Diagnosis of Seasonal Rainfall Variability over East Africa: A Case Study of 2010-2011 Drought over Kenya

V. Ongoma, T Guirong, B A Ogwang, J P Ngarukiyimana

Abstract


The primary objective of this study was to investigate the recent climate variability over the East African region; with focus on the 2010-2011 rainfall failure over Kenya. The seasonal rainfall over the region is bimodal, mainly influenced by the Inter-Tropical Convergence Zone (ITCZ) and El-Nino Southern Oscillation (ENSO).The observed rainfall in October – December (OND) 2010 and March-May (MAM) 2011 was below normal with respect to the respective long term means (LTMs). The low level divergence was observed during 2010 OND, especially in the eastern and western parts of the country. Although the western parts of the country experienced low level convergence during MAM, the south easterlies that partly transport moisture from the Indian Ocean were generally observed to be very strong as compared to the seasonal climatology. The condition reduces the chances of low level convergence, leading to a reduction in rainfall. Relative humidity was noted to be below normal in the northeastern sector of the study area, as opposed to the western sector where it was above normal. This is associated with the observed positive anomaly of rainfall in the western sector. The combination of the observed phenomena led to the observed drought in 2010 - 2011 over most parts of the country. Similar phenomena should be keenly monitored in future especially during seasonal weather forecasting to detect the possible occurrence of drought for planning purposes.

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Asnani, G.C., 1993: Tropical Meteorology, G.C. Asnani, Pune, India, 1202 pp. Camberlin, P., and R.E. Okoola, 2003: The onset and cessation of the ‘long rains’ in eastern Africa and their interannual variability. Theor. Appl. Climatol., 75, 43-54. Davies, T.D., C.E. Vincent, and A.K.C. Beresford, 1985: July-August rainfall in west-central Kenya. Int. J. Climatol., 5, 17–33 Dee, D.P., S.M. Uppala, A.J. Simmons, P. Berrisford, P. Poli, S. Kobayashi, U. Andrae, M.A. Balmaseda, G. Balsamo, P. Bauer, P. Bechtold, A. Beljaars, L. van de Berg, J. Bidlot, N. Bormann, C. Delsol, R. Dragani, M. Fuentes, A.J. Geer, L. Haimberger, S. Healy, H. Hersbach, E.V. Holm, L. Isaksen, P. Kallberg, M. Koehler, M. Matricardi, A.P. McNally, B.M. MongeSanz, J.J. Morcrette, C. Peubey, P. de Rosnay, C. Tavolato, J.N. Thepaut, and F. Vitart, 2011: The ERA-Interim reanalysis: Configuration and performance of the data assimilation system, Q. J. Roy. Meteorol. Soc., 137, 553-597. Eguru, A., 2012: Water Productivity in Agriculture: Challenges and Opportunities for Smallholder Farmers in the Drylands of Eastern and Southern Africa, Report, University of Nairobi, Kenya, 21 pp. Fox, P., and J. Rockström, 2005: Risk analysis and economic viability of water harvesting for supplemental irrigation in semi-arid Burkina Faso and Kenya. Agric Systems, 83, 231–250. Funk, C., G. Senay, A. Asfaw, J. Verdin, J. Rowland, J. Michaelson, G. Eilerts, D. Korecha, and R. Choularton, 2005: Recent Drought Tendencies in Ethiopia and Equatorial-Subtropical Eastern Africa Famine Early Warning System Network (Washington, DC: USAID) Funk, C., M.D. Dettinger, J.C. Michaelsen, J.P. Verdin, M.E. Brown, M. Barlow, and A. Hoell, 2008: Warming of the Indian Ocean threatens eastern and southern African food security but could be mitigated by agricultural development. Proc. Natl. Acad. Sci., 105, 1–6 Harris, I., P.D. Jones, T.J. Osborn, and D.H. Lister, 2013: Updated high-resolution grids of monthly climatic observations-the CRU TS3.10 Dataset. Int. J. Climatol., 34(3), 623-642 Hastenrath, S., D., Polzin and C. Mutai, 2010: Diagnosing the Droughts and Floods in Equatorial East Africa during Boreal Autumn 2005-08. J. Climate, 23, 813-817. DOI: 10.1175/2009JCLI3094.1 Hastenrath, S., D. Polzin, and C. Mutai, 2006: Diagnosing the 2005 Drought in Equatorial East Africa. J. Climate, 20, 4628 - 4637. Hillbruner, C., and G. Moloney, 2012: When early warning is not enough-lessons learned from the 2011 Somalia famine. Glob. Food Security, 1, 20-28 Huho, J.M., J.K. Ngaira, and H.O. Ogindo, 2011: Living with drought: the case of the Maasai pastoralists of northern Kenya. Educ. Res. 2, 779-789 Indeje, M., F.H.M. Semazzi, and L.J. Ogallo, 2000: ENSO signals in East African rainfall seasons Int. J. Climatol., 20, 19 - 46 Indeje, M., F.H.M. Semazzi, L. Xie, and L.J. Ogallo, 2001: Mechanistic model simulations of the East African Climate using NCAR Regional Climate Model: Influence of large scale orography on the Turkana Low-Level Jet. J. Climate, 14, 2710 -2724. Koumare, I., 2014: Temporal/Spatial Distribution of Rainfall and the Associated Circulation Anomalies over West Africa. Pak. J. Meteorol., 10, 1 -11. Lautze, S., Bell, W., Alinovi, L., and L. Russo, 2012: Early warning, late response (again): the 2011 famine in Somalia. Glob. Food Security, 1, 43-49. Lu, E., and E.S. Takle, 2010: Concurrent variations of water vapor and temperature corresponding to the interannual variation of precipitation in the North American Regional Reanalysis., J. Geophys. Res, 115, D11101, doi:10.1029/2009JD012956

