阿留申低压环流指数及其异常分析

分析近60年冬季各月阿留申低压的气候态和异常变化,及其与中国气候异常变化的相关,结果表明:(1)阿留申低压在1月份的强度最强;整个冬季其中心基本位于阿留申群岛附近,以经向散布为主;主要控制区域位于30?N以北的北太平洋海域;(2)70?s之前强度指数P基本处于高值期,阿留申低压比较弱,70?s中到2000? s强度P指数基本处于低值期,阿留申低压比较强;从本世纪初开始强度指数P逐渐增大,阿留申低压相应减弱.     

2017年冬季内蒙古气候异常偏冷成因分析

2017年冬季内蒙古气温偏低,冬季各月气温偏低持续时间长,影响范围广。利用107站1961—2017年冬季各月气温资料、NECP环流场和NOAA海温场资料,从欧亚环流特征和赤道中东太平洋海温异常影响角度,分析了2017年冬季气温异常偏低特征及其成因。结果表明:(1)2017年冬季气温以偏低为主,且东部地区持续异常偏低特征比较突出;(2)北半球500hPa高度距平场上,欧亚中高纬度环流形势呈现出与异常偏冷年的环流特征;(3)赤道中东太平洋海温异常偏冷、东亚冬季风偏强均是导致内蒙古东部地区冬季异常偏冷的主要成因。     

CAM3模式模拟厄尔尼诺事件对大气环流异常的影响

采用CAM3（Community Atmosphere Model Version3）模式中海气湍流通量参数化原方案和改进方案,利用观测海温驱动CAM3模式进行气候模拟,以分析模式对厄尔尼诺事件影响气候变化的模拟能力。结果表明,采用CAM3模式海气湍流通量参数化改进方案,模式能够更好地模拟出由厄尔尼诺事件引起的北太平洋和北美地区大气环流的变化,尤其是对厄尔尼诺年冬季阿留申低压强度和与PNA遥相关型有关的500hPa位势高度异常的模拟。     

北太平洋次表层海温异常对中国夏季降水影响的可能途径

利用Godas月平均次表层海温资料, 分析了冬、春季和夏季北太平洋次表层海温层际相似性特征, 据此对次表层海温进行分层。在此基础上研究了500 hPa位势高度场、北太平洋次表层海温、中国夏季降水三者之间的时滞相关关系, 发现春季北太平洋次表层海温场是联系前、后期大气环流的关键因素。前期冬季大气环流对春季北太平洋次表层海温场影响最显著, 春季北太平洋次表层海温场又持续影响同期及后期夏季大气环流异常。异常的夏季大气环流与同期表层、次表层海温相互作用, 共同造成夏季长江流域与华北、华南降水出现相反异常的分布型式。     

冬季太平洋三种海温异常型及其对欧亚大气环流的影响

通过对冬季太平洋海温场及滞后0—6月的欧亚500hPa高度场的联合REOF相关分析发现,与500hPa环流异常相联系的冬季海温异常分布可分为三种类型:EC型、KC型和WD型,其异常中心区域分别对应于赤道中东太平洋——加利福利亚海流区、黑潮区和北太平洋西风漂流区。各型海温异常对欧亚500hPa环流具有不同的滞后影响特征,滞后0—3月的影响区主要是低纬度地区,4个月以后可达中纬度地区,尤其是对我国东部上空环流的影响。无论是中纬度海洋还是低纬度海洋均可对滞后4个月以后的东亚中纬度环流产生明显影响。      

冬,春季海温异常关键区对长江中下游夏季降水影响的敏感性试验

本文利用9层菱形截断15波的全球大气环流谱模式（L9R15）研究了前期冬季和春季海温异常的关键区对我国长江中下游地区夏季降水的影响,数值试验结果表明,冬季赤道东太平洋和黑潮区海温异常及春季印度洋和黑潮区海温异常使得长江中下游地区的夏季降水明显增多,同时500hPa副热带高压和100hPa南亚高压增强,但从范围和强度上来看,冬季赤道东太平洋和黑潮区海温异常时我国西南至长江中下游地区一带的夏季降水异常比春季印度洋和黑潮区海温异常时更明显,由此证实了观测资料的分析结果。     

冬季极涡的长期预报

利用北半球500 hPa高度场及北太平洋海温场资料，进行统计分析，重点讨论了对我国气温影响颇为显著的冬季Ⅰ区极涡面积指数的预报问题。结果表明:前期3月北大西洋西风环流及5月北美大槽强度对冬季Ⅰ区极涡强弱变化具有很好的指示性。Ⅰ区极涡异常强弱年份，北太平洋海温距平分布表现出截然相反的两种类型。北太平洋中南部地区海温经向差及北太平洋中西部地区海温纬向差对Ⅰ区极涡面积具有显著影响。     

