冬季全球大气季节内振荡的特征分析

利用欧洲中期数值天气预报中心的ERA-40逐日再分析资料,计算得到350 K等熵面上45年冬季气候平均位势高度场,再利用Butterworth滤波器得到等熵面上位势高度30～60 d低频波.应用经验正交分解(EOF)对冬季350 K等熵面上的低频位势高度场进行时空分析,结果表明:在第1主分量场上,空间分布特征最明显的是南极涛动(AAO)、北极涛动(AO)、北美-太平洋涛动(PNA)以及经向偶极型低频变化.这种空间分布形式说明在350 K等熵面上南北半球间通过太平洋地区的经向低频波列传播,使得AAO与AO相互影响,相互作用.第2主分量场上,空间分布特征则表现出全球经向和纬向上的低频波列特征,以及南北半球在大西洋地区的相互作用.将EOF分解得到的前2个主分量场的时间系数投影到1957—2002年冬季的时间序列中,发现冬季全球大气低频振荡在20世纪70年代末80年代初发生了明显的年代际突变,并在80年代末以后逐渐加强.说明在80年代末以后冬季南北半球的低频变化相互作用有所加强,也说明太平洋,大西洋上的经向传播特征更为明显.     

中国海海表风场、海浪场与El Nino的相关性分析

利用CCMP风场,分析了中国海海表风场与El Nino之间的关系,并利用CCMP风场驱动WW3海浪模式,对19882009年的中国海海浪场进行数值模拟,探索中国海的海浪场与El Nino的内在联系,以期能利用El Nino指标辅助中国海海浪场、海表风场的中长期预测、防灾减灾等.结果表明中国海的海表风场、海浪场与nino3指数关系密切:①同期及1~4个月后的海表风场、海浪场与当月的nino3指数表现出显著性负相关,尤其是2个月后的海浪场、海表风场与nino3指数之间的负相关性最显著;7~10个月后的海表风场、海浪场与当月的nino3指数表现出显著性正相关,尤其是8个月后的海浪场、海表风场与nino3指数之间的正相关性最显著.②19881997年期间、19992009年期间,8个月后的海表风场、海浪场与当月nino3指数的走势表现出非常好的一致性.③nino3指数、中国海的海浪场、海表风场三者存在较为显著的、共同的半年周期（5.87~6.29个月）、年周期（11.00~13.54个月）.④nino3指数的突变期为20世纪80年代后期、1999年7月2000年11月、20052009年;海表风场与海浪场的显著性突变期完全一致,为2000年11月2001年5月,其中nino3指数在1999年7月2000年11月期间的突变期比海表风场和海浪场的突变期超前约半年左右,nino3区海温的突变可能是中国海海浪场、海表风场突变的主要诱发因素之一.     

盘龙河流域近45年气温和降水变化特征分析

应用线性趋势法、方差分析和M-K检验法就盘龙河流域1961-2005年的气温和降水进行了变化趋势、年际和年代际变化及突变特征分析.结果表明:该流域近45 a来年均温呈上升趋势,与其他季节相比,冬季增温趋势显著,幅度最大,气温倾向率为0.232℃/10 a;年降水量与季节降水量变化趋势不明显,降水量倾向率均未通过95%的信度检验;气温和降水量年际和年代际变化显著;气候突变时段多集中于20世纪60至70年代和90年代以后,主要表现为上世纪60至70年代的降温突变和降水量增加突变,90年代以后以增温突变和降水量减少突变为主.     

北太平洋海面高度低频变化特征及其影响因素

为了解北太平洋海面高度年际、年代际变化特征及其影响,基于1961年1月至2010年12月的简单海洋资料同化(SODA)海面高度再分析资料,采用经验正交函数(EOF)、小波分析、交叉小波等方法研究北太平洋海面高度低频时空变化特征及其影响因素。结果表明:1961-2010年期间,北太平洋沿岸地区和副热带海域海面高度存在明显上升趋势,而中纬度太平洋存在下降趋势;海面高度EOF第一模态为年际变化,呈东西反位相分布;第二模态为年代际变化,以黑潮主轴(约30°N)为界,呈"跷跷板"式分布;海面高度异常与Nino3.4指数在热带太平洋和东太平洋呈正相关,在西太平洋为负相关,且相关性随纬度升高而减弱;海面高度异常与太平洋10年涛动(PDO)指数在大洋中纬度海域显著相关,热带中东太平洋海域二者为正相关;北太平洋海面高度年代际变化和年际变化的主要影响因素分别为PDO振荡、厄尔尼诺/南方涛动现象(ENSO)。     

