Study Of Rainfall Trends And Variability Over Tanzania
The study deals with the analysis of monthly rainfall trends and variability over Tanzania. The monthly rainfall data from 1982 to 2012 was obtained from the Tanzania Meteorological Agency, Dar es Salaam, Tanzania. The monthly rainfall data from representative stations in the homogeneous rainfall zones over Tanzania were analyzed for trends by graphical and statistical Methods. In order to achieve the main and specific objectives, the data were subjected to various analyses including quality control. The core methodology used in analysis of rainfall trends and variability over Tanzania were the time series analysis, single mass curve analysis, coefficient of variation and spatial analysis using surfer program. The results from the study showed that there were trends in the rainfall data for all stations used. However the trends are not significant except in Tanga and Pemba. Also results from seasonal and annual coefficient of variation found that the largest value of variability was observed during OND at Kilimanjaro while the lowest variability was found in Kigoma, Sumbawanga and Mbeya during November-April (NA) season which implies that rainfall in these regions is very reliable and Kilimanjaro rainfall is less reliable. Moreover result from spatial analysis revealed that Bukoba region has the highest mean annual rainfall followed by Zanzibar and Pemba. The lowest mean annual rainfall was at Kilimanjaro, which confirms that Kilimanjaro received lowest amount of rainfall. Furthermore the study has demonstrated that there are both spatial and temporal variability of rainfall over Tanzania. These findings may be used for monitoring and forecasting extreme weather events like droughts and floods. This would therefore contribute significantly to the effective management and sustainable development of the national social economic activities which are heavily rain- dependent.