Abstract: Variations in weather and climate have a significant impact on rain-fed banana yields in East Africa. This study examined empirical linkages between banana yields and variations in rainfall and temperature over Uganda for the historical period (1971-2009)
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Publication Date: 2012
Abstract: This study evaluates the ability of 10 regional climate models (RCMs) from the Coordinated Regional Climate Downscaling Experiment (CORDEX) in simulating the characteristics of rainfall patterns over eastern Africa. The seasonal climatology, annual rainfall cycles, and interannual variability of RCM output have been assessed over three homogeneous subregions against a number of observational datasets. The ability of the RCMs in simulating large-scale global climate forcing signals is further assessed by compositing the El Nino–Southern Oscillation (ENSO) and Indian Ocean dipole (IOD) ~ events. It is found that most RCMs reasonably simulate the main features of the rainfall climatology over the three subregions and also reproduce the majority of the documented regional responses to ENSO and IOD forcings. At the same time the analysis shows significant biases in individual models depending on subregion and season; however, the ensemble mean has better agreement with observation than individual models. In general, the analysis herein demonstrates that the multimodel ensemble mean simulates eastern Africa rainfall adequately and can therefore be used for the assessment of future climate projections for the region
Publication Date: 2012
Abstract: Recent special reports on climate extremes have shown evidences of changes in the patterns of climate extremes at global, regional and local scales. Understanding the characteristics of climate extremes at regional and local levels is critical not only for the development of preparedness and early warning systems, but is also fundamental in the development of any adaptation strategies. There is still very limited knowledge regarding the past, present and future patterns of climate extremes in the Greater Horn of Africa (GHA). This study, which was supported by the World Bank Global Facility for Disaster Reduction and Recovery (WB-GFDRR) and implemented by the World Meteorological Organization, was organized in terms of three workshops with three main objectives; (1) analysis of daily rainfall and temperature extremes for ten countries in the GHA region using observed in situ data running from 1971 to 2006, (2) assessing whether the United Kingdom Met-office and Hadley centre Providing REgional Climates for Impact Studies (UK-PRECIS) modelling system can provide realistic representation of the past and present climate extremes as observed by available in situ data, and (3) studying the future regional climate extremes under different scenarios to further assess the expected changes in climate extremes. This paper, therefore, uses the outputs of these workshops and also includes post-workshop analyses to assess the changes of climate extremes within the GHA. The results showed a significant decrease in total precipitation in wet days greater than 1 mm and increasing warm extremes, particularly at night, while cold extremes are decreasing. Considering a combination of geophysical models and satellite gravimetry observations from the Gravity Recovery and Climate Experiment (GRACE) mission in the frame of GRACE daily Kalman-smoothing models, for the years 2002 to 2010, we explored a decline in total water storage variations over the GHA.
Publication Date: 2013
Abstract: Impacts of Climate change and the associated vulnerabilities have increasingly become significant environmental issues of concern across the globe. Climate change is one of the greatest impediments to the realization of the first Millennium Development Goal of reducing poverty and food insecurity globally since it directly influences agricultural production and community livelihoods. Africa is highly vulnerable and especially the arid and semi arid lands which have low adaptive capacities. Approximately 80% of the African population is dependent on agriculture which it is currently facing myriad of challenges ranging from climate change to technology adoption. The sector therefore needs better support from policy makers, service providers and/or development agencies to remain the engine for economic growth and rural development. Analysis of climate trends in relation to regional production sectors such as crops using available scientific tools would create opportunities to incorporate relevant adaptation measures from the planning stages. This study found that the return periods for extreme climatic events such as drought as decreased from approximately 4 to 5 years before the year 2000 to about 2 years or less at present in the lower Tana River basin. Maize production in the region remains climatically undermined and farmers need to upscale the production of mangoes and cassava which grows and have good yields in the region. There is need to maximize the production opportunities of better yielding crops and encourage cross border trades in the country. Keywords: Climate change; Climate variability; Crop yields; Tana River basin.
