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University of Cape Town (1997)

Latent heat flux and South African summer rainfall variability

Courtney, Shaun

Titre : Latent heat flux and South African summer rainfall variability

Auteur : Courtney, Shaun

Université de soutenance : University of Cape Town.

Grade : Master of Science (MS) 1997

Résumé
The main purpose of this study was to determine if a relationship exists between oceanic latent heat flux and the summer rainfall of South Africa. Such a link would be useful for a better understanding and the prediction of monthly variability in the summer rainfall for South Africa. In order to investigate possible relationships between oceanic latent heat flux and summer rainfall in South Africa, point to point and point to field statistical correlations were made between gridded monthly COADS derived bulk oceanic heat fluxes and area averaged rainfall for the period 1950 to 1988. Correlations with the oceanic latent heat flux were not significant when the summer area averaged rainfall was divided into early and late summer seasons. This is due to the fact that different oceanic latent heat flux regions correlate with a different rainfall region each month. The results of monthly latent heat flux and summer rainfall demonstrated that there exists a statistical link between oceanic latent heat flux and summer rainfall and that this link could prove useful in the prediction of summer rainfall patterns. These results of the correlation between monthly latent heat flux and summer rainfall show that summer rainfall can be grouped into an all-area index that can be used as a proxy for the entire summer rainfall region. Results of these correlations further show that there are three major mechanisms that are at work over the six month summer rainfall period. These mechanisms show a link between the oceanic latent heat flux and summer rainfall variability. This study has shown that various oceanographic areas in the surrounding oceans correlate at different lags with South African summer rainfall. These correlations can be useful as precursors in predicting wetter or dryer rainfall events. Areas identified by correlation of oceanic latent heat flux regions as important as precursors for summer rainfall prediction are similar to those areas other researches have identified in studies using OLR, SST and upper level winds (Jury 1995). This study adds weight to the already existing knowledge of these precursors of rainfall predictability.

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