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1.
利用我国气象台站观测资料和再分析格点数据,诊断研究了前期春季(4-5月份)北大西洋涛动(North Atlantic Oscillation,NAO)和南半球环状模(Southern Annular Mode,SAM)在不同位相配置下对我国南方夏季降水异常变化的协同影响作用.分析结果表明,在剔除ENSO最强信号影响后,我国南方夏季降水异常分布显著地依赖于前期春季两个较为独立的年际变率主模态(NAO和SAM)位相的不同配置,即降水异常型主要表现为两个因子单独作用的叠加效果,当前春SAM正位相偏强而NAO负位相偏强时,二者的影响呈现协同正效应,我国南方夏季(6-7月份)降水表现为全区正异常,特别在长江中下游及其以南附近地区最为显著;反之,当前春SAM呈偏强的负位相而NAO偏强的正位相配置时,二者的影响呈现协同负效应,对应我国夏季长江中下游地区降水表现为显著负异常.对其可能的影响机理研究表明,在SAM与NAO位相相反情况下,二者均会通过海气相互作用过程影响到热带大西洋北部海温的异常变化,进而形成协同作用,增强北大西洋海温三极子模态异常信号,从而通过欧亚大陆的遥相关波列对东亚夏季风和我国南方降水产生显著影响.相比之下,当SAM与NAO同位相时,可能表现为抵消效应,不利于北大西洋海温三极子发展,从而削弱对我国南方夏季降水的影响,此方面还有待进一步研究. 相似文献
2.
分析了中国北方沙尘气候的时间变化特征, 重点研究与沙尘气侯的年代际变化相应的冬、春季气候和大气环流异常特征. 文章揭示: 在沙尘活动频繁年代(1956~1970)和稀少年代(1985~1999)冬、春季的气候和大气环流有显著差别. 与前一个年代相比, 在后一个年代里冬季极涡异常加深, 50°N附近的西风增强, 东亚极锋锋区位置偏北, 东亚大槽偏弱; 西伯利亚高压北部及中心强度变弱, 阿留申低压明显升压; 东亚季风强度变弱, 影响中国的冷空气势力减弱, 冬、春季大风天气变少. 同时中国北方广大地区冬季温度显著升高, 西北和内蒙古的沙源地区春季降水明显增多. 研究还发现, 在年际尺度上, 中国北方的沙尘活动频次与前冬的西风指数、北极涛动指数呈显著的负相关, 与冬、春季东亚季风指数呈显著的正相关. 相似文献
3.
通过对挪威卑尔根全球大气-海洋-海冰耦合模式300a控制积分结果进行交叉子波分析,揭示了东亚夏季风（EASM）与同期Nio3区（90°W～150°W,5°S～5°N）海洋表面温度异常的相关关系在长期变化中是不稳定的,呈现出明显的阶段性特征.气候要素场在二者联系的紧密（HCP）和微弱（LCP）时期差别显著,在HCP时期,西北太平洋对流层低层出现一对耦合的异常气旋和反气旋性环流系统;东南亚地区对流层低层表现为强东风异常,风速的年际变率加大;热带西太平洋对流层温度和位势高度场的年际变率普遍加强.此外,中国夏季降水与同期Nio3区海洋表面温度异常的相关关系在上述两种时期也存在较大差别. 相似文献
4.
利用1958～2002年的NCEP-R1和ERA-40逐日再分析资料以及中国160站点月平均降水资料探讨了亚洲夏季风水汽输送的年际年代际变化及其与中国降水异常的关系. 分析结果表明,亚洲夏季风水汽输送和中国夏季降水的异常主模态呈现显著的准两年变化周期. 当南亚夏季风纬向水汽输送偏强（弱）时,东亚—西北太平洋地区水汽输送的偶极型异常有利于长江中下游地区和江淮流域的水汽辐合负（正）异常与华南和华北地区的水汽辐合正（负）异常,从而引起中国东部的经向三极子雨型,即长江中下游地区和江淮流域的偏旱（涝）与华南和华北地区的偏涝（旱）. 1970s年代末之后,亚洲夏季风水汽输送的年代际减弱与西北太平洋地区水汽输送的偶极型异常相配合,导致长江中下游地区的持续偏涝与华南和华北地区的持续偏旱. 从中国夏季降水异常与水汽通量辐合异常的同相对应关系来看,ERA-40资料对亚洲夏季风水汽输送年际年代际变化的描述能力强于NCEP-R1资料. 相似文献
5.
