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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L23707, doi:10.1029/2005GL024411, 2005

How accurate did GCMs compute the insolation at TOA for AMIP-2?

Ehrhard Raschke

Institute of Meteorology, University of Hamburg, Hamburg, Germany


Marco A. Giorgetta

Max Planck Institute for Meteorology, Hamburg, Germany


Stefan Kinne

Max Planck Institute for Meteorology, Hamburg, Germany


Martin Wild

ETH-Zürich, Zürich, Germany


Abstract

Monthly averages of solar radiation reaching the Top of the Atmosphere (TOA) as simulated by 20 General Circulation Models (GCMs) during the period 1985–1988 are compared. They were part of submissions to AMIP-2 (Atmospheric Model Intercomparison Project). Monthly averages of ISCCP-FD (International Satellite Cloud Climatology Project – Flux Data) are considered as reference. Considerable discrepancies are found: Most models reproduce the prescribed Total Solar Irradiance (TSI) value within ±0.7 Wm−2. Monthly zonal averages disagree between ±2 to ±7 Wm−2, depending on latitude and season. The largest model diversity occurs near polar regions. Some models display a zonally symmetric insolation, while others and ISCCP show longitudinal deviations of the order of ±1 Wm−2. With such differences in meridional gradients impacts in multi-annual simulations cannot be excluded. Sensitivity studies are recommended.

Received 19 August 2005; accepted 27 October 2005; published 10 December 2005.

Index Terms: 0321 Atmospheric Composition and Structure: Cloud/radiation interaction; 0429 Biogeosciences: Climate dynamics (1620); 1616 Global Change: Climate variability (1635, 3305, 3309, 4215, 4513); 1622 Global Change: Earth system modeling (1225); 1626 Global Change: Global climate models (3337, 4928).

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Citation: Raschke, E., M. A. Giorgetta, S. Kinne, and M. Wild (2005), How accurate did GCMs compute the insolation at TOA for AMIP-2?, Geophys. Res. Lett., 32, L23707, doi:10.1029/2005GL024411.