Influence of NAO and clouds on long‐term seasonal variations of surface solar radiation in Europe

[1] This study is an analysis of the seasonal all-sky surface solar radiation variability in Europe during 1970–2000 using surface observations from the Global Energy Balance Archive (GEBA). On the basis of the annual means period 1970–1985, there is a statistically significant decline of −3.0% decade−1 (−3.8 Wm−2 decade−1) followed by a nonsignificant rise of 0.3% decade−1 (0.4 Wm−2 decade−1) during 1985–2000. The behavior of the solar radiation for spring is similar to the annual series and has the strongest increase of 1.6% decade−1 (2.5 Wm−2 decade−1) during 1985–2000. In summer a similar evolution to the annual and spring time series is shown but has a stronger decline of −3.2% decade−1 (−6.8 Wm−2 decade−1) during 1970–1985. A small positive nonsignificant trend is reported for the winter means time series while a statistically significant negative trend of −2.5% decade−1 (−2.1 Wm−2 decade−1) was found in autumn during 1970–2000. By comparing variations in all-sky solar radiation with changes in cloud cover and NAO, we attribute the winter and autumn trends mainly to the NAO through the modification of mid-to-low cloud cover in southern Europe and the spring and summer trends to mid-to-low cloud cover in northern Europe. However, because the cloud cover and solar radiation relationship weakens in the low-frequency variability, it suggests that other effects such as aerosols may also play a role. In addition, aerosols could be interfering with the relationship between solar radiation and NAO, contributing to a strengthening of their correlation in the low-frequency variability during winter and autumn.

[1]  James W. Hurrell,et al.  The North Atlantic Oscillation: Climatic Significance and Environmental Impact , 2003 .

[2]  Martin Wild,et al.  On the relationship between diurnal temperature range and surface solar radiation in Europe , 2009 .

[3]  K. Trenberth,et al.  Observations: Surface and Atmospheric Climate Change , 2007 .

[4]  C. Long,et al.  From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth's Surface , 2005, Science.

[5]  E. Dutton,et al.  Do Satellites Detect Trends in Surface Solar Radiation? , 2004, Science.

[6]  Christian Mätzler,et al.  Aerosol and cloud effects on solar brightening and the recent rapid warming , 2008 .

[7]  J. Martín-Vide,et al.  Spatial and Temporal Trends in Sunshine Duration over Western Europe (1938–2004) , 2008 .

[8]  D. Koch,et al.  Trends in tropospheric aerosol loads and corresponding impact on direct radiative forcing between 1950 and 1990: A model study , 2000 .

[9]  A. Ohmura.  Observed Long-Term Variations of Solar Irradiance at the Earth’s Surface , 2007 .

[10]  R. Trigo,et al.  The North Atlantic Oscillation influence on Europe: climate impacts and associated physical mechanisms , 2002 .

[11]  Y. Kaufman,et al.  Global dimming or local dimming?: Effect of urbanization on sunlight availability , 2005 .

[12]  Martin Wild,et al.  Decadal changes in shortwave irradiance at the surface in the period from 1960 to 2000 estimated from Global Energy Balance Archive Data , 2009 .

[13]  Gerald Stanhill,et al.  Global dimming: a review of the evidence for a widespread and significant reduction in global radiation with discussion of its probable causes and possible agricultural consequences , 2001 .

[14]  E. Feigelson,et al.  Evaluation of Long-Term Changes in Radiation, Cloudiness, and Surface Temperature on the Territory of the Former Soviet Union , 1996 .

[15]  Ina Tegen,et al.  Multidecadal solar radiation trends in the United States and Germany and direct tropospheric aerosol forcing , 2002 .

[16]  J. Hurrell.  Decadal Trends in the North Atlantic Oscillation: Regional Temperatures and Precipitation , 1995, Science.

[17]  David Pozo-Vázquez,et al.  NAO and solar radiation variability in the European North Atlantic region , 2004 .

[18]  B. Liepert,et al.  Observed reductions of surface solar radiation at sites in the United States and worldwide from 1961 to 1990 , 2002 .

[19]  H. C. Power,et al.  Trends in solar radiation over Germany and an assessment of the role of aerosols and sunshine duration , 2003 .

[20]  Robert S. Stone,et al.  Decadal variations in surface solar irradiance as observed in a globally remote network , 2006 .

[21]  S. Mylona,et al.  Sulphur dioxide emissions in Europe 1880–1991 and their effect on sulphur concentrations and depositions , 1996 .

[22]  Martin Wild,et al.  Global dimming and brightening: A review , 2009 .

