Thomas Reichler and Junsu Kim Univ. of Utah, Salt Lake City, USA Supported by the Center for High Performance Computing, Univ. of Utah 3 rd WCRP International Conference on Reanalysis, Tokyo, Japan, 28 th January 1 st February 2008 Motivation bb Multi-variate model performance index worse better avg. Some models outperform NCEP/NCAR reanalysis Error Models Questions 1. Why are NCEP/NCAR reanalyses not better than freely evolving coupled model? 2. How do the other reanalyses do? 3. Can the reanalyses be improved? 4. How large are the observational uncertainties? 3 Data ObservationsMany global datasets; often multiple data for same quantity ReanalysesNCEP/NCAR NNR NCEP/DOE NDR ERA40 ERA JRA25 JRA ModelGFDL CM2.1 GFD Base period79-99 (in most cases) 4 Climate Quantities 5 Physics (18) Dynamics (13) ERA-40 as reference ( )( )( ) RSUT: Observations Annual mean outgoing shortwave radiation TOA