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Accueil du site → Doctorat → Kenya → Teleconnections between decadal rainfall variability and global sea surface temparatures and simulation of future climate scenarios over East Africa

University of Nairobi (2010)

Teleconnections between decadal rainfall variability and global sea surface temparatures and simulation of future climate scenarios over East Africa

Aming’o, Philip O

Titre : Teleconnections between decadal rainfall variability and global sea surface temparatures and simulation of future climate scenarios over East Africa

Auteur : Aming’o, Philip O

Université de soutenance : University of Nairobi

Grade : Doctor of Philosophy (PhD) 2010

Résumé partiel
The overall objective of this study is to investigate the dominant spatial and temporal decadal rainfall variability modes and their teleconnection with decadal variability modes of the specific global oceans. Knowledge derived from the teleconnection is used to examine the predictability potentials of the modes of decadal variability of East African rainfall. Specific objectives that were undertaken to achieve the overall objective of the study include delineation of the region into homogenous zones with similar decadal variability modes ; investigation of the teleconnection of the regional decadal rainfall variability patterns with global Sea Surface Temperatures modes ; examination of the predictability potentials of the regional decadal rainfall variability patterns together with probable future regional climate scenarios and compare near-term projections with predicted decadal rainfall using Regional Climate Model (RCM). The data sets used in the study include monthly observed rainfall over East Africa and global sea surface temperature covering the period 1950 to 2008. Other data sets used include gridded data of the University of East Anglia’s Climate Research Unit (CRU) for the period 1961 to 1990 ; the European Centre for Medium-range Weather Forecasts (ECMWF) 40-year Re-Analysis (ERA40) and European Community Hamburg Model version 4 (ECHAM4) model output. The observed rainfall and sea surface temperature data used in the study were smoothed using a nine point binomial coefficient filter to remove all fluctuations equal to and less than 9 years. The methods used to investigate the specific objectives included mass curve analysis to assess the quality of data used, trend and spectral analyses to investigate the dominant patterns of the existing decadal rainfall variability. Principal Component Analysis (PCA) was used to delineate the region into homogenous decadal rainfall zones while Cannonical Correlation Analysis (CCA) and Singular Value Decomposition (SVD) techniques were used to investigate teleconnection amongst decadal rainfall with Sea Surface Temperature (SST) modes over various parts of the global oceans. The predictability potentials of the regional decadal rainfall variability patterns were assessed using correlation and Multiple Linear Regression (MLR) methods. A high resolution Regional Climate Model (RCM), PRECIS (Providing Regional Climates for Impacts Studies), was applied to generate regional climate scenarios. Besides, PRECIS model was applied to produce hindcasts, that were compared with observed rainfall, and nearterm future projections that were compared with predicted decadal rainfall. The patterns of decadal varaibility showed that although wet and dry decades were recurrent, and sometimes extend over large areas, there were very few decades when floods or drought covered the whole of East Africa region except for the wet decade of 1961-1970 during the short rains (October-December) season. Results from spectral density analysis of rainfall time series smoothed with a 9-point binomial coefficients filter showed dominance of ten years period that were significant at 95% confidence level when both white and red noise hypotheses were used.

Présentation

Page publiée le 12 décembre 2014, mise à jour le 28 décembre 2017