利用多通道奇异谱方法（MSSA）分析了1953~2003年亚洲和北美Palmer干旱指数（PDSI）与热带和北半球温带海洋海表面温度异常（SSTA）的主要周期振荡特征及其相互联系.结果表明：亚洲和北美PDSI以及SSTA均存在明显的3~6年的年际以及10年左右的年代尺度振荡;此外,亚洲PDSI还存在显著的6~8年的年际振荡.SSTA的年际振荡主要体现了ENSO的变化特征,而其年代尺度振荡的空间分布具有热带太平洋和北太平洋共同作用的类ENSO型.同时,MSSA的分析结果给出了亚洲和北美主要振荡信号的时间和空间演变特征.相关性分析表明,亚洲和北美PDSI的年际及年代尺度振荡均显示明显的对SSTA强迫信号的响应.对于年际振荡,亚洲PDSI对SSTA响应强于北美,但年代尺度振荡则反之.此外,亚洲和北美PDSI对于SSTA信号响应的关键区域也随时间尺度的不同而发生变化.亚洲的西西伯利亚、青藏高原东西两侧以及中西伯利亚东部在年际和年代尺度上均为受SSTA影响最显著的区域;在年际尺度上,北美中部地区的干湿变化与SSTA存在显著相关,而在年代尺度上,美国西部更易受SSTA年代尺度振荡的影响. 相似文献
6.
众多研究表明,太平洋年代际振荡(PDO)与东亚季风以及我国气候的年代际异常存在显著影响,然而其影响途径及机制仍不明确.本文分别分析了年代际尺度上的太平洋年代际振荡(PDO)、南北半球际大气质量振荡(IHO)以及东亚季风的变化特征,据此建立了三者之间的关系,并进一步分析了它们对我国东部冬夏两季年代际气候异常的影响,所得主要结果包括:(1)PDO与IHO以及东亚季风强度具有明显的年代际波动特征,三者之间存在较好联系,其中它们在70年代和90年代后期处于负位相,而在80年代至90年代中期均处于正位相期.PDO和IHO对全球大范围的低层气温异常,以及大气质量迁移尤其是东半球30°S-50°N区域的质量变化具有显著并且空间一致的影响;(2)当PDO为正位相时,整层大气质量年代际异常呈偶极型的自东半球向西半球太平洋区域输出,造成了南北半球际以及海陆间大气质量迁移,同时引起Walker环流的上升和下沉支位置变化,以及越赤道大气质量流的向北异常输送,并由此建立起东亚季风与PDO和IHO之间的联系;(3)PDO年代际异常与冬夏季节蒙古地区地表气压变动存在密切联系.当PDO指数增强时,冬夏季850hPa均出现显著反气旋风场异常,并在我国东部形成异常北风,从而显著影响东亚冬夏季风强度变化.与之对应,PDO指数与我国东部大部分地区的站点气温、降水的年代际分量保持显著的同期相关. 相似文献
7.
北极涛动(AO)、北大西洋涛动(NAO)和太平洋-北美型(PNA)等北半球大气遥相关型,可以用大气位势高度的物理分解扰动分量解释.结果发现,AO反映的是北极地区行星尺度纬圈平均扰动分量的变化,PNA与持续性天气尺度扰动分量相联系,NAO是行星尺度纬圈平均扰动与天气尺度扰动共同作用的结果.对行星尺度纬圈平均扰动分量和天气尺度扰动分量用旋转经验正交函数(REOF)展开,不但可以证实人们已经命名的区域性大气涛动,还新发现了北极地区的两对偶极涛动、欧亚涛动(EAO)和"大西洋-欧亚型"(AEA)波列.这些涛动连接了相邻地区的异常天气和异常气候. 相似文献
8.
研究了南极涛动的年际变化及其对冬春两季东亚气候的影响, 结果表明, 南极涛动强年不利于东亚冬春两季冷空气的活动. 通过平均经圈环流分析发现, 在南极涛动异常年有从南极到北极分布的经向遥相关, 并且该遥相关具有正压的结构. 此遥相关冬季在欧亚地区显著, 春季在太平洋地区显著. 研究还表明, 南半球高纬的平均纬圈西风, 在冬季与欧亚西风有显著的正相关关系, 因而在一定程度上证实了冬季经向遥相关的存在; 在春季, 则与太平洋北美型遥相关有显著的反相关关系. 因此, 局地经向遥相关是冬、春两季中南北半球中高纬大气环流相互作用的一个可能途径. 相似文献
9.