基于EOF分析的江苏省沿江7市梅雨量变化特征

使用江苏省沿江7市(南京、苏州、无锡、常州、镇江、扬州、南通)梅雨期具有典型代表性的梅雨量序列,1954—2013年共60 a资料,通过EOF分解法计算出特征向量分布、时间系数序列,并根据特征向量方差贡献,确定出梅雨季东旱西涝或东涝西旱的基本空间分布型,同时结合分解出的时间系数,分析出江苏省沿江地区梅雨季降水量的长期趋势及年代际变化具有明显的区域特征.20世纪80年代末以前地区梅雨季降水量表现为东涝西旱,而20世纪90年代以后则表现为东旱西涝.进入20世纪80年代以来,南京、无锡、常州、镇江的梅雨季节降水量异常明显,其余各地区整体上变化不明显.同时,辅助以Morlet小波分析方法,通过小波能量密度研究了第1主分量时间系数的年际及年代际振荡随时间的演变及其方差贡献率.结果表明,江苏省沿江地区的梅雨量存在一个显著3~4 a的年际振荡周期和13~14 a的年代际振荡周期,1975到1980年,3~4 a振荡对年际振荡贡献较大,而13~14 a尺度振荡对年代际振荡的方差贡献则主要集中在20世纪70年代以后.     

太平洋地区地球主磁场长期变化特征的研究

研究太平洋地区主磁场的长期变化特征,对揭示该地区的“偶极子窗”的时间演变和长期变化规律有重要意义.作者使用最新的国际地磁参考场IGRF13模型资料,分析1900—2020年期间太平洋地区主磁场的长期变化特征.结果表明1900—2020年太平洋地区主磁场的空间展布符合“太平洋偶极子窗”的分布特征.该地区主磁场的长期变化在赤道以北为缓慢变化,以南则是较快变化.偶极子场成分变化缓慢,非偶极子场成分变化较快.非偶极子场的长期变化以西向漂移为主,但各分量的西漂速率有显著的差异.垂直分量（Z）和北向分量（X）的西漂速率分别为0.23°/a和0.21°/a,均接近于0.2°/a的全球非偶极子西漂速率;东向分量（Y）的西漂速率为0.17°/a,低于全球非偶极子西漂速率. Y分量的长期变化在34°N附近发生扭曲并且在北太平洋表现为缓慢东漂,这一长期变化特征可能与太平洋北部的30°N和45°N之间在核幔边界处存在的古板块的俯冲过程有关.     

我国东部梅雨雨区的年际和年代际的变化分析

从气候学的角度,利用1961-2000年梅雨期我国东部180站的逐日降水资料生成了历年的梅雨期雨区,采用累积距平、滑动平均值和Morlet小波分析等方法研究了梅雨期雨区边界和面积指数的年际和年代际变化以及雨区边界在地域上的差异及其梅雨量与边界和面积指数的关系.结果表明:近40年来雨区边界的平均位置为:28.3°N～32.0°N,呈准水平的带状分布.雨区边界40年来经历了一个振荡期即20世纪60年代～70年代末期雨区逐渐北进;80年代初期～90年代末期雨区逐渐南撤,从地域上可将雨区分为西部和东部两个部分而且二者都存在主要周期为6年.雨区面积指数从变化趋势近40年来也只经历了一个振荡过程:60年代初期～80年代初期为雨区面积指数的下降期;80年代中期～90年代末期为雨区面积指数的上升期,其主要周期为4年.在年际(6年)变化时间尺度上,梅雨量的变化落后面积指数的变化1～2年,雨区面积的变化落后于西部和东部雨区边界变化约1～1.5年;在年代际(16年)变化的时间尺度上雨区面积与雨区边界的变化趋势几乎相反,梅雨量则表现出比雨区面积和边界变化更长的周期.总的来说,近40年雨区边界和面积指数受10年以下的周期影响较大.不论雨区边界还是雨区面积指数在80年代初期都为其突变期.     

