Preparing the ISLSCP data for the ORCHIDEE scheme

This page describes how to prepare the ISLSCP Initiative I data for forcing the ORCHIDEE model. To do this you first need the ISLSCP Iniative I data set which is either available from the CD-rom or from the Web Then you need the code (Version last updated on 15-May-2000 (Conforms to the ALMA convention now)) which transforms it into a netCDF file.

The tar-file contains a shell-script (do_allfiles) which should do everything for you but still a few explanations are needed. First of all, the CD-roms 3, 4 and 5 need to be downloaded to a disk and put into directories cdrom3, cdrom4 and cdrom5. The path to these directories will be an input to islscp2nc.

The code islscp2nc will prompt you for the following information :

The time at which the data on the netCDF should start. The format is yymm.
The time at which the data on the netCDF should end. The format is yymm.
Path to the directories cdrom3, cdrom4 and cdrom5. It is also in this directory that islscp2nc will put the resulting netCDF file.
Path of the directory in which the netCDf file will be written.
Should the data be compressed by gathering all land points ? Options are y or n.
The name of the file to be created.
Longitude interval for which the netCDf file should be generated.
Same in latitude.

For the moment the tasks of the islscp2nc program are very simple. Read the original data, change the units and output the forcing in a netCDF file so that it can be used by ORCHIDEE. In the futur a number of corrections on the data should be done. This would for instance be to bring the wind, which is given at 10m to the same level as humidity and temperature (2m).

Something islscp2nc will never do is to change the time stepping. We believe that this should be done in the driver of ORCHIDEE. The main reason beeing that it something which will evolve over time and would generate too much data if done off-line. When doing the temporal interpolation on the fly we have the advantage to have available the evolution of the surface and fluxes. This allows to develop interpolation schemes which take this information into account.

The files created by islscp2nc can readily be read by the IOIPSL package. The flinget routine will even uncompress the data on the fly.

Configuring ORCHIDEE for the ISLSCP data

Nothing special needs to be provided for the ISLSCP data as the scheme runs in the same mode as in the GCM. This means that it interpolates itself its vegetation map, constructs the albedo and roughness maps with the vegetation and soil color data sets.
A sample run.def file is available.

Jan Polcher

Last modified: Fri Sep 15 12:50:13 CEST 2000