A Wavelet-based Algorithm for the Computation of Intraseasonal Oscillations Intensity and Frequency Indices and Application to Central Africa
International Journal of Environmental Monitoring and Analysis
Volume 8, Issue 4, August 2020, Pages: 111-116
Received: May 19, 2020;
Accepted: Jul. 7, 2020;
Published: Aug. 31, 2020
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Alain Tchakoutio Sandjon, Laboratory of Environmental Modeling and Atmospheric Physics, University of Yaoundé I, Yaoundé, Cameroon; Department of Computer Science Including Basic Sciences, Higher Technical Teacher's Training College Kumba, University of Buea, Kumba, Cameroon; Laboratory of Industrial Systems and Environmental Engineering, Fotso Victor University Institute of Technology, University of Dschang, Bandjoun, Cameroon
Armand Nzeukou Takougang, Laboratory of Industrial Systems and Environmental Engineering, Fotso Victor University Institute of Technology, University of Dschang, Bandjoun, Cameroon
The rainfall modeling at regional scale remains a great challenge in the tropics because of the complexity of the processes that induce rainfall variability. Then the good parameterization of some atmospheric processes will be of great contribution towards the improvement of regional models. In this paper we applied wavelet transform on 2.5°×2.5° daily Outgoing Long-wave Radiation (OLR) datasets for the period 1981-2015 (35 years) to extract Intraseasonal Intensity (ISOI) and intraseasonal Period (ISOP), with application to Central Africa (CA). In fact for each grid point in the study area, the wavelet transform was applied to the 25-70-day filtered daily OLR time series and the wavelet spectrum is obtained. In the resulting spectrum, the maximum variance for each day is taken as ISOI and the period exhibiting that maximum variance is the ISOP. The plots of seasonal mean ISOI and ISOP obtained showed that the ISO characteristics (amplitude, frequency) strongly vary from season to another. The ISO amplitude is extremely high during December-February (DJF) and March-May (MAM) and lower during JJA and SON seasons. As for the period of oscillations, the ISOP peaks during MAM and JJA seasons. But for the four seasons, the period is predominantly contained between 40-50 days, suggesting the dominance of Madden-Julian Oscillation (MJO) signal.
Alain Tchakoutio Sandjon,
Armand Nzeukou Takougang,
A Wavelet-based Algorithm for the Computation of Intraseasonal Oscillations Intensity and Frequency Indices and Application to Central Africa, International Journal of Environmental Monitoring and Analysis.
Vol. 8, No. 4,
2020, pp. 111-116.
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