中国南部区域偏强的低层风速,进而提升了模式对东亚低层西南风的模拟能力。  相似文献   

10.
基于观测分析的结果,采用NCARCCM3模式,设计4组7个数值试验,研究太平洋海表温度异常对中国东部夏季降水影响及其可能的物理过程。结果表明:数值模拟与观测分析所得的结果一致,前期冬季西北太平洋黑潮海区海温异常,引起亚洲中高纬和东亚东部地区大气环流异常,导致长江流域夏季降水异常;前期春季赤道中东太平洋海温异常,西太平洋副热带高压异常;同期夏季北太平洋中纬中太平洋海区海温异常,激发夏季EUP遥相关型,影响东部夏季降水。  相似文献   

11.
The relationships between ENSO and the East Asian-western North Pacific monsoon simulated by the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 (FGOALS-s2), a state-of-the-art coupled general circulation model (CGCM), are evaluated. For El Nio developing summers, FGOALS-s2 reproduces the anomalous cyclone over the western North Pacific (WNP) and associated negative precipitation anomalies in situ. In the observation, the anomalous cyclone is transformed to an anomalous anticyclone over the WNP (WNPAC) during El Nio mature winters. The model reproduces the WNPAC and associated positive precipitation anomalies over southeastern China during winter. However, the model fails to simulate the asymmetry of the wintertime circulation anomalies over the WNP between El Nio and La Nia. The simulated anomalous cyclone over the WNP (WNPC) associated with La Nia is generally symmetric about the WNPAC associated with El Nio, rather than shifted westward as that in the observation. The discrepancy can partially explain why simulated La Nin a events decay much faster than observed. In the observation, the WNPAC maintains throughout the El Nio decaying summer under the combined effects of local forcing of the WNP cold sea surface temperature anomaly (SSTA) and remote forcing from basinwide warming in the tropical Indian Ocean. FGOALS-s2 captures the two mechanisms and reproduces the WNPAC throughout the summer. However, owing to biases in the mean state, the precipitation anomalies over East Asia, especially those of the Meiyu rain belt, are much weaker than that in the observation.  相似文献   

12.
NUMERICAL SIMULATION OF LAG INFLUENCE OF ENSO ON EAST-ASIAN MONSOON   总被引:2,自引:0,他引:2  
By prescribing sea surface temperature anomalies(SSTAs)over eastern equatorial Pacific inJanuary—March,the lag influence of ENSO(El Nino and La Nina)on monsoon over East Asiahas been studied.The results suggest that,due to the excitation of atmospheric low-frequencyoscillation by the SSTA,ENSO has significant lag influence on the monsoon over East Asia.During the summer after E1 Nino,the subtropical high over western Pacific is intensified andshows the northward and westward displacement,meanwhile,the rainfall over East China isbelow normal,especially in North China:during the winter after E1 Nino,both the Asian troughand the winter monsoon over East Asia are strengthened.During the summer after La Nina,theanomalous subtropical high prevails over the lower reaches of Yangtze(Changjiang)River,therainfall between Yangtze and Huaihe Rivers is below normal:during the winter after La Nina,both the Asian trough and the winter monsoon over East Asia are weaker.Compared with LaNina,the effect of El Nino is stronger,but it is not always opposite to the one of La Nina.  相似文献   