利用相关、合成、奇异值分解等统计诊断和数值模拟方法,分析了前冬(12—2月)南半球环状模(SAM)对春季(3—5月)中国华南降水的可能影响及其机理.诊断分析的结果表明,前冬南半球环状模与春季华南降水存在显著的负相关关系,也即前冬SAM偏强(弱),对应春季华南降水偏少(多).为了探讨这种南半球中高纬信号影响滞后一个季节的华南降水的物理机制,需要考虑下垫面海洋的桥梁作用.诊断分析的结果表明,当前冬SAM偏强时,南半球中高纬海洋的潜热释放受到海表风速影响发生变化,导致30°S—45°S海温偏高, 45°S—70°S海温偏低,并且异常的海温信号可以持续到次年春季.这种前冬SAM偏强时的春季海温异常信号,对应着春季西北太平洋副热带高压位置偏东且强度偏弱,西北太平洋上盛行异常气旋式环流,华南地区上空对流层低层有异常东北风和风场辐散,西南水汽输送较常年减弱,为春季降水偏少提供了有利的条件.前冬SAM偏弱时,南半球中高纬的海温异常及其引起的华南区域大气环流异常相反,有利于华南降水偏多.利用CAM3进行海温敏感性试验,也证明了上述南半球中高纬海温异常对应的环流异常.模拟结果表明,SAM偏强时的海温异常,对应着华南上空对流层低层的东北风异常、风场辐散、以及下沉运动,不利于华南降水生成;SAM偏弱时的海温异常,对应的环流异常相反,有利于华南降水增多,验证了资料诊断的结论.综上,在前冬SAM影响春季华南降水的过程中,体现了海气耦合桥的作用,即:海洋储存了冬季SAM的异常信号并在春季释放,通过影响春季大气环流,进一步影响华南春季降水.因此,前冬SAM为华南春季降水预测提供了一个有意义的前期信号. 相似文献
10.
观测事实揭示,春季Hadley环流在年际时间尺度上与东亚夏季风环流和降水具有密切联系.在未来全球变暖背景下,春季Hadley环流与东亚夏季风环流和降水的这种年际关系是否会发生变化？针对该问题,本文在评估的基础上选取五个气候模式,分析了A1B排放情景下春季北半球Hadley环流年际变率的未来变化及其与东亚夏季风环流和降水的年际关系.多模式集合(MME)预估结果表明,在全球变暖背景下,与20世纪末期(1970—1999年)相比,到21世纪末期(2070—2099年),春季北半球Hadley环流的年际变率强度将减弱,减弱幅度达32%.随着春季Hadley环流年际变率的减弱,其与夏季西太平洋副热带高压和东亚夏季风强度的联系将变弱.MME模拟结果还显示,春季Hadley环流与夏季东亚西风急流和降水的关系也降低,但各单个模式间存在较大差异. 相似文献
11.
利用降水、大气环流和海表温度等多种再分析资料和偏相关方法,研究了1951—2007年南太平洋年代际振荡（SPDO）和北太平洋年代际振荡（即PDO,本文称为NPDO）分别与华北盛夏（7—8月）降水在年代际时间尺度上的关系及其可能物理机制.结果表明：在去除SPDO和NPDO的相关性之前,它们与华北盛夏降水的关系均偏弱;但在去除两者相关性之后,SPDO（NPDO）与华北盛夏降水存在显著正（负）相关关系.去除两者相关性之后,当SPDO处于正位相时,热带西北太平洋海温异常显著偏暖,这将在对流层中下层从热带西太平洋—东亚沿岸激发出"气旋-反气旋-气旋"的负位相东亚—太平洋型遥相关（EAP）波列,该波列导致东亚夏季风异常增强,有利于低纬地区水汽输送至华北地区,从而使得华北盛夏降水异常偏多,反之,当SPDO处于负位相时,华北盛夏降水异常将偏少;对NPDO来说,当其处于正位相时,不仅热带西北太平洋异常显著偏冷,而且印度洋大部分海温异常显著偏暖,在两者共同作用下,对流层中下层从热带西太平洋—东亚沿岸出现"反气旋-气旋-反气旋"的正位相EAP波列,这将引起东亚夏季风异常减弱,不利于低纬地区水汽输送至华北地区,华北盛夏降水异常因此减少,反之,当NPDO处于负位相时,华北盛夏降水异常将偏多. 相似文献
12.
