High-resolution simulations of global climate, part 1: present climate

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Article  

  Climate Dynamics
Publisher: Springer-Verlag Heidelberg
ISSN: 0930-7575 (Paper) 1432-0894 (Online)
DOI: 10.1007/s00382-003-0339-z
Issue: Volume 21, Numbers 5-6

Date:  November 2003
Pages: 371 - 390  
High-resolution simulations of global climate, part 1: present climate
P. B. Duffy1 , B. Govindasamy1, J. P. Iorio1, J. Milovich2, K. R. Sperber3, K. E. Taylor3, M. F. Wehner3, 4 and S. L. Thompson1

(1)  Climate and Carbon Cycle Modeling Group, Lawrence Livermore National Laboratory (LLNL), PO Box 808, Livermore, CA 94550, USA,  
(2)  Center for Applied Scientific Computing, LLNL, USA,  
(3)  Program for Climate Model Diagnosis and Intercomparison, LLNL, USA,  
(4)  Present address: National Energy Research Supercomputer Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS-50F, Berkeley, CA 94720, USA,  


P. B. Duffy
Email: pduffy@llnl.gov

Received: 8 July 2002  Accepted: 17 April 2003  Published online: 26 August 2003

Abstract   We examine simulations of today''s climate performed with a global atmospheric general circulation model run at spectral truncations of T42, T170, and T239, corresponding to grid cell sizes of roughly 310 km, 75 km, and 55 km, respectively. The simulations were forced with observed sea-surface temperatures and sea-ice concentrations. The T42 simulations and initial simulations at T170 and T239 were performed using a model version that was carefully "tuned" to optimize results at T42; subsequent simulations at T170 and T239 used a model version that was partly re-tuned to improve results at T170. On the scales of a T42 grid cell and larger, nearly all quantities we examined in all the T170 and T239 simulations agree better with observations, at least in terms of spatial patterns, than in the T42 simulations. In some cases the improvements are very substantial. Improvements are seen in all-season, global domain results, and in results pertaining to most seasons and latitude bands. Increasing the model resolution from T42 introduces biases (errors in the mean) into some simulated quantities; the worst of these were removed by the partial retuning we performed at T170. This retuning has little effect on the spatial patterns of results, except in Northern Hemisphere winter at T170, where it tends to bring improvements. We discuss aspects of simulated regional climates, and their dependence on model resolution.