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Gitau W, Camberlin P, Ogallo L, Okoola R. "Oceanic and Atmospheric Linkages with Short Rainfall Season Intraseasonal Statistics over Equatorial Eastern Africa and their Predictive Potential." International Journal of Climatology. 2015;35(9):2382-2399. AbstractRoyal Meteorological Society

Despite earlier studies over various parts of the world including equatorial Eastern Africa (EEA) showing that intraseasonal statistics of wet and dry spells have spatially coherent signals and thus greater predictability potential, no attempts have been made to identify the predictors for these intraseasonal statistics. This study therefore attempts to identify the predictors (with a 1‐month lead time) for some of the subregional intraseasonal statistics of wet and dry spells (SRISS) which showed the greatest predictability potential during the short rainfall season over EEA. Correlation analysis between the SRISS and seasonal rainfall totals on one hand and the predefined predictors on the other hand were initially computed and those that were significant at 95% confidence levels retained. To identify additional potential predictors, partial correlation analyses were undertaken between SRISS and large‐scale oceanic and atmospheric fields while controlling the effects of the predefined predictors retained earlier. Cross‐validated multivariate linear regression (MLR) models were finally developed and their residuals assessed for independence and for normal distribution. Four large‐scale oceanic and atmospheric predictors with robust physical/dynamical linkages with SRISS were identified for the first time. The cross‐validated MLR models for the SRISS of wet spells and seasonal rainfall totals mainly picked two of these predictors around the Bay of Bengal. The two predictors combined accounted for 39.5% of the magnitude of the SST changes between the July–August and October–November–December periods over the Western Pole of the Indian Ocean Dipole, subsequently impacting EEA rainfall. MLR models were defined yielding cross‐validated correlations between observed and predicted values of seasonal totals and number of wet days ranging from 0.60 to 0.75, depending on the subregion. MLR models could not be developed over a few of the subregions suggesting that the local factors could have masked the global and regional signals encompassed in the additional potential predictors.

Philippon N, Camberlin P, Moron V, Gitau W, Ozer P. "Recent Evolution of the March-May Rainfall in East Africa: Spatial Patterns and Sub-seasonal Scenarios." Actes du 27e Colloque International de l'Association Internationale de Climatologie. 2014:687-692. AbstractORBi

Using raingauge daily rainfall data documenting the Horn of Africa and the Long Rains over the period 1961-2012, the aim of this study is three-fold:1/ confirming the drying trend detected by Lyon et DeWitt (2012) during the Long Rains using gridded rainfall, 2/ understanding how this drying is expressed at the intraannual time scale using the sub-seasonal scenario approach developed by Moron et al. (2013) and 3/ assess its impact on vegetation. A drying is actually measured using raingauge data but is less severe than the one measured using gridded data. It is the strongest at the driest stations and during the rainfall climatological peak (April). It seems to be associated with a higher frequency of the dry subseasonal scenarios i.e. characterized by negative rainfall anomalies through the whole or the core of the seasonal cycle. But we don't observe yet a diminution of the vegetation photosynthetic activity in response to the rainfall decrease. To the contrary, the Rainfall Use Efficiency (RUE) displays a slightly positive trend.

PROF CAMBERLIN PIERRE, DR GITAU WILSON, DR OETTLI PASCAL, PROF OGALLO LABAN, DR BOIS BENJAMIN. "Spatial interpolation of daily rainfall stochastic generation parameters over East Africa." Climate Research. 2014;59(1):39-60.Abstract weblink
MR ONGOMA VICTOR, PROF MUTHAMA JOHN, DR GITAU WILSON. "Evaluation of urbanization influences on the urban winds of Kenyan cities." Ethiopian Journal of Environmental studies and Management . 2013;6(2):223-231.Abstract weblink
MR ONGOMA VICTOR, PROF MUTHAMA JOHN, DR GITAU WILSON. "Evaluation of urbanization influences on urban temperature of Nairobi City, Kenya." Global Meteorology. 2013;2(1):1-5.Abstract weblink
DR GITAU WILSON, PROF OGALLO LABAN, PROF CAMBERLIN PIERRE, DR OKOOLA RAPHAEL. "Spatial coherence and potential predictability assessment of intraseasonal statistics of wet and dry spells over Equatorial Eastern Africa." International Journal of Climatology. 2013;33(12):2690-2705.Abstract weblink
DR GITAU WILSON, DR OLUDHE CHRISTOPHER, PROF OGALLO LABAN, MR ATHERU ZACHARY, MR AMBENJE PETER. "[Regional Climates] Eastern Africa [in "State of the Climate in 2011"]." Bulletin of America Meteorological Society. 2012;93(7):S180-S182.
MR GITAU WILSON. Diagnosis and Predictability of Intraseasonal characteristics of wet and dry spells over Equatorial East Africa. PROF OGALLO LABAN, PROF CAMBERLIN PIERRE, DR OKOOLA RAPHAEL, eds. Nairobi: University of Nairobi; 2011.
DR OLUDHE CHRISTOPHER, PROF OGALLO LABAN, MR AMBENJE PETER, MR ATHERU ZACHARY, DR GITAU WILSON. "[Regional Climates] Eastern Africa [in "State of the Climate in 2010"]." Bulletin of America Meteorological Society. 2011;92(6):S194-S196.
DR. CHRISTOPHER-OLUDHE, PROF. LABAN-OGALLO, MR. PETER-AMBENJE, MR. ZACHARY-ATHERU, MR. WILSON-GITAU. "[Regional Climates] Eastern Africa [in "State of the Climate in 2009"]." Bulletin of America Meteorological Society. 2010;91(7):S154-S156.
Githui F, Gitau W, Mutua F, Bauwens W. "Climate Change Impact on SWAT Simulated Streamflow in Western Kenya." International Journal of Climatology. 2009;29(12):1823-1834. AbstractRoyal Meteorological Society