冬季北太平洋风暴轴的年际变化及其与500hPa高度以及热带和北太平洋海温的联系

文中研究了冬季北太平洋风暴轴的年际异常及其与500hPa高度以及热带和北太平洋海温的联系。结果发现,各年冬季北太平洋风暴轴的中心强度和位置具有显著的年际差异。对15个冬季北太平洋风暴轴区域500hPa天气尺度滤波位势高度方差与热带和北太平洋海温的SVD分析表明,第一对空间典型分布反映了赤道中、东太平洋区域海温异常对风暴轴年际变化的影响,而第二对空间典型分布反映了黑潮区域海温异常对风暴轴年际变化的影响。进一步的合成分析显示,赤道中、东太平洋区域海温异常主要影响冬季北太平洋风暴轴的东西摆动和中、东端的强度变化,而黑潮区域海温异常则主要影响冬季北太平洋风暴轴中、西端的强度变化和南北位移。并且这种影响分别与500hPa高度场上的PNA遥相关型和WP遥相关型有密切联系。     

热带太平洋和印度洋海温异常对东亚冬季风影响的一个物理机制

本文利用NCEP／NCAR提供的大气环流资料和海表温度异常资料,在分析热带太平洋和印度洋海温异常与冬季大气环流之间关系的基础上提出了一个综合反映热带太平洋和印度洋海温异常的综合指数。分析表明,冬季太平洋和印度洋海温异常指数的值越大（小）,东亚冬季风指数的值越大（小）,东亚地区将出现异常的南（北）风的响应,东亚冬季风将越弱（强）。应用加热强迫影响热带环流的简单模式研究r热带太平洋印度洋异常海温对东亚冬季风影响的物理机制。结果表明,当冬季热带太平洋和印度洋海温异常指数处于正（负）位相时,西太平洋区域强迫出异常南（北）风。这是使得东亚冬季风偏弱（强）的重要原因之一。冬季热带太平洋和印度洋海温异常对东亚冬季风影响最为显著的关键区是赤道西太平洋。     

北太平洋海表温度与500hPa西太平洋副高和极涡相互作用的统计分析

本文采用斜交PROMAX因子分析方法分析了1954—1986年北太平洋逐月海表温度与500hPa西太平洋副高和极涡环流指数(7个因子)的相互关系,指出(1)500hPa西太平洋副高和极涡指数与北太平洋海温的相关值存在明显的年变化,以赤道太平洋区最敏感,(2)赤道东太平洋海表温度的变化与10个月前的极涡中心强度、同期和1—3个月前西太平洋副高面积、强度、位置变化有联系,(3)500hPa西太平洋副高面积和强度的变化受到前3—5个月赤道东太平洋和3个月前赤道中太平洋海表温度的影响,500hPa西太平洋副高位置与前3—5个月赤道东太平洋海表温度有联系.     

阿留申低压低频变化及其相关的瞬变动力学过程分析

利用NCEP/NCAR 1979—2013年的再分析资料,研究了冬季阿留申低压低频变化的环流特征,探讨了阿留申低压低频变化形成和维持的相关天气尺度瞬变强迫机制。冬季阿留申低压的低频变化在850 h Pa环流场上表现为北太平洋海盆区一个异常气旋/异常反气旋在局地强弱变化的过程,即阿留申低压在低频尺度上先异常增强/减弱随后逐渐恢复正常态的演变过程;850 h Pa上大气温度低频变化表现为低频冷中心在西北太平洋建立并逐渐东移的过程。对天气尺度瞬变扰动活动及其强迫的异常进行分析表明,北太平洋海盆区上空的瞬变动力强迫在阿留申低压异常增强的时期为负异常,有利于阿留申低压低频变化异常空间型的形成和维持。由瞬变热力强迫异常引起的温度倾向异常场表现为北太平洋中部以40°N为界南正—北负的空间分布,其南部正异常在一定程度上抑制和削弱了低频冷中心向南的扩张。     

中国东部气温异常型与海表温度异常模关系的诊断

基于国家气候中心整编的160站常规观测气温资料和HADLEY中心的海表温度资料,应用最大协方差分析方法,诊断了中国东部各季节气温异常型和前期海表温度异常(SSTA)模的关系,并重点分析冬季气温与SSTA模的最佳耦合模态及海温异常对大气环流的影响。结果表明:中国东部四季气温异常型与前期海盆SSTA模的显著耦合关系表现出不同的特征。超前6个月的热带太平洋第二模和南印度洋第二模与东部地区冬季气温一致变化型耦合关系最佳。西南冷东北暖的气温异常型与超前4个月热带大西洋一致增暖模有最佳耦合关系。大气环流对与全区气温一致偏冷型对应的SSTA模的回归表现为:西伯利亚高压和阿留申低压增强,东亚大槽加深,中纬度西风加强。对与气温西南冷东北暖型对应的SSTA模的回归表现为:西伯利亚高压和阿留申低压略有增强,东亚大槽槽区附近位势升高,大槽变浅,槽线偏向西南,东部40°N以北风速加强,以南风速减弱。     

