Climate extremes have increased in the recent past and they are further being exacerbated by climate change and variability. In this paper, we sought to determine rainfall characteristics over the Lake Victoria Basin of Kenya in 1987-2016, as a basis of understanding climate variability. The methodology used included; Standardized Precipitation Index to depict variability, coefficient of variation for spatial analysis and the Mann-Kendall test to test the presence of trends in data. We established that Lake Victoria basin is relatively wet through-out the year, with two distinct rainfall seasons March-April-May (MAM) and October-November-December (OND) that support human livelihood and ecology. The normal wetness conditions have declined over time, paving way for both dry and wet extremes conditions between 1997-1998 and 2002-2006, respectively. The rainfall extremes have become frequent in the last decade in 2007-2016. We also established a decline in the MAM rainfall seasons, and an increase during the October-December rainfall seasons in 1987-2016. Furthermore, the number of rainy days has declined with the onset and cessations of both long rains and short rains having shown a variability of at least 50% and 30% respectively, in a range of about 100 to 200 Julian days. The decline in wet condition is likely to affect economic activities especially the rainfed agriculture. The changing rainfall trends over the basin therefore, call for proper human livelihood planning and ecological monitoring in order to achieve ecological sustainability.
References
[1]
A Müller, C., Cramer, W., Hare, W.L. and Lotze-Campen, H. (2011) Climate Change Risks for African Agriculture. Proceedings of the National Academy of Sciences, 108, 4313-4315. https://doi.org/10.1073/pnas.1015078108
[2]
Awange, J.L., Anyah, R., Agola, N., Forootan, E. and Omondi, P. (2013) Potential Impacts of Climate and Environmental Change on the Stored Water of Lake Victoria Basin and Economic Implications. Water Resources Research, 49, 8160-8173. https://doi.org/10.1002/2013WR014350
[3]
Shongwe, M.E., van Oldenborgh, G.J., van den Hurk, B. and van Aalst, M. (2011) Projected Changes in Mean and Extreme Precipitation in Africa under Global Warming. Part II: East Africa. Journal of Climate, 24, 3718-3733. https://doi.org/10.1175/2010JCLI2883.1
[4]
Tennant, W.J. and Hewitson, B.C. (2002) Intra-Seasonal Rainfall Characteristics and Their Importance to the Seasonal Prediction Problem. International Journal of Climatology: A Journal of the Royal Meteorological Society, 22, 1033-1048. https://doi.org/10.1002/joc.778
[5]
Boko, M., Niang, I., Nyong, A., Vogel, A., Githeko, A., Medany, M., Yanda, P.Z., et al. (2018) Africa Climate Change 2007: Impacts, Adaptation and Vulnerability: Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.
[6]
Lyon, B. and DeWitt, D.G. (2012) A Recent and Abrupt Decline in the East African Long Rains. Geophysical Research Letters, 39, L02702. https://doi.org/10.1029/2011GL050337
[7]
Thornton, P.K., Jones, P.G., Alagarswamy, G., Andresen, J. and Herrero, M. (2010) Adapting to Climate Change: Agricultural System and Household Impacts in East Africa. Agricultural Systems, 103, 73-82. https://doi.org/10.1016/j.agsy.2009.09.003
[8]
Schlesinger, M.E. (2012) Physically-Based Modelling and Simulation of Climate and Climatic Change. Volume 243, Springer Science & Business Media, New York.
[9]
Otieno, G., Mutemi, J.N., Opijah, F.J., et al. (2020) The Sensitivity of Rainfall Characteristics to Cumulus Parameterization Schemes from a WRF Model. Part I: A Case Study Over East Africa During Wet Years. Pure and Applied Geophysics, 177, 1095-1110. https://doi.org/10.1007/s00024-019-02293-2
[10]
Mugume, I., Waiswa, D., Mesquita, M.D.S., Reuder, J., Basalirwa, C., Bamutaze, Y., et al. (2017) Assessing the Performance of WRF Model in Simulating Rainfall over Western Uganda. Journal of Climatology and Weather Forecasting, 5, 197.
