= Change climate forcing =

Author: S. Luyssaert\\
Last revision: 2020/28/02, A. Ducharne 

This page is only relevant for offline runs, of course!

The list of available climate forcing datasets is provided on https://forge.ipsl.jussieu.fr/orchidee/wiki/Documentation/Forcings. This page also gives information on two drivers which are are available to run ORCHIDEE offline, and the required structure of the forcing files for each driver.

== 1. If you use the "old" driver

This driver can make use of all the shared atmospheric forcing datasets.
The standard libIGCM configurations already offer the choice between two forcings:
- CRU-NCEP at 2° with [https://forge.ipsl.jussieu.fr/orchidee/browser/trunk/ORCHIDEE_OL/OOL_SEC_STO_FG2/COMP/orchidee_ol.card OOL_SEC_STO_FG2]
- WFDEI_GPCC/v1 at 0.5° with [https://forge.ipsl.jussieu.fr/orchidee/browser/trunk/ORCHIDEE_OL/OOL_SEC_STO_FG3/COMP/orchidee_ol.card OOL_SEC_STO_FG3]

If you want to change the default forcing of the above configurations, you must change the following line in COMP/orchidee_ol.card, like below to change CRU-NCEP with PGF

{{{
[BoundaryFiles]
#List=  (${R_IN}/SRF/METEO/CRU-NCEP/v5.3.2/twodeg/cruncep_twodeg_${year}.nc, forcing_file.nc)
List=  (${R_IN}/SRF/METEO/Princeton_GPCC/v1/1deg_3h/PGF_GPCC_1deg_3h__${year}.nc, forcing_file.nc)
ListNonDel= ()
}}}

A special case is if you want loop over certain years, usually for spin-up.
To do so, you need to change "${year}" in the above line by "${!CyclicYear}", and to define the nb of years that you "recycle" by adding the following lines in your config.card:

{{{
# Forcing data between 1901 and 1920
CyclicBegin=1901
CyclicEnd=1910
}}}

This example is taken from the standard configuration [https://forge.ipsl.jussieu.fr/orchidee/browser/trunk/ORCHIDEE_OL/OOL_SEC_STO_FG1trans OOL_SEC_STO_FG1trans], designed to make a spin-up over 140 years by recycling A 10-yr period (but with time avrying CO2 and vegatation maps). 

== 2. If you use the "new" driver

An example with libIGCM is provided in the standard ORCHIDEE_OL configurations under the name OOL_SEC_STO_FG3nd, designed to use WFDEI_GPCC/v2, see https://forge.ipsl.jussieu.fr/orchidee/browser/trunk/ORCHIDEE_OL/OOL_SEC_STO_FG3nd

The atmospheric forcing dataset is defined in ochidedriver.card, where you must insert a line for the simulated year, and two other lines for the previous and following years:

{{{
[BoundaryFiles]
List=  (${R_IN}/SRF/METEO/WFDEI_GPCC/v2/leap/WFDEI_GPCC_${year_m1}.nc, forcing_yearm1.nc),\
       (${R_IN}/SRF/METEO/WFDEI_GPCC/v2/leap/WFDEI_GPCC_${year}.nc, forcing_year.nc),\
       (${R_IN}/SRF/METEO/WFDEI_GPCC/v2/leap/WFDEI_GPCC_${year_p1}.nc, forcing_yearp1.nc)
}}}