Lyon, B., and D.G. DeWitt, 2012: A recent and abrupt decline in the East African long rains. Geophys. Res. Lett., 39(2). L02702. Lott, F.C, N. Christidis, and P.A. Stott, 2013: Can the 2011 East African drought be attributed to human-induced climate change? Geophys. Res. Lett. 40, 1177 – 1181 Mosley, J., 2012: Translating famine early warning into early action: an East Africa case study. www.chathamhouse.org/sites/default/files/public/Research/Africa/1112pp_mosley.pdf (Accessed 9 November 2014). Mukabana, J.R., and R.A. Pielke, 1996: Investigating the influence of synoptic-scale monsoonal winds and mesoscale circulations on diurnal weather patterns over Kenya using a mesoscale numerical model. Mon. Wea. Rev., 124, 224-243. Mutai, C.C., M.N. Ward, and A.W. Colman, 1998: Towards the prediction of East African short rains based on sea surface temperature-atmosphere coupling. Int. J. Climatol., 17:117–135 Mutemi, J.N., 2003: Climate anomalies over eastern Africa associated with various ENSO evolution phases: Ph.D. Thesis, University of Nairobi, Kenya Ngetich, K.F., M. Mucheru-Muna, J.N. Mugwe, C.A. Shisanya, J. Diels, and D.N. Mugendi, 2014: Length of growing season, rainfall temporal distribution, onset and cessation dates in the Kenyan highlands. Agric. Forest Meteorol., 188, 24–32. http://dx.doi.org/10.1016/j.agrformet. 2013.12.011 Nicholson, S.E., and J. Kim, 1997: The relationship of the El-Nino Southern Oscillation to African rainfall. Int. J. Climatol., 17, 117-135. Nicholson, S.E., 2014: A detailed look at the recent drought situation in the Greater Horn of Africa. J. Arid Environ. 103, 71-79. http://dx.doi.org/10.1016/j.jaridenv.2013.12.003 Nyakwada, W., 2009: Predictability of East African seasonal rainfall with sea surface temperature gradient modes. PhD Thesis, University of Nairobi, Kenya. Oettli, P., and P. Camberlin, 2005: Influence of topography on monthly rainfall distribution over East Africa. Clim. Res., 28, 199 - 212. Ogallo, L.J, and C. Oludhe, 2009: Climate information in decision making in the greater horn of Africa: lessons and experiences. WMO Bull. 58(3), 1-5 Ogallo, L.J. 1989: The spatial and temporal patterns of the Eastern Africa seasonal rainfall derived from principal component analysis. Int. J. Climatol., 9, 145-167. Ogwang, B.A., T. Guirong, and C. Haishan, 2012: Diagnosis of September - November Drought and the Associated Circulation Anomalies Over Uganda. Pak. J. Meteorol., 9, 11-24 Ogwang, B.A., H. Chen, X. Li, and C. Gao, 2014: The influence of Topography on East African October to December climate: Sensitivity experiments with RegCM4. Adv. Meteorol., doi:10.1155/2014/143917. Ogwang B.A., H. Chen, X. Li and C. Gao, 2015: Evaluation of the capability of RegCM4.0 in simulating East African climate. Theor. Appl. Climatol., DOI 10.1007/s00704-015-1420-3 Okoola, R.E., 1996: Space-Time Characteristics of ITCZ over Equatorial East Africa during anomalous rainfall years. PhD. Thesis, University of Nairobi, Kenya Okoola, R.E., 1999: A diagnostic study of the eastern Africa monsoon circulation during the northern hemisphere spring season. Int. J. Climatol., 19, 143-168. Ongoma V., 2013: A review on the Effects of Climate Change on occurrence of Aflatoxin and its impacts on Food Security in Semi-Arid Areas of Kenya. Int. J. Agric. Sci. Res., 2, 307-311 Owiti, Z., and W. Zhu, 2012: Spatial distribution of rainfall seasonality over East Africa. J. Geogr. Reg. Plann., 5, 409-421.

Rasmusson, E.M., and T.H. Carpenter, 1982: Variation in tropical seas surface temperature and surface winds associated with the southern oscillation/El Nino. Mon. Wea. Rev., 110, 354 - 384. Schreck, J.C, and F.H.M. Semazzi, 2004: Variability of the Recent Climate of Eastern Africa. Int. J. Climatol., 24, 681-701. Shisanya, C.A., C. Recha, and A. Anyamba, 2011: Rainfall Variability and Its Impact on Normalized Difference Vegetation Index in Arid and Semi-Arid Lands of Kenya. Int. J. Geosci., 2, 36-47. Verdin, J., C. Funk, G. Senay, and R. Choularton, 2005: Climate science and famine early warning. Philos. Trans. Roy. Soc. London, 360B, 2155 - 2168. Ververs, M.T., 2012: The East African food crisis: did regional early warning systems function? J. Nutr. 142, 131-133. Williams, A.P., and C. Funk, 2011: A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa. Clim. Dyn., 37, 2417-2435.


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