East African Rainfall Anomaly Patterns in Association with El Niño/Southern Oscillation
Publication: Journal of Hydrologic Engineering
Volume 9, Issue 4
Abstract
By applying harmonic analysis to El Niño–Southern Oscillation (ENSO) composites of the 6-month Standardized Precipitation Index (SPI) and rainfall anomalies for the 1900–1996 period, and based on the 90% confidence limits established from bootstrap resampling, it was found that ENSO responses in East African rainfall are region and season dependent, and the influence of El Niño is stronger and opposite that of La Niña. Among five regions of unique ENSO responses identified, northeastern (R4) and southern Tanzania (R5) seem to have the most consistent (in terms of vector coherence, percentage of variance extracted by the first harmonic, and SPI magnitude) ENSO responses. R5 experiences positive (negative) response under La Niña (El Niño) influence during January and June of the post-ENSO year. Southern Uganda and much of the Lake Victoria basin show some significant positive ENSO response for November, December, and January. The temporal and regional patterns of ENSO response periods were also analyzed using the index time series and boxplots on the 6-month SPI. Boxplots confirm a shift in the distribution of 6-month SPI between ENSO and non-ENSO affected seasons.
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References
Basalirwa, C. P. K.(1995). “Delineation of Uganda into climatological rainfall zones using the method of principal component analysis.” Int. J. Climatol.,15, 1161–1177.
Dracup, J. A., and Kahya, E.(1994). “The relationships between U.S. streamflow and La Niña events.” Water Resour. Res., 30(7), 2133–2141.
East African Meteorological Department. (1963). “Climatic seasons of East Africa.” Rep. No. 8, Nairobi, Kenya.
Edwards, C. D., and McKee, B. T. (1997). “Characteristics of 20th century drought in the United States at multiple time scales.” Atmospheric Science Paper No. 634, Climatology Rep. No. 97-2, Dept. of Atmospheric Sciences, Colorado State Univ., Fort Collins, Colo.
Efron, B. (1982). “The jackknife, the bootstrap, and other re-sampling plans.” Proc., CBMS-NSF Regional Conf. Series in Applied Mathematics, Society Ind. and Appl. Maths, Vol. 38, Philadelphia.
Efron, B., and Tibishirani, R. J. (1993). An introduction to the bootstrap, Chapman and Hall, San Francisco.
Halpert, M. S., and Ropeleweski, C. F.(1992). “Surface temperature patterns associated with the Southern Oscillation.” J. Clim., 5, 577–593.
Hosking, J. R. M., and Wallis, J. R. (1997). Regional flood frequency analysis: An approach based on L-moments, Cambridge University Press, Cambridge, U.K.
Hulme, M. (1994). “Validation of large-scale precipitation fields in general circulation models.” Global precipitations and climate change, M. Desbois and F. Desalmand, eds., Springer, Berlin, 387–406.
Indejje, M., Semazzi, H. M. F., and Ogallo, L. J.(2000). “ENSO signals in East African rainfall seasons.” Int. J. Climatol.,20, 19–46.
International CLIVAR Project Office (CLIVAR). (1999). “Climate research for Africa.” WCRP Informal Rep. No. 16/1999, Southampton, U.K.
Mathsoft. (1997). S-PLUS 4: Guide to statistics, Data Analysis Products Division, Seattle.
McKee, T. B., Doesken, N. J., and Kleist, J. (1993). “The relationship of drought frequency and duration to time scales.” Preprints, 8th Conf. on Applied Climatology, Anaheim, Calif., 179–184.
Mutai, C. C., Ward, M. N., and Colman, A. W.(1998). “Towards the prediction of the East Africa short rains based on sea-surface temperature-atmosphere coupling.” Int. J. Climatol.,18, 975–997.
Ntale, H. K. (2001). “The analysis and prediction of droughts in East Africa.” PhD thesis, Univ. of Alberta, Edmonton, Ale., Canada.
Ntale, H. K., and Gan, T. Y.(2003). “Drought indices and their application to East Africa.” Int. J. Climatol.,23(11), 1335–1357.
Nicholson, S. E., and Kim, J.(1997). “The relationship of El Niño–Southern Oscillation to African rainfall.” Int. J. Climatol.,17, 117–135.
Nicholson, S. E., and Selato, J. C.(2000). “The influence of La Niña on African rainfall.” Int. J. Climatol.,20, 1761–1776.
Ogallo, L. J.(1988). “Relationship between seasonal rainfall in East Africa and Southern Oscillation.” Int. J. Climatol.,8, 34–43.
Panofsky, H. A., and Brier, G. W. (1965). Some applications of statistics in meteorology, Penn State Univ., College Park, Pa.
Piechota, T. C., and Dracup, J. A.(1996). “Drought and regional hydrologic variation in the United States: Associations with the El Niño–Southern Oscillation.” Water Resour. Res., 32, 1359–1373.
Rasmusson, E. M., and Carpenter, T. H.(1983). “The relation between Eastern equatorial Pacific Sea surface temperature and rainfall over India and Sri Lanka.” Mon. Weather Rev., 111, 517–528.
Rasmusson, E. M., and Wallace, J. M.(1983). “Meteorological aspects of El Niño/Southern Oscillation.” Science, 222, 1195–1202.
Rayner, J. N. (1971). An introduction to spectral analysis, Pion, London.
Ropeleweski, C. F., and Halpert, M. S.(1986). “North American precipitation and temperatures patterns associated with El Niño/Southern Oscillation.” Mon. Weather Rev., 114, 2352–2362.
Ropeleweski, C. F., and Halpert, M. S.(1987). “Global and regional scale precipitation patterns associated with El Niño/Southern Oscillation.” Mon. Weather Rev., 115, 1606–1626.
Ropeleweski, C. F., and Halpert, M. S.(1996). “Quantifying Southern Oscillation–precipitation relationships.” J. Clim., 9, 1043–1059.
Thiaw, W. M., Barnston, A. G., and Kumar, V.(1999). “Predictions of African rainfall on the seasonal timescale.” J. Geophys. Res., 104(24), 31589–31597.
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Published In
Journal of Hydrologic Engineering
Volume 9 • Issue 4 • July 2004
Pages: 257 - 268
Copyright
Copyright © 2004 American Society of Civil Engineers.
History
Received: Sep 10, 2002
Accepted: Sep 19, 2003
Published online: Jun 15, 2004
Published in print: Jul 2004
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