[1] U.R. de Bioclimatologie,
[2] INRA,undefined
[3] F-78850 Thiverval-Grignon,undefined
[4] France,undefined
[5] IRISA,undefined
[6] Campus de Beaulieu,undefined
[7] F-35042 Rennes Cedex,undefined
[8] France E-mail: chelle@bcgn.grignon.inra.fr,undefined