@BeginModule
@Name      = Fdns
@Title     = Frost days where no snow index per time period
@Section   = Miscellaneous
@Arguments = ifile1 ifile2 ofile
@Operators = fdns

@BeginDescription
Let @file{ifile1} be a time series of the daily minimum temperature TN
and @file{ifile2} be a corresponding series of daily surface snow
amounts. Then the number of days where TN < 0 @celsius and the surface 
snow amount is less than 1 cm is counted. The temperature TN
have to be given in units of Kelvin.
The date information of a timestep in @file{ofile} is the date of
the last contributing timestep in @file{ifile}.
@EndDescription
@EndModule


@BeginOperator_fdns
@Title     = Frost days where no snow index per time period
@EndOperator
