A new analysis of variability and predictability of seasonal rainfall of central southern Africa for 1950–94

Using wavelet analysis and wavelet-based empirical orthogonal function analysis on scale-averaged-wavelet power and individual scale power, we identified the non-stationary sea-surface temperature (SST) fields of the South Atlantic and Indian Oceans that are associated with coherent regions of rainfall variability in central southern Africa (CSA). The dominant mode of CSA rainfall is out of phase between the coastal areas and the centre of CSA and has been decreasing consistently since 1970. The frequencies associated with this mode are between 2–2.4 and 5.6–8 years. The Benguela ocean current SSTs form the dominant spatial pattern of the South Atlantic Ocean, and the Brazil and Guinea ocean current SSTs form the second leading mode. The Benguela spatial patterns were found to migrate seasonally between Africa's west coast and South America's east coast. The northern Indian Ocean SST forms the leading mode of variability, followed by the south Indian Ocean SST. Using predictor fields identified from both oceans, we achieved encouraging results of predicted CSA rainfall using a non-linear statistical teleconnection artificial neural network–genetic algorithm model. At 3 month lead time, correlations of between 0.8 and 0.9, root-mean-square errors of between 0.4 and 0.9 and Hansen Kuipers skill scores of between 0.4 and 0.8 were obtained between observed and predicted CSA rainfall. Copyright © 2004 Royal Meteorological Society

[1]  Yan Wang,et al.  Temporal structure of the southern oscillation as revealed by waveform and wavelet analysis , 1996 .

[2]  W. Landman,et al.  Change in the association between Indian Ocean sea‐surface temperatures and summer rainfall over South Africa and Namibia , 1999 .

[3]  N. Huang,et al.  The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis , 1998, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[4]  M. Jury,et al.  Teleconnections modulating inter‐annual climate variability over northern Namibia , 1999 .

[5]  S. Mason,et al.  The occurrence and predictability of droughts over southern Africa. , 2000 .

[6]  Michael E. Mann,et al.  Interannual Temperature Events and Shifts in Global Temperature: A ''Multiwavelet'' Correlation Approach , 2000 .

[7]  A. Barnston,et al.  Long-Lead Forecasts of Seasonal Precipitation in Africa Using CCA , 1996 .

[8]  B. Bakshi.  Multiscale PCA with application to multivariate statistical process monitoring , 1998 .

[9]  M. B. Priestley,et al.  Non-linear and non-stationary time series analysis , 1990 .

[10]  P. Webster,et al.  The monsoon as a self-regulating coupled ocean—atmosphere system , 2002 .

[11]  Simon J. Mason,et al.  Sea-surface temperature — South African rainfall associations, 1910–1989 , 1995 .

[12]  John E. Kutzbach,et al.  Empirical Eigenvectors of Sea-Level Pressure, Surface Temperature and Precipitation Complexes over North America , 1967 .

[13]  James L. McClelland,et al.  Parallel distributed processing: explorations in the microstructure of cognition, vol. 1: foundations , 1986 .

[14]  Laurence C. Smith,et al.  Stream flow characterization and feature detection using a discrete wavelet transform , 1998 .

[15]  W. Landman,et al.  Retro‐active skill of multi‐tiered forecasts of summer rainfall over southern Africa , 2001 .

[16]  C. Ropelewski,et al.  Global and Regional Scale Precipitation Patterns Associated with the El Niño/Southern Oscillation , 1987 .

[17]  Willem A. Landman,et al.  Statistical downscaling of monthly forecasts , 2000 .

[18]  M. Ward,et al.  Towards the prediction of the East Africa short rains based on sea‐surface temperature–atmosphere coupling , 1998 .

[19]  William W. Hsieh,et al.  Applying Neural Network Models to Prediction and Data Analysis in Meteorology and Oceanography. , 1998 .

[20]  T. Gan,et al.  NOTES AND CORRESPONDENCE Prediction of East African Seasonal Rainfall Using Simplex Canonical Correlation Analysis , 2003 .

[21]  C. Reason,et al.  Relationships between South African rainfall and SST anomalies in the Southwest Indian Ocean , 1999 .

[22]  M. Hulme.  Validation of Large-Scale Precipitation Fields in General Circulation Models , 1994 .

[23]  B. Zaake,et al.  A study of variability of annual river flow of the southern African region , 2001 .

[24]  S. Nicholson.  The nature of rainfall variability in Africa South of the Equator , 1986 .

[25]  M. Hulme,et al.  A 1961-90 climatology for Africa south of the equator and a comparison of PE estimates for the region , 1996 .

[26]  T. Gan,et al.  Prediction of East African Seasonal Rainfall Using Simplex Canonical Correlation Analysis , 2003 .

[27]  W. Lau,et al.  A Canonical Ensemble Correlation Prediction Model for Seasonal Precipitation Anomaly , 2001 .

[28]  L. Mysak,et al.  Atmosphere–Ocean Coupled Variability in the South Atlantic , 1997 .

[29]  C. Basalirwa.  Delineation of Uganda into climatological rainfall zones using the method of principal component analysis , 1995 .

[30]  M. Jury.  REGIONAL TELECONNECTION PATTERNS ASSOCIATED WITH SUMMER RAINFALL OVER SOUTH AFRICA, NAMIBIA AND ZIMBABWE , 1996 .

[31]  Yves M. Tourre,et al.  Characteristics of Low-Frequency Sea Surface Temperature Fluctuations in the Tropical Atlantic , 1992 .

[32]  C. Reason,et al.  Multidecadal Variability in the Climate System over the Indian Ocean Region during the Austral Summer. , 1995 .

[33]  C. Torrence,et al.  A Practical Guide to Wavelet Analysis. , 1998 .

[34]  Geoffrey E. Hinton,et al.  Learning internal representations by error propagation , 1986 .

[35]  P. Roucou,et al.  Modification of the southern African rainfall variability/ENSO relationship since the late 1960s , 2000 .

[36]  David E. Goldberg,et al.  Genetic Algorithms in Search Optimization and Machine Learning , 1988 .