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
Updates
- 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,
- $ cd gsm (or rsm) ; cvs update src/p2sig ; cvs update src/mtn ; cvs update configure-model
- $ configure-model (make Makefile)
- $ cd gsm/src/p2sig ; make
- $ cd gsm/src/mtn ; make
- $ cd gruns/runscr ; cvs co p2sig.in p2sig_era.in
- $ 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).
Notes
- 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.
Example
- 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
Thanks Kei, You guessed it right, It was not readable with wgrib, I made some changes in the download script to get the proper wgrib readable files and now I can successfully run p2sig_era. However, my model is blowing on very first time step. Initially I though it is due to unit issue of (Geopotential Height; ECMWF uses z*9.8(g)), but my guess was not right. I have another followup question in this regard, are we supposed to follow certain order while preparing grib files for p2sig? For example vertical levels from surface to top and variables in a predefined order? Is there anyway I can verify that my p2sig_era output is rightly written?
Once again many thanks for your response.
Regards
Akhilesh