Variability of summer rainfall over southwestern Madagascar

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dc.contributor.advisorReason, Chrisen_ZA
dc.contributor.authorRandriamahefasoa,Tsinampoizina Marie Sophieen_ZA
dc.date.accessioned2014-11-28T09:55:11Z
dc.date.available2014-11-28T09:55:11Z
dc.date.issued2013en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractThis study investigates the interannual variability of the frequency of wet days during the rainy season over southwestern Madagascar, and its associated regional and global circulation patterns. The number of wet days was counted for each summer season (December to March) of the period 1971 to 2000 at four rainfall stations in southwestern Madagascar. For each station, the frequency of wet days was correlated with ENSO indices, SIOD index, SST, 850 hPa geopotential height, zonal and meridional winds at the surface. Composite anomalies of moisture flux and moisture flux convergence at 850 hPa, 500 hPa omega and velocity potential at .995 sigma level, using NCEP/NCAR reanalysis data, associated with El Niño events, La Niña events that occurred during the period of study were examined. Also, circulation anomalies during neutral years having anomalously high frequency of wet days or anomalously low frequency of wet days were analysed separately. It was found that the number of wet days rarely exceeds half of the total days in summer for each station. Inverse relationship between the equatorial Pacific SST anomalies and the frequency of wet days anomalies was identified. Statistics showed that years characterised by high frequency of wet days often occur with La Niña seasons whereas years having low frequency of wet days tend to occur with El Niño seasons. A strong relationship between the southern Indian Ocean SST and the frequency of wet days was found at Ranohira (45.3° E, 22.5° S) and Toliara (43.72° E, 23.38° S). Increased number of wet days over southwestern Madagascar is associated with low atmospheric pressure over the southern Mozambique Channel. Neutral years having anomalously high (low) frequency of wet days are marked by northwesterly (southeasterly) moisture flux anomalies at 850 hPa over southwestern Madagascar.en_ZA
dc.identifier.apacitation (2013). <i>Variability of summer rainfall over southwestern Madagascar</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Oceanography. Retrieved from http://hdl.handle.net/11427/9809en_ZA
dc.identifier.chicagocitation. <i>"Variability of summer rainfall over southwestern Madagascar."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Oceanography, 2013. http://hdl.handle.net/11427/9809en_ZA
dc.identifier.citation 2013. Variability of summer rainfall over southwestern Madagascar. Thesis. University of Cape Town ,Faculty of Science ,Department of Oceanography. http://hdl.handle.net/11427/9809en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Randriamahefasoa,Tsinampoizina Marie Sophie AB - This study investigates the interannual variability of the frequency of wet days during the rainy season over southwestern Madagascar, and its associated regional and global circulation patterns. The number of wet days was counted for each summer season (December to March) of the period 1971 to 2000 at four rainfall stations in southwestern Madagascar. For each station, the frequency of wet days was correlated with ENSO indices, SIOD index, SST, 850 hPa geopotential height, zonal and meridional winds at the surface. Composite anomalies of moisture flux and moisture flux convergence at 850 hPa, 500 hPa omega and velocity potential at .995 sigma level, using NCEP/NCAR reanalysis data, associated with El Niño events, La Niña events that occurred during the period of study were examined. Also, circulation anomalies during neutral years having anomalously high frequency of wet days or anomalously low frequency of wet days were analysed separately. It was found that the number of wet days rarely exceeds half of the total days in summer for each station. Inverse relationship between the equatorial Pacific SST anomalies and the frequency of wet days anomalies was identified. Statistics showed that years characterised by high frequency of wet days often occur with La Niña seasons whereas years having low frequency of wet days tend to occur with El Niño seasons. A strong relationship between the southern Indian Ocean SST and the frequency of wet days was found at Ranohira (45.3° E, 22.5° S) and Toliara (43.72° E, 23.38° S). Increased number of wet days over southwestern Madagascar is associated with low atmospheric pressure over the southern Mozambique Channel. Neutral years having anomalously high (low) frequency of wet days are marked by northwesterly (southeasterly) moisture flux anomalies at 850 hPa over southwestern Madagascar. DA - 2013 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2013 T1 - Variability of summer rainfall over southwestern Madagascar TI - Variability of summer rainfall over southwestern Madagascar UR - http://hdl.handle.net/11427/9809 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/9809
dc.identifier.vancouvercitation. Variability of summer rainfall over southwestern Madagascar. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Oceanography, 2013 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/9809en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Oceanographyen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.titleVariability of summer rainfall over southwestern Madagascaren_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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