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1.
北大西洋涛动和北极涛动与新疆河川径流变化 总被引：4，自引：2，他引：2
分析了冬季北大西洋涛动(NAO)和北极涛动(AO)与新疆天山南北不同流域河川径流变化的关系.结果表明:影响北半球气温、降水等气候驱动因子的NAO和AO同样与新疆河川径流的变化具有显著的遥相关.在年际变化上,NAO和AO的强弱分别与径流变化的相关性具有明显的区域性差异;在年代际尺度上,NAO和AO有超前于新疆河流年径流5 a的显著相关,相关关系分别超过了95%和99%置信水平.NAO和AO变化对预测新疆河川径流的变化有很好的实际意义. 相似文献
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《地球科学进展》2016,(11)
20世纪90年代中后期北大西洋涛动(NAO)年代际变率的发现与北极涛动(AO)概念的提出,引发了持续至今的古AO/NAO研究热潮。从观测和模拟两方面对多时间尺度的古AO/NAO研究进展做了系统的回顾与总结,包括近千年AO/NAO序列的重建,全新世AO/NAO变化趋势的争议,末次冰盛期AO/NAO振幅的减弱,末次间冰期AO/NAO的异常偏正,以及AO/NAO的气候平均态与振幅2个关键概念的区分。其中对不同时段AO/NAO的变化机理做了简要概括与讨论。在此基础上,建议在今后的古AO/NAO研究中,除了寻找时间更长、与AO/NAO显著相关的代用资料外,还要着力加强气候模拟方面的工作,特别是长时间瞬变模拟及对关键外强迫因子开展敏感性试验。只有将观测与数值模拟相结合,才可进一步增进对AO/NAO与气候背景间动力机制的理解。在过去20年间,气候学界对AO/NAO的广泛研究,对于理解全球变暖背景下AO/NAO的变化过程、并提高其可预报性都具有重要意义。 相似文献
4.
《地球科学进展》2016,(6)
北大西洋涛动(NAO)和阻塞等大气大尺度低频模态对北半球天气气候起着重要的调控作用。首先回顾了NAO年代际变率物理机制的研究进展,并从季节内尺度NAO位相转换的角度讨论了其对NAO年代际变率的影响。介绍了NAO与阻塞时空关系的研究进展,讨论了年代际NAO变率对阻塞时空分布的可能影响。另外,以2次极端暴雪天气事件为例,从观测事实方面讨论了NAO和阻塞对极端暴雪天气的影响机制,同时从理论模型方面部分解释了其可能的物理机制。总结了有关NAO和阻塞理论模式的研究进展,介绍了非线性多尺度相互作用模型的发展过程和应用。最后,基于对以上研究进展的总结,给出了NAO-阻塞—极端暴雪天气的机制示意图,概括部分研究的特点和不同之处,并提出了该领域有待解决的几个问题和未来可能的研究方向,为相关的研究提供参考。 相似文献
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1951—2016年中亚努尔苏丹与乌鲁木齐寒潮过程频数变化及其主要影响因子对比分析 总被引：1，自引：1，他引：0
利用1951—2016年努尔苏丹和乌鲁木齐的逐日最低气温资料, 以当年7月到翌年6月为统计年, 对比分析了中亚地区的努尔苏丹与乌鲁木齐的寒潮、 强寒潮和超强寒潮过程频数气候变化特征, 并初步分析了冬季北极涛动（AO）、 北大西洋涛动（NAO）与中亚两个城市同期寒潮活动关系。结果显示： 努尔苏丹的年平均寒潮过程频数（15.7次·a-1）是乌鲁木齐（4.1次·a-1）的3.88倍, 强寒潮和超强寒潮过程频数分别是乌鲁木齐的5.91倍和7.55倍; 努尔苏丹的超强寒潮过程频数月分布呈单峰型, 1月最多, 乌鲁木齐的呈双峰型, 峰值分别出现在11月和4月。努尔苏丹的寒潮过程持续日数普遍比乌鲁木齐短。65 a来, 努尔苏丹与乌鲁木齐的春季寒潮过程频数之间的相关关系显著。努尔苏丹和乌鲁木齐的年寒潮过程频数的线性递减率分别为-0.111次·（10a）-1和-0.445次·（10a）-1; 两城市秋、 冬、 春季寒潮、 强寒潮和超强寒潮过程频数线性趋势大多以递减为主, 但是努尔苏丹冬季和乌鲁木齐春季的超强寒潮过程频数均呈递增趋势。努尔苏丹的年超强寒潮过程频数在近5 a最多。努尔苏丹的年寒潮过程频数序列有31 a、 20 a左右的显著周期, 乌鲁木齐的年寒潮过程频数序列有39 a、 8 a左右显著周期。北大西洋涛动（NAO）与努尔苏丹和乌鲁木齐寒潮过程的关联程度比北极涛动（AO）与它们之间的关联程度更为密切; 努尔苏丹的寒潮过程频数受NAO以及AO的影响程度更深。 相似文献
