Climate Dynamics

, Volume 37, Issue 7, pp 1643-1660

First online:

A transitioning Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud radiative forcing

  • Joseph SedlarAffiliated withDepartment of Meteorology, Stockholm University Email author 
  • , Michael TjernströmAffiliated withDepartment of Meteorology, Stockholm University
  • , Thorsten MauritsenAffiliated withMax Planck Institute for Meteorology
  • , Matthew D. ShupeAffiliated withUniversity of Colorado and NOAA-ESRL-PSD
  • , Ian M. BrooksAffiliated withSchool of Earth and Environment, University of Leeds
  • , P. Ola G. PerssonAffiliated withUniversity of Colorado and NOAA-ESRL-PSD
  • , Cathryn E. BirchAffiliated withSchool of Earth and Environment, University of Leeds
  • , Caroline LeckAffiliated withDepartment of Meteorology, Stockholm University
  • , Anders SirevaagAffiliated withUniversity of Bergen and Bjerknes Center for Climate Research
    • , Marcel NicolausAffiliated with Norwegian Polar InstituteAlfred Wegener Institute for Polar and Marine Research

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Snow surface and sea-ice energy budgets were measured near 87.5°N during the Arctic Summer Cloud Ocean Study (ASCOS), from August to early September 2008. Surface temperature indicated four distinct temperature regimes, characterized by varying cloud, thermodynamic and solar properties. An initial warm, melt-season regime was interrupted by a 3-day cold regime where temperatures dropped from near zero to −7°C. Subsequently mean energy budget residuals remained small and near zero for 1 week until once again temperatures dropped rapidly and the energy budget residuals became negative. Energy budget transitions were dominated by the net radiative fluxes, largely controlled by the cloudiness. Variable heat, moisture and cloud distributions were associated with changing air-masses. Surface cloud radiative forcing, the net radiative effect of clouds on the surface relative to clear skies, is estimated. Shortwave cloud forcing ranged between −50 W m−2 and zero and varied significantly with surface albedo, solar zenith angle and cloud liquid water. Longwave cloud forcing was larger and generally ranged between 65 and 85 W m−2, except when the cloud fraction was tenuous or contained little liquid water; thus the net effect of the clouds was to warm the surface. Both cold periods occurred under tenuous, or altogether absent, low-level clouds containing little liquid water, effectively reducing the cloud greenhouse effect. Freeze-up progression was enhanced by a combination of increasing solar zenith angles and surface albedo, while inhibited by a large, positive surface cloud forcing until a new air-mass with considerably less cloudiness advected over the experiment area.


Arctic Sea ice Surface energy budget Cloud radiative forcing Shortwave radiation Longwave radiation