@BeginModule
@NewPage
@Name      = EcaGsl
@Title     = Growing season length index
@Section   = Climate indices
@Class     = Climate index
@Arguments = ifile1 ifile2 ofile
@Operators = eca_gsl

@BeginDescription
Let @file{ifile1} be a time series of daily mean temperatures TG,
and @file{ifile2} be a land-water mask.
Then counted are the number of days between the first occurrence
of at least nday consecutive days with TG > T and the first occurrence
after 1 July of at least nday consecutive days with TG < T. The
numbers nday and T are optional parameter with default nday = 6
and T = 5° Celsius. The number fland is an optional parameter with
default value fland = 0.5 and denotes the fraction of a grid point that
must be covered by land in order to be included in the calculation. A
further output variable is the start day of year of the growing season.
Note that TG must be given in units of Kelvin, whereas T must be given
in degrees Celsius.
The date information for a time step in @file{ofile} is the date of
the last contributing time step in @file{ifile}.
@EndDescription
@EndModule


@BeginOperator_eca_gsl
@Title     = Growing season length index
@Parameter = [nday] [T] [fland]
@EndOperator


@BeginParameter
@Item = nday
INTEGER  Number of consecutive days (default: nday = 6)
@Item = T
DOUBLE   Temperature threshold (° Celsius, default: T = 5° Celsius)
@Item = fland
DOUBLE   Land fraction threshold (default: fland = 0.5)
@EndParameter


@BeginExample
To get the growing season length for a time series of daily
mean temperatures, use:
@BeginVerbatim
   cdo eca_gsl tgfile maskfile ofile
@EndVerbatim
@EndExample