青岛附近海域SST长期变化趋势分析

本文利用来自青岛附近海域1961～2009年的海表温度（SST——Sea Surface Temperature）资料,对该海域SST的变化趋势、突变形式、变化周期等进行分析。结果表明：（1）1961～2009年期间,青岛附近海域的SST以0.029℃/a的速度显著性线性递增;（2）青岛附近海域的SST存在明显的2.1～2.7年、3.8～5.0年的变化周期以及30年以上的长周期震荡;（3）青岛附近海域的SST存在明显的突变形势,且突变期为20世纪80年代末期至90年初期;逐夏季SST的突变期为1988年;逐冬季SST的突变期为1992年前后。     

近50年吉林省干湿指数时空分布特征分析

采用桑斯维特在气候分类法中定义的干湿指数,结合趋势系数分析、小波分析、M-K检验等统计方法,对吉林省近50年气候干湿变化状况进行了分析,结果表明:吉林省表现出4次相对的干湿交替,即20世纪60年代的偏湿润期,70年代的相对干旱期,80年代的偏湿润期,90年代中后期以后的偏干旱期;存在10～15 a和3a的变化周期,突变发生在1979- 1980年;在空间变化上表现出湿润区范围不断扩大,半湿润区显著缩小,半干旱区范围略有扩大的特点.     

福建省冬季持续性低温变化特征分析

该文应用福建省66个气象观测站1961年~2014年冬季逐日气温和极低气温资料,通过定义冬季低温指数、低温日、持续性低温过程及起止时间,并以持续性低温日数和低温指数为指标,运用累积距平法(CA)、滑动T检验法(MTT)和小波分析等方法研究了福建省冬季持续性低温的变化特征。结果表明:福建冬季持续性低温过程发生的频率、持续日数和强度具有明显的年代际变化特征,20世纪60~70年代为多发期,强度偏强,20世纪80~90年代为波动期,20世纪90年代之后转为减少期,强度相对减弱。通过小波分析和突变分析发现,福建省持续低温过程爆发突变位置主要位于20世纪80年代中期~90年初期之间。     

The interdecadal trend and shift of dry/wet over the central part of North China and their relationship to the Pacific Decadal Oscillation （PDO）

Based on monthly precipitation and monthly mean surface air temperature (SAT),the dry/wet trends and shift of the central part of North China and their relationship to the Pacific Decadal Oscillation (PDO) from 1951 to 2005 have been analyzed through calculating surface wetness index (SWI). The results indicate that there was a prominent drying trend and an abrupt change in the analysis period. A per-sistent warming period with less precipitation from the mid and late 1970s to present was found,and a shift process exists from the wet to the dry in the central part of North China during 1951-2005. The transition is located in the mid to late 1970s,which should be related to the shift variation of large-scale climate background. The correlation analysis has brought about a finding of significant correlativity between PDO index (PDOI) and SAT,precipitation and SWI in this region. The correlation exhibits that the positive phase of PDOI (warm PDO phase) matches warming,less precipitation and the drought period,and the negative PDOI phase corresponds to low SAT,more precipitation and the wet period. The duration of various phases is more than 25 years. The decadal variation of sea surface temperature (SST) in the North Pacific Ocean is one of the possible causes in forming the decadal dry/wet trend and shift of the central part of North China.     

