Advanced Search
Article Contents

Modulation of the Aleutian-Icelandic Low Seesaw and Its Surface Impacts by the Atlantic Multidecadal Oscillation


doi: 10.1007/s00376-017-7028-z

  • Early studies suggested that the Aleutian-Icelandic low seesaw (AIS) features multidecadal variation. In this study, the multidecadal modulation of the AIS and associated surface climate by the Atlantic Multidecadal Oscillation (AMO) during late winter (February-March) is explored with observational data. It is shown that, in the cold phase of the AMO (AMO|-), a clear AIS is established, while this is not the case in the warm phase of the AMO (AMO|+). The surface climate over Eurasia is significantly influenced by the AMO's modulation of the Aleutian low (AL). For example, the weak AL in AMO|- displays warmer surface temperatures over the entire Far East and along the Russian Arctic coast and into Northern Europe, but only over the Russian Far East in AMO|+. Similarly, precipitation decreases over central Europe with the weak AL in AMO|-, but decreases over northern Europe and increases over southern Europe in AMO|+. The mechanism underlying the influence of AMO|- on the AIS can be described as follows: AMO|- weakens the upward component of the Eliassen-Palm flux along the polar waveguide by reducing atmospheric blocking occurrence over the Euro-Atlantic sector, and hence drives an enhanced stratospheric polar vortex. With the intensified polar night jet, the wave trains originating over the central North Pacific can propagate horizontally through North America and extend into the North Atlantic, favoring an eastward-extended Pacific-North America-Atlantic pattern, and resulting in a significant AIS at the surface during late winter.
    摘要: 早期研究表明了阿留申-冰岛低压振荡的多年代际变化, 本文主要利用观测资料揭示了北大西洋多年代际振荡(AMO)对后冬(2-3月)阿留申-冰岛低压振荡、以及相关地表气候的多年代际调制作用. 结果表明, 只有在AMO冷位相的背景下, 显著的阿留申-冰岛低压振荡才会形成. AMO对阿留申低压的调制作用对欧亚地表气候有显著影响, 比如, 在AMO冷位相背景下, 弱的阿留申低压对应整个东亚地区、以及从俄罗斯北极沿岸到欧洲北部的气温偏高;而在AMO暖位相时, 暖异常只出现在俄罗斯远东地区. 类似地, AMO冷位相对弱阿留申低压的调制, 使得欧洲中部降水减少; 而在AMO暖位相的调制下, 欧洲北部降水减少、南部降水增多.AMO冷位相影响阿留申-冰岛低压振荡的机制解释如下: AMO冷位相通过减少欧洲-北大西洋大气阻塞的发生频次, 使得通过极地波导向上传播的行星波减弱, 平流层极涡加强. 因此, 由于极夜急流的加强, 从北太平洋中部激发的波列可以从北美传播到北大西洋, 有助于向东延伸的太平洋-北美-大西洋型的形成. 最终, 在后冬出现显著的阿留申-冰岛低压振荡.
  • 加载中
  • Allan R., T. Ansell, 2006: A new globally complete monthly historical gridded mean sea level pressure dataset (HadSLP2): 1850-2004.J. Climate,19,5816-5842, https://doi.org/10.1175/JCLI3937.1.10.1175/JCLI3937.1d44c3a0167c2587043914d0ce0b1b468http%3A%2F%2Fwww.readcube.com%2Farticles%2F10.1175%2FJCLI3937.1http://journals.ametsoc.org/doi/abs/10.1175/JCLI3937.1An upgraded version of the Hadley Centre's monthly historical mean sea level pressure (MSLP) dataset (HadSLP2) is presented. HadSLP2 covers the period from 1850 to date, and is based on numerous terrestrial and marine data compilations. Each terrestrial pressure series used in HadSLP2 underwent a series of quality control tests, and erroneous or suspect values were either corrected, where possible, or removed. Marine observations from the International Comprehensive Ocean Atmosphere Data Set were quality controlled (assessed against climatology and near neighbors) and then gridded. The final gridded form of HadSLP2 was created by blending together the processed terrestrial and gridded marine MSLP data. MSLP fields were made spatially complete using reduced-space optimal interpolation. Gridpoint error estimates were also produced. HadSLP2 was found to have generally stronger subtropical anticyclones and higher-latitude features across the Northern Hemisphere than an earlier product (HadSLPI). During the austral winter, however, it appears that the pressures in the southern Atlantic and Indian Ocean midlatitude regions are too high; this is seen in comparisons with both HadSLP1 and the 40-yr ECMWF Re-Analysis (ERA-40). Over regions of high altitude, HadSLP2 and ERA-40 showed consistent differences suggestive of potential biases in the reanalysis model, though the region over the Himalayas in HadSLP2 is biased compared with HadSLP1 and improvements are required in this region. Consistent differences were also observed in regions of sparse data, particularly over the higher latitudes of the Southern Ocean and in the southeastern Pacific. Unlike the earlier HadSLP1 product, error estimates are available with HadSLP2 to guide the user in these regions of low confidence. An evaluation of major phenomena in the climate system using HadSLP2 provided further validation of the dataset. Important climatic features/indices such as the North Atlantic Oscillation, Arctic Oscillation, North Pacific index, Southern Oscillation index, Trans-Polar index, Antarctic Oscillation, Antarctic Circumpolar Wave, East Asian Summer Monsoon index, and the Siberian High index have all been resolved in HadSLP2, with extensions back to the mid-nineteenth century.
    Andrews D. G., 1987: On the interpretation of the eliassen-palm flux divergence.Quart. J. Roy. Meteor. Soc.,113(475),323-338, https://doi.org/10.1002/qj.49711347518.10.1002/qj.4971134751827c3328c114ccb3e5c3386d3944e5c9fhttp%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fqj.49711347518%2Ffullhttp://doi.wiley.com/10.1002/qj.49711347518New expressions are presented for the wave-activity density and the non-conservative source of wave activity in the small amplitude Eliassen-Palm theorem for the primitive equations in log(pressure) and isentropic coordinates. These expressions involve Ertel's potential vorticity, and include versions that are of Eulerian form.The theoretical results are used as a basis for investigating the interpretation of the Eliassen-Palm flux divergence in terms of physical wave properties. Implications for modelling and observational studies of planetary waves are discussed and connections with stability theory and the definition of orthogonality of normal modes are mentioned.
    Castanheira J. M., H.-F. Graf, 2003: North Pacific-North Atlantic relationships under stratospheric control? J.Geophys. Res.,108,ACL 11-1-ACL 11-10, https://doi.org/10.1029/2002JD002754.10.1029/2002JD0027542071cb28929f7e3a11dcdee0d0d07743http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2002JD002754%2Ffullhttp://adsabs.harvard.edu/abs/2002EGSGA..27.6603CAn analysis of monthly mean atmospheric sea level pressure data from NCEP reanal- ysis (1948-2000) shows a significant anticorrelation between pressure in the northern North Atlantic and North Pacific only if the stratospheric circulation is in the "strong polar vortex" regime, but not when the vortex is weak. Since general circulation mod- els in most cases are biased towards the strong vortex regime, they tend to reproduce this anticorrelation already in the mean. This allows an explanation for the results of some works that obtain a correlation between PNA and NAO greater in simulation experiments than in the observations.
    Dickinson R. E., 1968: Planetary Rossby waves propagating vertically through weak westerly wind wave guides. J. Atmos. Sci., 25, 984-1002, https://doi.org/10.1175/1520-0469 (1968)025<0984:PRWPVT>2.0,CO;2.10.1175/1520-0469(1968)0252.0.CO;223bbe7d8816e1025b52805db03a4fcechttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1968JAtS...25..984Dhttp://journals.ametsoc.org/doi/abs/10.1175/1520-0469%281968%29025%3C0984%3APRWPVT%3E2.0.CO%3B2The role of horizontal wind shears in the vertical propagation of planetary Rossby waves is investigated using an adiabatic linear model. We discuss wave guides formed by regions of weak westerly wind. If the wave guide is formed by trapping of waves between strong westerlies and/or the geometric poles, the ducting occurs as a wave propagation in discrete normal modes of the internal wave guide. On the other hand, for wave guides formed by one or more lines of zero wind, waves are absorbed rather than reflected at the zero wind line so that there are no normal modes of the wave guide. Disturbances excited in the lower stratosphere in the equatorial zero wind wave guide will terminate somewhere in the equatorial stratosphere, but eddy motions may be maintained in the tropics at higher levels by leakage from the Aleutian high planetary wave propagating vertically in a polar wave guide. The Aleutian high should he significantly attenuated by such leakage. The theory of zero wind line absorption suggests a planetary wave coupling with the biennial oscillation.
