Dynamics of the Inter Tropical Front and Rainy Season Onset in Benin

Rainfall onset in Benin is one of the major problems that the farmers face. This climatic factor is of a great importance for the productivity in Benin.

In this work, based on two criteria, we elaborated a new criterion, that allows us to determine with more precision, the rainy season onset in five synoptic stations in Benin: Cotonou, Bohicon, Savè, Parakou and Kandi. Then, we studied the InterTropical Front (ITF) position compared to each station at the onset date.

We used in this study, the daily rainfall data provided by the Agency for the Safety of air Navigation in Africa and Madagascar (ASECNA) for (1987-2016) years and the dekadal (10-day) ITF position data produced by the National Oceanic and Atmospheric Administration (NOAA) for (1989-2016) years.

Using these daily rain of the five stations and the ITF data, we calculated, the dekadal, monthly and annual rain amount, then we established a relation between the ITF position and the precipitation for each station.

Results obtained show that Cotonou have two rainy seasons. The long rainy season begins on April 7th and short season on September 11th. Bohicon, Savè, Parakou and Kandi know one rainy season that starts on April 8th, April 14th, April 29th and May 17th, respectively. Compared to these dates, the ITF islocated 679.04 km north to Cotonou, 604.46 km north to Bohicon, 597.78 km north to Savè, 573.29 km north to Parakou, and 475.33 km north to Kandi. The good correlation is obtained between the ITF position and the monthly precipitations for Parakou and Kandi regions. The correlation are good enough in Bohicon, Savè and Cotonou regions during the monsoon period.