SPATIO-TEMPORAL VARIABILITY OF THE ONSET AND END DATES OF THE RAINY SEASONS IN THE BOUNKANI REGION (NORTH-EAST OF COTE D IVOIRE)

In Cote d Ivoire,80% of rural activities are based on rain fed agriculture, although the country has been experiencing a disruption of its rainfall regime for several decades. This study was conducted in this context in order to deepen the previous knowledge on the rainfall regime of the Bounkani region through the spatio-temporal distribution of the dates of the beginning and end of the rainy season. The rainfall data used are of the CHIRPS type for the 1981-2020 period. The application of rainfall indices allowed us to observe surplus and deficit years. These variations indicate a downward trend. The average rainfall has decreased from 1050 mm during the decade 1985-1995 to 950 mm in 2011-2020, a loss of 100 mm. This deficit was reflected in the onset and end dates as well as the number of rainy days of the rainy seasons. The study of the number of rainy days of the rainy season reveals that they have a very low downward trend. Indeed, the starting dates of the rainy season are increasingly late. On average, the start of the season, which was between April 6 and 10 in the years 1981-1995, has shifted from May 1 to 5 in the decade 2011-2020 in the North of the region. While, the South records an average date of season start from April 1 to 5 in the years 1981-1995 and from May 6 to 10 in the decade 2011-2020, a shift of more than 30 days. The start of the rainy season is progressive along the South-North gradient. Conversely, the end of the rainy season occurs first in the North and then extends to the South.