Analysis of rainfall variability and impact on the start and end dates of rainy seasons in the urban humid tropical zone: a case of the Yaoundé Town, Cameroon (Central Africa)

This study aims to evaluate the influence of current and changing rainfall dynamics on the start and end dates of the rainy seasons in Yaoundé town. Thus, classical statistical tests, trend detection, and break tests were applied for the analysis of different daily rainfall parameters recorded between 1964 and 2020. The results show that annual rainfall fluctuates between 1083 and 2196.7 mm for an interannual average of 1562 ± 271 mm without a significant break, with a downward trend of about − 3.352 mm/year. The increasing order of magnitude of seasonal precipitation is as follows: Small Dry Season < Great Dry Season < Small Rainy Season < Great Rainy Season. The Small Rainy Season, Great Rainy Season, and Great Dry Season show decreasing trends and magnitudes in the order of − 2.181 mm/year, − 1.741 mm/year, and − 1.015 mm/year, respectively, but without influence on the delineation of the seasons. On the daily level, the number of rainy days per year, per month, per season, and the rainfall height classes also show decreasing trends with multiple breaks except for the class [5.1–15 mm]. The analysis of the start and end dates of the rainy seasons shows that the Small Rainy Season extends from March 19 to June 21, and the Great Rainy Season is between August 20 and November 28. This information is of critical importance for activity planning.