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Observed and simulated impacts of the summer NAO in Europe: implications for projected drying in the Mediterranean region

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Abstract

Climate models predict substantial summer precipitation reductions in Europe and the Mediterranean region in the twenty-first century, but the extent to which these models correctly represent the mechanisms of summertime precipitation in this region is uncertain. Here an analysis is conducted to compare the observed and simulated impacts of the dominant large-scale driver of summer rainfall variability in Europe and the Mediterranean, the summer North Atlantic Oscillation (SNAO). The SNAO is defined as the leading mode of July–August sea level pressure variability in the North Atlantic sector. Although the SNAO is weaker and confined to northern latitudes compared to its winter counterpart, with a southern lobe located over the UK, it significantly affects precipitation in the Mediterranean, particularly Italy and the Balkans (correlations of up to 0.6). During high SNAO summers, when strong anticyclonic conditions and suppressed precipitation prevail over the UK, the Mediterranean region instead is anomalously wet. This enhanced precipitation is related to the presence of a strong upper-level trough over the Balkans—part of a hemispheric pattern of anomalies that develops in association with the SNAO—that leads to mid-level cooling and increased potential instability. Neither this downstream extension nor the surface influence of the SNAO is captured in the two CMIP3 models examined (HadCM3 and GFDL-CM2.1), with weak or non-existent correlations between the SNAO and Mediterranean precipitation. Because these models also predict a strong upward SNAO trend in the future, the error in their representation of the SNAO surface signature impacts the projected precipitation trends. In particular, the attendant increase in precipitation that, based on observations, should occur in the Mediterranean and offset some of the non-SNAO related drying does not occur. Furthermore, the fact that neither the observed SNAO nor summer precipitation in Europe/Mediterranean region exhibits any significant trend so far (for either the full century or the recent half of the record) does not increase our confidence in these model projections.

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Notes

  1. The spatial correlation between the June pattern and the July/August patterns is r s  ~ 0.65 for the 1950–2010 period; the correlation using the June EOF-2 is even lower. An SNAO-like EOF is also not found in September.

  2. The spatial (temporal) correlation r s (r t ) is 0.98 (0.92) and 0.94 (0.86), respectively, when computed for the 1950–2010 period. The resemblance can be verified by comparing Fig. 1a, b, d to fig. 6 in Hurrell et al. (2003), which shows the leading EOF of JJA SLP computed over the wider domain for the 1899–2001 period—although the southern lobe is centered west of the British Isles rather than right over them.

  3. Note that in Folland et al. (2009) the anomalies in fig. 1 are normalized regressions weighted by the square root of the cosine of latitude (S. Ineson 2010, personal communication), which explains the difference in magnitude between their fig. 1b and our Fig. 1d.

  4. For instance, the GHCN database contains only three Greenland stations with 40 years or more of data in the period 1899–1949, but none of them has 40 years of data in the period 1950–2010.

  5. For the 1950–2010 period, this projected SNAO index coincides, of course, with the time series (PC) of the leading EOF for that period (or baseline pattern). For the entire 1899–2010 period, the projected index is correlated at 0.98 with the PC of the leading EOF for that period (Fig. 1d). For the early period (1899–1949), however, the correlation with the PC of the leading EOF (Fig. 1e) is only 0.76.

  6. See Liebmann et al. (2010) for a method to illustrate the sensitivity of trends to end points.

  7. Almost identical results are obtained when data are detrended prior to the regression calculations, consistent with the weak SNAO trend.

  8. In a very recent paper, Mariotti and Dell’Aquila (2011) find a strong (0.79) correlation between a detrended JJA SNAO index and detrended mean precipitation averaged over the entire Mediterranean domain, which is not inconsistent with our undetrended results.

  9. We have verified that this SNAO trend is not associated with climate drift in the GFDL-CM2.1 model: the SNAO trend in the first 300 years of the corresponding control run (Knutson et al. 2006), obtained once again by projecting the model’s SNAO pattern, is one order of magnitude smaller and not statistically significant (regardless of which of the runs is used to define the pattern).

