On the Annual Variations in the Amplitude of 25-70-Day Intraseasonal Atmospheric Oscillations in Central Africa
Volume 5, Issue 3, June 2016, Pages: 39-47
Received: May 25, 2016;
Accepted: Jul. 13, 2016;
Published: Jul. 23, 2016
Views 3418 Downloads 127
Alain Tchakoutio Sandjon, Department of Computer Science, Higher Technical Teachers Training College (HTTTC), University of Buea, Kumba, Cameroon; Laboratory of Industrial Systems and Environmental Engineering, Fotso Victor Technology Institute, University of Dschang, Bandjoun, Cameroon; Laboratory for Environmental Modeling and Atmospheric Physics, Department of Physics, Faculty of Sciences, University of Yaoundé 1, Yaoundé, Cameroon
Armand Nzeukou, Laboratory of Industrial Systems and Environmental Engineering, Fotso Victor Technology Institute, University of Dschang, Bandjoun, Cameroon
In this paper we analyzed the annual variations in the 25-70-day intraseasonal atmospheric oscillations in central Africa, for the period 1981-2010, using the Outgoing Longwave OLR data. We then extracted the amplitude time series of the dominant modes of intraseasonal variability in 25-70 days filtered OLR anomalies, using Empirical Orthogonal Functions (EOF) analysis. The EOF analysis has shown that three dominant modes characterized the intraseasonal atmospheric oscillation in Central Africa. The amount of variance explained by these three retained EOFs are 19.3%, 13.6% and 11.8% respectively, and they exhibit higher spatial loading over Northern Congo, Southern Ethiopia, and Southwestern Tanzania, respectively. The analysis of Principal Components (PCs) time series showed that the amplitude and of the intraseasonal oscillations (ISO) exhibit large annual variations. In fact the highest values of ISO amplitude are generally observed during October-April season, and much weakened signal the rest of the year. The fraction of yearly Madden Julian Oscillation (MJO) power, occurring within October-April season are 79.3%, 77.92%, 78.73% for EOF1, EOF2, and EOF3, respectively.
Alain Tchakoutio Sandjon,
On the Annual Variations in the Amplitude of 25-70-Day Intraseasonal Atmospheric Oscillations in Central Africa, Earth Sciences.
Vol. 5, No. 3,
2016, pp. 39-47.
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.
Madden, R. A.; Julian, P. R.; Observations of the 40–50 day tropical oscillation: A review. Mon. Wea. Rev., 1994, 122, 814–837.
Yamagata, T.; Hayachi, Y. A simple diagnostic model for the 30-50 days oscillation in the tropics. J. Meteorol. Soc. Jpn, 1984, 62, 709–717.
Jury, M. R.; Mpeta, J. Intraseasonal convective structure and evolution over tropical East Africa. Climate Res., 2010, 17, 83–92.
Jones, C.; Higgins, R. W.; Waliser, D. E.; Schem, J. K. E.; and Carvalho, L. M. V. Climatology of tropical intraseasonal convective anomalies.1979-2002. J. Climate, 1999, 17, 523–539.
Harry, H. H.; Chindong, Z. Propagating and Standing components of the Intraseasonal Oscillation in Tropical Convection. J. Atmos.sci, 1996, 54, 741–751.
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.
Maloney, E. D.; Jeffrey, S. Intraseasonal Variability of the West African Monsoon and Atlantic ITCZ. J. climate, 2008, 21, 2898-2918.
Slingo, J. M.; Rowell, D. B.; Sperber, K. R.; Nortley, F. On the predictability of the inner annual behavior of the Madden-Julian Oscillation and its relationship with El Niño, Q. J. R. Meteorol. Soc., 1999, 125, 583–609.
Kessler, W. EOF Representations of the Madden-Julian Oscillation and its connection with ENSO. J. Climate, 1999, 14, 3055–3061.
Hendon, H. H.; Wheeler, M.; Zhang, C. Seasonal dependence of the MJO-ENSO relationship, J. Climate, 2007, 20, 531–543.
Tchakoutio, A. S.; Nzeukou, A.; Tchawoua, C. Intraseasonal atmospheric variability and its interannual modulation in central Africa. Meteorol Atmos Phys, 2012, 117, 167–179.
Hendon, H. H.; Zhang, C.; and Glick, J. Interannual variation of the Madden Julian oscillation during austral summer, J. Climate, 1999, 12, 2538–2550.
Zhang, C.; Hendon, H., Glick, J. Interannual variation of the madden-julian oscillation during austral summer. J. Climate, 1999, 12, 2538–2550.
Gruber, A.; Krueger, A. F. The status of the NOAA outgoing longwave radiation data set. Bull. Amer. Meteor. Soc, 1984, 65, 958–962.
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, 539pp.
Duchon, C. E. Lanczos filtering in one and two dimensions. J. Appl. Meteor.1979, 18, 1016-1022.
Torrence, C.; Compo, G. P. A practical guide to wavelet analysis. Bull. Amer. Meteor. Soc., 1998, 79: 61-78.
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,” Theoretical and Applied Climatology, 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. Theoretical and Applied Climatology, 2013b, DOI: 10.1007/s00704-013-1063-1.
Matthew, C. W.; Harry, 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.
Tang, Y.; Yu, B. An analysis of nonlinear relationship between the MJO and ENSO, J. Geophys. Res. Ocean. 2010.
Cattell, R. B. The scree test for the number of factors, Multivariate Behavioral Res.1996, 1(2), 245–276.
North, G. R. and co-authors. Sampling errors in the estimation of empirical orthogonal functions, Mon. Wea. Rev., 1982, 110, 699–706.
Trenberth, K. E. The deﬁnition of El Niño. Bull Am Meteor Soc., 2010, 78, 2771–2777.
Rui, H. and Wang, B. Development characteristics and dynamic structure of tropical intraseasonal convection anomalies, J. Atmos. Sci., 2010, 47, 357-379.