Using correlation and EOF analyses on sea level pressure from 57-year NCEP-NCAR reanalysis data, the Arabian Peninsula-North Pacific Oscillation (APNPO) is identified. The APNPO reflects the co-variability between the North Pacific high and South Asian summer monsoon low. This teleconnec- tion pattern is closely related to the Asian summer monsoon. On interannual timescale, it co-varies with both the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM); on decadal timescale, it co-varies with the EASM: both exhibit two abrupt climate changes in the middle 1960s and the late 1970s respectively. The possible physical process for the connections between the APNPO and Asian summer monsoon is then explored by analyzing the APNPO-related atmospheric circulations. The results show that with a strong APNPO, the Somali Jet, SASM flow, EASM flow, and South Asian high are all enhanced, and an anomalous anticyclone is produced at the upper level over northeast China via a zonal wave train. Meanwhile, the moisture transportation to the Asian monsoon regions is also strengthened in a strong APNPO year, leading to a strong moisture convergence over India and northern China. All these changes of circulations and moisture conditions finally result in an anoma- lous Asian summer monsoon and monsoon rainfall over India and northern China. In addition, the APNPO has a good persistence from spring to summer. The spring APNPO is also significantly corre- lated with Asian summer monsoon variability. The spring APNPO might therefore provide valuable in- formation for the prediction of Asian summer monsoon. 相似文献
13.
Twenty-four years of AVHRR-derived sea surface temperature (SST) data (1985–2008) and 35 years of NOCS (V.2) in situ-based
SST data (1973–2008) were used to investigate the decadal scale variability of this parameter in the Mediterranean Sea in
relation to local air–sea interaction and large-scale atmospheric variability. Satellite and in situ-derived data indicate
a strong eastward increasing sea surface warming trend from the early 1990s onwards. The satellite-derived mean annual warming
rate is about 0.037°C year –1 for the whole basin, about 0.026°C year –1 for the western sub-basin and about 0.042°C year –1 for the eastern sub-basin over 1985–2008. NOCS-derived data indicate similar variability but with lower warming trends for
both sub-basins over the same period. The long-term Mediterranean SST spatiotemporal variability is mainly associated with
horizontal heat advection variations and an increasing warming of the Atlantic inflow. Analysis of SST and net heat flux inter-annual
variations indicates a negative correlation, with the long-term SST increase, driving a net air–sea heat flux decrease in
the Mediterranean Sea through a large increase in the latent heat loss. Empirical orthogonal function (EOF) analysis of the
monthly average anomaly satellite-derived time series showed that the first EOF mode is associated with a long-term warming
trend throughout the whole Mediterranean surface and it is highly correlated with both the Eastern Atlantic (EA) pattern and
the Atlantic Multidecadal Oscillation (AMO) index. On the other hand, SST basin-average yearly anomaly and NAO variations
show low and not statistically significant correlations of opposite sign for the eastern (negative correlation) and western
(positive correlation) sub-basins. However, there seems to be a link between NAO and SST decadal-scale variations that is
particularly evidenced in the second EOF mode of SST anomalies. NOCS SST time series show a significant SST rise in the western
basin from 1973 to the late 1980s following a large warming of the inflowing surface Atlantic waters and a long-term increase
of the NAO index, whereas SST slowly increased in the eastern basin. In the early 1990s, there is an abrupt change from a
very high positive to a low NAO phase which coincides with a large change in the SST spatiotemporal variability pattern. This
pronounced variability shift is followed by an acceleration of the warming rate in the Mediterranean Sea and a change in the
direction (from westward to eastward) of its spatial increasing tendency. 相似文献
14.
The day-to-day effects of the strong geomagnetic disturbances on geopotential heights (GPH) in the winter lower atmosphere were described in many papers in the beginning of 1970s. These works focused on the North-East Pacific, while the North Atlantic was until now omitted. Our aim is therefore to investigate the possible effect of strong geomagnetic disturbances on the lower atmosphere GPH changes over the winter North Atlantic on the day-to-day time scale, represented by the daily index of the North Atlantic Oscillation (NAO). The investigated intervals are winter periods (December-March) of 1951–2003. The daily NAO average values in 3-day intervals before and after the disturbance onsets are compared. The graphs of NAO differences are complemented by the maps of GPH differences. The NAO response to geomagnetic disturbance, as registered on the day-to-day time scale, also shows a change in its behaviour around the year 1970. This response reaches its highest values in the years 1951–1969, usually 2–5 days following the onset of geomagnetic disturbances. Intensity of the response depends on the disturbance intensity (the largest differences were associated with extremely strong disturbances). 相似文献
15.
