GICC-Rhone Project

Background Information

    Model simulations from four climate models were used to provide six future climate change scenarios resulting from a presumed doubling of the atmospheric concentration of CO₂. The four models which were utilized are from the LMD (Laboratoire Météorologique Dynamique), CNRM (Centre National Recherches Météorologiques), HC (Hadley Centre) and UR (University of Reading). In addition, relatively high spatial resolution (HR) CNRM and LMD model outputs were used to make a total of six model datasets. Each model provided a baseline (1xCO₂) present climate (PC) and a future (2xCO₂) modified climate (MC) which were based on a 10 year average for the years 2050-2060 after an initial spin-up period. All model scenarios were assumed to have an equal probability for the current study. The monthly average atmospheric forcing comprising a set of six variables was extracted from the model output datasets: incoming solar radiation, incoming atmospheric longwave radiation, air temperature, wind speed, specific humidity and total precipitation. The present climate from the Rhone database was then used together with the GCM anomalies to calculate 6 future climates. These climates were then used to drive the coupled ISBA-MODCOU model in order to explore the impact of possible future climate change on the hydrological cycle of the Rhone basin.

For more information, please see the Rhone-GICC report.

Forcing Database Information

    Basic information on the Rhone Atmospheric forcing database is presented in this section relative to the GICC Project: the generation of Modified Climate Scenarios for the period August, 1981, though July, 1998. This page also contains information about the GICC-Rhone CDROMs which are currently available.

* = Modified Climate variable = Present Climate variable + effect of anomalies

VV_YEAR.MODEL.RES.forc

MC Files, Types I and II:

CIG Files, Types I and II:

    The PC, MC-I and MC-II files are available in single-precision binary format at a temporal resolution of 3 hours for 17 years at 1471 grid points. Due to the large data file size, however, the files have also been compressed using a simple linear algorithm. This format change causes a small loss in precision, however, the impact on modeled discharge was found to be negligible. This format change results in a signifigant space savings. Note, this format change is applied to the PC, MC-I and MC-II databases, not the CIG files (which are in UNIX compressed ASCII format).

    The transform is simply expressed as

where V^* is an INTEGER*2 (or short) variable and the original variable V is REAL*4 (usual default). The symbols are defined as

• INT = integer
• i = space index (i = 1, 1471)
• j = time steps each year [j = 1, (365 or 366)x8]
• k = year index (k=1, 17)
• I_o = 32766 (approximate range of INTEGER*2 variables)
• V_{i j k}^* INTEGER*2 transformed variable
• V_{i j k} REAL*4 original variable (true value)
• V_{k max} REAL*4 file maximum (for all i and j)
• V_{k min} REAL*4 file minimum (for all i and j)

Note that the single yearly-domain maximum and minimum for each variable are also provided in a seperate file (maximum and minimum for each variable for each file). The inflation algorithm named inflate.f90 (f77) is provided in both FORTRAN90 and FORTRAN77. The newly formatted files are compressed using gzip.

    The file naming convention is the same as above, except that the extension _RED is added to denote REDuced format:

VV_YEAR.MODEL.RES_RED.forc

The files using the same naming convention but with the extension _MAX-MIN each contain 2 values on one line, the maximum and minimum annual-domain value for each variable for each year:

VV_YEAR.MODEL.RES_MAX-MIN.forc

These values are read in by the provided inflation program along with the reduced format data to produce (by default) REAL*4 variables in binary format. The user can change this output format simply by editing the file inflate.f90 (f77).

    Please note that there is also a simple bit-swapping program which is provided for converting the _RED INTEGER*2 files to the binary format needed by some machines (if you compile inflate.f90 and it can not read the _RED files on your machine) or you don't get the correct transformation (see README.inflate file in the /progs directory on the CDROMs).

Selected Figures and Images from the GICC-Rhone report, November 2000

Entitled: GICC-Rhone Climate Scenarios

by A. Boone, J. Noilhan and P. Etchevers

    This directory contains selected figures from the above report as color images (they are listed below). Monthly anomalies for the 6 GCM model simulations for the Rhone basin and various observed-climate fields are shown.