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基于SPEI指数的兰州干旱特征与气候指数的关系 总被引：2，自引：0，他引：2
基于1961~2012年逐日气象及同期4个气候因子资料系列,采用标准化降水蒸散发指数(SPEI)定量描述兰州地区干旱状况,利用M-K检验分析了该地干旱变化趋势,采用皮尔逊相关系数法以及交叉小波变换法研究了SPEI与北大西洋涛动(NAO)、北极振荡(AO)、太平洋十年涛动(PDO)以及厄尔尼诺-南方涛动(ENSO)四个气候因子之间的关系。研究结果表明:干旱指数SPEI在月、春、夏、秋及年尺度上均呈显著下降趋势、冬季增长趋势不显著,未来兰州春、夏和秋季缺水有加重趋势,冬季有变湿润倾向;SPEI与PDO、ENSO在秋季呈显著负相关;ENSO主要影响干旱短周期的年际变化;干旱与PDO和AO呈滞后的负相关关系,两指数主要影响较长周期干旱的年际和年代际变化。 相似文献
8.
大尺度大气环流变化及其对北半球冬季温度的影响 总被引：6，自引：0，他引：6
近半个世纪来的全球温度的变化表现出有很大的空间尺度和显著的线性趋势 ,许多研究强调温室效应对全球气候变暖的影响。文中的研究表明大尺度的大气环流的变化对北半球冬季温度有很重要的影响。最近一些学者侧重北大西洋涛动 (NAO)和北太平洋涛动 (NPO)的作用 ,而NAO和NPO都是行星尺度大气环流在区域的特殊表现形式。全球西风环流系统可能具有根本性的作用。当西风环流处于高指数时期时 ,则温度偏高 ;当处于低指数时期时 ,则温度偏低。西风强度及NAO和NPO能解释近 50年来北半球冬季温度变化方差的 2 7 2 %。 相似文献
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大高加索山脉位于黑海和里海之间,是欧洲与亚洲的分界线,该区域气候受到北大西洋涛动 (North Atlantic Oscillation, NAO)的强烈影响。为了对该区域的大气降水δ18O (δ18OP) 与NAO的关系有更加深入的认识,本文利用大高加索山以南6个全球降水同位素监测网(Global Network of Isotope in Precipitation, GNIP)站点的δ18OP数据,分析该区域δ18OP 的季节变化规律,以及δ18OP与温度和降水量等气象要素及大气环流之间的关系。得到以下主要认识:① 在月时间尺度上,δ18OP与月平均温度之间有着显著的正相关关系(p<0.01),表明该区域δ18OP主要受当地温度控制,表现出“温度效应”。② 北大西洋涛动通过改变西风的强度和位置从而影响δ18OP 的变化:当NAO呈现负相位时,此时西风输送较弱,使得来自地中海的富含18O的水汽能够达到大高加索山以南,该地区δ18OP偏正。而当NAO正相位时,西风急流输送较强,从北大西洋穿越黑海带来更多的δ18OP 偏轻的降水。因此,NAO所导致的水汽输送路径的变化可能是影响大高加索山以南地区δ18OP的重要因素,这一研究结果为利用该地区地质记录中的δ18O记录来重建过去的NAO变化提供了前提。 相似文献
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北大西洋涛动对青藏高原夏季降水的影响 总被引：4，自引：2，他引：2
利用青藏高原中东部1961-2004年60个气象台站夏季(6-8月)降水资料,通过旋转经验正交函数分解发现青藏高原夏季降水存在南北反向变化的空间模态,分析表明这种变化模态与北大西洋涛动(NAO)密切相关.利用NCEP/NCAR再分析资料进行环流场分析,探讨了NAO对青藏高原这种降水空间变化模态的影响机制.结果表明:强NAO年份时,高原北部水汽输送通量强度增强,水汽辐合增强,而高原南部水汽输送通量强度减弱,此时高原切变线位置明显偏北,正是在这种水汽输送和环流形式配置下使得高原北部降水偏多而高原南部降水偏少;在弱NAO年份,上述情况基本相反. 相似文献
11.