References

  • Ansell TJ et al (2006) Daily mean sea level pressure reconstructions for the European-North Atlantic region for the period 1850–2003. J Climate 19:2717–2742

    Article  Google Scholar 

  • Barnston AG, Livezey RE (1987) Classification, seasonality and persistence of low-frequency atmospheric circulation patterns. Mon Wea Rev 115:1083–1126

    Article  Google Scholar 

  • Boé J, Terray L, Cassou C, Najac J (2009) Uncertainties in European summer precipitation changes: role of large scale circulation. Clim Dyn 33:265–276

    Article  Google Scholar 

  • Branstator G (2002) Circumglobal teleconnections, the jet stream waveguide, and the North Atlantic Oscillation. J Climate 15:1893–1910

    Article  Google Scholar 

  • Chronis T, Raitsos DE, Kassis D, Sarantopoulos A (2011) The summer North Atlantic Oscillation Influence on the Eastern Mediterranean. J Climate 24:5584–5596. doi:10.1175/2011JCLI3839.1

    Google Scholar 

  • Feidas H, Noulopoulou N, Makrogiannis T, Bora-Senta E (2007) Trend analysis of precipitation time series in Greece and their relationship with circulation using surface and satellite data: 1955–2001. Theor Appl Climatol 87:155–177

    Article  Google Scholar 

  • Feldstein SB (2007) The dynamics of the North Atlantic Oscillation during the summer season. Quart J Roy Meteor Soc 133:1509–1518

    Google Scholar 

  • Folland CK, Knight J, Linderholm HW, Fereday D, Ineson S, Hurrell JW (2009) The summer North Atlantic Oscillation: past, present, and future. J Climate 22:1082–1103

    Article  Google Scholar 

  • Giorgi F, Lionello P (2008) Climate change projections for the Mediterranean region. Global Planet Change 63:90–104

    Article  Google Scholar 

  • Greatbatch RJ, Rong P–P (2006) Discrepancies between different Northern Hemisphere summer atmospheric data products. J Climate 19:1261–1273

    Article  Google Scholar 

  • Haarsma RJ, Selten F, vd Hurk B, Hazeleger W, Wang X (2009) Drier Mediterranean soils due to greenhouse warming bring easterly winds over summertime central Europe. Geophys Res Lett 36:L04705. doi:10.1029/2008GL036617

    Article  Google Scholar 

  • Hatzianastassiou N, Katsoulis B, Pnevmatikos J, Antakis V (2008) Spatial and temporal variation of precipitation in Greece and surrounding regions based on global precipitation climatology project data. J Climate 21:1349–1370

    Article  Google Scholar 

  • Haylock MR, Hofstra N, Klein Tank AMG, Klok EJ, Jones PD, New M (2008) A European daily high-resolution gridded data set of surface temperature and precipitation for 1950–2006. J Geophys Res 113:D20119

    Article  Google Scholar 

  • Hulme M, Osborn TJ, Johns TC (1998) Precipitation sensitivity to global warming: comparison of observations with HadCM2 simulations. Geophys Res Lett 25:3379–3382

    Article  Google Scholar 

  • Hurrell JW (1995) Decadal trends in the North Atlantic Oscillation: regional temperatures and precipitation. Science 269:676–679

    Article  Google Scholar 

  • Hurrell JW, Deser C (2009) North Atlantic climate variability: the role of the North Atlantic Oscillation. J Mar Syst 78(1):28–41. doi:10.1016/j.jmarsys.2008.11.026

    Google Scholar 

  • Hurrell JW, Folland CK (2002). A change in the summer circulation over the North Atlantic. CLIVAR Exchanges, No. 25, International CLIVAR Project Office, Southampton, United Kingdom, pp 52–54

  • Hurrell JW, Kushnir Y, Ottersen G, Visbeck M (2003) An overview of the North Atlantic Oscillation. The North Atlantic Oscillation: climatic significance and environmental impact. Geophys Monogr. Am Geophys Union 134:1–35

    Google Scholar 

  • Jones PD, Jonsson T, Wheeler D (1997) Extension to the North Atlantic Oscillation using early instrumental pressure observations from Gibraltar and South-West Iceland. Int J Climatol 17:1433–1450

    Google Scholar 

  • Kalnay E et al. (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteor Soc 77:437–471

    Google Scholar 

  • Knutson TR, Delworth TL, Dixon KW, Held IM, Lu J, Ramaswamy V, Schwarzkopf MD, Stenchikov G, Stouffer RJ (2006) Assessment of twentieth-century regional surface temperature trends using the GFDL CM2 coupled models. J Climate 19:1624–1651

    Article  Google Scholar 

  • Liebmann B, Dole RM, Jones C, Bladé I, Allured D (2010) Influence of choice of time period on global surface temperature trend estimates. Bull Am Meteorol Soc 91:1485–1491

    Article  Google Scholar 

  • Mariotti A, Arkin P (2007) The North Atlantic Oscillation and oceanic precipitation variability. Clim Dyn 28(1):35–51

    Article  Google Scholar 

  • Mariotti A, Dell’Aquila A (2011) Decadal climate variability in the mediterranean region: roles of large-scale forcings and regional processes. Clim Dyn (in press). doi:10.1007/s00382-011-1056-7

