Preparing the WG data for the ORCHIDEE scheme

This data  consist in low frequency forcing input created from CRU data (Climatic Research ,Unit  University of East Anglia, cru@uea.ac.uk).

You need to download this file . The file contains all the following fields :

In order to generate daily weather conditions, the model uses a series of 'weather generator' approaches, which generate random combinations of weather conditions based upon the climatological conditions.
In general, this weather generator is based upon the so-called Richardson weather generator.

Appropriate references include:

Geng, S., F.W.T. Penning de Vries, and L. Supit, 1985: A simple method for generating rainfall data,
Agricultural and Forest Meteorology, 36, 363-376.

Richardson, C. W. and Wright, D. A., 1984: WGEN: A model for generating daily weather variables.
 U. S. Department of Agriculture, Agricultural Research Service.

Richardson, C., 1981: Stochastic simulation of daily precipitation, temperature, and solar radiation.
Water Resources Research 17, 182-190.

Configuring ORCHIDEE for the WG data

Using the Weather Generator is determined in  the run.def, the following flags are necessary :

ALLOW_WEATHERGEN=y
FORCING_FILE=WG_cru.nc

You can also activate the following flags :

IPREC=1 : default value is 0, if this is set to 1, the weather generator uses the monthly mean values for daily means. it is set to 0, the weather generator uses statistical relationships to derive daily values from monthly means.

WEATHGEN_PRECIP_EXACT=y : default is false, if this is set to y, the weather generator  will generate pseudo-random precipitations whose monthly mean is exactly the prescribed one. In this case, the daily precipitation (for rainy days) is constant.

DUMP_WEATHER=y : default is false, this flag aims to write the weather genrated for ORCHIDEE in an output file defined with flag DUMP_WEATHER_FILE .
 
Rachid Benshila
Last modified: Wed March 12 :11:10 CEST 2004