This paper highlights the global warming of the lower atmosphere of West African tropical area using in-situ data. The study is based on the analysis of 500-m interval vertical profiles of radiosonde temperature above Niamey (13.47 ° N; 2.16 ° E) a sub-Saharan meteorological station. The annual cycle of surface temperatures shows seasonally two peaks located in April/May and in October and two minimum in December/January and August respectively. In the mid-troposphere (between 5 km and 10 km height), time series of monthly mean temperatures from January 2001 to December 2018, shows an annual variability with a slight downward trend of -0.036 ° C per decade. In the lower stratosphere (25 - 30 km altitude) a cooling of -0.64 ° C/decade is observed. Temperatures time series also highlight the presence of two breaking points associated with the El Ni ñ o-Southern Oscillation (ENSO) events. When performing a separation regarding Southern Oscillation Index (SOI) time series, model parameters of the linear regression indicate a tropospheric warming during the neutral and La Ni ñ a phases and a stratospheric cooling. The analysis of the lower stratosphere zonal wind highlights different behaviours of the quasi-biennial oscillation (QBO) during the neutral and La Ni ñ a phases.
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