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1.
An assessment and interpretation of the observed warming of West Antarctica in the austral spring 总被引：1，自引：1，他引：0
We synthesize variability and trends in multiple analyses of Antarctic near-surface temperature representing several independent source datasets and spatially complete reconstructions, and place these into the broader context of the behavior of other components of the climate system during the past 30–50?years. Along with an annual-mean trend during the past 50?years of about 0.1°C/decade averaged over Antarctica, there is a distinct seasonality to the trends, with insignificant change (and even some cooling) in austral summer and autumn in East Antarctica, contrasting with warming in austral winter and spring. Apart from the Peninsula, the seasonal warming is largest and most significant in West Antarctica in the austral spring since the late 1970s. Concurrent trends in sea ice are independent evidence of the observed warming over West Antarctic, with the decrease in sea ice area in the Amundsen and Bellingshausen Seas congruent with at least 50% of the inland warming of West Antarctica. Trends in near surface winds and geopotential heights over the high-latitude South Pacific are consistent with a role for atmospheric forcing of the sea ice and air temperature anomalies. Most of the circulation trend projects onto the two Pacific South American (PSA) modes of atmospheric circulation variability, while the Southern Annular Mode lacks a positive trend in spring that would otherwise cause a cooling tendency. The largest circulation trend is associated with the PSA-1 mode, a wave-train extending from the tropics to the high Southern latitudes. The PSA-1 mode is significantly correlated with SSTs in the southwestern tropical and subtropical Pacific. The increased SSTs in this region, together with the observed increase in rainfall, suggest that anomalous deep convection has strengthened or increased the occurrence of the Rossby wave-train associated with PSA-1. This hypothesis is supported by results from two ensembles of SST-forced atmospheric general circulation model simulations. Finally, the implications of the seasonality, timing, and spatial patterns of Antarctic temperature trends with respect to interpreting the relative roles of stratospheric ozone depletion, SSTs and increased atmospheric concentrations of greenhouse gasses are discussed. 相似文献
2.
As leading modes of the planetary-scale atmospheric circulation in the extratropics, the Northern Hemisphere(NH)annular mode(NAM) and Southern Hemisphere(SH) annular mode(SAM) are important components of global circulation, and their variabilities substantially impact the climate in mid-high latitudes. A 35-yr(1979-2013) simulation by the climate system model developed at the Chinese Academy of Meteorological Sciences(CAMS-CSM) was carried out based on observed sea surface temperature and sea ice data. The ability of CAMS-CSM in simulating horizontal and vertical structures of the NAM and SAM, relation of the NAM to the East Asian climate, and temporal variability of the SAM is examined and validated against the observational data. The results show that CAMS-CSM captures the zonally symmetric and out-of-phase variations of sea level pressure anomaly between the midlatitudes and polar zones in the extratropics of the NH and SH. The model has also captured the equivalent barotropic structure in tropospheric geopotential height and the meridional shifts of the NH and SH jet systems associated with the NAM and SAM anomalies. Furthermore, the model is able to reflect the variability of northern and southern Ferrel cells corresponding to the NAM and SAM anomalies. The model reproduces the observed relationship of the boreal winter NAM with the East Asian trough and air temperature over East Asia. It also captures the upward trend of the austral summer SAM index during recent decades. However, compared with the observation, the model shows biases in both the intensity and center locations of the NAM's and SAM's horizontal and vertical structures. Specifically, it overestimates their intensities. 相似文献
3.
J. Garc��a-Serrano B. Rodr��guez-Fonseca I. Blad�� P. Zurita-Gotor A. de la C��mara 《Climate Dynamics》2011,37(9-10):1727-1743
The dominant variability modes of the North Atlantic-European rotational flow are examined by applying a principal component analysis (PCA/EOF) to the 200?hPa streamfunction mid-winter anomalies (Jan?CFeb monthly means). The results reveal that, when this norm is used, the leading mode (EOF1) does not correspond to the traditional North Atlantic Oscillation (NAO, which appears in our analysis as the second leading mode, EOF2) but is the local manifestation of the leading hemispheric streamfunction EOF. The regression of this regional mode onto the global SST field exhibits a clear El Ni?o signature, with no signal over the Atlantic, while the associated upper height anomalies resemble the Tropical/Northern Hemisphere (TNH) pattern. East of North America, this TNH-like wavetrain produces a meridional dipole-like pattern at lower levels. Although in some ways this pattern resembles the NAO (EOF2), the dynamics of these two modes are very different in that only EOF2 is associated with a latitudinal shift of the North Atlantic stormtrack. Thus, the choice of the streamfunction norm in the EOF analysis allows the separation of two different phenomena that can produce similar dipolar surface pressure anomalies over the North Atlantic but that have different impact on European climate. These two modes also differ on their contribution to variability at lower levels: while NAO-EOF2 is mostly confined to the North Atlantic, TNH-EOF1 has a more annular, global character. At upper levels NAO-EOF2 also produces a global pattern but with no annular structure, reminiscent of the ??circumglobal?? teleconnection. 相似文献
4.