太平洋海气相互作用的时空变化

本文根据1957—1976年赤道太平洋海温和北太平洋海平面气压的月平均资料,计算了它们之间全年(1—12月)逐月的时滞相关,分析了北太平洋副热带反气旋影响赤道海温和赤道海温对副高反馈的季节变化。发现它们之间的联系不同季节、不同地区有明显差异:副热带反气旋对赤道海温的影响(负相关)以春季最大,秋季最小;赤道海温的反馈,对副高的不同部分作用不同,对副高主体的作用(正相关)以冬半年最大、夏半年较小(尤其是盛夏),对西部副高脊的作用(负相关)相反,以夏半年最大,冬半年较小。其过渡期为5月和11月。同时对其季节变化的可能原因也提出了一些初步看法。其中特别强调了大型环流背景的基本状态(包括平均垂直环流)对海气相互作用过程的重要性。     

北极海冰的厚度和面积变化对大气环流影响的数值模拟

文中利用中国科学院大气物理研究所设计的两层大气环流模式 ,模拟研究了北极海冰厚度和面积变化对大气环流的影响 ,尤其是对东亚区域气候变化的影响。模式中海冰厚度处理趋于合理分布 ,导致东亚冬、夏季风偏强 ,使冬季西伯利亚高压和冰岛低压的模拟结果更趋合理 ;另一方面 ,海冰厚度变化可以激发出跨越欧亚大陆的行星波传播 ,在低纬度地区 ,该行星波由西太平洋向东太平洋地区传播 ;海冰厚度变化对低纬度地区的对流活动也有影响。冬季北极巴伦支海海冰变化对后期大气环流也有显著的影响。数值模拟结果表明 :冬季巴伦支海海冰偏多 (少 )时 ,春季 (4～ 6月 )北太平洋中部海平面气压升高 (降低 ) ,阿留申低压减弱 (加深 ) ,有利于春季白令海海冰偏少 (多 ) ;而夏季 ,亚洲大陆热低压加深 (减弱 ) ,5 0 0 h Pa西太平洋副热带高压位置偏北 (南 )、强度偏强 (弱 ) ,东亚夏季风易偏强 (弱 )。     

Interannual to decadal variability of the winter Aleutian Low intensity during 1900–2004

A new winter Aleutian Low (AL) intensity index was defined in this paper. A centurial-long time series of this index was constructed using the sea level pressure (SLP) data of nearly 100 years. The features of interannual and decadal variability of the winter AL intensity since 1900 were analyzed by applying the wavelet analysis. The relationship between the winter AL intensity and atmospheric circulation was examined. The cross-wavelet analysis technique was used to further reveal the relationship between the AL intensity and sea surface temperature (SST) in the equatorial eastern Pacific (EEP) and tropical Indian Ocean (TIO) in winter. The results indicate that: 1) On the interannual timescale, the winter AL intensity displays 3–7-yr oscillations, while on the decadal timescale, 8–10-yr and 16–22-yr oscillations are more obvious. 2) Of the linkage to atmospheric circulation, both AO (Arctic Oscillation) and PNA (Pacific North America pattern) are closely associated with winter AL intensity on the interannual timescale, but only PNA contributes to the variation of winter AL intensity on the decadal timescale. 3) As to the ocean impact, winter EEP SST is a major factor affecting the winter AL intensity on the interannual timescale, especially on the 3–7-yr periods. However, on the decadal timescale, though both the TIO and EEP SSTs are associated with the AL intensity in winter, the TIO SST impact is more significant.     

ON THE KEY REGIONS OF 500 hPa GEOPOTENTIAL HEIGHTS OVER NORTHERN HEMISPHERE IN WINTER

Variance analysis, correlation analysis and regression analysis methods are applied to analyze the variation of circulation at 500 hPa. In winter, there are three regions (180°E – 150°W, 45°N – 60°N, 70°W – 100 °W，45°N – 75°N, 60°E – 100°E, 65°N – 80°N) whose variations are strong. Those regions are the key regions in which atmospheric circulation can change. Those regions are correlated to some teleconnections and can present a part of variations of 500 hPa to some degree. The linear contemporary correlation between those regions and the height at 500 hPa is significant. Those regions can account for 88 % of variations of concurrent height at 500 hPa. Those regions can present and forecast some variations to some degree in March and April. The longer the time interval, the worse the forecast effect will be. The interannual variations of Q1, Q2 and the SST are weak in the western Pacific.     