[11]
Marteau, R., Richard, Y., Pohl, B., Smith, C.C. and Castel, T. (2015) High-Resolution Rainfall Variability Simulated by the WRF RCM: Application to Eastern France. Climate Dynamics, 44, 1093-1107. https://doi.org/10.1007/s00382-014-2125-5
[12]
Gbode, I.E., Dudhia, J., Ogunjobi, K.O. and Ajayi, V.O. (2018) Sensitivity of Different Physics Schemes in the WRF Model during a West African Monsoon Regime. Theoretical and Applied Climatology, 136, 1-19. https://doi.org/10.1007/s00704-018-2538-x
[13]
Nicholson, S.E. (1996) A Review of Climate Dynamics and Climate Variability in Eastern Africa. In: The Limnology, Climatology and Paleoclimatology of the East African Lakes, Gordon and Breach Publishers, Amsterdam.
[14]
Hulme, M., Doherty, R., Ngara, T., New, M. and Lister, D. (2001) African Climate Change: 1900-2100. Climate Research, 17, 145-168. https://doi.org/10.3354/cr017145
[15]
Kendall, R.L. (1969) An Ecological History of the Lake Victoria Basin. Ecological Monographs, 39, 121-176. https://doi.org/10.2307/1950740
[16]
Kizza, M., Rodhe, A., Xu, C.Y., Ntale, H.K. and Halldin, S. (2009) Temporal Rainfall Variability in the Lake Victoria Basin in East Africa during the Twentieth Century. Theoretical and Applied Climatology, 98, 119-135. https://doi.org/10.1007/s00704-008-0093-6
[17]
Sylla, M.B., Giorgi, F., Coppola, E. and Mariotti, L. (2013) Uncertainties in Daily Rainfall over Africa: Assessment of Gridded Observation Products and Evaluation of a Regional Climate Model Simulation. International Journal of Climatology, 33, 1805-1817. https://doi.org/10.1002/joc.3551
[18]
Anyah, R.O. and Qiu, W. (2012) Characteristic 20th and 21st Century Precipitation and Temperature Patterns and Changes over the Greater Horn of Africa. International Journal of Climatology, 32, 347-363. https://doi.org/10.1002/joc.2270
[19]
Indeje, M., Semazzi, F.H.M, Ogallo, L.J. (2000) ENSO Signals in East African Rainfall Seasons. International Journal of Climatology, 20, 19-46. https://doi.org/10.1002/(SICI)1097-0088(200001)20:1<19::AID-JOC449>3.0.CO;2-0
[20]
Awange, J.L., Aluoch, J., Ogallo, L.A., Omulo, M. and Omondi, P. (2007) Frequency and Severity of Drought in the Lake Victoria Region (Kenya) and Its Effects on Food Security. Climate Research, 33, 135-142. https://doi.org/10.3354/cr033135
[21]
Odada, E.O., Ochola, W.O. and Olago, D.O. (2009) Drivers of Ecosystem Change and Their Impacts on Human Well-Being in Lake Victoria Basin. African Journal of Ecology, 47, 46-54. https://doi.org/10.1111/j.1365-2028.2008.01049.x
[22]
Williams, A.P., Funk, C., Michaelsen, J., Rauscher, S.A., Robertson, I., Wils, T.H., Koprowski, M., Eshetu, Z. and Loader, N.J. (2012) Recent Summer Precipitation Trends in the Greater Horn of Africa and the Emerging Role of Indian Ocean Sea Surface Temperature. Climate Dynamics, 39, 2307-2328. https://doi.org/10.1007/s00382-011-1222-y
[23]
Intergovernmental Panel on Climate Change (2007) Climate Change 2007: The Physical Science Basis: Contribution of Working Group 1 to the Fourth Assessment Report of the IPCC. Cambridge University Press, Cambridge.
[24]
Intergovernmental Panel on Climate Change (2014) Summary for Policymakers. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom, and New York.