Interannual and interdecadal variability of ocean temperature along the equatorial Pacific in conjunction with ENSO 总被引：1，自引：1，他引：0
In this paper, the leading modes of ocean temperature anomalies (OTA) along the equatorial Pacific Ocean are analyzed and their connection with El Niño-Southern Oscillation (ENSO) and interdecadal variation is investigated. The first two leading modes of OTA are connected with the different phases of the canonical ENSO and display asymmetric features of ENSO evolution. The third leading mode depicts a tripole pattern with opposite variation of OTA above the thermocline in the central Pacific to that along the thermocline in the eastern and western Pacific. This mode is found to be associated with so-called ENSO-Modoki. Insignificant correlations of this mode with the first two leading modes suggest that ENSO-Modoki may be a mode that is independent to the canonical ENSO and also has longer time scales compared with the canonical ENSO. The fourth mode reflects a warming (cooling) tendency above (below) the thermocline since 2000. Both the first and second modes have a large contribution to the interdecadal change in thermocline during 1979–2012. Also, the analysis also documents that both ENSO and OTA shifted into higher frequency since 2000 compared with that during 1979–1999. Interestingly, the ENSO-Modoki related OTA mode does not have any trend or significant interdecadal shift during 1979–2012. In addition, it is shown that first four EOF modes seem robust before and after 1999/2000, suggesting that the interdecadal shift of the climate system in the tropical Pacific is mainly a frequency shift and the changes in spatial pattern are relatively small, although the mean states over two periods experienced some significant changes. 相似文献
5.
In order to study the physical nature of the Arctic Oscillation (AO) or the Northern Hemisphere annular mode (NAM), the linear stochastic model, constructed empirically from the output of a GCM run, is used to investigate the modal aspects of this climate variability mode. Theoretical analysis on the dominant modal response to the stochastic forcing is performed in terms of the maximum variance contribution. As the modal aspect of AO/NAM, two dominant normal modes are found to resemble the spatial structure of the AO/NAM represented by the leading EOF. These stochastically forced normal modes are regarded to be physical modes and thus can explain many fundamental features of the AO/NAM such as the barotropic annular dipole, tropospher–stratosphere coupling, and its dominance over the wintertime Northern Hemisphere. It then follows that the origin or physical nature of the AO/NAM can be attributed to the behaviors of the dominant annular normal modes. A key distinction of this study from previous eddy driving theories is that, to drive the variability, eddy forcing needs not to have a spatial structure completely coinciding with the pattern of the NAM, since the latter is mainly decided by the linear normal modes. 相似文献
6.
为了在动力季节预测中更好地运用统计经验来改进预报, 从研究气候系统物理因子影响模式预报误差的角度入手, 探讨了与气候模式有关的统计经验获取问题, 并利用国家气候中心海-气耦合模式的历史回报数据, 考察了动力季节预测中夏季环流和降水的预报误差与主要物理因子, 包括Ni?o3区海温指数、太平洋年代际振荡指数、南北半球环状模指数以及北大西洋涛动指数相关关系。分析结果显示:上述物理因子与模式预报的夏季环流和降水误差之间存在前期或同期的某种显著相关关系, 并且显著关系分布随因子的不同而表现出明显不同的区域性特征, 这为发展一种基于预报因子的误差订正新方法提供了新思路。 相似文献
7.
