@BeginModule
@NewPage
@Name      = Afterburner
@Title     = ECHAM standard post processor
@Section   = Miscellaneous
@Arguments = ifiles ofile
@Operators = after
@EndModule


@BeginOperator_after
@Title     = ECHAM standard post processor

@BeginDescription
The "afterburner" is the standard post processor for @cite{ECHAM} data which provides the following operations:

@BeginItemize
@Item = Extract specified variables and levels
@Item = Compute derived variables
@Item = Transform spectral data to Gaussian grid representation
@Item = Vertical interpolation to pressure levels
@Item = Compute temporal means
@EndItemize

This operator reads selection parameters as namelist from stdin.
Use the UNIX redirection "<namelistfile" to read the namelist from file.
@EndDescription
@EndOperator

@BeginNamelist
Namelist parameter and there defaults:
@BeginListing
  TYPE=0, CODE=-1, LEVEL=-1, INTERVAL=0, MEAN=0, EXTRAPOLATE=0
@EndListing

@boldtt{TYPE} controls the transformation and vertical interpolation. Transforming spectral data to Gaussian grid
representation and vertical interpolation to pressure levels are performed in a chain of steps.
The @boldtt{TYPE} parameter may be used to stop the chain at a certain step. Valid values are:

@BeginListing
  TYPE  =  0 : Hybrid   level spectral coefficients
  TYPE  = 10 : Hybrid   level fourier  coefficients
  TYPE  = 11 : Hybrid   level zonal mean sections
  TYPE  = 20 : Hybrid   level gauss grids
  TYPE  = 30 : Pressure level gauss grids
  TYPE  = 40 : Pressure level fourier  coefficients
  TYPE  = 41 : Pressure level zonal mean sections
  TYPE  = 50 : Pressure level spectral coefficients
  TYPE  = 60 : Pressure level fourier  coefficients
  TYPE  = 61 : Pressure level zonal mean sections
  TYPE  = 70 : Pressure level gauss grids
@EndListing

Vorticity, divergence, streamfunction and velocity potential need special treatment in the vertical transformation.
They are not available as types 30, 40 and 41. If you select one of these combinations, type is automatically
switched to the equivalent types 70, 60 and 61. The type of all other variables will be switched too, because 
the type is a global parameter.

@boldtt{CODE} selects the variables by the ECHAM GRIB1 code number (1-255). The default value @boldtt{-1} processes all detected codes.
Derived variables computed by the afterburner:

@BeginTable5
@bold{Code}  & @bold{Name}      & @bold{Longname}                       & @bold{Level}       & @bold{Needed Codes/Computation}
 34   & low_cld   & low cloud                      & single      & 223 on modellevel  
 35   & mid_cld   & mid cloud                      & single      & 223 on modellevel  
 36   & hih_cld   & high cloud                     & single      & 223 on modellevel  
 131  & u         & u-velocity                     & atm (ml+pl) & 138, 155           
 132  & v         & v-velocity                     & atm (ml+pl) & 138, 155           
 135  & omega     & vertical velocity              & atm (ml+pl) & 138, 152, 155      
 148  & stream    & streamfunction                 & atm (ml+pl) & 131, 132           
 149  & velopot   & velocity potential             & atm (ml+pl) & 131, 132           
 151  & slp       & mean sea level pressure        & surface     & 129, 130, 152       
 156  & geopoth   & geopotential height            & atm (ml+pl) & 129, 130, 133, 152 
 157  & rhumidity & relative humidity              & atm (ml+pl) & 130, 133, 152      
 189  & sclfs     & surface solar cloud forcing    & surface     & 176-185            
 190  & tclfs     & surface thermal cloud forcing  & surface     & 177-186            
 191  & sclf0     & top solar cloud forcing        & surface     & 178-187             
 192  & tclf0     & top thermal cloud forcing      & surface     & 179-188            
 259  & windspeed & windspeed                      & atm (ml+pl) & sqrt(u*u+v*v)      
 260  & precip    & total precipitation            & surface     & 142+143            
@EndTable

@boldtt{LEVEL} selects the hybrid or pressure levels. The allowed values depends on the parameter @boldtt{TYPE}.
The default value @boldtt{-1} processes all detected levels.

@boldtt{INTERVAL} selects the processing interval. The default value @boldtt{0} process data on monthly intervals.
@boldtt{INTERVAL=1} sets the interval to daily.

@boldtt{MEAN=1} compute and write monthly or daily mean fields. The default value @boldtt{0} writes out all timesteps.

@boldtt{EXTRAPOLATE=0} switch of the extrapolation of missing values during the interpolation from model to pressure
level (only available with @boldtt{MEAN=0} and @boldtt{TYPE=30}). The default value @boldtt{1} extrapolate missing values.

Possible combinations of TYPE, CODE and MEAN:

@BeginTable
      @bold{TYPE}   & @bold{CODE}                    & @bold{MEAN}
    0/10/11  & 130  temperature        &  0
    0/10/11  & 131  u-velocity         &  0
    0/10/11  & 132  v-velocity         &  0
    0/10/11  & 133  specific humidity  &  0
    0/10/11  & 138  vorticity          &  0
    0/10/11  & 148  streamfunction     &  0
    0/10/11  & 149  velocity potential &  0
    0/10/11  & 152  LnPs               &  0
    0/10/11  & 155  divergence         &  0
     >11     & all codes               &  0/1
@EndTable
@EndNamelist

@BeginExample
To interpolate ECHAM hybrid model level data to pressure levels of 925, 850, 500 and 200 hPa, use:
@BeginVerbatim
   cdo after ifile ofile << EON
      TYPE=30  LEVEL=92500,85000,50000,20000
   EON
@EndVerbatim
@EndExample
