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A Wavelet-based Algorithm for the Computation of Intraseasonal Oscillations Intensity and Frequency Indices and Application to Central Africa

Received: 19 May 2020     Accepted: 7 July 2020     Published: 31 August 2020
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Abstract

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.

Published in International Journal of Environmental Monitoring and Analysis (Volume 8, Issue 4)
DOI 10.11648/j.ijema.20200804.14
Page(s) 111-116
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2020. Published by Science Publishing Group

Keywords

Intraseasonal Oscillations, Central Africa, Wavelets Analysis, Intensity, Frequency

References
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Cite This Article
  • APA Style

    Alain Tchakoutio Sandjon, Armand Nzeukou Takougang. (2020). 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, 8(4), 111-116. https://doi.org/10.11648/j.ijema.20200804.14

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    ACS Style

    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. Int. J. Environ. Monit. Anal. 2020, 8(4), 111-116. doi: 10.11648/j.ijema.20200804.14

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    AMA Style

    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. Int J Environ Monit Anal. 2020;8(4):111-116. doi: 10.11648/j.ijema.20200804.14

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  • @article{10.11648/j.ijema.20200804.14,
      author = {Alain Tchakoutio Sandjon and Armand Nzeukou Takougang},
      title = {A Wavelet-based Algorithm for the Computation of Intraseasonal Oscillations Intensity and Frequency Indices and Application to Central Africa},
      journal = {International Journal of Environmental Monitoring and Analysis},
      volume = {8},
      number = {4},
      pages = {111-116},
      doi = {10.11648/j.ijema.20200804.14},
      url = {https://doi.org/10.11648/j.ijema.20200804.14},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijema.20200804.14},
      abstract = {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.},
     year = {2020}
    }
    

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  • TY  - JOUR
    T1  - A Wavelet-based Algorithm for the Computation of Intraseasonal Oscillations Intensity and Frequency Indices and Application to Central Africa
    AU  - Alain Tchakoutio Sandjon
    AU  - Armand Nzeukou Takougang
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    T2  - International Journal of Environmental Monitoring and Analysis
    JF  - International Journal of Environmental Monitoring and Analysis
    JO  - International Journal of Environmental Monitoring and Analysis
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    PB  - Science Publishing Group
    SN  - 2328-7667
    UR  - https://doi.org/10.11648/j.ijema.20200804.14
    AB  - 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.
    VL  - 8
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    ER  - 

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Author Information
  • Laboratory of Environmental Modeling and Atmospheric Physics, University of Yaoundé I, Yaoundé, Cameroon

  • Laboratory of Industrial Systems and Environmental Engineering, Fotso Victor University Institute of Technology, University of Dschang, Bandjoun, Cameroon

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