Fractal Analysis of the Long-Term Memory in Precipitation over Bénin (West Africa)

Abstract

This study analyzed the long-term memory (LTM) in precipitation over Bénin synoptic stations from 1951 to 2010 using the detrended fluctuation analysis (DFA) method. Results reveal the existence of positive long-term memory characteristic in rainfall field. DFA exponent values are different regarding the concerned synoptic stations, reflecting the effect of geographical position and climate on the LTM. These values were related to the type of climate. The best DFA1-4 method depends on the geographical position of the studied station. However, DFA2 is generally the best in terms of spatial average from DFA1 to DFA4. In Bénin synoptic stations, except the Parakou station, the long-term temporal correlations are systematically the source of multifractality in rainfall. Except Natitingou, the strength of long-term memory characteristic decreases each twenty years in the study period. Considering the fractal approach, our results show that the subperiod 1991–2010 is not really a transition period as shown before. Thus, the drought is prolonging until 2010. So, fractal theory reveals more Bénin climatic characteristics.

Assessing Nonlinear Dynamics and Trends in Precipitation by Ensemble Empirical Mode Decomposition (EEMD) and Fractal Approach in Benin Republic (West Africa)

“…From the figure, one can notice that whatever the synoptic stations and the subperiods considered, all the multifractal spectra f (α) exhibit the shape of a parabolic curve, indicating the multifractal structure of the precipitation time series but with varying degree, since the curves are all different. is conforms to the results obtained by Agbazo et al [11] in the same study stations. e analysis of Complexity the multifractal spectra obtained at all synoptic stations reveals evident differences in the dynamics of the precipitations processes for Benin.…”

“…So, Natitingou and Parakou remain more humid (∼1300 mm/year and 1200 mm/ year annual amount of precipitation, respectively) than Kandi (∼700 mm/year) [32]. Benin is characterized from the South to North by three climatic zones in which stations are located [11,33]: Cotonou, Bohicon, and Save are located in the subequatorial region where March is the hottest month (∼26°C), while August is the coldest month (∼24°C). e daily and annual thermal amplitudes are, respectively, ∼10°C and∼5°C.…”

“…However, it is not always easy to analyze them because precipitations are highly complex and variable process, exhibiting enormous variability over a wide range of time and space scales [9,10]. Furthermore, precipitation variations are extremely complex [10], and their time series show obvious nonstationary characteristics in the climatic system [6,11]. In fact, it is not feasible to detect intrinsic dynamic properties of precipitations due to nonstationarity and nonlinearity by using some traditional approaches, such as the power spectrum, correlation analysis, and the nonparametric Mann-Kendall (MK) test (the most popularly used for trend analysis).…”

“…In fact, it is not feasible to detect intrinsic dynamic properties of precipitations due to nonstationarity and nonlinearity by using some traditional approaches, such as the power spectrum, correlation analysis, and the nonparametric Mann-Kendall (MK) test (the most popularly used for trend analysis). ese methods are, in general, insufficient and unreliable for a complete analysis of meteorological time series like precipitations [9,[11][12][13].…”

Intrinsic mode functions and fractal characteristics of the solar Incoming Shortwave Radiation observed at Nalohou (Benin Republic)

“…Thirdly, as the trend of the series has been eliminated in Step 1, we do not need the least squares (LS) method fitting detrending step of the original MFDFA (Kantelhardt et al, 2002;Agbazo et al, 2019). One then calculates the 2 ( , ) of each window as follows:…”