13.
The relationship between summer rainfall anomalies in northeast China and two types of El Ni?o events is investigated by using observation data and an AGCM. It is shown that, for different types of El Ni?o events, there is different rainfall anomaly pattern in the following summer. In the following year of a typical El Ni?o event, there are remarkable positive rainfall anomalies in the central-western region of northeast China, whereas the pattern of more rainfall in the south end and less rainfall in the north end of northeast China easily appears in an El Ni?o Modoki event. The reason for the distinct differences is that, associated with the different sea surface temperature anomalies (SSTA) along the equatorial Pacific, the large-scale circulation anomalies along east coast of East Asia shift northward in the following summer of El Ni?o Modoki events. Influenced by the anomalous anticyclone in Philippine Sea, southwesterly anomalies over eastern China strengthens summer monsoon and bring more water vapor to Northeast China. Meanwhile, convergence and updraft is strengthened by the anomalous cyclone right in Northeast China in typical El Ni?o events. These moisture and atmospheric circulation conditions are favorable for enhanced precipitation. However, because of the northward shift, the anomalous anticyclone which is in Philippine Sea in typical El Ni?o cases shifts to the south of Japan in Modoki years, and the anomalous cyclone which is in the Northeast China in typical El Ni?o cases shifts to the north of Northeast China, leading to the “dipole pattern” of rainfall anomalies. According to the results of numerical experiments, we further conform that the tropical SSTA in different types of El Ni?o event can give rise to observed rainfall anomaly patterns in Northeast China.  相似文献   

14.
El Niño–Southern Oscillation (ENSO) events significantly affect the year-by-year variations of the East Asian winter monsoon (EAWM). However, the effect of La Niña events on the EAWM is not a mirror image of that of El Niño events. Although the EAWM becomes generally weaker during El Niño events and stronger during La Niña winters, the enhanced precipitation over the southeastern China and warmer surface air temperature along the East Asian coastline during El Niño years are more significant. These asymmetric effects are caused by the asymmetric longitudinal positions of the western North Pacific (WNP) anticyclone during El Niño events and the WNP cyclone during La Niña events; specifically, the center of the WNP cyclone during La Niña events is westward-shifted relative to its El Niño counterpart. This central-position shift results from the longitudinal shift of remote El Niño and La Niña anomalous heating, and asymmetry in the amplitude of local sea surface temperature anomalies over the WNP. However, such asymmetric effects of ENSO on the EAWM are barely reproduced by the atmospheric models of Phase 5 of the Coupled Model Intercomparison Project (CMIP5), although the spatial patterns of anomalous circulations are reasonably reproduced. The major limitation of the CMIP5 models is an overestimation of the anomalous WNP anticyclone/cyclone, which leads to stronger EAWM rainfall responses. The overestimated latent heat flux anomalies near the South China Sea and the northern WNP might be a key factor behind the overestimated anomalous circulations.  相似文献   

15.
This study investigates the influences of tropical Indian Ocean(TIO) warming on tropical cyclone(TC)genesis in different regions of the western North Pacific(WNP) from July to October(JASO) during the decaying El Nio. The results show significant negative TC frequency anomalies localized in the southeastern WNP. Correlation analysis indicates that a warm sea surface temperature anomaly(SSTA) in the TIO strongly suppresses TC genesis south of 21°N and east of 140°E in JASO. Reduced TC genesis over the southeastern WNP results from a weak monsoon trough and divergence and subsidence anomalies associated with an equatorial baroclinic Kelvin wave. Moreover,suppressed convection in response to a cold local SSTA, induced by the increased northeasterly connected by the wind-evaporation-SST positive feedback mechanism, is found unfavorable for TC genesis. Positive TC genesis anomalies are observed over higher latitudinal regions(at around 21°N, 140°E) and the western WNP because of enhanced convection along the northern flank of the WNP anomalous anticyclone and low-level convergence,respectively. Although local modulation(e.g., local SST) could have greater dominance over TC activity at higher latitudes in certain anomalous years(e.g., 1988), a warm TIO SSTA can still suppress TC genesis in lower latitudinal regions of the WNP. A better understanding of the contributions of TIO warming could help improve seasonal TC predictions over different regions of the WNP in years of decaying El Nio.  相似文献   