    Garreaud R. D., 2007: Precipitation and circulation covariability in the extratropics.J. Climate,20(18),4789-4797, https://doi.org/10.1175/JCLI4257.1.10.1175/JCLI4257.1f018095afeec8e0874e0af1ecd7454a8http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2007JCli...20.4789Ghttp://journals.ametsoc.org/doi/abs/10.1175/JCLI4257.1Extratropical precipitation is primarily produced by cold and warm fronts associated with surface cyclones and upper-level troughs. The growth of these midlatitude storms is partially controlled by the dry baroclinicity of the troposphere, which in turn can be roughly quantified by the intensity of the upper-level zonal flow. Orographic rainfall, an important component of the precipitation in several midlatitude regions, is also partially determined by the intensity of the cross-mountain midlevel winds. Thus, at monthly and longer time scales, variations of precipitation and zonal flow aloft (as well as wind shear) at a given location should exhibit some degree of coherence. In this work the local covariability of these variables is documented over intermonthly and interannual time scales, using global precipitation products and atmospheric reanalysis from 1979 to 2004. The spatial correspondence between the precipitation and two indices of synoptic activity in the extratropics is also documented. The local correlation (r0) between monthly anomalies of precipitation and upper-level (300 hPa) zonal flow varies in space, from moderately and even highly significant values (r0 090304 0.3 to 0.7) over the midlatitude oceans to near zero over the interior of continental areas. Broadly similar results are found when considering the monthly variance of the high-pass-filtered meridional wind (an index of eddy activity) or the midlevel Eady growth rate. The local correlation map between precipitation and low-level (850 hPa) zonal flow is similar to its upper-level counterpart, but the correlations over open ocean are somewhat weaker, while orographic effects show up more clearly. The correlations are positive and large upstream of the major north09“south-oriented mountain ranges, as strong westerlies promote upslope rain in addition to storm-related precipitation. In contrast, the correlation tends to be negative downstream of the ranges, as strong westerlies enhance the rain shadow effects over the lee side.
    Häkkinen, S., P. B. Rhines, D. L. Worthen, 2011: Atmospheric blocking and Atlantic Multidecadal Ocean variability.Science,334,655-659, https://doi.org/10.1126/science.1205683.10.1126/science.1205683220530466e18240803eb40f14feb04f620393b08http%3A%2F%2Fwww.jstor.org%2Fstable%2F41351640http://www.sciencemag.org/cgi/doi/10.1126/science.1205683Abstract Atmospheric blocking over the northern North Atlantic, which involves isolation of large regions of air from the westerly circulation for 5 days or more, influences fundamentally the ocean circulation and upper ocean properties by affecting wind patterns. Winters with clusters of more frequent blocking between Greenland and western Europe correspond to a warmer, more saline subpolar ocean. The correspondence between blocked westerly winds and warm ocean holds in recent decadal episodes (especially 1996 to 2010). It also describes much longer time scale Atlantic multidecadal ocean variability (AMV), including the extreme pre-greenhouse-gas northern warming of the 1930s to 1960s. The space-time structure of the wind forcing associated with a blocked regime leads to weaker ocean gyres and weaker heat exchange, both of which contribute to the warm phase of AMV.
    Harris I., P. D. Jones, T. J. Osborn, and D. H. Lister, 2014: Updated high-resolution grids of monthly climatic observations-the CRU TS3.10 Dataset. International Journal of Climatology,34(3),623-642, https://doi.org/10.1002/joc.3711.10.1002/joc.3711e2795603b39ca772a29510810a516f17http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.3711%2Fpdfhttp://doi.wiley.com/10.1002/joc.3711This paper describes the construction of an updated gridded climate dataset (referred to as CRU TS3.10) from monthly observations at meteorological stations across the world's land areas. Station anomalies (from 1961 to 1990 means) were interpolated into 0.5º latitude/longitude grid cells covering the global land surface (excluding Antarctica), and combined with an existing climatology to obtain absolute monthly values. The dataset includes six mostly independent climate variables (mean temperature, diurnal temperature range, precipitation, wet-day frequency, vapour pressure and cloud cover). Maximum and minimum temperatures have been arithmetically derived from these. Secondary variables (frost day frequency and potential evapotranspiration) have been estimated from the six primary variables using well-known formulae. Time series for hemispheric averages and 20 large sub-continental scale regions were calculated (for mean, maximum and minimum temperature and precipitation totals) and compared to a number of similar gridded products. The new dataset compares very favourably, with the major deviations mostly in regions and/or time periods with sparser observational data. CRU TS3.10 includes diagnostics associated with each interpolated value that indicates the number of stations used in the interpolation, allowing determination of the reliability of values in an objective way. This gridded product will be publicly available, including the input station series (http://www.cru.uea.ac.uk/ and http://badc.nerc.ac.uk/data/cru/). 2013 Royal Meteorological Society
    Honda M., H. Nakamura, 2001: Interannual seesaw between the Aleutian and Icelandic lows. Part II: Its significance in the interannual variability over the wintertime Northern Hemisphere. J. Climate, 14, 4512-4529, https://doi.org/10.1175/1520-0442(2001)014<4512:ISBTAA>2.0,CO;2.
    Honda M., H. Nakamura, J. Ukita, I. Kousaka, and K. Takeuchi, 2001: Interannual seesaw between the Aleutian and Icelandic lows. Part I: Seasonal dependence and life cycle. J. Climate, 14, 1029-1042, https://doi.org/10.1175/1520-0442(2001)014<1029:ISBTAA>2.0,CO;2.
    Honda M., Y. Kushnir, H. Nakamura, S. Yamane, and S. E. Zebiak, 2005a: Formation,mechanisms,and predictability of the Aleutian-Icelandic low seesaw in ensemble AGCM simulations. J. Climate,18, 1423-1434,https://doi.org/10.1175/JCLI3353.1.
    Honda M., S. Yamane, and H. Nakamura, 2005b: Impacts of the Aleutian-Icelandic low seesaw on surface climate during the twentieth century.J. Climate,18(14),2793-2802, https://doi.org/10.1175/JCLI3419.1.10.1175/JCLI3419.1fd1f65eb4f2158b8dca596f6579cce10http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2005JCli...18.2793Hhttp://journals.ametsoc.org/doi/abs/10.1175/JCLI3419.1Abstract An interannual seesaw between the intensities of the Icelandic and Aleutian lows and its impact on surface climate observed during the twentieth century are investigated. In a recent period from the late 1960s to the early 1990s, their seesaw relationship was particularly apparent in late winter. The associated anomalies in surface air temperature were significant in many regions over the extratropical Northern Hemisphere except in central portions of the continents. The seesaw also modified the ocean–atmosphere exchange of heat and moisture extensively over the North Atlantic and North Pacific by changing evaporation and precipitation. Since the seesaw formation was triggered by eastward propagation of stationary Rossby wave trains from the North Pacific into the North Atlantic, anomalous circulation over the North Pacific in January was identified as a good precursor for February surface air temperatures in the Euro–Atlantic sector during that period. The seesaw relationship between the two low...
    Kalnay, E., Coauthors, 1996: The NCEP/NCAR 40-year reanalysis project. Bull. Amer. Meteor. Soc., 77, 437-471, https://doi.org/10.1175/1520-0477(1996)077 <0437:TNYRP>2.0,CO;2.10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;29bfeacc7ab553b364e43408563ad850bhttp%3A%2F%2Fintl-icb.oxfordjournals.org%2Fexternal-ref%3Faccess_num%3D10.1175%2F1520-0477%281996%290772.0.CO%3B2%26amp%3Blink_type%3DDOIhttp://journals.ametsoc.org/doi/abs/10.1175/1520-0477%281996%29077%3C0437%3ATNYRP%3E2.0.CO%3B2
    Kaplan A., M. A. Cane, Y. Kushnir, A. C. Clement, M. B. Blumenthal, and B. Rajagopalan, 1998: Analyses of global sea surface temperature 1856-1991.J. Geophys. Res.,103,18 567-18 589, https://doi.org/10.1029/97JC01736.10.1029/97JC0173617a0641d8f21e698d600b0b023977c69http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F97JC01736%2Ffull%3FscrollTo%3Dreferenceshttp://doi.wiley.com/10.1029/97JC01736Global analyses of monthly sea surface temperature (SST) anomalies from 1856 to 1991 are produced using three statistically based methods: optimal smoothing (OS), the Kaiman filter (KF) and optimal interpolation (OI). Each of these is accompanied by estimates of the error covariance of the analyzed fields. The spatial covariance function these methods require is estimated from the available data; the timemarching model is a first-order autoregressive model again estimated from data. The data input for the analyses are monthly anomalies from the United Kingdom Meteorological Office historical sea surface temperature data set (MOHSST5) [Parker et al., 1994] of the Global Ocean Surface Temperature Atlas (GOSTA) [Bottomley et al., 1990]. These analyses are compared with each other, with GOSTA, and with an analysis generated by projection (P) onto a set of empirical orthogonal functions (as in Smith et al. [1996]). In theory, the quality of the analyses should rank in the order OS, KF, OI, P, and GOSTA. It is found that the first four give comparable results in the data-rich periods (1951-1991), but at times when data is sparse the first three differ significantly from P and GOSTA. At these times the latter two often have extreme and fluctuating values, prima facie evidence of error. The statistical schemes are also verified against data not used in any of the analyses (proxy records derived from corals and air temperature records from coastal and island stations). We also present evidence that the analysis error estimates are indeed indicative of the quality of the products. At most times the OS and KF products are close to the OI product, but at times of especially poor coverage their use of information from other times is advantageous. The methods appear to reconstruct the major features of the global SST field from very sparse data. Comparison with other indications of the El Niño-Southern Oscillation cycle show that the analyses provide usable information on interannual variability as far back as the 1860s.
