Abstract:
This study investigates the trend in monthly and annual rainfall, and minimum and
maximum temperature (Tmin and Tmax) in the Savannah region of Togo. The historical data of
Mango and Dapaong weather stations from 1981 to 2019 were used. A serial correlation test was
applied to all time series to identify serially independent series. A Non-parametric Mann–Kendall
(MK) test was applied to serially independent series. The magnitude of the trend was calculated using
the Sen’s slope (SS) method. For the data influenced by serial correlation, a modified version of the
Mann–Kendall test was applied. An open-source library package was developed in the R language,
namely, “mkmodified”. For annual rainfall, results showed a significant increasing trend at Dapaong
(p < 0.05) and a non-significant decreasing trend at Mango (p > 0.05) at 95%. There was an increasing
trend in the Tmin both at Mango and Dapaong. No statistically significant trend was found at Mango
(p > 0.05), while at Dapaong (p < 0.05), a significant trend was found at 95%. Simlarly, there was
a statistically increasing trend in the Tmax both at Mango and Dapaong. Rainfall in Dapaong has
increased (5.50 mm/year) whereas in Mango, it has decreased (0.93 mm/year). Tmn increased by
0.04 and 0.008 C per year in Mango and Dapaong, respectively. Tmax increased by 0.03 and 0.02 C
per year in Mango and Dapaong, respectively. A Rainfall Anomaly Index (RAI) was also used to
present a temporal variation in rainfall; the historical series presented drier years. Many studies have
analysed the trend of climate parameters in northern Togo, but none of them has specifically targeted
the Savannah region that is considered the poorest region of the country.
Description:
A Publication submitted to the West African Science Service Centre on Climate Change and Adapted Land Use, the Université de Lomé, Togo in partial fulfillment of the requirements for the requirements for the degree of Doctor of Philosophy Degree in Climate Change and Disaster Risk Management