SST and circulation trend biases cause an underestimation of European precipitation trends 总被引：2，自引：0，他引：2
Ronald van Haren Geert Jan van Oldenborgh Geert Lenderink Matthew Collins Wilco Hazeleger 《Climate Dynamics》2013,40(1-2):1-20
Clear precipitation trends have been observed in Europe over the past century. In winter, precipitation has increased in north-western Europe. In summer, there has been an increase along many coasts in the same area. Over the second half of the past century precipitation also decreased in southern Europe in winter. An investigation of precipitation trends in two multi-model ensembles including both global and regional climate models shows that these models fail to reproduce the observed trends. In many regions the model spread does not cover the trend in the observations. In contrast, regional climate model (RCM) experiments with observed boundary conditions reproduce the observed precipitation trends much better. The observed trends are largely compatible with the range of uncertainties spanned by the ensemble, indicating that the boundary conditions of RCMs are responsible for large parts of the trend biases. We find that the main factor in setting the trend in winter is atmospheric circulation, for summer sea surface temperature (SST) is important in setting precipitation trends along the North Sea and Atlantic coasts. The causes of the large trends in atmospheric circulation and summer SST are not known. For SST there may be a connection with the well-known ocean circulation biases in low-resolution ocean models. A quantitative understanding of the causes of these trends is needed so that climate model based projections of future climate can be corrected for these precipitation trend biases. 相似文献
8.
We test for the existence of long-term trends in 25- to 50-year long series of monthly rainfall, average river discharges, and minimum air temperatures in Colombia. The Empirical Mode Decomposition method is used as a mathematical filter to decompose a given time series into a finite number of intrinsic mode functions, assuming the coexistence of different frequency oscillatory modes in the series, and that the residual captures the likely existing long-term trends. The Mann-Kendall test for autocorrelated data is used to assess the statistical significance of the identified trends, and the Sen test is used to quantify their magnitudes. Results show that 62 % of river discharge series exhibit significant decreasing trends between 0.01-1.92 m 3 s ?1 per year, which are highly consistent downstream albeit with different ratios between the trend magnitudes and mean discharges. Most minimum temperature series (87 %) exhibit increasing trends (0.01-0.08 °Cyr ?1). Results for precipitation series are inconclusive owing to the mixing between increasing trends (41 %, between 0.1-7.0 mm yr ?1) and decreasing trends (44 %, between 0.1-7.4 mm yr ?1), with no clear-cut geographical pattern, except for the increasing trend identified along the Pacific region, consistent with the increasing trend identified in the strength of the Chocó low-level wind jet off the Pacific coast of Colombia, an important moisture source of continental precipitation. Our results contribute to discerning between signals of climate change and climate variability in tropical South America. 相似文献
9.
北京气候中心气候模式1.1版预估中亚地区未来50年地面气温时空变化特征 总被引：4，自引：0，他引：4
利用IPCC AR5中BCC-CSM1.1(Beijing Climate Center Climate System Model version 1.1)的历史试验和4类典型 排放路径情景下未来预估试验结果, 在使用CRU(Climatic Research Unit)资料验证BCC-CSM1.1性能的基础上, 采用趋势分 析、滑动平均以及经验正交函数(EOF)等方法, 研究2011-2060年中亚地区年平均气温的时空演变特征。与CRU 资料的对 比分析发现BCC-CSM1.1能较好地模拟过去109a(1901-2009年)中亚地区气温的显着上升趋势及气候态的空间分布特征。 预估试验结果表明, 中亚地区在未来50a整体呈现变暖趋势, 并且, 随着温室气体排放浓度的升高, 气温的升高趋势愈加明 显, 同时增温显着区域也明显增大。经验正交函数分解主要模态还是延续过去的分布特征:经验正交函数分解第1模态及其 所对应的时间系数显示中亚地区年平均地面气温在未来50a(2011-2060年)呈现出全场一致的升高趋势, 升高强度随着温 室气体排放浓度的增加而增强, 进一步的分析表明, 不同典型排放路径下预估的未来50a中亚地区年平均地面气温的经验正 交函数分解第1模态在中亚上空850hPa等压面上均对应有一个反气旋(气旋)性异常环流, 在这个异常环流控制下, 中亚地 区年平均地面气温变化表现为全场一致的特征。经验正交函数分解第2模态呈现出中亚地区地面气温变化南北反位相的基 本特征, 相应的时间系数主要表现为小幅度波动, 变化趋势特征不明显。 相似文献
10.
