Investigating the frequencies of the monthly mean velocities of the wind in Ndjaména during two consecutive climatic periods and comparing the results have permitted us to come to the next main conclusions. Since the winds of velocities in the interval [0, 2.5[ were predominant during the first climatic period compared to the ones of velocities in the interval [2.5, 5.0[, and inversely during the second climatic period, we conclude that the wind velocities were increasing with time in Ndjaména, indicating that the atmospheric turbulences were progressively increasing. As these velocities were allover below 18 km/h, it is obvious that these turbulences could be classified as moderated. In fact, visual observations made by the authors have indicated winds with velocities far above what given by the present data, particularly at the beginning of each season. Consequently, our results should be considered as preliminary.