16.
山西省夏季年际气候异常研究1.山西省一致多雨或少雨型   总被引:3,自引:0,他引:3  
李智才  宋燕  朱临洪  张世英 《气象》2008,34(1):86-93
利用美国国家环境预报中心(NCEP)再分析资料以及山西64个测站的月降水量等资料,采用EOF分解和合成分析方法研究了1960-2003年山西夏季降水的年际变化异常以及时空特征.利用EOF方法分析山西夏季降水,第一类雨型是山西省夏季一致多雨型,并给出此类异常雨型的时空分布和相应的典型年份.山西省夏季降水趋势分析表明,自1960年以来山西省夏季降水趋于减少.从500hPa位势高度场、纬向风、850hPa风场、700hPa水汽场、海温场等物理量场分析表明,山西夏季一致多雨年对应偏强的东亚夏季风,一般出现在La Nina事件(冷水事件)发生的当年和El Nino事件(暖水事件)发生的来年,中高纬度地区易出现纬向排列的 - -环流异常纬向分布型,大陆地区为一个异常槽和两个异常脊,乌拉尔山以东地区和鄂霍次克海是异常高压脊,而贝加尔湖地区是一个异常低压槽.山西省夏季一致少雨年对应偏弱的东亚夏季风,一般出现在El Nino事件(暖水事件)发生的当年和La Nina事件(冷水事件)发生的来年,与一致多雨年相反,中高纬度地区通常呈现纬向排列的- - 环流异常纬向分布型,大陆地区出现两个异常槽和一个异常脊.山西省夏季第一类雨型的发生与中高纬度地区纬向排列的环流异常分布和赤道太平洋海温异常有关系.  相似文献   

17.
A seasonal forecast system based on a global, fully coupled ocean?Catmosphere general circulation model is used to (1) evaluate the interannual predictability of the Northwest Pacific climate during June?CAugust following El Ni?o [JJA(1)], and (2) examine the contribution from the tropical Indian Ocean (TIO) variability. The model retrospective forecast for 1983?C2006 captures major modes of atmospheric variability over the Northwest Pacific during JJA(1), including a rise in sea level pressure (SLP), an anomalous anticyclone at the surface, and a reduction in subtropical rainfall, and increased rainfall to the northeast over East Asia. The anomaly correlation coefficient (ACC) for the leading principal components (PCs) of SLP and rainfall stays above 0.5 for lead time up to 3?C4?months. The predictability for zonal wind is slightly better. An additional experiment is performed by prescribing the SST climatology over the TIO. In this run, designated as NoTIO, the Northwest Pacific anticyclone during JJA(1) weakens considerably and reduces its westward extension. Without an interactive TIO, the ACC for PC prediction drops significantly. To diagnose the TIO effect on the circulation, the differences between the two runs (Control minus NoTIO) are analyzed. The diagnosis shows that El Nino causes the TIO SST to rise and to remain high until JJA(1). In response to the higher than usual SST, precipitation increases over the TIO and excites a warm atmospheric Kelvin wave, which propagates into the western Pacific along the equator. The decrease in equatorial SLP drives northeasterly wind anomalies, induces surface wind divergence, and suppresses convection over the subtropical Northwest Pacific. An anomalous anticyclone forms in the Northwest Pacific, and the intensified moisture transport on its northwest flank causes rainfall to increase over East Asia. In the NoTIO experiment, the Northwest Pacific anticyclone weakens but does not disappear. Other mechanisms for maintaining this anomalous circulation are discussed.  相似文献   

18.
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   

19.
亚澳季风异常与ENSO准四年变化的联系分析   总被引:2,自引:0,他引:2  
分析了赤道地区纬向风的年际变化特征,以及亚澳季风与ENSO在各个位相的联系。结果表明:赤道纬向风变化与中东太平洋海温变化在准四年周期上是强烈耦合的;在El Eino期间东亚冬季风弱,夏季风强,而南亚夏季风弱,反之,在La Nina期间东亚冬季风强,夏季风弱,而南亚夏季风强;东亚地区的异常北风有利于西太平洋西风异常爆发,使得东太平洋海温升高,但只有随后在中东太平洋出现持续性西风异常,El Nino才能发展,其中来自太平洋中部的异常北风(并不是来自东亚大陆地区)和南太平洋中部的异常南风的辐合对中东太平洋出现持续性西风异常起重要的作用,尤其是澳大利亚东北部的季风异常的影响更为显。  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