ENSO amplitude change in observation and coupled models     

张琼  关月  杨海军 《大气科学进展》2008,25(3):361-366

Observations show that the tropical E1 Nifio-Southern Oscillation （ENSO） variability, after removing both the long term trend and decadal change of the background climate, has been enhanced by as much as 60% during the past 50 years. This shift in ENSO amplitude can be related to mean state changes in global climate. Past global warming has caused a weakening of the Walker circulation over the equatorial Indo-Pacific oceans, as well as a weakening of the trade winds and a reduction in the equatorial upwelling. These changes in tropical climatology play as stabilizing factors of the tropical coupling system. However, the shallower and strengthening thermocline in the equatorial Pacific increases the SST sensitivity to thermocline and wind stress variabilities and tend to destabilize the tropical coupling system. Observations suggest that the destabilizing factors, such as the strengthening thermocline, may have overwhelmed the stabilizing effects of the atmosphere, and played a deterministic role in the enhanced ENSO variability, at least during the past half century. This is different from the recent assessment of IPCC-AR4 coupled models.  相似文献   

A Study of the Teleconnections in the Asian-Pacific Monsoon Region   总被引：2，自引：0，他引：2       下载免费PDF全文

DING Yihui  LIU Yunyun 《Acta Meteorologica Sinica》2008,22(4):404-418

The interactions among the Asian-Pacific monsoon subsystems have significant impacts on the climatic regimes in the monsoon region and even the whole world. Based on the domestic and foreign related research, an analysis is made of four different teleconnection modes found in the Asian-Pacific monsoon region, which reveal clearly the interactions among the Indian summer monsoon （ISM）, the East Asian summer monsoon （EASM）, and the western North Pacific summer monsoon （WNPSM）. The results show that： （1） In the period of the Asian monsoon onset, the date of ISM onset is two weeks earlier than the beginning of the Meiyu over the Yangtze River Basin, and a teleconnection mode is set up from the southwestern India via the Bay of Bengal （BOB） to the Yangtze River Basin and southern Japan, i.e., the ＂southern＂ teleconnection of the Asian summer monsoon. （2） In the Asian monsoon culmination period, the precipitation of the Yangtze River Basin is influenced significantly by the WNPSM through their teleconnection relationship, and is negatively related to the WNPSM rainfall, that is, when the WNPSM is weaker than normal, the precipitation of the Yangtze River Basin is more than normal. （3） In contrast to the rainfall over the Yangtze River Basin, the precipitation of northern China （from the 4th pentad of July to the 3rd pentad of August） is positively related to the WNPSM. When the WNPSM is stronger than normal, the position of the western Pacific subtropical high （WPSH） becomes farther northeast than normal, the anomalous northeastward water vapor transport along the southwestern flank of WPSH is converged over northern China, providing adequate moisture for more rainfalls than normal there. （4） The summer rainfall in northern China has also a positive correlation with the ISM. During the peak period of ISM, a teleconnection pattern is formed from Northwest India via the Tibetan Plateau to northern China, i.e., the ＂northern＂ teleconnection of the Asian summer monsoon. The  相似文献   

