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Comparing the patterns of 20–70 days intraseasonal oscillations over Central Africa during the last three decades

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Abstract

In this paper, we used the Outgoing Longwave Radiation (OLR) data to compare the intraseasonal atmospheric variability patterns over Central Africa, during the last three decades. The spectral analysis indicates that for the three decades, the intraseasonal variability is dominated by 20–80 days periods band with the center near 40–50 days. The results of Empirical Orthogonal Functions (EOFs) analysis have shown that the amount of variance explained by the three retained EOFs are 41.6 % for 1981–1990, 44.2 % for 1991–2000 and 42.6 % for 2001–2010. For the three decades, the three leading EOFs retained exhibit high spatial loadings over Northern Congo, Southern Ethiopia, and Southwestern Tanzania. The power spectra of the leading principal components have their peaks near 40 days for the three decades, indicating MJO signal. The PCs time series revealed that the amplitude of intraseasonal oscillations (ISO) globally decreases from decade to another. The plot of ISO and El Niño-Southern Oscillation (ENSO) indices revealed that the lowest values of ISO strength generally correspond to the relatively large values of ENSO indices and inversely. The mean ISO strength and ISO fluctuations were highest during 1981–1990, and this period also corresponds to the highest fluctuations of ENSO signal.

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Acknowledgments

Most of the scripts used in this study were produced from the NCL website http://www.ncl.ucar.edu. The GPCP and OLR data was obtained from the NOAA website, http://www.esrl.noaa.gov. All the administrator members of these websites are gratefully acknowledged for maintaining the updated data. We also thank the senior researchers of LEMAP and LISIE for helpful comments.

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Authors and Affiliations

  1. Laboratory for Environmental Modeling and Atmospheric Physics, Department of Physics, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon

    Alain Tchakoutio Sandjon, Clément Tchawoua & Brice Sonfack

  2. Laboratory of Industrial Systems and Environmental Engineering, Fotso Victor Technology Institute, University of Dschang, Dschang, Cameroon

    Alain Tchakoutio Sandjon, Armand Nzeukou & Tengeleng Siddi

  3. Laboratory of Mechanics, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon

    Clément Tchawoua

  4. Sahel High Institute, University of Maroua, Maroua, Cameroon

    Tengeleng Siddi

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  1. Alain Tchakoutio Sandjon
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  2. Armand Nzeukou
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  3. Clément Tchawoua
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  4. Brice Sonfack
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  5. Tengeleng Siddi
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Correspondence to Alain Tchakoutio Sandjon.

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Sandjon, A.T., Nzeukou, A., Tchawoua, C. et al. Comparing the patterns of 20–70 days intraseasonal oscillations over Central Africa during the last three decades. Theor Appl Climatol 118, 319–329 (2014). https://doi.org/10.1007/s00704-013-1063-1

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  • DOI: https://doi.org/10.1007/s00704-013-1063-1

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