Covarying modes of the Pacific SST and northern hemispheric midlatitude atmospheric circulation anomalies during winter

The interannual-to-interdecadal relationship between the Pacific sea surface temperature （SST） and the northern hemispheric midlatitude＇s atmosphere represented by the circumpolar vortex was documented with the global oceanic and atmospheric reanalysis data of recent 50 years. Two covarying modes of the Pacific SST and northern circumpolar vortex anomalies during winter were examined using the singular value decomposition and wavelet analysis techniques. One is the interannual, ENSO-related mode and the other is the interdecadal, North Pacific SST-related mode with a period of around 20 years. The two modes exhibit distinct spatial structures. For the interannual mode, the SST anomaly is characterized by a typical ENSO pattern with the principal signature in the tropical eastern Pacific and secondary one in the central North Pacific, while the atmospheric anomaly is regional, characterized by a Pacific-North American pattern. For the inter- decadal mode, large SST anomaly is located in the central North Pacific, while the atmospheric anomaly is zonally global, associated with the midlatitute＇s standing long-wave variations. When the central North Pacific is colder, the long-wave is stronger, and vice versa. Further investigations suggest that the interdecadal mode could involve an interaction between ＂two oceans and an atmosphere＂.     

Statistical characteristics of the double ridges of subtropical high in the Northern Hemisphere

The generality and some climatological characteristics of the double ridge systems of subtropical high （SH） are investigated statistically by using the daily NCEP/NCAR reanalysis data from 1958 to 1998. The results show that the SH double-ridge event is a common phenomenon in the Northern Hemisphere, with the distinct seasonal and regional features, that is, the majority of SH double-ridge geneses concentrate over the eastern North India Ocean-western North Pacific as well as the central North Pacific in the period from mid-July to mid-September. Especially over the western North Pacific subtropics, the SH double-ridge events are extremely active. It is found that the life cycle of most double-ridge events of western Pacific subtropical high （WPSH） is shorter but some still last longer. The WPSH double-ridge events occur most frequently from July to September, while there is a paucity of occurrences during November-March. Also, it is shown that the WPSH double-ridge events have a strong interannual variation with a certain periodicity which possesses a remarkably abrupt change in the mid-1970s. Additionally, the relationship between the WPSH double ridges and the meridional movement of WPSH is discussed.     

Multiscale characteristics of the rainy season rainfall and interdecadal decaying of summer monsoon in North China

This paper focuses on the rainfall spectrum and its evolution of North China in rainy season with summer monsoon decaying in interdecadal time scale. The interannual component of the rainfall is the dominant part, accounting for 85% of the total variance, and has been changed significantly during the last 30 years. According to wavelet analysis its 5a periodic spectrum suddenly disappeared in the late 1960s, and its biennial oscillation gradually become weaker and weaker since 1970, accompanied by the summer monsoon decaying. Contrarily, the interdecadal component is principal in the summer monsoon over North China and is very similar to the counterpart of the rainfall. Their interdecadal parts are significantly correlated, and the correlation coefficient is nearly equal to the one of the original sequences.Besides, the dry and wet climate alternated with the monsoon abrupt changes in the 1960s and the 1970s over East Asia, apart from North China, climate drifted from a light drought to a severe drought during the past 30 years.     

重庆地区秋季连阴雨气候特征及前兆信号分析

根据1961—2012年重庆地区34个气象观测站的逐日降水资料、NCEP/NCAR再分析数据集中的高度场格点资料和NOAA的海温逐月资料,分析了重庆地区秋季连阴雨的气候特征、气候背景与前兆信号.结果表明:近52年来重庆地区秋季连阴雨频数呈线性增多趋势.重庆地区秋季连阴雨偏多(偏少)同期环流对应乌拉尔山地区高度场偏低(高),欧亚中高纬度地区盛行经向(纬向)环流,赤道东太平洋区域海温偏低(偏高).前期春季、夏季孟加拉湾地区、我国南海地区500hPa高度场、赤道中东太平洋地区海温,特别是Nio3.4区的海温异常变化是重庆地区秋季连阴雨出现异常偏多(少)值得关注的前兆信号.     