The long-term variability of sea level and surface flows in the Gulf of Mexico (GOM) is studied using global monthly sea level reconstruction (RecSL) for 1900–2015. The study explored the long-term relation between the dynamics of the GOM and inflows/outflows through the Yucatan Channel (YC) and the Florida Straits (FS). The results show a century-long trend of increased mean velocity and variability in the Loop Current (LC); however, no significant upward trend was found in the YC and FS flows, only increased variability. Empirical orthogonal function (EOF) analysis of sea surface height found spatial patterns dominated by variations in the LC and temporal variations on time scales ranging from a few months to multidecadal. The time evolution of each EOF mode of sea level is correlated with the velocity of either the LC, the YC, or the FS or some combination of the different flows. The mean sea level difference between the GOM and the northwestern Caribbean Sea was found to be influenced by the North Atlantic Oscillation (NAO), with unusually high differences during the 1970s when the NAO index was low and the Atlantic Ocean circulation was weak. Extreme peaks in SL difference coincide with the extension of the LC and the seasonal eddy shedding pattern. The observed seasonal cycle in the extension area of the LC as obtained from 20 years of altimeter data is significantly correlated (R = 0.63; confidence level = 98%) with the seasonal YC flow obtained from 116 years of the RecSL data. However, the same LC extension record had lower correlation (R = 0.45; confidence level = 90%) with the observed YC transport obtained from direct moored measurements over ~ 5 years, indicating the need for much longer measurements, since the LC extension and the YC flow are strongly affected by interannual and decadal variations. The study demonstrates the usefulness of even a coarse-resolution reconstruction for studies of regional ocean variability and climate change over longer time scales than current direct observations allow. 相似文献
16.
北极海冰的急剧消融在近年来欧亚大陆频发的低温事件中扮演着关键角色.秋季北极海冰的偏少对应着冬季欧亚大陆的低温天气,然而二者的联系在年代际和年际两种时间尺度上存在显著区别.本文运用1979—2012年哈德莱中心第一套海冰覆盖率(HadISST1)、欧洲中心(ERA_Interim)的2m温度、风场、海平面气压场、高度场等资料,分别研究了年代际和年际时间尺度上前期秋季北极海冰与欧亚冬季气温的联系.结果表明,欧亚和北极地区(0°—160°E,15°N—90°N)的冬季气温具有显著的年代际和年际变化.在年代际尺度上,温度异常分布在21世纪初由北极冷-大陆暖转为北极暖-大陆冷.这一年代际转折与前期秋季整个北极地区的海冰年代际减少联系密切.秋季北极全区海冰年代际偏少对应冬季欧亚大陆中高纬地区的高压异常,有利于北大西洋的暖湿气流北上和北极的冷空气南侵,造成北极暖-大陆冷的温度分布;在年际时间尺度上,温度异常分布主要由第一模态的年际变化部分和第二模态组成,且第一模态包含的年际变率信号也存在显著的年代际变化.年际尺度上全区北极海冰对欧亚冬季气温的影响远不及位于北冰洋西南边缘的巴伦支海、喀拉海和拉普捷夫海西部(30°E—120°E,75°N—85°N)的关键区海冰影响显著.关键区内海冰的偏少会引发冬季的北大西洋涛动负位相,导致北大西洋吹往欧亚大陆的暖湿气流减弱和欧亚大陆中高纬地区的气温偏低. 相似文献
17.
This paper presents the effect of the North Atlantic Oscillation (NAO) on the thermal characteristics of lakes in Poland. In the analysis, the use was made of monthly air temperatures recorded at fifteen meteorological stations, water temperatures of twelve lakes, and Hurrell’s winter NAO indices. Over the study period (1971–2010), there was a marked increase in the temperatures of both, air and lake waters. Depending on the NAO phase, water temperatures were observed to depart from mean values, being markedly higher than average (even by 1°C) in the positive winter NAO phase. The differences in water temperatures were statistically significant in the winter-spring season. In turn, in the negative NAODJFM phase lake water temperatures in winter and spring were markedly lower than average (in March even by 1.0°C). The unique response of some lakes depends on their morphometric parameters, including their mean depth. 相似文献
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