Interdecadal mode and its propagating characteristics of SSTA in the South Pacific

Summary This paper is to promote a further understanding of the interdecadal mode of the South Pacific. With this focus, we will specifically aim at better understanding the difference between interannual and interdecadal SSTA modes over South Pacific. We define the difference of the normalization area-averaged SSTA in the southern extratropical Pacific (160° W–110° W, 40° S–25° S) and the south subpolar Pacific (150° W–110° W, 60° S–45° S) as the South Pacific interdecadal index (I _spd). It is found that the interannual mode is more coherent than the interdecadal mode in the central and eastern tropical Pacific, and the interdecadal mode is significant only during boreal winter (DJF). The interdecadal variation of SSTA firstly occurring in the extratropic South Pacific propagates to the western boundary of the South Pacific, then moves northeast to cross the equator, and finally reaches the central tropic Pacific. It takes about 8 years to propagate from southeast subtropical Pacific to the north hemisphere. The previous studies have suggested the mechanism of waves in the subsurface in the South Pacific. Our study also highlights the Rossby waves play important roles in linkage between the extratropics-tropics South Pacific SSTA on interdecadal time scales. Moreover, the paper shows that the interdecadal variability originated in the extrotropic southeast Pacific is mainly induced by interannual variability in the tropic Pacific.     

SPATIAL VARIATION OF WINTER SEA SURFACE TEMPERATURE IN NORTH PACIFIC AND ITS RELATION TO ATMOSPHERIC OSCILLATION MODES

The spatial variation of sea surface temperature anomalies(SSTA) in the North Pacific Ocean during winter is investigated using the EOF decomposition method.The first two main modes of SSTA are associated with Pacific Decadal Oscillation(PDO) mode and North Pacific Gyre Oscillation(NPGO) mode,respectively.Moreover,the first mode(PDO) is switched to the second mode(NPGO),a dominant mode after mid-1980.The mechanism of the modes’ transition is analyzed.As the two oceanic modes are forced by the Aleutian Low(AL) and North Pacific Oscillation(NPO) modes,the AR-1 model is further used to examine the possible effect and mechanism of AL and NPO in generating the PDO and NPGO.The results show that compared to the NPO,the AL plays a more important role in generating the NPGO mode since the 1970s.Likewise,both the AL and NPO affect the PDO mode since the 1980s.     

CLIMATIC FEATURES OF SEA TEMPERATURE OF WARM POOL AND RELATIONSHIP WITH SST OF ITS ADJACENT REGIONS*

In this paper,climatic features of sea temperature of western Pacific warm pool and the relationship with sea surface temperature (SST) of its adjacent regions are analyzed based on the observed sea temperature on vertical cross section along 137°E in western Pacific,the monthly mean SST of Xisha Station in South China Sea and the global monthly mean SST with resolution of 1°×1° (U.K./GISST2.2).The results indicate that (1) in a sense of correlation.SST of western Pacific warm pool can represent its sea subsurface temperature from surface to 200 m-depth level in winter,and it can only represent sea temperature from surface to 70 m depth in summer.The sea subsurface temperature anomaly of warm pool may be more suitable for representing thermal regime of western Pacific warm pool.The sea subsurface temperature of warm pool has a characteristic of quasi-biennial oscillation.(2)Warm pool and Kuroshio current are subject to different ocean current systems (3)Furthermore,the relationship between SST of Xisha Station and SST of warm pool has a characteristic of negative correlation in winter and positive correlation in summer,and a better lag negative correlation of SST of Xisha Station with sea subsurface temperature of warm pool exists.(4)Additionally,oscillation structure of sea temperature like "a seesaw" exists in between warm pool and Regions Nino3 and Nino4.January (June) maximum (minimum) sea subsurface temperature anomaly of warm pool may serve as a strong signal that indicates maturity phase (development phase) of La Nina (El Nino) event,it also acts as a strong signal which reveals variations of SST of Regions Nino3 and Nino4.     

亚太地区冬季海平面气压异常的偶极型结构及其与海温的关系

利用全球月平均海平面气压资料以及海表温度资料,采用旋转经验正交函数分解(REOF)、Morlet小波分析、相关分析及合成分析等方法研究了亚洲—太平洋地区(20°N～70°N,40°E～120°W)冬季海平面气压异常的空间结构与时间演变特征,并进—步分析了该地区冬季海平面气压异常与全球海温异常的关系.结果表明:亚太地区冬...