  • Meehl GA et al. (2007) Global climate projections. In: Solomon S et al. (eds) Climate change 2007: the physical science basis. Cambridge University Press, Cambridge, pp 747–845

  • Mitchell TD, Jones PD (2005) An improved method of constructing a database of monthly climate observations and associated high-resolution grids. Int J Clim 25:693–712

    Article  Google Scholar 

  • North GR, Bell TL, Cahalan RF, Moeng FJ (1982) Sampling errors in the estimation of empirical orthogonal functions. Mon Wea Rev 110:699–706

    Google Scholar 

  • Obregón A, Bissolli P, Kennedy JJ, Parker DE (2010) Regional climates: Europe [in “State of the Climate in 2009”]. Bull Am Meteor Soc 91(7):S160–S162

    Google Scholar 

  • Pal JS, Giorgi F, Bi X (2004) Consistency of recent European summer precipitation trends and extremes with future regional climate projections. Geophys Res Lett 31:L13202. doi:10.1029/2004GL019836

  • Portis DH, Walsh JE, El Hamly M, Lamb PJ (2001) Seasonality of the North Atlantic Oscillation. J Clim 14:2069–2078

    Google Scholar 

  • Reynolds RW, Smith TM, Liu C, Chelton DB, Casey KS, Schlax MG (2007) Daily high-resolution-blended analyses for sea surface temperature. J Clim 20:5473–5496

    Article  Google Scholar 

  • Rodwell MJ, Hoskins BJ (1996) Monsoons and the dynamics of deserts. Quart J Roy Meteor Soc 122:1385–1404

    Article  Google Scholar 

  • Rowell DP, Jones RG (2006) Causes and uncertainty of future summer drying over Europe. Clim Dyn 27:281–299. doi:10.1007/s00382-006-0125-9

    Article  Google Scholar 

  • Rudolf B, Schneider U (2005) Calculation of gridded precipitation data for the global land-surface using in situ gauge observations. In: Proceedings of the 2nd workshop of the International Precipitation Working Group IPWG. Monterey, 2004, pp 231–247

  • Sun J, Huijun W, Wei Y (2009) Role of the tropical Atlantic sea surface temperature in the decadal change of the summer North Atlantic Oscillation. J Geophys Res 114:D20110. doi:10.1029/2009JD01239

    Article  Google Scholar 

  • Trenberth KE, Paolino DA Jr (1980) The Northern Hemisphere sea-level pressure data set: trends, errors and discontinuities. Mon Wea Rev 108:855–872

    Article  Google Scholar 

  • Watanabe M (2004) Asian jet waveguide and a downstream extension of the North Atlantic Oscillation. J Clim 17:4674–4691

    Article  Google Scholar 

  • Zveryaev II, Allan RP (2010) Summertime precipitation variability over Europe and links to atmospheric dynamics and precipitation. J Geophys Res 115:D12102. doi:10.1029/2008JD011213

Download references

Acknowledgments

We thank Pablo Zurita for his comments on the manuscript and Nate Mantua, Javier García-Serrano and Vicent Altava for useful discussion of our work. We also thank Ricardo Trigo and an anonymous reviewer for their useful suggestions, which have helped clarify several points in the manuscript. Roy Mendelssohn kindly supplied the SST data. DF was supported by grant Consolider 2007-CSD2007-00050. The work was funded by grant CGL2009-06944 of the Spanish MICINN. We acknowledge the modeling groups, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) and the WCRP's Working Group on Coupled Modelling (WGCM) for their roles in making available the WCRP CMIP3 multi-model dataset. Support of this dataset is provided by the Office of Science, U.S. Department of Energy.

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Authors and Affiliations

  1. Facultat de Física, Departament d’Astronomia i Meteorologia, Universitat de Barcelona, c/Martí i Franqués 1, 08028, Barcelona, Spain

    Ileana Bladé & Didac Fortuny

  2. NOAA/Earth System Research Laboratory, CIRES Climate Diagnostics Center, Boulder, CO, USA

    Brant Liebmann

  3. Royal Dutch Meteorological Institute, De Bilt, Netherlands

    Geert Jan van Oldenborgh

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  1. Ileana Bladé
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  2. Brant Liebmann
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  4. Geert Jan van Oldenborgh
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Correspondence to Ileana Bladé.

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Bladé, I., Liebmann, B., Fortuny, D. et al. Observed and simulated impacts of the summer NAO in Europe: implications for projected drying in the Mediterranean region. Clim Dyn 39, 709–727 (2012). https://doi.org/10.1007/s00382-011-1195-x

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