Malagasy Climate Variability Characteristics Modes Mechanisms Modelling Teleconnection And Prediction

Actually, the water resource becomes increasingly limited and difficult to exploit.rnTheir quantity on the Malagasy territory is unevenly spread; it is relatively abundant in thernEast coast while the area of South-east presents a periodic situation vulnerable to the dryness.rnThe water resource is especially conditioned by precipitations in the form of rain having arngreat effect in society’s life.rnPrior to different tasks linked to the Malagasy rainfall, better understanding of thernmeteorological and orographical influences are very useful as Madagascar is situated in thernsouthwest zone of the Indian Ocean closed to the African continent with a channel sea on thernWest (Channel of Mozambica) and the Indian Ocean on the East, located between 12° and 25°rn30' of southern latitude, crossed by the austral Capricorn tropic. It is an Island whoserntransversal profile of its orography is marked by a strong asymmetry of slopes: in the East,rnthe altitude rises quickly and reaches the central areas through a sharp cliff. Its Eastern coastalrnplains are very narrow. However, in the West the relief declines progressively attaining lowrnstretched areas.rnIn the synoptic scale, tropical weather is prevailing in this island with dry seasonrnduring the austral winter (May to October) and wet season during the austral summerrn(November to April). Strong trade winds and extra tropical perturbations are the mostrndominant meteorological patterns prevailing in the island.rnDespite the establishment of the rainfall climatology over Madagascar gaps are stillrnidentified in that previous analysis for instance the spatial and temporal variation rainfall withrntremendous spatial gradient of rainfall in all directions. It is therefore vital to optimallyrncompute space-time modes of variability of the country by the mean of the PrincipalrnComponent Analysis (PCA) as this type of research is not yet attempted for Madagascarrndespite its popularity. Most importantly, salient factors that determine these modes arern9rninvestigated to better understand the rainfall mechanisms in the country using the worldwidernPCA tools.rnTherefore, tropical cyclone having mutual relationship with the leading moderncomponent opens an interesting research field on the role of tropical cyclone in thernmodification of Madagascar climate and its contribution in different regions during the rainyrnseason.rnFurthermore, extreme precipitation events in Madagascar can be related to a varietyrnof catastrophic events including drought, famine, flooding, and the spread of disease. It isrnimportant to attempt to anticipate when these extreme events are likely to (Doncques, 1975)rnoccur so that disaster relief efforts can be implemented which could reduce the potentialrnimpacts of these extreme events. In order to predict and prepare areas that may be susceptiblernto food shortages as a result of rainfall anomalies, SPI (Standardized Precipitation Index) andrnEV (Extreme Value) Analysis applied to the precipitation records are adopted. Specifically,rnthe aim is not only to study the quantile of Madagascar rainfall record but also its tails andrnrisk measures using the Extreme Value theory. Another important issue of this analysis is thernreturn level of the excess of the precipitation record in order to extract the main temporalrnpattern of severe rain which occurred in Madagascar.rnAs a crucial natural resource for Madagascar, rainwater is unevenly distributed.rnSome regions are extremely ‘fragilized’ by the cyclone passage that provokes importantrnfloods. Other areas are recurrently hit by drought especially the southern part of the country,rnbut in the other regions it seems periodic. In fact, the extreme South of the island is a semiaridrnarea where the annual average precipitation is less than 600 mm with 9 to 11 monthsrnwater deficiency. So, whatever classification adopted and criteria employed, the Southrnremains as the driest region (Doncques, 1975). This study is devoted to understanding therndynamics of dry events in the atmosphere over the southern part of Madagascar. The studyrn10rnreveals that Southern Madagascar rainfall during the austral summer season depends onrnquantitative dynamical atmospheric variables. It is with this simple conceptual framework thatrnwe manage to predict the seasonal mean rainfall during its active phase on the relativerncontribution of these externally forced components. Moreover, it is important to develop anrnearly warning system for rainfall variability based on a sound scientific understanding of itsrncauses. This step of analysis considers which components of the ocean-atmosphere systemrncontribute to its water resource then it compares the predicted result by model with thernobserved datasets of southern rainfall. Finally, it is aimed to give contribution to thernpredictability of Malagasy rainfall through applied climatology

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