The radiation balance of the Earth plays a fundamental role in the global climate system and in the radiatively-induced climate change. It is therefore essential that General Circulation Models (GCM) which attempt to re-

M Beniston and M.M. Verstraete (eds.),

Remote Sensing and Climate Modeling: Synergies and Limitations, 85-102. © 2001 Kluwer Academic Publishers. Printed in the Netherlands.

produce the Earth system should be able to simulated the radiative processes with high confidence. Due to recent satellite programs such as ERBE, the total amount of solar energy absorbed by the global climate system is well established (Barkstrom et al. 1990). To date the current generation of GCMs simulates this net exchange of solar energy between outer space and the global climate system realistically when compared to the satellite observation. However, the good agreement between the satellite-observed and simulated fluxes at the top of atmosphere (TOA) only implies that the total absorption of solar energy in the climate system is quantitatively correctly captured in the GCMs. It does not ensure that the solar energy is absorbed at the proper places within the climate system.

Therefore, rather than relying on a validation of the TOA budgets using satellite data only, validation studies trying to assess radiation in GCMs should make use of the additional information available from ground observations.

The present study outlines how such combined surface/satellite data sets can improve our knowledge on the distribution of solar energy in the climate system and its representation in GCMs.

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