Uncertainty in future climate change presents a key challenge for adaptation planning. In this study, uncertainty arising from internal climate variability is investigated using a new 40-member ensemble conducted with the National Center for Atmospheric Research Community Climate System Model Version 3 (CCSM3) under the SRES A1B greenhouse gas and ozone recovery forcing scenarios during 2000–2060. The contribution of intrinsic atmospheric variability to the total uncertainty is further examined using a 10,000-year control integration of the atmospheric model component of CCSM3 under fixed boundary conditions. The global climate response is characterized in terms of air temperature, precipitation, and sea level pressure during winter and summer. The dominant source of uncertainty in the simulated climate response at middle and high latitudes is internal atmospheric variability associated with the annular modes of circulation variability. Coupled ocean-atmosphere variability plays a dominant role in the tropics, with attendant effects at higher latitudes via atmospheric teleconnections. Uncertainties in the forced response are generally larger for sea level pressure than precipitation, and smallest for air temperature. Accordingly, forced changes in air temperature can be detected earlier and with fewer ensemble members than those in atmospheric circulation and precipitation. Implications of the results for detection and attribution of observed climate change and for multi-model climate assessments are discussed. Internal variability is estimated to account for at least half of the inter-model spread in projected climate trends during 2005–2060 in the CMIP3 multi-model ensemble. 相似文献
11.
Neville Nicholls 《Climate Dynamics》2010,34(6):835-845
The 1958–2007 decline in March–August rainfall over southern Australia (south of 30°S) is very closely related to an increase in surface atmospheric pressure over Australia. Sea surface temperatures around northern Australia are strongly correlated with southern Australian rainfall but the recent warming of the ocean should have led to increased rainfall rather than the observed rainfall decline. The relationships between the rainfall and indices of several modes of the atmosphere/ocean system are investigated to determine a cause of the rainfall decline. Indices of the modes that only use data remote from the Australian region are used to avoid the possibility that a relationship between the mode and Australian rainfall is simply reflecting the behaviour of “local” portions of the index. Thus a climate mode index that incorporates Australian pressure would, of course, be related to southern Australian rainfall, even if the remote parts of the mode were unrelated to Australian rainfall. Unless the remote contributions to the mode index were also related to Australian rainfall it seems physically unrealistic to consider that the mode, per se, was affecting Australian rainfall (rather than simply reflecting the influence of the local pressure changes). The rainfall decline does not appear to be explainable by a change in the behaviour of the El Niño-Southern Oscillation (remote indices of this phenomenon do not exhibit a trend over this period) or the Indian Ocean Dipole (which is not strongly correlated with Australian rainfall on detrended data). The strong 1958–2007 trend in the southern annular mode (SAM) appears able to explain much of the rainfall decline since its year-to-year variations are correlated with year-to-year variations in southern Australian rainfall, and the sense of the correlation and the SAM trend would lead to a decline in rainfall (and an increase in pressure over Australia). The observed trend in SAM can reproduce over 70% of the observed rainfall trend. All these conclusions also apply to the rainfall declines in the southeast and southwest sub-regions. 相似文献
12.
与北极涛动或北半球环状模相关的纬向对称的正规模态 总被引：3，自引：3，他引：3
作为一个全球气候变率的重要模态,北极涛动或北半球环状模态(AO/NAM)一般由北半球海平面气压变率的EOF1来表示。但是通常认为EOF1仅有统计学意义而并不能够表明它是否是一种实际的物理模态。另一方面,现有的波-流相互作用理论也仅能给出纬向风的纬向平均状况,而不能够保证沿着某一纬圈的变化,所以它并不意味着一个具有半球尺度的纬向对称的相干结构能够组织起来。因此AO/NAM的形成机制仍然是一个具有争议的问题。文章提出纬向对称的或环状的正规模态与基本气候态附近的线性(进而非线性)动力学之间有着最直接的联系,因而可能在AO/NAM动力学的理解中扮演重要角色。为了深入探讨AO/NAM的动力学本质,使用p-坐标球面原始方程计算了冬季北半球及全球气候基本态附近的线性动力系统纬向对称的正规模态,发现在半球尺度上的纬向对称正规模态具有AO/NAM的经向偶极子及垂直方向近似正压的空间结构特征。而这些纬向对称正规模的时间变化尺度取决于与其他非纬向对称正规模间的相互作用。从而说明了AO/NAM可能是半球尺度上纬向对称正规模态的动力学行为的反映。 相似文献
13.