[23]  V. Russak.  Trends of solar radiation, cloudiness and atmospheric transparency during recent decades in Estonia , 1990 .

[24]  Stephen G. Warren,et al.  A Survey of Changes in Cloud Cover and Cloud Types over Land from Surface Observations, 1971–96 , 2007 .

[25]  H. Fagerli,et al.  Direct shortwave radiative forcing of sulfate aerosol over Europe from 1900 to 2000 , 2007 .

[26]  Martin Wild,et al.  Trends in aerosol radiative effects over Europe inferred from observed cloud cover, solar “dimming,” and solar “brightening” , 2007 .

[27]  J. Kalma,et al.  Solar dimming and urban heating at Hong Kong , 1995 .

[28]  James W. Hurrell,et al.  The North Atlantic Oscillation: Climate Significance and Environmental Impact , 2003 .

[29]  Martin Wild,et al.  How well do IPCC‐AR4/CMIP3 climate models simulate global dimming/brightening and twentieth‐century daytime and nighttime warming? , 2009 .

[30]  P. Jones,et al.  Extension to the North Atlantic oscillation using early instrumental pressure observations from Gibraltar and south‐west Iceland , 1997 .

[31]  Uwe Ulbrich,et al.  A shift of the NAO and increasing storm track activity over Europe due to anthropogenic greenhouse gas forcing , 1999 .

[32]  Trends in Italian total cloud amount, 1951‐1996 , 2001 .

[33]  A. Ohmura,et al.  Radiative forcing ‐ measured at Earth's surface ‐ corroborate the increasing greenhouse effect , 2003 .

[34]  G. Schmidt,et al.  20th century changes in surface solar irradiance in simulations and observations , 2007 .

[35]  Bruce A. Wielicki,et al.  Statistical Analyses of Satellite Cloud Object Data from CERES. Part I: Methodology and Preliminary Results of the 1998 El Niño/2000 La Niña , 2005 .

[36]  T. L. Wolfe,et al.  An assessment of the impact of pollution on global cloud albedo , 1984 .

[37]  A. Ångström.  Atmospheric turbidity, global illumination and planetary albedo of the earth , 1962 .

[38]  A. Ohmura,et al.  The Global Energy Balance Archive , 1999 .

[39]  Michael Schulz,et al.  Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations , 2006 .

[40]  David G. Streets,et al.  Two‐decadal aerosol trends as a likely explanation of the global dimming/brightening transition , 2006 .

[41]  M. Rodwell,et al.  Oceanic forcing of the wintertime North Atlantic Oscillation and European climate , 1999, Nature.

[42]  D. W. Nelson,et al.  Long‐term variations in the occurrence and effective solar transmission of clouds as determined from surface‐based total irradiance observations , 2004 .

[43]  Sally A. McFarlane,et al.  Significant decadal brightening of downwelling shortwave in the continental United States , 2009 .

[44]  F. Berger,et al.  Long-time global radiation for Central Europe derived from ISCCP Dx data , 2007 .

[45]  Stefan Reis,et al.  Twenty-five years of continuous sulphur dioxide emission reduction in Europe , 2007 .

[46]  Martin Wild,et al.  Means and Trends of Shortwave Irradiance at the Surface Estimated from Global Energy Balance Archive Data. , 1998 .

[47]  F. Monti,et al.  Sea‐level pressure variability in the Po Plain (1765–2000) from homogenized daily secular records , 2004 .

[48]  U. Lohmann,et al.  Global indirect aerosol effects: a review , 2004 .

[49]  J. Kristjánsson,et al.  Global dimming and global brightening—an analysis of surface radiation and cloud cover data in northern Europe , 2009 .

[50]  G. Kukla,et al.  Decline in Global Solar Radiation with Increased Horizontal Visibility in Germany between 1964 and 1990 , 1997 .

[51]  Shabtai Cohen,et al.  Solar Radiation Changes in the United States during the Twentieth Century: Evidence from Sunshine Duration Measurements , 2005 .

[52]  J. Hurrell,et al.  DECADAL VARIATIONS IN CLIMATE ASSOCIATED WITH THE NORTH ATLANTIC OSCILLATION , 1997 .

[53]  U. Cubasch,et al.  GCM-Simulated Surface Energy Fluxes in Climate Change Experiments , 1997 .

[54]  Maria Stella Chiacchio,et al.  The WCRP/GEWEX Surface Radiation Budget Project Release 2: An Assessment of Surface Fluxes at 1 Degree Resolution , 2000 .