Weather and climate extremes such as droughts and floods have far reaching impacts in Kenya. They havehad implications in a variety of sectors including agriculture, water resources, health, energy, and disaster managementamong others. Lake Victoria and its catchment support millions of people and any impact on its ability to support thelivelihoods of the communities in this region is of major concern. Thus, the main objective of this study was to assess thepotential future climatic changes on the Nzoia catchment in the Lake Victoria basin, and how they might affect streamflow.The Soil and Water Assessment Tool was used to investigate the impact of climatic change on streamflow of the study area.The model was set up using readily available s patial and temporal data, and calibrated against measured daily streamflow.Climate change scenarios were obtained from general circulation models.Results obtained showed increased amounts of annual rainfall for all the scenarios but with variations on a monthlybasis. All – but one – global circulation models (GCMs) showed consistency in the monthly rainfall amounts. Rainfall washigher in the 2050s than in the 2020s. According to climate change scenarios, temperature will increase i n t his region,with the 2050s experiencing much higher increases than the 2020s with a monthly temperature change range of 0–1.7°C.The range of change in mean annual rainfall o f 2.4–23.2% corresponded to a change in streamflow of about 6–115%. Theanalysis revealed important rainfall–runoff linear relationships for certain months that could be extrapolated to estimateamounts of streamflow under various scenarios of change in rainfall. Streamflow response was not sensitive to changesin temperature. If all other variables, e.g. land cover, population growth etc., were held constant, a significant increase instreamflow may be expected in the coming decades as a consequence of increased rainfall amounts. Copyright 2008Royal Meteorological SocietyKEY WORDS climate change; streamflow; runoff; general circulation models; hydrology; modelling

DR. PIERRE-CAMBERLIN, DR. VINCENT-MORON, DR. RAPHAEL-OKOOLA, DR. NATHALIE-PHILIPHON, MR. WILSON-GITAU. "Components of rainy seasons variability in Equatorial East Africa: Onset, cessation, rainfall frequency and intensity." Theoretical and Applied Climatology. 2009;98(3-4):237-249.Weblink
MR. WILSON-GITAU. "Trends of the intra-seasonal statistics of daily rainfall over East Africa.". In: African drought: Observations, Modeling, Predictability and Impacts. ICTP-UNESCO, Trieste, Italy: International Journal of Climatology; 2008.
DR. FAITH-GITHUI, MR. WILSON-GITAU, PROF. WILLY-BAUMENS, PROF. FRANCIS-MUTUA. "Climate change impact on SWAT simulated streamflow in Western Kenya." International Journal of Climatology. 2008;29(12):1823-1834.Weblink
DR. WILSON-GITAU, PROF. LABAN-OGALLO, DR. JOSEPH-MUTEMI. "Intraseasonal characteristics of wet and dry spells over Kenya." Journal of Meteorology and Related Sciences. 2008;2(1):18-28.Weblink
MR WILSON-GITAU. "Influence of the wet spells on the Lake Levels.". In: Young Water Professionals (YWP) workshop in support of the 4th World Lake Conference. KCCT, Mbagathi, Nairobi, Kenya: International Journal of Climatology; 2005.
MR GITAU WILSON. Characteristics of the wet and dry spells during the wet seasons over Kenya. PROF OGALLO LABAN, DR MUTEMI JOSEPH, eds. Nairobi: University of Nairobi; 2005.
MR. WILSON-GITAU. "Towards the stabilization of price and income from agricultural products.". In: Weather Risks and Actuarial Valuation workshop. SPS Boardroom, Chiromo Campus, Nairobi, Kenya: International Journal of Climatology; 2003.

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