Dear all

I downloaded the CRU dataset from  the web. When I was trying to interpolate the Osbservation data and compare with the model output. I get the following error:
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INPUT FILE:/home/lv/data/CRU/CRUPRE.CDF
/home/lv/data/CRU/CRUTMP.CDF
/home/lv/data/CRU/CRUDTR.CDF
/home/lv/data/CRU/CRUVAP.CDF
/home/lv/data/CRU/CRUCLD.CDF
OUTPUT FILE:PRE1997.nc
TMP1997.nc
DTR1997.nc
VAP1997.nc
CLD1997.nc
CALL PARAM
DS=   60.00000    DDEG=  5.3967768E-04
    11.09378  43.71408  1050.000  16.66089 47.62470

    1050.000   
OPENING NetCDF FILE: PRE1997.nc
ncopen: filename "/home/lv/data/CRU/CRUPRE.CDF": Not a netCDF file
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It seems that there are some problems relate to my NETCDF version, but I've try both 3.6.3 and 4.0.1. The result turn out the same.How can I solve it? Thanks.