The discovery of decadal variability of North Atlantic Oscillation (NAO) and the introduction of Arctic oscillation (AO) concept have initiated a series of paleo-AO/NAO related studies since the mid-to-late 1990s. The progress and new findings of paleo-AO/NAO works after that time were comprehensively reviewed. The new results from the observations and modelings at four key timescales were summarized in detail: ①the reconstructions of the AO/NAO annual index over the past millennium; ②the debate on AO/NAO’s trend since early Holocene; ③the weakening of AO/NAO’s amplitude during the Last Glacial Maximum; and ④the anomalous positive phase of AO/NAO during the Last Interglacial. In addition, the possible mechanism for different timescales of AO/NAO is also summarized. Furthermore, the distinction between AO/NAO’ was mean state and amplitude, which were not explicitly separated in previous studies, were comprehensively discussed. Considering the current uncertainties related to paleo-AO/NAO studies, we encourage the community to search for more proxies having longer-than-10,000-year length with annual resolution around AO/NAO highly correlated regions. Another, we encourage long-term transient modeling on AO/NAO can be performed in order to improve our understanding of the dynamics and interaction between AO/NAO’s high-frequency variability and the climatological background, so as to further improve AO/NAO’s predictability on global warming context. 相似文献
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The North Atlantic Oscillation (NAO) is one of the modes of climate variability in the North Atlantic region. The atmospheric circulation during the winter season in this region commonly displays a strong meridional (north–south) pressure contrast, with low air pressure (cyclone) centred close to Iceland and high air pressure (anticyclone) near the Azores. This pressure gradient drives the mean surface winds and the mid‐latitude winter storms from west to east across the North Atlantic, bringing mild moist air to northwest Europe. The NAO index is based on the difference of normalised sea‐level pressures (SLP) between Ponta Delgada, Azores and Stykkisholmur, Iceland. The SLP anomalies at these stations are normalised by division of each monthly pressure by the long‐term (1865–1984) standard deviation. Interannual atmospheric climate variability in northwest Europe, especially over Great Britain and western Scandinavia has, during the last decades, been attributed mainly to the NAO, causing variations in the winter weather over the northeast North Atlantic and the adjacent land areas. A comparison between the NAO index and the winter (December–March) precipitation between ad 1864 and 1995 in western Norway shows that these are strongly linked (correlation coefficient 0.77). Variations in the NAO index are also reflected in the mass balance records of glaciers in western Scandinavia. The NAO index is best correlated with mass balance data from maritime glaciers in southern Norway (e.g. Ålfotbreen R2 = 0.51). The record of Holocene (last ca. 11 500 cal. yr) glacier variations of maritime glaciers in western Scandinavia is thus a proxy of pre‐instrumental NAO variations. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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全球变暖背景下,偶发极端冷事件产生的重大灾害损失不容忽视。探究区域极端冷事件的大尺度驱动因子的耦合影响,对预估和应对气候变化产生的极端灾害具有重要意义。本文基于新疆1961—2016年53个气象站点的逐日气温资料,通过反距离加权等方法对极端冷事件的时空演变特征进行分析;利用交叉小波变换对6个极端冷指数与大尺度驱动因子——北极涛动（AO）、北大西洋涛动（NAO）和厄尔尼诺-南方涛动（ENSO）进行多尺度分析;使用参数假设检验对大尺度驱动因子单一/耦合模态下的冷指数变化进行统计学显著性检验,随后对大尺度环流机制进行距平合成分析。结果表明：年均冷指数在时间尺度上均有显著性变化,新疆气温有明显的变暖趋势;空间尺度上冷指数在北疆、东疆和伊犁河谷地区的变化幅度远大于其他区域,存在空间差异性。AO、NAO与冷指数的相关性较强,ENSO与冷指数相关关系最弱但存在明显的时滞效应,大尺度驱动因子对极端冷指数的总体影响程度为AO>NAO>ENSO。单一模态下,极端冷事件在AO负位相、NAO负位相和La Ni?a事件期间易发生。耦合模态下,EI Ni?o-AO正位相和EI Ni?o-NAO正位相配置下冷日日数偏多;EI Ni?o-NAO负位相配置时极端低温值更小;La Ni?a-AO负位相和La Ni?a-NAO正位相时极端冷事件发生的可能性更大。EI Ni?o（La Ni?a）事件对AO（NAO）有一定的调制作用。新疆极端冷事件更易出现在La Ni?a-AO负位相、La Ni?a-NAO正位相时期,成因与亚欧大陆中高纬度位势异常导致冷空气路径偏西、乌拉尔阻塞加强与偏北气流影响新疆有关。 相似文献
14.
