p2sig: conversion from pressure level to sigma level

p2sig converts pressure leveled grib data to sigma leveled spectral coefficients data. Usage is;
$ runscr/p2sig input(pressure) output(sigma) YYYY:MM:DD:HH:FF


  • Added ISFCP=2 option for using mean sea level pressure. (2008/11/12)
  • Added IINTP for interpolation option. (2008/11/12)

How to install

p2sig will be installed with the latest version of GSM and RSM. If you want to install it separately,
  1. $ cd gsm (or rsm) ; cvs update src/p2sig ; cvs update src/mtn ; cvs update configure-model
  2. $ configure-model (make Makefile)
  3. $ cd gsm/src/p2sig ; make
  4. $ cd gsm/src/mtn ; make
  5. $ cd gruns/runscr ; cvs co p2sig.in p2sig_era.in
  6. $ cd gruns ; configure-scr gsm (or rsm, rsim, etc)

Options (see runscr/p2sig)

  • STDPRS: choices of pressure levels.
  • INDMOIS: 0 Using specific humidity, 1 Using relative humidity.
  • ISFCP: 0 Using geopotential height data (without topography), 1 Using surface pressure and topography data, 2 Using mean sea level pressure only.
  • INST: 0 for NCEP-Reanalysis, 1 for ECMWF Reanalysis (ERA40).
  • IINTP: 0 for horizontal interpolation, 1 for using closest grid (when undefined values are filled in original data).


  • Only for global data.
  • Input data should be GRIB format and in a single file. (If not, some pre-processes should be needed.)
  • Both gaussian and lon-lat coordinates can be used. But all variables should be the same coordinate and the coordinate information should be correctly written in the input GRIB file.
  • GRIB ID sensitive: Default GRIB ID is set for NCEP convention. In case of using ECMWF data, you should change the codes.
  • Time stamp sensitive: If you want to change the time stamp of GRIB file, use libs/etc/force_grib_date_mon
    • Forecast time should be 00. If not, use libs/etc/force_grib_date_mon to change the time stamp of grib file.


  • Using NCEP reanalysis (pgb) data
    • Download any pgb file (pgb.anl.YYYYMMDDHH.grib) from ECPC Data server.
    • runscr/p2sig pgb.anl.YYYYMMDDHH.grib test.sig YYYY:MM:DD:HH:00
  • Using ERA40 data
    • runscr/p2sig_era ../libs/con/era40_19900309.grib test_era.sig 1990:03:09:00:00