THE ONSET OF THE RAINY-SEASON IN YUNNAN PROVINCE, PEOPLES-REPUBLIC-OF-CHINA AND ITS SIGNIFICANCE FOR AGRICULTURAL OPERATIONS

Data of 134 stations located in Yunnan province, PR China were analysed in order to study the temporal and spatial characteristics of the onset of the rainy season and to investigate the consequences for farming operations. Using a precipitation threshold value, a time span of 12 weeks was found for the complete onset of the rainy season, while the range of onset dates varied from 37 days to 155 days. The onset occurred at different places across the province and showed active and break phases due to the interaction of four different branches of the atmospheric circulation. The onset of the growing season, determined by summing up decade precipitation totals, showed the same general pattern. Probabilities are given for the beginning and the variability of sowing dates of dry-seeded crops together with dates of preparation of paddy fields.