Temporal Change Characteristics of Climatic and Its Relationships with Atmospheric Circulation Patterns in Qinghai Lake Basin 总被引：1，自引：0，他引：1
Based on monthly meteorological data from 11 stations(1959-2015)in Qinghai Basin(QHB) and its surrounding area, we analyzed monthly average temperature(Tmean), average maximum(TXam), minimum temperature(TNam) and precipitation variation characteristics as well as the influence of atmospheric oscillation on these parameters using Mann-Kendall trend analysis, mutation analysis, continuous Morlet wavelet transform, Pearson correlation analysis and R/S analysis method. In addition, the future trend of climate change in the regional scale was also discussed. We found that the temperature and precipitation increment were obvious in the region, especially the Tmean in autumn, winter, TXam and TNam in summer and winter precipitation showing significant increase. Temperature and precipitation experienced abrupt changes around 1986 and 2002, respectively. The period of oscillation of each temperature indices was similar featuring 2~3 years,8~10 years short- cycle and 30~32 years middle- cycle, while that for the precipitation featured 3~4 years,6~7 years short- cycle and 30~32 years middle- cycle. The East Asian Summer Monsoon Index(EASMI) anomaly is an important factor for the anomaly of autumn temperature and summer precipitation in QHB, while the Indian Summer Monsoon Index(ISMI) mainly affects the spring temperature and precipitation in the research area. The effects of Arctic Oscillation Index (AO) were relatively strong on temperature variation, especially in autumn and winter, and AO had significant effect on the precipitation in spring, summer and winter, too. The North Atlantic Oscillation Index (NAO) and ENSO have weak influence on the study area, NAO mainly affects summer and winter precipitation, while ENSO mainly affects autumn precipitation. The Hurst index of Tmean and annual precipitation in QHB are higher than 0.5, indicating that the temperature and precipitation in the study area will continue to be the positive trend in the future period. 相似文献
15.
The Influence of the North Atlantic Oscillation on Rainfall Triggering of Landslides near Lisbon 总被引：1，自引：0，他引：1
The majority of landsliding episodes in the area north of Lisbon are associated with rainfall events of short (less than 5
days) medium (5–20 days) or long duration (more than 20 days). The precipitation regime in Portugal is highly irregular, with
large differences between wet and dry years. We have assessed the impact of the North Atlantic Oscillation (NAO) on both the
winter precipitation and the timing and magnitude of associated landslide events. Results show that the large inter-annual
variability of winter precipitation is largely modulated by the NAO mode. The precipitation composite corresponding to high
NAO index presents a considerable lower median value (47 mm/month) than the corresponding low NAO index class (134 mm/month).
The entire precipitation distribution associated with the low NAO index composite encompasses a wider range of values than
the corresponding high NAO index composite. This non-linear behavior is reflected in the probability of occurrence of a very
wet month (precipitation above the 90% percentile) that is just 1% for the positive NAO class and 23% for low NAO index months.
Results for the low NAO class are crucial because these months are more likely associated with long-lasting rainfall episodes
responsible for large landslide events. This is confirmed by the application of a 3-month moving average to both NAO index
and precipitation time series. This procedure allowed the identification of many months with landslide activity as being characterized
by negative average values of the NAO index and high values of average precipitation (above 100 mm/month). Finally, using
daily data we have computed the return periods associated with the entire set of landslide episodes and, based on these results,
obtained a strong linear relationship between critical cumulative rainfall and the corresponding critical rainfall event duration. 相似文献
16.
Several studies demonstrate that North Atlantic Oscillation (NAO) has dominant influence on the variability of climate over Southwest Asia. We deconstruct the NAO into its two components, the Azores High and the Icelandic Low. Regional circulations are influenced by changes not only in the pressure but also the positions of the Azores High and the Icelandic Low. The results presented in this paper exhibit that significantly great portions of interannual variance of winter precipitation over Indo-Pak Region (consists of Northeast Pakistan and Northwest India) can be explained by including the contributions of the Icelandic Low pressure in addition to ENSO and AO. This contribution also explains the physical mechanisms to establish the relationships between the COA and regional climate by examining composite maps of large-scale circulation fields using NCEP/NCAR reanalysis data. 相似文献
17.
