Abstract:
Drought is a natural hazard which shows a creeping phenomena, and vary spatially and temporally with a significant impacts on the economy, environment and society. The occurrence of drought over Upper Blue Nile indirectly affects the North Sudan, South Sudan and Egypt socio economic activities. Hence, there must be work on environmental conservation over Upper Blue Nile for the sake of mutual benifits of each countries. Recently, potentially increasing in global temperature is likely to be associated with impacts on the hydrologic cycle, including negative anomaly of precipitation and the increment in extreme events like drought. A preliminary aspect of drought preparedness and mitigation plan usually evolve from a reliable drought quantification or assessment, from which a reliable drought data are obtained, verified and used for simple or complex drought predictions, monitoring and early warnings. The quantifications have been based mainly on the amount of rainfall, soil moisture, wind and using some other derived characteristics. Based on the methodology, we used meteorological, agricultural and hydrological variables. Multiple linear regression, the joint disribution for copula model and others statistical mothods are applied in the methodology. Climate variables directly and inversely related to drought are identified to develop drought indices. A single drought index may not be efficient to quantify or characterize the complexity and relationship among meteorological, agricultural and hydrological drought types. For such reasons, this study intends to characterize the drought conditions over the Upper Blue Nile using multi drought indices based on different time scales. The performance of these multiple drought indices will also be evaluated so as to identify the order of their significance in relation to their capability of revealing and quantifying the historical drought in the Upper Blue Nile. Further applying multivariate drought indices may not
xx
be enough according to the topography and climate condition. Therefore,developing operational new drought indices the best mechanism over Upper Blue Nile by considering with and without climate signal information to over come problems such as hazard, early warning and preparedness of drought. Drought frequently occured due to El Nin˜o effects over Upper Blue Nile, but studying strength level of ENSO and its link to the drought threshold over Upper Blue Nile to understanding the frequent time occurrence of drought threshold according to ENSO severity level. Temperature of Upper Blue Nile is maximum during El Nin˜o phase. Similarly, the heat waveis strong over the GERD in the period of El Nin˜o phase. Furthermore, considering upward and downward propagation of wind in the lower stratosphere and tropospheric by including thier influence for dryness are other methods that predict or forcast the drought condition. In lower stratosphere of QBO, except the 2015 years, the 1983, 1984, 2002, and 2009 meteorological drought years are associated to easterly phases of QBO. This study is expected to contribute scientific knowledge on the basis of studying single and multi drought indices which leads to the development of the new operational drought indices to improve drought analysis over Upper Blue Nile. Keywords: ENSO, Climate change, Heatwave, Climate variables, TEJ, Forecast, Predict, Copula model, Drought, Drought indices