Summer precipitation anomalies over eastern China are characterized spatially by meridionally banded structures fluctuating on interannual and interdecadal timescales,leading to regional droughts and floods.In addition to long-term trends,how these patterns may change under global warming has important implications for agricultural planning and water resources over this densely populated area.Using the latest Hadley Centre climate model,Had GEM3-GC2,this paper investigates the potential response of summer precipitation patterns over this region,by comparing the leading modes between a 4×CO_2 simulation and the model's pre-industrial control simulation.Empirical Orthogonal Function(EOF) analyses show that the first two leading modes account for about 20% of summer rainfall variability.EOF1 is a monopole mode associated with the developing phase of ENSO events and EOF2 is a dipole mode associated with the decaying phase of ENSO.Under 4×CO_2 forcing,the dipole mode with a south–north orientation becomes dominant because of a strengthened influence from excessive warming of the Indian Ocean.On interdecadal time scales,the first EOF looks very different from the control simulation,showing a dipole mode of east–west contrast with enhanced influence from high latitudes. 相似文献
14.
Simulated climate variables in a simple energy balance model subject to linearly increasing external forcing (due to increasing greenhouse gas emissions) and random internal forcings have been studied for more accurate climate prediction. The numerical method for such a system requires careful treatment of random forcings. Mathematical analyses show that the effect of random forcings should be diminished in the numerical integration method by the reciprocal of the root of the integration time step $ \left( {1/\sqrt {{\Delta t}} } \right) $ , which we call an attenuator. Our simulations consistently show that the attenuator desirably reduces variances of simulated climate variables and eliminates overestimation of the variances. However, the attenuator tends to bias the estimates of the climate feedback parameter obtained from a simple regression analysis of simulated variables toward unrealistically low values. This is because the reduced random forcings amplify the negative effect of a warming trend due to greenhouse emissions (when added to random forcing) on feedback estimation. Without the attenuator, the estimated feedback is much more accurate. The bias induced from the attenuator was largely resolved for the feedback estimation by the methodology of Lindzen and Choi (Asia-Pacific J Atmos Sci 47(4):377–390, 2011), which minimizes the negative effect of the warming trends by isolating short (few months) segments of increasing and decreasing temperature changes. 相似文献
15.
Three primary global modes of sea surface temperature (SST) variability during the period of 1871–2010 are identified through cyclostationary empirical orthogonal function analysis. The first mode exhibits a clear trend and represents global SST warming with an ‘El Niño-like’ SST pattern in the tropical Pacific. The second mode is characterized by considerable low-frequency variability in both the tropical Pacific and the North Pacific regions, indicating that there is a close connection between the two regions on interannual and decadal time scales. The third mode shows a seesaw pattern between El Niño and La Niña within a two-year period; this mode is derived by the oscillatory tendency of the tropical Pacific ocean–atmosphere coupled system. A SST reconstruction based on these three modes captures a significant portion of the SST variability in the raw data, which is primarily associated with El Niño-Southern Oscillation (ENSO) events in the tropical Pacific. Additionally, this study attempts to interpret the major ENSO events that have occurred since the 1970s in terms of the interplay originating from these three modes of variability. In particular, two key points are derived from this analysis: (1) the most extreme El Niño events occurred in 1982/1983 and 1997/1998 are attributed to the positive contributions of all three modes; and (2) the central Pacific (CP) El Niño events in the 1990s and 2000s have different physical mechanisms, that is, the CP El Niño events in the early 1990s originated mainly from the low-frequency mode, while those in the early 2000s derived mainly from the global warming mode. 相似文献
16.
17.
A data adaptive method called ensemble empirical mode decomposition (EEMD) is used to examine the 154-year record of monthly sea level at San Francisco. The mode that is lowest in frequency corresponds to the long-term trend. The next highest mode corresponds to an oscillation with a period of ~100?years and may be related to solar variability. When this mode is combined with the long-term trend, the rate of increase in sea level starts to decrease by ~1980. The next lower mode corresponds to interdecadal time scales and thus includes the Pacific Decadal Oscillation. When combined with the two lower modes, sea level itself starts to decrease by the mid-1990s. These results are consistent with the most recent results from the intergovernmental panel on climate change (IPCC), and may be the first obtained from a tidal record. Prior to conducting EEMD, corrections for glacial isostatic adjustment (GIA) and the inverse barometer (IB) effect were applied. The effect of applying the GIA correction was relatively small, but the IB correction reduced the slope of the long-term trend in sea level by almost 15%. This reduction is due to a long-term increase in the variance of sea level pressure. To determine if the 10?C15?year ENSO modulation cycle could be detected from the decomposition we first compared the envelope from the mode associated with ENSO, with the two adjacent modes that were lower in frequency. Spectral analysis revealed no significant maxima in the ENSO mode envelope, but a major peak in the spectrum for the two adjacent modes, with a period of 12.8?years. This is consistent with a local response to El Ni?o warming for the ENSO mode, but a non-local response for the two adjacent modes. A similar analysis was performed for the Southern Oscillation Index and a spectral maximum was found between 12 and 16?years, consistent with our non-local interpretation of the previous two modes. 相似文献
18.