SAMULI HELAMA ALAR LÄÄNELAID HANNA TIETÄVÄINEN MARC MACIAS FAURIA ILMO T. KUKKONEN JARI HOLOPAINEN JAN K. NIELSEN ILMARI VALOVIRTA 《Boreas: An International Journal of Quaternary Research》2010,39(4):734-748
Helama, S., Läänelaid, A., Tietäväinen, H., Macias Fauria, M., Kukkonen, I. T., Holopainen, J., Nielsen, J. K. & Valovirta, I. 2010: Late Holocene climatic variability reconstructed from incremental data from pines and pearl mussels – a multi‐proxy comparison of air and subsurface temperatures. Boreas, Vol. 39, pp. 734–748. 10.1111/j.1502‐3885.2010.00165.x. ISSN 0300‐9483. Dendrochronological and sclerochronological records are mean series of arboreal and molluscan increments that are correctly aligned in time by rigorous dating. These records of tree rings and annual shell‐growth increments exhibit climate signals that can be used to reconstruct fluctuations and trends in past climates. Here we present a multi‐proxy reconstruction of temperature histories using a combination of dendrochronological and sclerochronological evidence. Regional curve standardization (RCS) was used to remove the non‐climatic variations from dendrochronological and sclerochronological series prior to palaeoclimatic interpretation. Conventional and signal‐free methods of RCS were compared. It was found that the signal‐free methods produced more reliable chronologies and systematically higher climate–proxy correlations. Consequently, the temperature reconstructions were derived using the chronologies constructed by this method. Proxy‐based histories of summer (July–August) temperatures were reconstructed from AD 1767 onwards. The compound use of proxies resulted in reconstructions that were of higher quality than single‐proxy reconstructions. Further improvement of reconstructions was accomplished by the inclusion of lagging increment values in the transfer functions. The final multi‐proxy model explained 58% of the temperature variance over the instrumental period. The multi‐proxy temperature reconstruction correlated well with the long records of instrumental temperatures from Tornedalen, St. Petersburg, Uppsala and Stockholm. Overall, the reconstruction for the past 250 years agreed reasonably well with borehole temperature reconstructions obtained in northern Finland. In general, this study demonstrates the benefits of the compound use of several proxies in reconstructing climate histories. In particular, the study emphasizes the so far largely unexploited advantages of multi‐proxy data sets obtained by rigorously cross‐dated incremental chronologies to produce more robust palaeoclimatic reconstructions. 相似文献
18.
《Quaternary Science Reviews》2007,26(19-21):2322-2336
According to tree ring and other records, a series of severe droughts that lasted for decades afflicted western North America during the Medieval period resulting in a more arid climate than in subsequent centuries. A review of proxy evidence from around the world indicates that North American megadroughts were part of a global pattern of Medieval hydroclimate that was distinct from that of today. In particular, the Medieval hydroclimate was wet in northern South America, dry in mid-latitude South America, dry in eastern Africa but with strong Nile River floods and a strong Indian monsoon. This pattern is similar to that accompanying persistent North American droughts in the instrumental era. This pattern is compared to that associated with familiar climate phenomena. The best fit comes from a persistently La Niña-like tropical Pacific and the warm phase of the so-called Atlantic Multidecadal Oscillation. A positive North Atlantic Oscillation (NAO) also helps to explain the Medieval hydroclimate pattern. Limited sea surface temperature reconstructions support the contention that the tropical Pacific was cold and the subtropical North Atlantic was warm, ideal conditions for North American drought. Tentative modeling results indicate that a multi-century La Niña-like state could have arisen as a coupled atmosphere–ocean response to high irradiance and weak volcanism during the Medieval period and that this could in turn have induced a persistently positive NAO state. A La Niña-like state could also induce a strengthening of the North Atlantic meridional overturning circulation, and hence warming of the North Atlantic Ocean, by (i) the ocean response to the positive NAO and by shifting the southern mid-latitude westerlies poleward which (ii) will increase the salt flux from the Indian Ocean into the South Atlantic and (iii) drive stronger Southern Ocean upwelling. 相似文献