Publication Date: 2012
Abstract: The aim of this study was to derive components of the intraseasonal rainfall variations from the daily rainfall in the Equatorial Eastern Africa region and assess their spatial coherence, a pointer to their potential predictability. Daily rainfall observations from 36 stations distributed over Equatorial Eastern Africa and extending from 1962 to 2000 were used. The March to May and October to December periods commonly referred to as the long and short rainfall seasons respectively were considered. Seasonal and intraseasonal statistics at the local (station) level were first defined. The stations were also grouped into near-homogeneous (sub-regional) zones based on daily rainfall. Similarly, seasonal and intraseasonal statistics were then derived at sub-regional level using three different approaches. Inter-station correlation coefficients of the intraseasonal statistics at local levels were finally computed and plotted as box-plots. For the two rainfall seasons, the two statistics showing the highest spatial coherence were the seasonal rainfall totals and the number of the wet days at sub-regional level. The local variance explained for these two variables, as an average over all the sub-regions, was more than 40%. At the bottom of the hierarchy were the mean rainfall intensity and frequency of dry spells of 5 days or more which showed the least coherence, with the local variance explained being less than 10% in each season. For each of the intraseasonal components of daily rainfall considered, the short rainfall season statistics were more coherent compared to the long rainfall season. Lag-correlations with key indices depicting sea-surface temperatures in the Pacific and Indian Oceans showed that the hierarchy between the rainfall statistics in the strength of the teleconnections reflected that of spatial coherence.
Publication Date: 2013
Abstract: The changing climatic patterns and increasing human population within the Lake Victoria Basin (LVB), together with overexploitation of water for economic activities call for assessment of water management for the entire basin. This study focused on the analysis of a combination of available in-situ climate data, Gravity And Climate Experiment (GRACE), Tropical Rainfall Measuring Mission (TRMM) observations, and high resolution Re- gional Climate simulations during recent decade(s) to assess the water storage changes within LVB that may be linked to recent climatic variability/changes and anomalies. We employed trend analysis, principal component analysis (PCA), and temporal/spatial correlations to explore the associations and co-variability among LVB stored water, rainfall variability, and large scale forcings associated with El-Ni˜no/Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Potential economic impacts of human and climate- induced changes in LVB stored water are also explored. Email address: J.Awange@curtin.edu.au (J.L. Awange) Preprint submitted to Water Resources Research October 2, 2013 Journal of Research Resources; How to Cite Awange, J. L., R. Anyah, N. Agola, E. Forootan, and P. Omondi (2013), Potential impacts of climate and environmental change on the stored water of Lake Victoria Basin and economic implications, Water Resour. Res., 49, 8160–8173, doi:10.1002/2013WR014350. Find the final version from: URL: http://onlinelibrary.wiley.com/doi/10.1002/2013WR014350/abstract Overall observed in-situ rainfall from lake-shore stations showed a modest increasing trend during the recent decades. The dominant patterns of rainfall data from the TRMM satellite estimates suggest that the spatial and tem- poral distribution of precipitation have not changed much during the period 30 of 1998-2012 over the basin consistent with in-situ observations. However, GRACE-derived water storage changes over LVB indicate an average de- cline of 38.2 mm/yr for 2003-2006, likely due to the extension of the Owen Fall/Nalubale dam, and an increase of 4.5 mm/yr over 2007-2013, likely due to two massive rainfalls in 2006-2007 and 2010-2011. The temporal correlations between rainfall and ENSO/IOD indices during the study period, based 36 on TRMM and model simulations, suggest significant influence of large scale forcing on LVB rainfall, and thus stored water. The contributions of ENSO 38 and IOD on the amplitude of TRMM-rainfall and GRACE-derived water storage changes, for the period of 2003-2013, are estimated to be ∼ 2.5 cm and ∼ 1.5 cm, respectively. Key words: Lake Victoria Basin, surface and groundwater, climate change, ENSO, GRACE, environmental change, economic impact