@BeginModule
@NewPage
@Name      = Ymonarith
@Title     = Multi-year monthly arithmetic
@Section   = Arithmetic
@Class     = Arithmetic
@Arguments = ifile1 ifile2 ofile
@Operators = ymonadd ymonsub ymonmul ymondiv

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


@BeginOperator_ymonadd
@Title     = Add multi-year monthly time series

@BeginDescription
Adds a time series and a multi-year monthly time series.
@EndDescription
@EndOperator


@BeginOperator_ymonsub
@Title     = Subtract multi-year monthly time series

@BeginDescription
Subtracts a time series and a multi-year monthly time series.
@EndDescription
@EndOperator


@BeginOperator_ymonmul
@Title     = Multiply multi-year monthly time series

@BeginDescription
Multiplies a time series and a multi-year monthly time series.
@EndDescription
@EndOperator


@BeginOperator_ymondiv
@Title     = Divide multi-year monthly time series

@BeginDescription
Divides a time series and a multi-year monthly time series.
@EndDescription
@EndOperator


@BeginExample
To subtract a multi-year monthly time average from a time series, use:
@BeginVerbatim
   cdo ymonsub ifile -ymonavg ifile ofile
@EndVerbatim
@EndExample