Ruichao Li Jinbo Xie Zhenghui Xie Junqiang Gao Binghao Jia Peihua Qin Longhuan Wang Yan Wang Bin Liu Si Chen 《大气和海洋科学快报》2021,14(1):40-45
在气候变化背景下,活动层厚度的变化会对多年冻土区水文,生态,寒区工程等产生较大的影响.本研究利用中科院气候系统模式CAS-FGOALS-g3和陆面过程模式CAS-LSM模拟分析了活动层厚度的变化趋势和相对变化.结果表明:活动层厚度整体上呈现出增加的趋势.1979-2014年,多年冻土区活动层厚度的区域平均为1.08 m,变化趋势为0.33 cm yr-1,其变化趋势与2m气温变化趋势基本一致,相对变化范围为1％-58％,平均为10.9％.在未来四种不同的气候情景(SSP-2.6,SSP2-4.5,SSP3-7.0和SSP5-8.5)下,到2100年预计活动层厚度的相对变化分别为10.3％,14.6％,30.1％和51％. 相似文献
19.
利用NCAR大气模式CAM3.0探讨了包括山脉和海陆分布等下边界条件对北极涛动(AO)或北半球环状模(NAM)形成的影响.主要进行了控制试验和两个地形敏感性数值试验,对比了控制试验结果与资料分析结果.控制试验和NCEP/NCAR资料分析结果对比指出,CAM3.0模式能够较好地模拟出AO的水平环状结构和垂直相当正压结构.在去除山脉的敏感性试验中发现,AO中纬度北太平洋和北大西洋两个活动中心的强度、范围和位置发生变化.在水球敏感性试验中发现,AO两个大洋上的活动中心被环绕极地主活动中心的环状结构代替.两个敏感性试验共同表明,AO是大气内部某种过程作用的结果,它的存在本身不取决于下边界条件的改变.山脉和海陆分布主要影响的是AO的具体形态.通过控制试验和两个敏感性试验对比,又分析了准定常波和瞬变波对AO的影响.去除山脉和海陆分布热力差异共同强迫的准定常波,AO纬向平均纬向风高纬地区平流层异常最大值活动中心消失,这表明在平流层准定常波和纬向平均流的相互作用与AO活动关系密切.在只有对流层瞬变波作用时,AO仍然存在,表明准定常波不是AO存在的必要条件.平流层准定常波与平均流的相互作用和对流层瞬变波与平均流的相互作用与AO形成之间的具体关系有待通过E-P通量诊断进一步确定. 相似文献
20.
E. Xoplaki J. González-Rouco D. Gyalistras J. Luterbacher R. Rickli H. Wanner 《Climate Dynamics》2003,20(5):537-554
The interannual and decadal variability of summer (June to September) air temperature in the northeastern Mediterranean is analysed for the period 1950 to 1999. Extremely hot and cool summers are illustrated by means of composite analysis. The combined influence of the large-scale atmospheric circulation and thermic predictors on local temperature is assessed by means of an objective approach based on empirical orthogonal functions and canonical correlation analysis. Monthly values of sea level pressure, geopotential heights, atmospheric thickness and Mediterranean sea surface temperatures are used as predictor fields and air temperature from 24 observational sites spread over Greece and western Turkey constitute the predictand variable. Results indicate that more than 50% of the total summer temperature variability can be explained linearly by the combination of eight large-scale predictor fields on two canonical correlation modes. The first canonical mode is related to a more meridional circulation at the upper tropospheric levels, which favours local land-sea contrasts in the associated local temperature pattern. Variations of this mode are found to be responsible for the occurrence of extreme events and decadal trends in regional temperature, the latter being characterized by a cooling in the early 1960s and a warming in the early 1990s. The second canonical mode pictures variations in the intensity of the zonal circulation over the Atlantic area that drive temperature anomalies affecting mainly the Aegean Sea and the west of Greece. Our results suggest the potential of statistical downscaling for Greek summer temperature with reliable climate forecasts for planetary-scale anomalies. 相似文献