    Kerr R. A., 2000: A North Atlantic climate pacemaker for the centuries.Science,288,1984-1986, https://doi.org/10.1126/science.288.5473.1984.10.1126/science.288.5473.19841783511079a588566eccc20d99c2a1030043a243http%3A%2F%2Fonlinelibrary.wiley.com%2Fresolve%2Freference%2FPMED%3Fid%3D17835110http://www.sciencemag.org/cgi/doi/10.1126/science.288.5473.1984Although El Ni09o and La Ni09a are the largest single sources of global interannual climate variability, climate shifts on longer time scales than El Ni09o's 2 to 7 years are also drawing the attention of researchers. On multidecadal time scales of 40 to 80 years, a restless North Atlantic seems to be at work, alternately countering and enhancing humankind's alterations of climate. The evidence for this is turning up in such records as tree rings, ice cores, and corals.
    Li S. L., G. T. Bates, 2007: Influence of the Atlantic multidecadal oscillation on the winter climate of East China.Adv. Atmos. Sci.,24(1),126-135, https://doi.org/10.1007/s00376-007-0126-6.10.1007/s00376-007-0126-6bccca0cb470212275f14af8e90e8ae65http%3A%2F%2Fwww.cqvip.com%2FMain%2FDetail.aspx%3Fid%3D23633572http://link.springer.com/10.1007/s00376-007-0126-6正The Atlantic Multidecadal Oscillation (AMO), the multidecadal variation of North Atlantic sea surface temperature (SST), exhibits an oscillation with a period of 65-80 years and an amplitude of 0.4℃. Observational composite analyses reveal that the warm phase AMO is linked to warmer winters in East
    Liu J., J. A. Curry, H. Wang, M. Song, and R. M. Horton, 2012: Impact of declining Arctic sea ice on winter snowfall.Proceedings of the National Academy of Sciences of the United States of America,109,4074-4079, 1114910109.https://doi.org/10.1073/pnas.10.1073/pnas.111491010922371563e869b196cae446b30762b978476557d4http%3A%2F%2Fwww.jstor.org%2Fstable%2F41507098http://www.pnas.org/cgi/doi/10.1073/pnas.1114910109While the Arctic region has been warming strongly in recent decades, anomalously large snowfall in recent winters has affected large parts of North America, Europe, and east Asia. Here we demonstrate that the decrease in autumn Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation that have some resemblance to the negative phase of the winter Arctic oscillation. However, the atmospheric circulation change linked to the reduction of sea ice shows much broader meridional meanders in midlatitudes and clearly different interannual variability than the classical Arctic oscillation. This circulation change results in more frequent episodes of blocking patterns that lead to increased cold surges over large parts of northern continents. Moreover, the increase in atmospheric water vapor content in the Arctic region during late autumn and winter driven locally by the reduction of sea ice provides enhanced moisture sources, supporting increased heavy snowfall in Europe during early winter and the northeastern and midwestern United States during winter. We conclude that the recent decline of Arctic sea ice has played a critical role in recent cold and snowy winters.
    Lu R. Y., B. W. Dong, and H. Ding, 2006: Impact of the Atlantic Multidecadal Oscillation on the Asian summer monsoon. Geophys. Res. Lett. 33(24), https://doi.org/10.1029/2006GL027655.10.1029/2006GL02765552398184b237301b9bb60b677c2aa390http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2006GL027655%2Fpdfhttp://onlinelibrary.wiley.com/doi/10.1029/2006GL027655/pdfThe impact of the Atlantic Multidecadal Oscillation (AMO) on the Asian summer monsoon is investigated using a coupled atmosphere-ocean global general circulation model by imposing the AMO-associated sea surface temperature anomalies in the Atlantic as boundary forcing, and allowing atmosphere-ocean interactions outside the Atlantic. The positive AMO phase, characterized by anomalous warm North Atlantic and cold South Atlantic, leads to strong Southeast and east Asian summer monsoons, and late withdrawal of the Indian summer monsoon. These changes of monsoons are mainly through coupled atmosphere-ocean feedbacks in the western Pacific and Indian Oceans and tropospheric temperature changes over Eurasia in response to the imposed forcing in the Atlantic. The results are in agreement with the observed climate changes in China corresponded to the AMO phases. They suggest a non-local mechanism for the Asian summer monsoon variability and provide an alternative view to understanding its interdecadal variation during the twentieth century.
    Nakamura H., M. Honda, 2002: Interannual seesaw between the Aleutian and Icelandic lows Part III: Its influence upon the stratospheric variability.J. Meteor. Soc. Japan,80(4B),1051-1067, https://doi.org/10.2151/jmsj.80.1051.10.2151/jmsj.80.1051http://joi.jlc.jst.go.jp/JST.JSTAGE/jmsj/80.1051?from=CrossRef
    Nishii K., H. Nakamura, and Y. J. Orsolini, 2011: Geographical dependence observed in blocking high influence on the stratospheric variability through enhancement and suppression of upward planetary-wave propagation.J. Climate,24(24),6408-6423, https://doi.org/10.1175/JCLI-D-10-05021.1.10.1175/JCLI-D-10-05021.1183381a16429fb893c42b07f71b21a0chttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2011JCli...24.6408Nhttp://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-10-05021.1Previous studies have suggested the importance of blocking high (BH) development for the occurrence of stratospheric sudden warming (SSW), while there is a recent study that failed to identify their statistical linkage. Through composite analysis applied to high-amplitude anticyclonic anomaly events observed around every grid point over the extratropical Northern Hemisphere, the present study reveals a distinct geographical dependence of BH influence on the upward propagation of planetary waves (PWs) into the stratosphere. Tropospheric BHs that develop over the Euro-Atlantic sector tend to enhance upward PW propagation, leading to the warming in the polar stratosphere and, in some cases, to major SSW events. In contrast, the upward PW propagation tends to be suppressed by BHs developing over the western Pacific and the Far East, resulting in the polar stratospheric cooling. This dependence is found to arise mainly from the sensitivity of the interference between the climatological PWs and upward-propagating Rossby wave packets emanating from BHs to their geographical locations. This study also reveals that whether a BH over the eastern Pacific and Alaska can enhance or reduce the upward PW propagation is case dependent. It is suggested that BHs that induce the stratospheric cooling can weaken the statistical relationship between BHs and SSWs.
    Omrani N.-E., N. S. Keenlyside, J. Bader, and E. Manzini, 2014: Stratosphere key for wintertime atmospheric response to warm Atlantic decadal conditions.Climate Dyn.,42,649-663, https://doi.org/10.1007/s00382-013-1860-3.10.1007/s00382-013-1860-39687bf74387cfd236248754b7d3d2abbhttp%3A%2F%2Flink.springer.com%2F10.1007%2Fs00382-013-1860-3http://link.springer.com/10.1007/s00382-013-1860-3There is evidence that the observed changes in winter North Atlantic Oscillation (NAO) drive a significant portion of Atlantic Multi Decadal Variability (AMV). However, whether the observed decadal NAO changes can be forced by the ocean is controversial. There is also evidence that artificially imposed multi-decadal stratospheric changes can impact the troposphere in winter. But the origins of such stratospheric changes are still unclear, especially in early to mid winter, where the radiative ozone-impact is negligible. Here we show, through observational analysis and atmospheric model experiments, that large-scale Atlantic warming associated with AMV drives high-latitude precursory stratospheric warming in early to mid winter that propagates downward resulting in a negative tropospheric NAO in late winter. The mechanism involves stratosphere/troposphere dynamical coupling, and can be simulated to a large extent, but only with a stratosphere resolving model (i.e., high-top). Further analysis shows that this precursory stratospheric response can be explained by the shift of the daily extremes toward more major stratospheric warming events. This shift cannot be simulated with the atmospheric (low-top) model configuration that poorly resolves the stratosphere and implements a sponge layer in upper model levels. While the potential role of the stratosphere in multi-decadal NAO and Atlantic meridional overturning circulation changes has been recognised, our results show that the stratosphere is an essential element of extra-tropical atmospheric response to ocean variability. Our findings suggest that the use of stratosphere resolving models should improve the simulation, prediction, and projection of extra-tropical climate, and lead to a better understanding of natural and anthropogenic climate change.
