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Model output surface temperature different from prescribed SST

Hi all:I just ran an F2000climo test case using CESM2.1.0.When I examined the monthly-mean output surface temperature (TS) in January, I found the TS over the ocean is a bit different from the prescribed SST.Here I compare with the variable "SST_cpl" in the input SST file: sst_HadOIBl_bc_0.9x1.25_2000climo_c180511.ncIs this difference reasonable? I think that the model-output SST or TS should be the same as the input SST data?    Jay
 

dbailey

CSEG and Liaisons
Staff member
There is a procedure called "diddling" where the monthly means in the input are adjusted so that the interpolated monthly means will give you back the correctly monthly mean. The SST and ICE will interpolated between the mid-month values by a linear interpolation.The variables used will be ice_cov/SST_cpl. They are obtained used the icesst tools. This dataset is specifically created for use with CAM and include the "diddling" procedure that ensures that the monthly mean of the daily-interpolated SST anomalies matches the monthly SST anomalies. This follows the protocol for AMIP simulation described in: Taylor, K.E., D. Williamson, and F. Zwiers (2000): The sea surface temperature and sea-ice concentration boundary conditions for AMIP II simulations. PCMDI Report No. 60 and UCRL-MI-125597, Lawrence Livermore National Laboratory, Livermore, CA, 25 pp.
pdf file available at http://www-pcmdi.llnl.gov/publications/pdf/60.pdf. You can compare to the SST_cpl_prediddle field.
 
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