@BeginModule
@Name      = EcaCwfi
@Title     = Cold-spell days index wrt 10th percentile of reference period
@Section   = Climate indices
@Class     = Climate index
@Arguments = ifile1 ifile2 ofile
@Operators = eca_cwfi

@BeginDescription
Let @file{ifile1} be a time series of daily mean temperatures TG, and 
@file{ifile2} be the 10th percentile TGn10 of daily mean temperatures
for any period used as reference. Then counted is the number of days
where, in intervals of at least nday consecutive days, TG < TGn10. The
number nday is an optional parameter with default nday = 6. A further
output variable is the number of cold-spell periods longer than or
equal to nday days. Note that both TG and TGn10 must be given in the
same units.
The date information for a time step in @file{ofile} is the date of
the last contributing time step in @file{ifile1}.
@EndDescription
@EndModule


@BeginOperator_eca_cwfi
@Title     = Cold-spell days index wrt 10th percentile of reference period
@Parameter = [nday]
@EndOperator


@BeginParameter
@Item = nday
INTEGER  Number of consecutive days (default: nday = 6)
@EndParameter


@BeginExample
To compute the number of cold-spell days for a time series of
daily mean temperatures, use:
@BeginVerbatim
   cdo eca_cwfi tgfile tgn10file ofile
@EndVerbatim
@EndExample