    Orsolini Y. J., 2004: Seesaw fluctuations in ozone between the North Pacific and North Atlantic.J. Meteor. Soc. Japan,82(3),941-949, 2004. 941.https://doi.org/10.2151/jmsj.10.2151/jmsj.2004.941http://joi.jlc.jst.go.jp/JST.JSTAGE/jmsj/2004.941?from=CrossRef
    Orsolini Y. J., N. G. Kvamst闁帮拷, I. T. Kindem, M. Honda, and H. Nakamura, 2008: Influence of the Aleutian-Icelandic low seesaw and ENSO onto the Stratosphere in ensemble winter hindcasts.J. Meteor. Soc. Japan,86(5),817-825, https://doi.org/10.2151/jmsj.86.817.10.2151/jmsj.86.81719dd4bba2fe2498008ce895e845b8359http%3A%2F%2Fci.nii.ac.jp%2Fnaid%2F110006991218http://joi.jlc.jst.go.jp/JST.JSTAGE/jmsj/86.817?from=CrossRefUsing an ensemble of wintertime hindcasts with a high-resolution (T106L60) Atmospheric General Circulation Model (AGCM) forced by observed sea surface temperatures (SSTs) and extending into the stratosphere, we investigate the formation and lifecycle of the Aleutian-Icelandic low Seesaw (AIS) during the 1978 to 1993 period. The AIS has been newly proposed to be an important mode of variability, linking the major wintertime surface lows, the Icelandic Low and the Aleutian Low, in late winter, and thereby linking climate variability over the North Pacific and the North Atlantic. We demonstrate for the first time with a stratosphere-troposphere model, that a coherent, ensemble-mean AIS extension into the stratosphere exists, where its presence modulates ultra-long planetary wave propagation and the polar night jet intensity. The model AIS peaks in February, when the Aleutian and Icelandic Low anti-correlation maximizes at -0.59. The AIS provides a new way to describe the El Niño-Southern Oscillation (ENSO) phenomenon influence into the stratosphere. For example, El-Nino conditions correspond to a deeper than normal Aleutian Low, extending its influence into the Icelandic sector as an AIS negative phase (weakened Icelandic Low), hence enhanced planetary wave vertical propagation and a weakened stratospheric polar vortex. This maturation of the AIS in late winter explains the intra-seasonal variability of the stratospheric response to ENSO, which peaks in late winter. Internal model variability is large and enhanced potential predictability is found primarily in the western hemisphere, with a western Atlantic maxima being more pronounced in the stratosphere than in the upper troposphere.
    Peings Y., G. Magnusdottir, 2014: Forcing of the wintertime atmospheric circulation by the multidecadal fluctuations of the North Atlantic ocean,Environmental Research Letters,9(3),034018, https://doi.org/10.1088/1748-9326/9/3/034018.10.1088/1748-9326/9/3/0340189b1c9024c7198675b4ac73193d07d04bhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2014ERL.....9c4018Phttp://stacks.iop.org/1748-9326/9/i=3/a=034018?key=crossref.78c09fa6ee45935be9d64175d1959d01The North Atlantic sea surface temperature exhibits fluctuations on the multidecadal time scale, a phenomenon known as the Atlantic Multidecadal Oscillation (AMO). This letter demonstrates that the multidecadal fluctuations of the wintertime North Atlantic Oscillation (NAO) are tied to the AMO, with an opposite-signed relationship between the polarities of the AMO and the NAO. Our statistical analyses suggest that the AMO signal precedes the NAO by 10-15 years with an interesting predictability window for decadal forecasting. The AMO footprint is also detected in the multidecadal variability of the intraseasonal weather regimes of the North Atlantic sector. This observational evidence is robust over the entire 20th century and it is supported by numerical experiments with an atmospheric global climate model. The simulations suggest that the AMO-related SST anomalies induce the atmospheric anomalies by shifting the atmospheric baroclinic zone over the North Atlantic basin. As in observations, the positive phase of the AMO results in more frequent negative NAO - and blocking episodes in winter that promote the occurrence of cold extreme temperatures over the eastern United States and Europe. Thus, it is plausible that the AMO plays a role in the recent resurgence of severe winter weather in these regions and that wintertime cold extremes will be promoted as long as the AMO remains positive. 2014 IOP Publishing Ltd.
    Peings Y., G. Magnusdottir, 2016: Wintertime atmospheric response to Atlantic multidecadal variability: Effect of stratospheric representation and ocean-atmosphere coupling.Climate Dyn.,47,1029-1047, https://doi.org/10.1007/s00382-015-2887-4.10.1007/s00382-015-2887-46b4ddb4fb9836c7d2a39332a9f3192a8http%3A%2F%2Flink.springer.com%2F10.1007%2Fs00382-015-2887-4http://link.springer.com/10.1007/s00382-015-2887-4The impact of the Atlantic multidecadal variability (AMV) on the wintertime atmosphere circulation is investigated using three different configurations of the Community Atmospheric Model version 5 (CAM5). Realistic SST and sea ice anomalies associated with the AMV in observations are prescribed in CAM5 (low-top model) and WACCM5 (high-top model) to assess the dependence of the results on the representation of the stratosphere. In a third experiment, the role of ocean-atmosphere feedback is investigated by coupling CAM5 to a slab-ocean model in which the AMV forcing is prescribed through oceanic heat flux anomalies. The three experiments give consistent results concerning the response of the NAO in winter, with a negative NAO signal in response to a warming of the North Atlantic ocean. This response is found in early winter when the high-top model is used, and in late winter with the low-top model. With the slab-ocean, the negative NAO response is more persistent in winter and shifted eastward over the continent due to the damping of the atmospheric response over the North Atlantic ocean. Additional experiments suggest that both tropical and extratropical SST anomalies are needed to obtain a significant modulation of the NAO, with small influence of sea ice anomalies. Warm tropical SST anomalies induce a northward shift of the ITCZ and a Rossby-wave response that is reinforced in the mid-latitudes by the extratropical SST anomalies through eddy-mean flow interactions. This modeling study supports that the positive phase of the AMV promotes the negative NAO in winter, while illustrating the impacts of the stratosphere and of the ocean-atmosphere feedbacks in the spatial pattern and timing of this response.
    Plumb R. A., 1985: On the three-dimensional propagation of stationary waves. J. Atmos. Sci., 42, 217-229, https://doi.org/10.1175/1520-0469(1985)042<0217:OTTDPO>2.0,CO;2.10.1175/1520-0469(1985)042<0217:OTTDPO>2.0.CO;2ccdb9bc2c2853e3ba3d7632e5f9db2c5http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1985jats...42..217phttp://journals.ametsoc.org/doi/abs/10.1175/1520-0469%281985%29042%3C0217%3AOTTDPO%3E2.0.CO%3B2A locally applicable (nonzonally-averaged) conservation relation is derived for quasi-geostrophic stationary waves on a zonal flow, a generalization of the Eliassen-Palm relation. The flux which appears in this relation constitutes, it is argued, a useful diagnostic of the three-dimensional propagation of stationary wave activity. This is illustrated by application to a simple theoretical model of a forced Rossby wave train and to a Northern Hemisphere winter climatology. Results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the Tibetan plateau and from nonorographic effects (diabatic heating and/or interaction with transient eddies) in the western North Atlantic and North Pacific Oceans and Siberia. No evidence is found in the data for wave trains of tropical origin; forcing by the orographic effects of the Rocky mountains seems to be of secondary importance.
    Reichler T., J. Kim, E. Manzini, and J. Kröger, 2012: A stratospheric connection to Atlantic climate variability.Nature Geoscience,5(11),783-787, https://doi.org/10.1038/ngeo1586.10.1038/ngeo1586dd8ef745da79b475b6f15308b68e2c7bhttp%3A%2F%2Fwww.nature.com%2Fngeo%2Fjournal%2Fv5%2Fn11%2Fabs%2Fngeo1586.htmlhttp://www.nature.com/doifinder/10.1038/ngeo1586It is well recognized that the stratosphere is connected to tropospheric weather and climate. In particular, extreme stratospheric circulation events and their dynamical feedback on the troposphere are known to play a major role1. However, what is not known to date is whether the state of the stratosphere also matters for the ocean and its circulation. Previous research suggests co-variability of decadal stratospheric flow variations and conditions in the North Atlantic Ocean, but such findings are based on short simulations with only one climate model2. Here we report that over the past 30 years the stratosphere and the Atlantic thermohaline circulation underwent low-frequency variations that were similar to each other.
