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.
Thomas, M.; John, C. H. C.; Alexander, G.; Nicolas J. C. Temporal precipitation variability versus altitude on a tropical high mountain: Observations and mesoscale atmospheric modeling. Q. J. R. Meteorol. Soc. 2009, 135, 1439–1455.
Vondou, D. A; Nzeukou, A.; Lenouo, A., Mkankam, K. F. Seasonal variations in the diurnal patterns of convection in Cameroon–Nigeria and their neighboring areas. Atmos.sci. Let. 2010, 11, 290–300.
Moore, A.; Ioschnigg, J.; Webster, P.; Leben, R. Coupled ocean-atmosphere dynamics in the Indian ocean during 1997-1998. 2010, J. climate, 401, 356–360.
Mutai, C.; Hastenrath, S.; Polzin, D. Diagnosing the 2005 drought in equatorial east Africa. J. Climate, 20, 4628–4637.
Mitchell, T. P.; Wallace, J. M. The annual cycle in equatorial convection and sea surface temperature. J. Climate, 1992, 1140–1156.
Tsuneaki, S. Seasonal variation of the ITCZ and its characteristics over central Africa. Theor. Appl. Climatol, 2011, 103, 39–60.
Gruber, A.; Krueger, A. F. The status of the NOAA outgoing longwave radiation data set. Bull. Amer. Meteor. Soc, 1984, 65, 958–962.
Huffman, G. J., Bolvin, D. T. Version 1.2 GPCP One-Degree Daily Precipitation Data Set Documentation. Mesoscale, Atmospheric Processes Laboratory, NASA Goddard Space Flight Center, 2013.
Kummerow, C., W. Barnes, T. Kozu, J. Shiue, and J. Simpson. The Tropical Rainfall Measuring Mission (TRMM) Sensor Package. Journal of Atmospheric and Oceanic Technology, 1998, 15, 809-817.
Blacutt, L. A., D. L. Herdies, L. G. G. de Gonçalves, D. A. Vila, and M. Andrade. Precipitation comparison for the CFSR, MERRA, TRMM3B42 and Combined Scheme datasets in Bolivia. Atmos. Res, 2015, 163, 117-131.
Madden, R. A.; Julian, P. R.; Observations of the 40–50 day tropical oscillation: A review. Mon. Wea. Rev., 1994, 122, 814–837.
Jury, M. R.; Mpeta, J. Intraseasonal convective structure and evolution over tropical East Africa. Climate Res., 2010, 17, 83–92.
Maloney, E. D.; Jeffrey, S. Intraseasonal Variability of the West African Monsoon and Atlantic ITCZ. J. climate, 2008, 21, 2898-2918.
Tchakoutio, A. S.; Nzeukou, A.; Tchawoua, C. Intraseasonal atmospheric variability and its interannual modulation in central Africa. Meteorol Atmos Phys, 2012, 117, 167–179.
Camberlin, P. and Pohl, B. Influence of the Madden-Julian Oscillation on east African rainfall. Part I: Intraseasonal variability and regional dependency. Int. J. climatol, 2006, 132, 2521–2539.
Janicot, S.; G. Caniaux, F.; Chauvin et al. Intraseasonal variability of the West African monsoon. 2011, Atm. Sci. Lett, 12 (1), 58–66.
Tchakoutio, A. S.; Nzeukou, A.; Tchawoua, C.; Kamga, F. M.; Vondou, D. A comparative analysis of intraseasonal variability in OLR and 1DD GPCP data over central Africa. Theor. Appl. Climatol, 2013a, 116, 1 (2), 37–49.
Tchakoutio, A. S.; Nzeukou, A.; Tchawoua, C.; Sonfack, B.; Siddi, T. Comparing the patterns of 20–70 days intraseasonal oscillations over Central Africa during the last three decades. Theor. Appl. Climatol, 2013b, DOI: 10.1007/s00704-013-1063-1.
Jury, M. R., Tazalika, L. Intra-seasonal rainfall oscillations over central Africa: space-time character and evolution. 2008, Theor. Appl. Climatol, 94, 67–80.
Wheeler C. M.; Hendon, H. H. An all-season real-time multivariate MJO Index: Development of an index for monitoring and prediction. Mon. Wea. Rev., 2004, 132, 1917–1932.
Jones, C.; Carvalho, L. M. V. Stochastic simulations of the Madden–Julian oscillation activity. Clim. Dyn, 2011, 36, 229–246. DOI 10.1007/s00382-009-0660-2.
Torrence, C.; Compo, G. P. A practical guide to wavelet analysis. Bull. Amer. Meteor. Soc., 1998, 79: 61-78.
Daubechies, I. The wavelet transform time-frequency localization and signal analysis. IEEE Trans. Inform. Theory, 1990, 36: 961–1004.
Liebmann, B.; Smith, C. A. Description of a Complete (Interpolated) Outgoing Longwave Radiation dataset. B. Am. Meteorol. Soc, 2001, 77, 1275–1277.
Arkin, P.; Richards, F. On the relationship between satellite-observed cloud cover and precipitation. Mon. Wea. Rev, 1981, 109, 1081–1093.
Arkin, P. A.; Meisner, N. The relationship between large scale convective rainfall and cold cloud over the Western Hemisphere during 1982–1984. Mon. Wea. Rev, 1982, 115, 51–74.
Arkin, P. A.; Xie, P. Global monthly precipitation estimates from satellite-observed Outgoing Longwave Radiation. J. Climate, 1997, 9, 840–858.
Lanczos, C. Applied Analysis. Prentice-Hall, 1956, 539 pp.
Duchon, C. E. Lanczos filtering in one and two dimensions. J. Appl. Meteor. 1979, 18, 1016-1022.
Chao, B. F.; Naito, I. Wavelet analysis provides a new tool for studying Earth’s rotation. 1995, EOS., 76: 161-165.
Lee T. L. D., Yamamoto, A. Wavelet Analysis: Theory and Applications. 1994, Hewlett Packard Journal, 44-52.