Etude de l'impact des précipitations sur les rendements de soja au Mato Grosso (Brésil)
Résumé
Nowadays, the soybean cultivation represents the first source of income for the Brazilian State of Mato Grosso. The importance of this cultivation can be partly explained by the regional natural conditions, and especially by the abondant precipitations enabling producers to get good yields. However, every year, this climate leads to siginifcant yields' losses in a few localizations due to weak rainfalls during the planting period. Thus, the producers have to determine as best as possible the onset date of the rainy season in order to plant in a relatively safe situation. The purpose of this work is to determine this onset date to analyse its spatio-temporal variability in Mato Grosso. The data used here are those of 116 meteorological stations managed by the Water National Agency (ANA) in the 1998-2006 period. These data will be compared to rainfall estimations issues from the Tropical Rainfall Measuring Mission (TRMM) satellite. The onset date is determined at a daily scale by the “Anomalous accumulation” method proposed by Liebmann (2006). This method allows us to detect a strong spatio-temporal variability of the rainy season attributes in Mato Grosso at regional and local scales.