    Schneider U., A. Becker, P. Finger, A. Meyer-Christoffer B. Rudolf, and M. Ziese, 2015: GPCC Full Data Reanalysis Version 7.0 at 1.0: Monthly Land-Surface Precipitation from Rain-Gauges built on GTS based and Historic Data, https://doi.org/10.5065/D6000072.
    Sun J., B. Tan, 2013: Mechanism of the wintertime Aleutian low-Icelandic low seesaw.Geophys. Res. Lett.,40(15),4103-4108, https://doi.org/10.1002/grl.50770.10.1002/grl.50770cd7dc4217aad74a745a7d58e0ae56f3bhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2013GeoRL..40.4103Shttp://doi.wiley.com/10.1002/grl.50770The driving mechanism for the wintertime (December-March) Aleutian Low-Icelandic Low (AL-IL) seesaw is investigated with National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data for 1948-2009. It is shown that the AL and the IL are dynamically linked through the eastern Pacific wave train (EPW) and that both the EPWs and the stratospheric polar vortex are found to work cooperatively to produce a significant AL-IL seesaw. In general, it is found that wave reflection by the polar vortex is crucial for the formation of the AL-IL seesaw. However, when the EPWs are extremely strong, the AL-IL seesaw appears to be caused primarily by horizontal wave propagation. It is further shown that the Pacific center of the traditional Arctic Oscillation pattern is present when the AL-IL seesaw is active, but it disappears when the AL-IL seesaw is absent.
    Tang Q. H., X. J. Zhang, X. H. Yang, and J. A. Francis, 2013: Cold winter extremes in northern continents linked to Arctic sea ice loss,Environmental Research Letters,8(1),014036, https://doi.org/10.1088/1748-9326/8/1/014036.10.1088/1748-9326/8/1/0140364a2689c416c3793196f6b65170ec673dhttp%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2013ERL.....8a4036Thttp://stacks.iop.org/1748-9326/8/i=1/a=014036?key=crossref.3b07e12952c5b61acb8cedc9b207e051中国科学院机构知识库(中国科学院机构知识库网格(CAS IR GRID))以发展机构知识能力和知识管理能力为目标,快速实现对本机构知识资产的收集、长期保存、合理传播利用,积极建设对知识内容进行捕获、转化、传播、利用和审计的能力,逐步建设包括知识内容分析、关系分析和能力审计在内的知识服务能力,开展综合知识管理。
    Thompson, D. W. J, J. M. Wallace, 2001: Regional climate impacts of the Northern Hemisphere annular mode.Science,293(5527),85-89, https://doi.org/10.1126/science.1058958.10.1126/science.105895811441178aae3355072278d18ed2819f35c5dc39dhttp%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpubmed%2F11441178http://www.sciencemag.org/cgi/doi/10.1126/science.1058958The Northern Hemisphere annular mode (NAM) (also known as the North Atlantic Oscillation) is shown to exert a strong influence on wintertime climate, not only over the Euro-Atlantic half of the hemisphere as documented in previous studies, but over the Pacific half as well. It affects not only the mean conditions, but also the day-to-day variability, modulating the intensity of mid-latitude storms and the frequency of occurrence of high-latitude blocking and cold air outbreaks throughout the hemisphere. The recent trend in the NAM toward its high-index polarity with stronger subpolar westerlies has tended to reduce the severity of winter weather over most middle- and high-latitude Northern Hemisphere continental regions.
    Wallace J. M., D. S. Gutzler, 1981: Teleconnections in the geopotential height field during the Northern Hemisphere winter.Monthly Weather Review,109(4),784-812, https://doi.org/10.1175/1520-0493(1981)109<0784:TITGHF>2.0.CO;210.1175/1520-0493(1981)109<0784:TITGHF>2.0.CO;23544b322a43213a44a5bb1db36c9aad9http%3A%2F%2Fwww.bioone.org%2Fservlet%2Flinkout%3Fsuffix%3Di0276-4741-32-4-431-Wallace1%26amp%3Bdbid%3D16%26amp%3Bdoi%3D10.1659%252FMRD-JOURNAL-D-12-00062.1%26amp%3Bkey%3D10.1175%252F1520-0493%281981%291092.0.CO%253B2http://journals.ametsoc.org/doi/abs/10.1175/1520-0493%281981%29109%3C0784%3ATITGHF%3E2.0.CO%3B2
  • [1] Zhe HAN, Feifei LUO, Shuanglin LI, Yongqi GAO, Tore FUREVIK, Lea SVENDSEN, 2016: Simulation by CMIP5 Models of the Atlantic Multidecadal Oscillation and Its Climate Impacts, ADVANCES IN ATMOSPHERIC SCIENCES, 33, 1329-1342.  doi: 10.1007/s00376-016-5270-4
    [2] ZHOU Xiaomin, LI Shuanglin, LUO Feifei, GAO Yongqi, Tore FUREVIK, 2015: Air-Sea Coupling Enhances the East Asian Winter Climate Response to the Atlantic Multidecadal Oscillation, ADVANCES IN ATMOSPHERIC SCIENCES, 32, 1647-1659.  doi: 10.1007/s00376-015-5030-x
    [3] Xueqian SUN, Shuanglin LI, Xiaowei HONG, Riyu LU, 2019: Simulated Influence of the Atlantic Multidecadal Oscillation on Summer Eurasian Nonuniform Warming since the Mid-1990s, ADVANCES IN ATMOSPHERIC SCIENCES, , 811-822.  doi: 10.1007/s00376-019-8169-z
    [4] Johnny C. L. CHAN, Kin Sik LIU, 2022: Recent Decrease in the Difference in Tropical Cyclone Occurrence between the Atlantic and the Western North Pacific, ADVANCES IN ATMOSPHERIC SCIENCES, 39, 1387-1397.  doi: 10.1007/s00376-022-1309-x
    [5] Shangfeng CHEN, Linye SONG, Wen CHEN, 2019: Interdecadal Modulation of AMO on the Winter North Pacific Oscillation−Following Winter ENSO Relationship, ADVANCES IN ATMOSPHERIC SCIENCES, 36, 1393-1403.  doi: 10.1007/s00376-019-9090-1
    [6] CHEN Wen, WEI Ke, 2009: Interannual Variability of the Winter Stratospheric Polar Vortex in the Northern Hemisphere and their Relations to QBO and ENSO, ADVANCES IN ATMOSPHERIC SCIENCES, 26, 855-863.  doi: 10.1007/s00376-009-8168-6
    [7] LI Qian, Hans-F. GRAF, CUI Xuefeng, 2011: The Role of Stationary and Transient Planetary Waves in the Maintenance of Stratospheric Polar Vortex Regimes in Northern Hemisphere Winter, ADVANCES IN ATMOSPHERIC SCIENCES, 28, 187-194.  doi: 10.1007/s00376-010-9163-7
    [8] Xiangdong ZHANG, Yunfei FU, Zhe HAN, James E. OVERLAND, Annette RINKE, Han TANG, Timo VIHMA, Muyin WANG, 2022: Extreme Cold Events from East Asia to North America in Winter 2020/21: Comparisons, Causes, and Future Implications, ADVANCES IN ATMOSPHERIC SCIENCES, 39, 553-565.  doi: 10.1007/s00376-021-1229-1
    [9] Yan XIA, Yongyun HU, Jiankai ZHANG, Fei XIE, Wenshou TIAN, 2021: Record Arctic Ozone Loss in Spring 2020 is Likely Caused by North Pacific Warm Sea Surface Temperature Anomalies, ADVANCES IN ATMOSPHERIC SCIENCES, 38, 1723-1736.  doi: 10.1007/s00376-021-0359-9
    [10] SHI Ning, and BUEH Cholaw, 2013: Three-dimensional dynamic features of two Arctic oscillation types, ADVANCES IN ATMOSPHERIC SCIENCES, 30, 1039-1052.  doi: 10.1007/s00376-012-2077-9
    [11] GAN Bolan, WU Lixin, 2012: Possible Origins of the Western Pacific Warm Pool Decadal Variability, ADVANCES IN ATMOSPHERIC SCIENCES, 29, 169-176.  doi: 10.1007/s00376-011-0193-6
    [12] Jianping LI, Tiejun XIE, Xinxin TANG, Hao WANG, Cheng SUN, Juan FENG, Fei ZHENG, Ruiqiang DING, 2022: Influence of the NAO on Wintertime Surface Air Temperature over East Asia: Multidecadal Variability and Decadal Prediction, ADVANCES IN ATMOSPHERIC SCIENCES, 39, 625-642.  doi: 10.1007/s00376-021-1075-1
    [13] WEI Ke, BAO Qing, 2012: Projections of the East Asian Winter Monsoon under the IPCC AR5 Scenarios Using a Coupled Model: IAP-FGOALS, ADVANCES IN ATMOSPHERIC SCIENCES, 29, 1200-1214.  doi: 10.1007/s00376-012-1226-5
    [14] Yali ZHU, Tao WANG, Jiehua MA, 2016: Influence of Internal Decadal Variability on the Summer Rainfall in Eastern China as Simulated by CCSM4, ADVANCES IN ATMOSPHERIC SCIENCES, 33, 706-714.  doi: 10.1007/s00376-016-5269-x
    [15] SONG Jie, LI Chongyin, ZHOU Wen, PAN Jing, 2009: The Linkage between the Pacific-North American Teleconnection Pattern and the North Atlantic Oscillation, ADVANCES IN ATMOSPHERIC SCIENCES, 26, 229-239.  doi: 10.1007/s00376-009-0229-3
    [16] LI Shuanglin, Gary T. BATES, 2007: Influence of the Atlantic Multidecadal Oscillation on the Winter Climate of East China, ADVANCES IN ATMOSPHERIC SCIENCES, 24, 126-135.  doi: 10.1007/s00376-007-0126-6
    [17] Tao WANG, Qiang FU, Wenshou TIAN, Hongwen LIU, Yifeng PENG, Fei XIE, Hongying TIAN, Jiali LUO, 2022: The Influence of Meridional Variation in North Pacific Sea Surface Temperature Anomalies on the Arctic Stratospheric Polar Vortex, ADVANCES IN ATMOSPHERIC SCIENCES.  doi: 10.1007/s00376-022-2033-2
    [18] LI Jianping, Julian X.L.WANG, 2003: A New North Atlantic Oscillation Index and Its Variability, ADVANCES IN ATMOSPHERIC SCIENCES, 20, 661-676.  doi: 10.1007/BF02915394
    [19] Guokun DAI, Mu MU, Zhina JIANG, 2019: Evaluation of the Forecast Performance for North Atlantic Oscillation Onset, ADVANCES IN ATMOSPHERIC SCIENCES, , 753-765.  doi: 10.1007/s00376-019-8277-9
    [20] REN Rongcai, Ming CAI, 2006: Polar Vortex Oscillation Viewed in an Isentropic Potential Vorticity Coordinate, ADVANCES IN ATMOSPHERIC SCIENCES, 23, 884-900.  doi: 10.1007/s00376-006-0884-6