中国东部—西太平洋副热带季风和降水的气候特征及成因分析   总被引：13，自引：2，他引：11  

赵平  周秀骥  陈隆勋  何金海 《气象学报》2008,66(6):940-954

利用1981—2000年候平均NCEP/NCAR再分析资料和CMAP全球降水资料,分析了从中国东部大陆到西太平洋副热带地区季风和降水季节变化的特征及其与热带季风降水的关系,探讨了季风建立和加强的原因。夏季东亚—西太平洋盛行的西南风开始于江南和西太平洋副热带的春初,并向北扩展到中纬度,热带西南风范围向北扩展的迹象不明显。从冬到夏,中国西部和西太平洋副热带的表面加热季节变化可以使副热带对流层向西的温度梯度反转比热带早,使西南季风在副热带最早开始;从大气环流看,青藏高原东侧低压槽的加强和向东延伸,以及西太平洋副热带高压的加强和向西移动,都影响着副热带西南季风的开始和发展;初夏江南的南风向北扩展与副热带高压向北移动有关,随着高原东侧低压槽向南延伸,槽前的偏南风范围向南扩展。随着副热带季风建立和向北扩展,其最大风速中心前方的低层空气质量辐合和水汽辐合以及上升运动也加强和向北移动,导致降水加强和雨带向北移动。热带季风雨季开始晚,主要维持在热带而没有明显进入副热带,江淮梅雨不是由热带季风雨带直接向北移动而致,而是由春季江南雨带北移而致。在热带季风爆发前,副热带季风区水汽输送主要来自中南半岛北部和中国华南沿海,而在热带季风爆发后,水汽输送来自孟加拉湾和热带西太平洋。  相似文献   

太平洋区域季内振荡的一种负反馈过程     

李丽平  王盘兴  管兆勇 《南京气象学院学报》2008,31(3):317-325

利用1981—2002年美国国家气象中心（National Meteorological Center,NMC）逐日海表温度（sea surface temperature,SST）、10 m高处风场（V）及逐月混合层厚度（mixed layer depth,mld）资料,研究了太平洋区域海表温度季内振荡的气候及异常特征,重点探讨了北太平洋区域海表温度季内振荡的维持机制。研究发现,太平洋区域海表温度存在3个季内振荡强度气候高值区,即热带东太平洋（终年存在）、西北太平洋（北半球春、夏、秋存在）、西南太平洋（南半球夏季前后存在）,它们出现在气候混合层厚度最小的区域和季节。海表温度季内振荡强度年际异常与混合层厚度年际异常存在显著负相关,在物理上,这种关系比它与海表温度异常的关系更直接。北太平洋区域5—9月地面风场与海表温度季节内振荡的基本耦合模态揭示出以漂流和感热输送为动力的一个负反馈过程,它存在于薄混合层海区,这是该海区强海表温度季内振荡的维持机制。  相似文献   

COMPARISONS OF THE WEST PACIFIC SUBTROPICAL HIGH AND THE SOUTH ASIA HIGH BETWEEN NCEP/NCAR AND ECMWF REANALYSIS DATASETS     

陈雯  智协飞 《热带气象学报(英文版)》2008,14(2):121-124

Comparisons of the west Pacific subtropical high with the South Asia High are made using the NCEP/NCAR and ECMWF 500 hPa and 100 hPa monthly boreal geopotential height fields for the period 1961 - 2000. Discrepancies are found for the time prior to 1980. The west Pacific subtropical high in the NCEP/NCAR data is less intense than in ECMWF data before 1980. The range and strength of the west Pacific subtropical high variation described by the NCEP/NCAR data are larger than those depicted by ECMWF data. The same situation appears in the 100-hPa geopotential field. These discoveries suggest that the interdecadal variation of the two systems as shown by the NCEP/NCAR data may not be true. Besides, the South Asia High center in the NCEP/NCAR data is obviously stronger than in the ECMWF data during the periods 1969, 1979 - 1991 and 1992 - 1995. Furthermore, the range is larger from 1992 to 1995.  相似文献   

气候平均场中的西太平洋副热带高压双脊线特征及其与季风槽准10天振荡的关系   总被引：4，自引：2，他引：2  

祁莉  管兆勇  张祖强 《大气科学》2008,32(1):165-174

副热带高压双脊线过程几乎历年均存在,其“季节锁相”与地域性使得在气候平均场上西太平洋副热带地区也存在明显的双脊线过程。作者利用43年NCEP/NCAR再分析资料对5～10月气候平均场中的西太平洋副热带高压双脊线过程进行了分析。气候平均场上5～10月西太平洋副热带高压共出现6次双脊线过程,集中发生在7月下旬至9月下旬,表明每年这个时段最易发生双脊线事件。每次双脊线过程均表现为副高南侧新生一脊线,发展几天后就减弱消失,北侧脊线（原脊线）继续维持。初步的诊断分析表明,6次双脊线过程中南侧脊线的生成与季风槽8～10天周期的“间歇性增强东伸”密切相关,这一准10天振荡在7月下旬至9月下旬的突然增强造就了双脊线的“季节锁相”。进一步分析发现,季风槽8～10天的“间歇性增强东伸”与两支分别来自西太平洋的西传准10天振荡和来自赤道的北传准10天振荡有关,这两支振荡同位相,其有利于位相同时传入南海季风区（10°N～15°N,110°E～120°E）,共同作用,引起季风槽的“间歇性增强东伸”。  相似文献   

