@BeginModule
@NewPage
@Name      = Intvert
@Title     = Vertical interpolation
@Section   = Interpolation
@Class     = Interpolation
@Arguments = ifile ofile
@Operators = ml2pl ml2hl

@BeginDescription
Interpolate 3D variables on hybrid model level to pressure or height level.
The input file must contain the log. surface pressure or the surface pressure.
To interpolate the temperature, the orography is also needed.
The pressure, temperature, and orography are identified by there code numbers.
Supported parameter tables are: WMO standard table number 2 and ECMWF local table number 128.
Use the alias  ml2plx/ml2hlx or the environment variable EXTRAPOLATE
to extrapolate missing values.
@EndDescription
@EndModule


@BeginOperator_ml2pl
@Title     = Model to pressure level interpolation
@Parameter = plevels

@BeginDescription
Interpolates 3D variables on hybrid model level to pressure level.
@EndDescription
@EndOperator


@BeginOperator_ml2hl
@Title     = Model to height level interpolation
@Parameter = hlevels

@BeginDescription
Interpolates 3D variables on hybrid model level to height level.
The procedure is the same as for operator @oper{mh2pl} except that 
the pressure levels are calculated from the heights by:
@math{plevel = 101325*exp(hlevel/-7000)}
@EndDescription
@EndOperator


@BeginParameter
@Item = plevels
FLOAT  Pressure levels in pascal
@Item = hlevels
FLOAT  Height levels in meter (max level: 65535 m)
@EndParameter


@BeginEnvironment
@Item = EXTRAPOLATE
If set to 1 extrapolate missing values.
@EndEnvironment


@BeginExample
To interpolate hybrid model level data to pressure levels of
925, 850, 500 and 200 hPa use:
@BeginVerbatim
   cdo ml2pl,92500,85000,50000,20000 ifile ofile
@EndVerbatim
@EndExample