Get Citation+

Export:  

Share Article

Manuscript History

Manuscript received: 01 February 2017
Manuscript revised: 30 May 2017
Manuscript accepted: 22 June 2017
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Modulation of the Aleutian-Icelandic Low Seesaw and Its Surface Impacts by the Atlantic Multidecadal Oscillation

  • 1. NILU——Norwegian Institute for Air Research, Kjeller 2007, Norway
  • 2. Nansen-Zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 3. Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Key Laboratory of Meteorological Disaster, Ministry of Education, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 4. Climate Change Research Center, Chinese Academy of Sciences, Beijing 100029, China
  • 5. Nansen Environmental and Remote Sensing Center and Bjerknes Center for Climate Research, Bergen 5006, Norway
  • 6. Geophysical Institute, University of Bergen and Bjerknes Center for Climate Research, Bergen 5007, Norway

Abstract: Early studies suggested that the Aleutian-Icelandic low seesaw (AIS) features multidecadal variation. In this study, the multidecadal modulation of the AIS and associated surface climate by the Atlantic Multidecadal Oscillation (AMO) during late winter (February-March) is explored with observational data. It is shown that, in the cold phase of the AMO (AMO|-), a clear AIS is established, while this is not the case in the warm phase of the AMO (AMO|+). The surface climate over Eurasia is significantly influenced by the AMO's modulation of the Aleutian low (AL). For example, the weak AL in AMO|- displays warmer surface temperatures over the entire Far East and along the Russian Arctic coast and into Northern Europe, but only over the Russian Far East in AMO|+. Similarly, precipitation decreases over central Europe with the weak AL in AMO|-, but decreases over northern Europe and increases over southern Europe in AMO|+. The mechanism underlying the influence of AMO|- on the AIS can be described as follows: AMO|- weakens the upward component of the Eliassen-Palm flux along the polar waveguide by reducing atmospheric blocking occurrence over the Euro-Atlantic sector, and hence drives an enhanced stratospheric polar vortex. With the intensified polar night jet, the wave trains originating over the central North Pacific can propagate horizontally through North America and extend into the North Atlantic, favoring an eastward-extended Pacific-North America-Atlantic pattern, and resulting in a significant AIS at the surface during late winter.

摘要: 早期研究表明了阿留申-冰岛低压振荡的多年代际变化, 本文主要利用观测资料揭示了北大西洋多年代际振荡(AMO)对后冬(2-3月)阿留申-冰岛低压振荡、以及相关地表气候的多年代际调制作用. 结果表明, 只有在AMO冷位相的背景下, 显著的阿留申-冰岛低压振荡才会形成. AMO对阿留申低压的调制作用对欧亚地表气候有显著影响, 比如, 在AMO冷位相背景下, 弱的阿留申低压对应整个东亚地区、以及从俄罗斯北极沿岸到欧洲北部的气温偏高;而在AMO暖位相时, 暖异常只出现在俄罗斯远东地区. 类似地, AMO冷位相对弱阿留申低压的调制, 使得欧洲中部降水减少; 而在AMO暖位相的调制下, 欧洲北部降水减少、南部降水增多.AMO冷位相影响阿留申-冰岛低压振荡的机制解释如下: AMO冷位相通过减少欧洲-北大西洋大气阻塞的发生频次, 使得通过极地波导向上传播的行星波减弱, 平流层极涡加强. 因此, 由于极夜急流的加强, 从北太平洋中部激发的波列可以从北美传播到北大西洋, 有助于向东延伸的太平洋-北美-大西洋型的形成. 最终, 在后冬出现显著的阿留申-冰岛低压振荡.

1. Introduction
  • During boreal winter, there are two major climatological surface low-pressure cells in the Northern Hemisphere: the Aleutian low (AL) and the Icelandic low (IL). Early studies indicated that the AL and IL vary in an anti-phase seesaw pattern on the interannual timescale, particularly during late winter (February-March) (Honda et al., 2001; Honda and Nakamura, 2001; Orsolini, 2004). (Honda et al., 2001) named this pattern the Aleutian and Icelandic low seesaw (AIS). Combining both observations and simulations with an atmospheric general circulation model (AGCM), (Honda et al., 2005a) put forward a dynamical pathway for the formation of the AIS, consisting of a three-step process: (1) the AIS starts with the North Pacific variability associated with the AL; (2) the North Pacific influence extends across North America through the eastward propagation of stationary Rossby wave trains, which corresponds to the Pacific-North America (PNA) pattern (Wallace and Gutzler, 1981); and (3) IL anomalies form as part of the Atlantic edge of the PNA-like wave trains. Typically, the formation of the AIS begins with an anomalous AL and ends with the Pacific-North America-Atlantic (PNAA) pattern (Honda et al., 2005b; focused on 1973-94), as well as upward propagation from the surface into the stratosphere during late winter (Nakamura and Honda, 2002; focus on 1966/67-1996/97). (Orsolini et al., 2008) used AGCM simulations to demonstrate that El Niño can extend its influence into the Icelandic sector, forming a PNAA pattern, and into the stratosphere, via the horizontal and vertical propagation of planetary waves modulated by the maturation of the AIS during late winter.

    (Honda et al., 2005b) showed a significant influence of the AIS on surface air temperature (TS) and precipitation over the extratropical Northern Hemisphere during late winter, except in central continental regions. The AIS modulates the storm-track activity over both Pacific and Atlantic basins, which produces a downstream increase in eddy activity and precipitation (Garreaud, 2007). However, they also noted that the anti-correlation between the AL and IL is not always significant during the 20th century, but undergoes multidecadal modulations. (Sun and Tan, 2013) explored the formation of the AIS pattern and attributed it to a stronger stratospheric polar vortex, which may act to reflect the eastern North Pacific wave trains (EPWs) in December-March (focused on 1948-2009). The role of the polar vortex in linking the Aleutian and North Atlantic variability was also noted by (Castanheira and Graf, 2003).

    The Atlantic Multidecadal Oscillation (AMO) is a basin-scale oceanic pattern of sea surface temperature (SST) variability on a multidecadal timescale [60-70 years (Kerr, 2000)]. Cold AMO phases (AMO|-) occur in the 1900s-1920s and 1970s-1990s, while warm AMO phases (AMO|+) occur in the 1930s-1950s and after the mid-1990s. The fluctuations of the AMO are associated with numerous climatic phenomena. For example, the AMO induces North Atlantic Oscillation (NAO)-like anomalies during late winter (Omrani et al., 2014). (Peings and Magnusdottir, 2016) also explored the wintertime atmospheric response to the Atlantic multidecadal variability, based on three different configurations of version 5 of the Community Atmosphere Model (low-top, high-top, and low-top coupled to a slab ocean). They suggested different timings of the NAO-like response, which they attributed to an earlier occurrence of the polar warming in the stratosphere in the high-top configuration. Remotely, the AMO modulates the East Asian monsoon through coupled atmosphere-ocean feedbacks in the western Pacific and Indian oceans (Lu et al., 2006; Li and Bates, 2007). Moreover, AMO|+ increases the frequency of atmospheric blocking highs over the Euro-Atlantic sector by changing the baroclinicity and the transient eddy activity (Häkkinen et al., 2011; Peings and Magnusdottir, 2014). The increased blocking highs over the Euro-Atlantic sector can further enhance upward planetary wave propagation, resulting in stratospheric warming (i.e., a weaker polar vortex) (Nishii et al., 2011).

    Despite our incomplete understanding of the connection between the AMO and the stratosphere (Reichler et al., 2012), we try in this study to determine whether the AMO is linked to the multi-decadal variability of the AIS and the associated surface climate during the 20th century using observational/reanalysis data, and whether the potential driver is the AMO's modulation of the stratospheric polar vortex.

2. Data, climatic index and method
  • We use five monthly mean datasets: (1) sea level pressure (SLP) from HadSLP2r (Allan and Ansell, 2006) during 1860-2016; (2) atmospheric fields from NCEP/NCAR Reanalysis 1 (Kalnay et al., 1996) during 1948-2016; (3) TS from CRU TS3.24 (Harris et al., 2014) during 1901-2015; (4) precipitation from GPCC Reanalysis 7.0 (Schneider et al., 2015) during 1901-2016; and (5) SST from Kaplan Extended SST V2 (Kaplan et al., 1998) during 1856-2017. The analyzed period extends from 1948 to 2011, which allows for atmospheric fields from the relatively reliable NCEP-1 to be used. Besides, our analysis focuses on late winter (February-March), when the AIS is mature and stable (Honda et al., 2001; also see Fig. S2).

    The AL and IL indices are defined as the average anomalies of SLP over (50°-60°N, 185°-215°E) and (55°-65°N, 315°-345°E), respectively (Orsolini et al., 2008; derived from HadSLP2r). The AIS index is the difference between the normalized AL and IL indices. A positive value of the AL (AIS) index corresponds to a weak AL (a weak AL and a stronger IL). The AIS index used here differs slightly from the one defined by (Honda et al., 2005b). The main difference is the geographical sector used for the AL definition, which in our case is situated farther north, in the region of strongest SLP variance in February. The correlation coefficient between the AIS index used here and that used by (Honda et al., 2005b) is 0.94 (over the 99% confidence level) (Fig. S1). The smoothed AMO index is based upon the average SST anomaly (SSTA) in the North Atlantic basin (0°-70°N) during 1861-2011 (available at https://www.esrl.noaa.gov/psd/data/timeseries/AMO/). Weak (strong) AL years are determined when the normalized AL index is above (below) a standard deviation from the mean of 0.8 (-0.8). The AMO|+ and AMO|- phases correspond to cases in which the smoothed AMO index is above and below zero, respectively. The classification of weak and strong AL years according to the different phases of the AMO, used for the composite analysis, is shown in Table 1.

