@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 the daily mean temperature 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 @math{nday} consecutive days, TG < TGn10. The
number @math{nday} is an optional parameter with default @math{nday} = 6. A further
output variable is the number of cold-spell periods longer than or
equal to @math{nday} days.
TGn10 is calculated as the 10th percentile of daily mean temperatures of a five 
day window centred on each calendar day of a given climate reference period.
Note that both TG and TGn10 have to be given in the same units.
The date information of a timestep in @file{ofile} is the date of
the last contributing timestep 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 of a time series of
daily mean temperatures use:
@BeginVerbatim
   cdo eca_cwfi tgfile tgn10file ofile
@EndVerbatim
@EndExample