[25]
United Nations Environmental Programme (2006) Lake Victoria Basin Environment Outlook: Environment and Development. UNEP, Nairobi.
[26]
Peterson, T.C., Easterling, D.R., Karl, T.R., Groisman, P., Nicholls, N., Plummer, N., Torok, S., Auer, I., Boehm, R., Gullett, D. and Vincent, L. (1998) Homogeneity Adjustments of in Situ Atmospheric Climate Data: A Review. International Journal of Climatology: A Journal of the Royal Meteorological Society, 18, 1493-1517. https://doi.org/10.1002/(SICI)1097-0088(19981115)18:13<1493::AID-JOC329>3.0.CO;2-T
[27]
Zhang, X., Zwiers, F.W. and Hegerl, G. (2009) The Influences of Data Precision on the Calculation of Temperature Percentile Indices. International Journal of Climatology: A Journal of the Royal Meteorological Society, 29, 321-327. https://doi.org/10.1002/joc.1738
[28]
R Core Team (2018) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/
[29]
World Meteorological Organization (2012) Standardized Precipitation Index User Guide, (WMO-No. 1090). World Meteorological Organization, Geneva, Switzerland.
[30]
Liebmann, B., Bladé, I., Kiladis, G.N., Carvalho, L.M., Senay, G.B., Allured, D., Leroux, S. and Funk, C. (2012) Seasonality of African Precipitation from 1996 to 2009. Journal of Climate, 25, 4304-4322. https://doi.org/10.1175/JCLI-D-11-00157.1
[31]
Ogallo, L.A., Omondi, P., Ouma, G. and Wayumba, G. (2018) Climate Change Projections and the Associated Potential Impacts for Somalia. American Journal of Climate Change, 7, 153. https://doi.org/10.4236/ajcc.2018.72011
[32]
Mbungu, W., Ntegeka, V., Kahimba, F.C., Taye, M. and Willems, P. (2012) Temporal and Spatial Variations in Hydro-Climatic Extremes in the Lake Victoria Basin. Physics and Chemistry of the Earth, Parts A/B/C, 50, 24-33. https://doi.org/10.1016/j.pce.2012.09.002
[33]
Camberlain, P., Janicot, S. and Poccard, I. (2001) Seasonality and Atmospheric Dynamics of the Teleconnection between African Rainfall and Tropical Sea-Surface Temperature: Atlantic vs. ENSO. International Journal of Climatology, 21, 973-1005. https://doi.org/10.1002/joc.673
[34]
Indeje, M., Semazzi, F.H.M. and Ogallo, L.J. (2000) ENSO Signals in East African Rainfall Seasons. International Journal of Climatology, 20, 19-46. https://doi.org/10.1002/(SICI)1097-0088(200001)20:1<19::AID-JOC449>3.0.CO;2-0
[35]
Ongoma, V., Chen, H. and Omony, G.W. (2018) Variability of Extreme Weather Events over the Equatorial East Africa: A Case Study of Rainfall in Kenya and Uganda. Theoretical and Applied Climatology, 131, 295-308. https://doi.org/10.1007/s00704-016-1973-9
[36]
Hulme, M. (1992) Rainfall Changes in Africa: 1931-1960 to 1961-1990. International Journal of Climatology, 12, 685-699. https://doi.org/10.1002/joc.3370120703
[37]
Anyamba, A., Tucker, C.J. and Mahoney, R. (2002) From El Niño to La Niña: Vegetation Response Patterns over East and Southern Africa during the 1997-2000 Period. Journal of Climate, 15, 3096-3103. https://doi.org/10.1175/1520-0442(2002)015<3096:FENOTL>2.0.CO;2
[38]
Camberlin, P. and Okoola, R. (2003) The Onset and Cessation of the “Long Rains” in Eastern Africa and Their Inter-Annual Variability. Theoretical and Applied Climatology, 75, 43-54. https://doi.org/10.1007/s00704-002-0721-5