    Regarding the statistical methods used in this study, we employ correlation analysis, linear regression, and composite analysis. The statistical significance of correlation is assessed using the two-tailed Student's t-test. The wave activity flux (WAF) is used to identify the origin and propagation of Rossby wave-like perturbations, which are calculated in the quasi-geostrophic framework (Plumb, 1985). The Eliassen-Palm (EP) flux (Andrews, 1987) is used to measure the planetary wave (wavenumbers 1-3) activity propagation. Blocking high events are defined as intervals in which daily 500-hPa height from the reanalysis exceeds a standard deviation of 1 above the monthly mean for each grid cell over five consecutive days (Thompson and Wallace, 2001; Liu et al., 2012; Tang et al., 2013). The incidence of blocking highs is measured as (1) the percentage relative to the blocking climatology during 1948-2011 or (2) the ratio of the number of days when a certain grid point is blocked to the total number of days.

    Figure 1.  (a) The AL (orange bars) and IL (blue line) indices from 1860 to 2016, February-March. (b) Correlations in a 25-year moving window between the AL and IL indices. The 90% and 95% confidence level for the correlations is indicated by the horizontal dashed lines. (c) Smoothed AMO index from 1861 to 2011, February-March. The vertical dashed lines reflect the analyzed period (1973-94) in (Honda et al., 2001). (d) Composite differences of February-March SST (units: °C) restricted to the Atlantic region between AMO\(\vert -\) and AMO|+ years. Crosshatched region is statistically significant at the 95% confidence level.

3. AIS connection to the AMO
  • Figure 1a illustrates the time series of the AL and IL indices from 1860 to 2016, February-March. The AL and IL indices have been detrended by removing the long-term linear trend. Year-to-year variations in the AL and IL show an anti-correlation over the 157 years, with a coefficient of -0.26 (over the 99% confidence level). The correlations between the AL and IL indices, computed over a 25-year moving window, are presented in Fig. 1b. The main result is that the AL-IL relationship displays multidecadal non-stationarity. The anti-correlation significance is higher than the 95% confidence level, over the 1900s-1920s and 1970s-1990s approximately. It is statistically insignificant before the 1900s and after the mid-1990s, and even changes sign over the 1930s-1950s. Note that the significant anti-correlation period (the 1970s-1990s) revealed by the present study is in good agreement with the analyzed period (1973-94) in (Honda et al., 2001).

    Figure 1c illustrates the time series of the smoothed AMO from 1861 to 2011, February-March. Composite analysis of February-March SSTAs between AMO|- and AMO|+ years (Fig. 1d) shows cold anomalies over the North Atlantic, with a minimum of -0.30°C over the subpolar region, and warm anomalies over the South Atlantic (up to 0.13°C). Interestingly, significant anti-correlations between the AL and IL exist only in AMO|-. The period of AMO|+ shows no significant correlation.

    Figure 2.  Composite differences of February-March SLP (units: hPa) (derived from HadSLP2r) between weak and strong AL years for (a) 1861-2011, and for (b) AMO\(\vert \)+ and (c) AMO|-. (d-f) As in (a-c), but for SLP (derived from NCEP-1, 1948-2011). Shaded regions indicate significance at the 95% confidence level.

    To investigate the effects of AMO phases on the intensity of the AL and IL and on the formation of the AIS, we conduct a composite analysis for the whole period, as well as for each phase of the AMO. The upper panel of Fig. 2 illustrates the composite differences of February-March SLP (derived from HadSLP2r) between weak and strong AL years for 1861-2011, as well as in AMO|+ and AMO|-. For the whole period, the weak AL is associated with positive SLP anomalies over the North Pacific, and negative SLP anomalies over the polar cap and Iceland (Fig. 2a). In AMO|+, the negative SLP anomalies retreat to the polar cap and even change to positive sign over the Barents Sea (Fig. 2b). There is no AL-IL correlation. In AMO|-, the negative SLP anomalies occupy the polar cap and subpolar North Atlantic, with the minimum located in the climatological center of the IL (Fig. 2c). A clear AIS pattern appears. The same conclusion is reached when using NCEP-1 (1948-2011) (Figs. 2d-f) instead of HadSLP2r.

    The upper panel of Fig. 3 illustrates the composite differences of February-March 250-hPa geopotential height (Z250) and horizontal WAF (departures from zonal means) between weak and strong AL years for 1948-2011, as well as in AMO|+ and AMO|-. In the following analysis, our description particularly focuses on the composites for AMO|+ and AMO|-. In AMO|+, the weak AL is associated with positive Z250 anomalies over the North Pacific and southern United States, and there is a negative Z250 center in central Canada (Fig. 3b). Meanwhile, the PNA-like stationary Rossby wave trains originate over the central North Pacific and stretch horizontally across North America. In AMO|-, the negative Z250 center in central Canada extends considerably farther across Newfoundland, past the south of Greenland (i.e., the subpolar North Atlantic; Fig. 3c), as another wave train emanates from the leading edge of the PNA-like Rossby wave to form the PNAA pattern (Honda et al., 2001, 2005a). This pattern is analogous to the EPWs in (Sun and Tan, 2013), which originate over the central North Pacific and propagate horizontally through North America and into the North Atlantic.

    The lower panel of Fig. 3 is the same as the upper panel, but for zonally averaged zonal wind. In AMO|+, anomalous westward flow is significant along the midlatitudes (30°-40°N) from the surface into the lower stratosphere (Fig. 3e). However, in AMO|-, both anomalous westward and eastward flows are significant, and of stronger magnitude, along the midlatitudes (30°-40°N) and high latitudes (north of 50°N), respectively, from the surface into the upper stratosphere (Fig. 3f), suggesting a stronger stratospheric polar vortex. Thus, the clear AIS seen in the SLP in AMO|- is strongly coupled with the PNAA pattern and EPWs in the upper troposphere, and the stronger stratospheric polar vortex; whereas, in AMO|+, there is no established AIS with the upper-tropospheric PNA pattern.

    Figure 3.  Composite differences of February-March Z250 (contours; units: gpm)/horizontal WAF (vectors; scale in m2 s-2) (departures from zonal means) between weak and strong AL years for (a) 1948-2011, and for (b) AMO|+ and (c) AMO|-. (d-f) As in (a-c), but for zonally averaged zonal wind (units: m s-1). Shaded regions indicate significance at the 95% confidence level.

    Figure 4.  Composite differences of February-March TS (units: °C) (derived from CRU) between weak and strong AL years for (a) 1948-2011, and for (b) AMO|+, and (c) AMO\(\vert -\). (d-f) As in (a-c), but for 1000-hPa horizontal temperature advection (scale in m K s-1). Dotted (a-c) and shaded (d-f) regions indicate significance at the 95% confidence level.

    Figure 5.  Composite differences of February-March precipitation (units: mm) (derived from GPCC) between weak and strong AL years for (a) 1948-2011, and for (b) AMO|+ and (c) AMO|-. (d-f) As in (a-c), but for U300 (contours; unit: m s-1)/variance of bandpass-filtered (3-7 days) V300 (shaded, units: m s-1). Dotted regions indicate significance at the 95% confidence level.

4. AIS-based surface climate
  • We extend our investigation into how the AL's impact on surface climate is influenced by the AMO phase. Figure 4 illustrates the composite differences of February-March TS and 1000-hPa horizontal temperature advection between weak and strong AL years for 1948-2011, as well as in AMO|+ and AMO|-. In AMO|+, the weak AL-related anticyclonic anomalies induce cold advection along the west coast of North America and warm advection along the Russian Far East coast; anticyclonic anomalies over the Barents Sea contribute to cold advection over Europe (Fig. 4e). Cold anomalies are pronounced over Canada and Europe (Fig. 4b). In AMO|-, cold anomalies over Canada are much weaker, and warm anomalies extend over the entire Far East and along the Russian Arctic coast (Fig. 4c). Besides, the intensified IL-related cyclonic anomalies (Fig. 4f) lead to cold anomalies over the Middle East, and warm anomalies over northern Europe stretching along the Russian Arctic coast.

    Figure 5 is the same as Fig. 4, but for precipitation and 300-hPa zonal wind (U300)/variance of bandpass-filtered (3-7 days) 300-hPa meridional wind (V300). The monthly variance of V300 is calculated from daily mean values, which are then band-pass filtered (3-7 days), to reflect the transient eddy activity. In AMO|+, positive band-passed U300 anomalies occur over the Bering Sea/Aleutian Islands and the United States, and negative band-passed U300 anomalies over the midlatitude North Pacific and Arctic Canada/Europe (Fig. 5e, contours), favoring enhanced (diminished) eddy activity downstream (Fig. 5e, vectors). Correspondingly, positive precipitation anomalies are over western Canada, and negative precipitation anomalies over the western United States and northern Europe (Fig. 5b). In AMO|-, the positive band-passed U300 anomalies over the United States extend eastwards through the North Atlantic, with opposite band-passed U300 anomalies over the Mediterranean Sea, which corresponds to diminished eddy activity and precipitation over southern Europe (Figs. 5c and f).

