@BeginModule
@NewPage
@Name      = Monarith
@Title     = Monthly arithmetic
@Section   = Arithmetic
@Class     = Arithmetic
@Arguments = ifile1 ifile2 ofile
@Operators = monadd monsub monmul mondiv

@BeginDescription
This module performs simple arithmetic of a time series and one
time step with the same month and year. For each field in @file{ifile1}
the corresponding field of the time step in @file{ifile2} with the
same month and year is used. The header information in @file{ifile1}
have to be the same as in @file{ifile2}. Usually @file{ifile2} is generated
by a call of the module @mod{MONSTAT}.
@EndDescription
@EndModule


@BeginOperator_monadd
@Title     = Add monthly time series

@BeginDescription
Adds a time series and a monthly time series.
@EndDescription
@EndOperator


@BeginOperator_monsub
@Title     = Subtract monthly time series

@BeginDescription
Subtracts a time series and a monthly time series.
@EndDescription
@EndOperator


@BeginOperator_monmul
@Title     = Multiply monthly time series

@BeginDescription
Multiplies a time series and a monthly time series.
@EndDescription
@EndOperator


@BeginOperator_mondiv
@Title     = Divide monthly time series

@BeginDescription
Divides a time series and a monthly time series.
@EndDescription
@EndOperator


@BeginExample
To subtract a monthly time average from a time series use:
@BeginVerbatim
   cdo monsub ifile -monavg ifile ofile
@EndVerbatim
@EndExample