气候平均场上西太平洋副热带高压双脊线过程可能成因的动力诊断分析     

祁莉  张祖强  何金海 《大气科学》2008,32(2):395-404

利用NCEP-DOE再分析数据集II,诊断分析了气候平均场上6次西太平洋副热带高压双脊线过程,借助一个两层半大气模式,从动力学上初步揭示了西太平洋热带大气准10天振荡（Quasi Ten-day Oscillation,简称QTO）向西北方向传播与季风槽东伸西撤之间的相互作用过程,探讨了气候平均场上西太副高双脊线可能的形成机制。分析表明季风槽准10天东西振荡是气候平均场上西太副高双脊线形成的主要原因,而季风槽东伸西撤与QTO传播密切相关。进一步分析发现,QTO向西北方向传播,东风切变作用于斜压辐散的经向梯度,在对流中心北侧生成正扰动涡度。QTO在季风槽东侧激发的气旋性扰动涡度,诱导季风槽东伸,侵入副高,造成副高外围变形,形成双脊线。因此,形成西太副高双脊线的主要原因之一可能是西太平洋热带大气QTO。尽管季风槽东伸直接引起副高双脊线发生,但是它只不过是受QTO影响的一种表现。本文仅为诊断结果,其结果还有待于模式敏感性试验的验证。  相似文献   

北太平洋海温与江淮流域汛期流量的关系研究   总被引：1，自引：1，他引：0  

李秋林 《气象与减灾研究》2008,31(2):62-64

利用自然正交函数分解法,对北太平洋海温与江淮流域汛期流量的关系进行了研究。结果表明,赤道东人平洋（10°S-10°N、180°-80°W）和西北太平洋（35°—45°N、150°E-140°W及30°N、170°-140°W）的海温变化与江淮流域汛期流量关系密切。当赤道东太平洋海温升高时,江淮流域汛期流量减少,反之则增加。依据这两个关键区的典型场时间系数所建立的流域预报模型,试报效果较为理想,除汉口8月流量预报误差为-10．7％外,其他要素流量预报误差均在±5％左右。  相似文献   

赤道波动转换在西北太平洋热带气旋生成中的作用          下载免费PDF全文

陈光华  黄荣辉 《大气和海洋科学快报》2008,1(1):64-68

This study associates tropical cyclone (TC) activity over the western North Pacific (WNP) with the equatorial wave transition from an interannual viewpoint, revealing that the tropical cyclogenesis mean location may be modulated by a longitudinal shift in the transition of Mixed Rossby-gravity (MRG) waves to off-equatorial tropical depression (TD) disturbances from year to year. To a large extent, the wave transition is attributable to the monsoon trough in response to the thermal state of the warm pool (WP) over the WNP. During the cold state years in the WP, the basic flow confluence region associated with the monsoon trough penetrates eastward, leading to an eastward shift in the location of the wave transition. Such an environment, in which wave accumulation and energy conversion occur, is favorable for tropical cyclogenesis; as a result, the averaged cyclogenesis location moves eastward. The condition is reserved during the warm years in the WP, resulting in the prominent westward-retreating mean TC formation. Citation: Chen, G. H., and R. H. Huang, 2008: Role of equatorial wave transitions in tropical cyclogenesis over the western north Pacific, Atmos. Oceanic Sci. Lett., 1, 64-68  相似文献   

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  

顾薇  李崇银  潘静 《气候与环境研究》2007,12(2):113-123

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