5. How does the AMO modulate the AIS?
  • How can the AMO be linked to the AIS multidecadal fluctuations through an anomalous stratospheric polar vortex? To answer this, the composite-differences of daily geopotential height averaged north of 60°N (pressure versus time) between AMO|- and AMO|+ years are presented in Fig. 6a. The subpolar North Atlantic cold SSTAs (see Fig. 1d) are associated with a precursory strengthening of the stratospheric polar vortex during early winter (November-January), which propagates downwards into the troposphere during late winter (February-March). The strengthening of the stratospheric polar vortex (i.e., stratospheric cooling) is mainly maintained by anomalous negative quasi-stationary eddy heat flux (Fig. 6b).

    Figure 6.  (a) Temporal evolution of daily geopotential height (units: gpm) averaged north of 60°N for the composite difference between AMO|- and AMO|+ years. (b) Temporal evolution of monthly quasi-stationary eddy heat flux (units: °C m s-1) averaged north of 60°N in the lowermost stratosphere (150 hPa) for the composite difference with both AMO|+ (red line) and AMO|- (blue line) years.

    Figure 7 illustrates the composite differences of November-January 20-hPa geopotential height (Z20) and February-March Z250/horizontal WAF (departures from zonal means) between AMO|- and AMO|+ years. The Z20 pattern related to AMO|- shows negative anomalies over the polar cap and positive anomalies in the midlatitudes (Fig. 7a), suggesting an enhanced stratospheric polar vortex during early winter, consistent with (Omrani et al., 2014). The negative Z20 anomalies in the Arctic extend downwards to 250 hPa during late winter, accompanied by EPWs that emanate over the eastern North Pacific and stretch horizontally through the western North America-North Atlantic-Europe sector (Fig. 7b).

    The composite differences of November-January and February-March EP flux cross sections and zonally averaged zonal wind between AMO|+ and AMO|- years are presented in Figs. 8a and b, respectively. In AMO|-, during early winter, the polar night jet accelerates (Fig. 8a, contours) because of anomalous equatorward-pointing EP flux in the uppermost stratosphere (20 hPa), and anomalous downward-pointing EP flux along the polar waveguide (Dickinson, 1968; Fig. 8a, vectors). During late winter, the anomalous upper-stratospheric equatorward-pointing EP flux disappears, while the anomalous downward-pointing EP flux is stronger in magnitude, moving directly from the upper stratosphere in the high latitudes to reach the surface (Fig. 8b, vectors). The high-latitude zonal wind anomaly strengthens not only in the stratosphere but also in the troposphere (Fig. 8b, contours).

    Figure 7.  Composite differences between AMO|- and AMO|+ years of (a) November-January Z20 (units: gpm) and (b) February-March Z250 (contours; units: gpm)/WAF (vectors; scale in m2 s-2; departures from zonal means) . Shaded regions indicate significance at the 95% confidence level.

    Figure 8.  Composite differences between AMO|- and AMO|+ years of (a) November-January and (b) February-March EP flux cross sections (vectors; scale in m2 s-2) and zonally averaged zonal wind (contours; units: m s-1) . Shaded regions indicate significance at the 95% confidence level. In order to display the EP flux throughout the stratosphere, the vectors are scaled by \(\sqrt1000/P\) and the inverse of air density. Additionally, the vertical component is multiplied by 125. February-March (c) 50-hPa and (d) 250-hPa vertical stationary WAFs in the climatology (1948-2011; contours; unit: 103 m2 s-2) and the composite difference between AMO|- and AMO|+ years (shaded; units: 103 m2 s-2). Crosshatched regions indicate significance at the 95% confidence level.

    Figure 9.  Composite differences between AMO\(\vert -\) and AMO|+ years of the incidence of (a) November-March, (b) November-January and (c) February-March blocking highs (measured as the percentage relative to the blocking climatology during 1948-2011) restricted to the Euro-Atlantic sector (25°-80°N, 85°W-30°E). (d) Distribution of seasonal regime frequencies (40°-80°N, 85°W-30°E; measured as the ratio of the number of days when a certain grid point is blocked to the total number of days) in AMO|+ (red boxplots) and AMO|- (blue boxplots) for November-March, November-January and February-March. Boxplots indicate the maximum, upper-quartile, median, lower-quartile and minimum of the distribution (horizontal bars). The mean of the distribution is shown by black diamonds, and asterisks indicate the significance level of the difference of the mean between AMO|- and AMO|+: one star, p<0.05; two stars, p<0.01.

    To better understand the spatial modulation of planetary waves associated with the anomalous downward-pointing EP flux at different levels, we calculate the February-March 50-hPa and 250-hPa vertical WAFs in the climatology and the composite difference between AMO|- and AMO|+ years (Figs. 8c and d). The positive (negative) contours represent the upward (downward) climatological stationary wave activity (Plumb, 1985). At 50 hPa, the anomalous downward stationary wave flux over the subpolar North Atlantic related to AMO|- (Fig. 8c, shaded) collocates with the climatological negative center (Fig. 8c, contours). This center of anomalous downward flux is also apparent over northeastern North America and Greenland at 250 hPa (Fig. 8d, shaded), and may superimpose on the horizontal EPWs (Fig. 7b), contributing to an eastward-extended PNAA pattern and the formation of the AIS (Sun and Tan, 2013).

    The results mentioned above indicate that the AMO|- phase has the potential to drive an intensified polar night jet because of anomalous downward-pointing EP flux along the polar waveguide (Figs. 8a and b) or, equivalently, because of the negative quasi-stationary eddy heat flux anomalies in the high latitudes (Fig. 6b). It is suggested that the EPWs propagate zonally along the intensified polar night jet in late winter (Fig. 7b). The central question remains as to why AMO|- is associated with an intensified polar vortex, and the answer can be found in how the AMO modulates the occurrence of atmospheric blockings over the Atlantic (Häkkinen et al., 2011; Peings and Magnusdottir, 2014). Reduced occurrence of blocking highs over the Euro-Atlantic sector would imply a lessening of the upward wave activity flux, resulting in a stronger stratospheric polar vortex (Nishii et al., 2011).

    To test this, we re-examine the composite differences of the incidence of November-March, November-January and February-March blockings highs (measured as the percentage relative to the blocking climatology during 1948-2011) between AMO|- and AMO|+ years (Fig. 9, left panel). In AMO|-, in early winter, the frequency of blocking highs decreases over the subpolar North Atlantic, while it increases in southern Europe (Fig. 9b). During late winter, the reduced blocking highs are of stronger magnitude over most parts of the Euro-Atlantic sector, except the midlatitude North Atlantic where increased blocking highs are found (Fig. 9c). Figure 9d further confirms that the frequency of blocking highs over the Euro-Atlantic sector (40°-80°N, 85°W-30°E) is lower in AMO|- compared to in AMO|+, especially during late winter. These findings on the occurrence of blockings are in agreement with (Peings and Magnusdottir, 2014), and support the association of AMO|- with a strengthened stratospheric vortex.

6. Discussion and conclusions
  • The present study, based on observations, shows:

    (1) The significant anti-correlation between the AL and IL in February-March is not a consistent feature during the 20th century, and emerges only in AMO|-. The AIS is clearly established and is strongly coupled with the PNAA pattern and EPWs in the upper troposphere, and the intensified polar night jet. On the contrary, in AMO|+ occurs, the AIS is not established, featuring the upper-tropospheric PNA pattern only.

    (2) The surface climate over Eurasia is sensitive to the establishment of the AIS. With an established AIS (weak AL and strong IL), the Middle East (Far East) is colder (warmer) than normal, and southern Europe experiences less rain. However, without an established AIS (weak AL only), Europe (the Russian Far East) is colder (warmer) than normal, and northern Europe receives less rain.

    (3) The AMO|- phase favors a clear AIS mainly because of its influence on the intensified polar night jet, via weakening the EP flux along the polar waveguide/negative quasi-stationary eddy heat flux anomalies in the high latitudes, which can be achieved by atmospheric blocking modulation (Häkkinen et al., 2011; Peings and Magnusdottir, 2014; see also Fig. 9). The EPWs propagate zonally along the intensified polar night jet during late winter, favoring an eastward-extended PNAA pattern and resulting in a significant AIS at the surface.

    It is important to note that, within a decadal period of AMO|-, the interannually varying AIS can be of either phase, with a concomitant weak or strong AL and an out-of-phase IL. By itself, AMO|- would favor a strong stratospheric polar vortex and IL (Omrani et al., 2014). Hence, the AMO may modulate the stratospheric polar vortex and IL superimposed on the active AIS. In this paper, we select the AMO phases based on the smoothed AMO index above and below zero, and hence the modulation of IL intensity is much weaker (Fig. 7c) compared to the results in (Omrani et al., 2014).

    In addition, the AIS' connection to different phases of the AMO and to the winter surface climate over Eurasia warrants a study using an AGCM externally forced with observed SST and extending into the stratosphere. This issue will be addressed in future work.

Reference

Catalog

    /

    DownLoad:  Full-Size Img  PowerPoint
    Return
    Return