东北夏季降水的时间变化特征及其与太平洋海温的相关关系

利用中国降水逐日站点观测资料以及HadISST海温资料,分析了1961-2010年东北地区70个观测站夏季降水的变化特征以及太平洋海温对东北夏季降水的可能影响。结果表明：东北夏季降水近50a来呈现下降趋势,具有多阶段性,在60年代以及80-90年代存在明显的突变;在1986-1985年以及1986-2010年2个阶段,热带外太平洋与热带太平洋春季和夏季海温都存在与东北夏季降水的相关关键区,两个阶段相关性显著不同甚至相反,是1961-2010年东北夏季降水与太平洋海温总体相关性较弱的原因。东北夏季降水与太平洋海温的相关性可能与海温冷暖背景有关系：在暖的海温背景下,东北降水与热带太平洋海温呈现显著的正相关;而对于热带外太平洋,暖的海温背景下,两者为负相关,冷的海温背景下,两者为正相关,尤其表现在春季,因此太平洋春季海温异常对于东北夏季降水预测有较好的指示意义。     

Linkage between the Asian-Pacific Oscillation and the sea surface temperature in the North Pacific

The linkage between the Asian-Pacific Oscillation (APO) and the sea surface temperature (SST) in the North Pacific during the summertime (June-August) is preliminarily investigated through an analysis of observed data.It is found that APO is significantly and positively correlated to the North Pacific SST,with the correlation coefficient being 0.58 on the interannual timescale during the period 1954-2003,which suggests that a strong (weak) APO corresponds to high (low) SST in the North Pacific.Their in-phas...     

Sea surface temperature east of Australia： A predictor of tropical cyclone frequency over the western North Pacific？

The relationship between sea surface temperature (SST) east of Australia and tropical cyclone frequency over the western North Pacific (WNPTCF) is analyzed by use of observation data.The WNPTCF from June to October is correlated negatively to spring SST east of Australia.When the spring SST is in the positive phase,a cyclonic circulation anomaly in the upper troposphere and an anticyclonic circulation anomaly in the lower troposphere prevail over the western North Pacific from June to October,concurrent with an anomalous atmospheric subsidence and an enlarged vertical zonal wind shear.These conditions are unfavorable for tropical cyclone genesis,and thus WNPTCF decreases.The negative phase of the spring SST east of Australia leads to more tropical cyclones over the western North Pacific.The spring SST east of Australia may give rise to simultaneous change in tropical atmospheric circulation via the teleconnection wave train,and then subsequently affect atmospheric circulation variation over the western North Pacific.     

Interannual variation of North China rainfall in rainy season and SSTs in the equatorial eastern Pacific

The rainfall in North China during rainy season （July and August （JA）） exhibits a strong interannual variability. In this study, the atmospheric circulation and SST anomalies associated with the interannual variation of JA North China rainfall are examined. It is found that on the interannual timescale, the JA North China rainfall is associated with significant SST anomalies in the equatorial eastern Pacific, and the North China rainfall and SST anomaly in the equatorial eastern Pacific correspond to the similar variation of the upper-level westerly jet stream over East Asia. A possible mechanism is proposed for the influence of the SST anomalies in the equatorial eastern Pacific on the North China rainfall.     

Some evidence of drying trend over northern China from 1951 to 2004

The surface wetness index, Palmer drought sererity index and the retrieval of soil moisture over China were calculated using monthly precipitation and monthly mean surface air temperature. Based on the contrast analysis of the variation of the above three indices and precipitation, the dry/wet spatio-temporal pattern of northern China in the last 54 years was revealed, and the evidence of drying trend over northern China was analyzed, especially. The results show the following four facts: (1) The drying trend is the main characteristic of the eastern part of Northwest China and the central part of North China since the 1980s and it was enhanced in the last 15 years mainly due to the precipitation decrease and the temperature increase; (2) During the last 54 years, there was only one dry/wet shift at the interdecadal scale occurring in the eastern part of Northwest China and the central part of North China in the late 1970s, which was related to 1977/1978 global abrupt change, whereas there were three shifts in Northeast China, one was in the mid 1990s and the other two were in 1965 and 1983, respectively; (3) Unlike the variation trend of other subregions of northern China, the western part of Northwest China is currently located in a relatively wetting period, which is weak-ened due to the temperature increase; (4) The extreme drought frequency is obviously increasing in the eastern part of Northwest China, the central part of North China and Northeast China since the 1980s, which is closely related to the precipitation decrease and temperature increase in these subregions.