An investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy season

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dc.contributor.advisorReason, Chrisen_ZA
dc.contributor.authorHachigonta, Sepo Promiseen_ZA
dc.date.accessioned2014-07-31T08:04:49Z
dc.date.available2014-07-31T08:04:49Z
dc.date.issued2005en_ZA
dc.descriptionIncludes bibliographical references (leaves 113-124).
dc.description.abstractRecurring dry/wet spells and decreased agricultural productivity during the last decade in the southern and northern parts of Zambia point to the need for a clearer understanding of these events, their frequencies and their possible connection to large-scale climate modes. Apart from having a high number of dry spells during the December-February (DJF) core rainy season, the southern part of Zambia is frequently subjected to late onset dates and short durations of the rainy season whereas the northern and northwestern region frequently have high numbers of wet spells which in most cases lead to flooding. Using CMAP and station data, rainfall variability in terms of dry spells, wet spells, onset and cessation dates of the Zambian rainy season and the associated circulation anomalies are investigated. The study also looks at relationship between these extreme events with Nin03.4 SST anomalies. Low level easterly anomalies over Zambia are enhanced during seasons with high dry spells. As a result, there is reduced moisture penetration into Zambia from the Angola low and reduced low level moisture convergence over the country and hence increased dry spells. During the seasons with high numbers of wet spells, there are low level westerly anomalies over southern Angola and western Zambia implying a strong moisture influx from the tropical South East Atlantic and increased convergence over Zambia. It was shown that El Nino (La Nina) events typically result in above (below) average DJF dry spell frequency in Zambia. Early onset dates over the northern parts of Zambia were observed to occur during strong El Nino seasons and the strength of the observed relationship with Nin03.4 SSTs seems to be stronger for years during the 1980s than those during the 1990s. Early onset dates tend to occur for years with higher than average dry spell frequency in the following DJF season. This suggests that early onset may be a disadvantage in that it often leads to more dry spells during the subsequent peak growing period of the season.en_ZA
dc.identifier.apacitationHachigonta, S. P. (2005). <i>An investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy season</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Environmental and Geographical Science. Retrieved from http://hdl.handle.net/11427/4857en_ZA
dc.identifier.chicagocitationHachigonta, Sepo Promise. <i>"An investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy season."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Environmental and Geographical Science, 2005. http://hdl.handle.net/11427/4857en_ZA
dc.identifier.citationHachigonta, S. 2005. An investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy season. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Hachigonta, Sepo Promise AB - Recurring dry/wet spells and decreased agricultural productivity during the last decade in the southern and northern parts of Zambia point to the need for a clearer understanding of these events, their frequencies and their possible connection to large-scale climate modes. Apart from having a high number of dry spells during the December-February (DJF) core rainy season, the southern part of Zambia is frequently subjected to late onset dates and short durations of the rainy season whereas the northern and northwestern region frequently have high numbers of wet spells which in most cases lead to flooding. Using CMAP and station data, rainfall variability in terms of dry spells, wet spells, onset and cessation dates of the Zambian rainy season and the associated circulation anomalies are investigated. The study also looks at relationship between these extreme events with Nin03.4 SST anomalies. Low level easterly anomalies over Zambia are enhanced during seasons with high dry spells. As a result, there is reduced moisture penetration into Zambia from the Angola low and reduced low level moisture convergence over the country and hence increased dry spells. During the seasons with high numbers of wet spells, there are low level westerly anomalies over southern Angola and western Zambia implying a strong moisture influx from the tropical South East Atlantic and increased convergence over Zambia. It was shown that El Nino (La Nina) events typically result in above (below) average DJF dry spell frequency in Zambia. Early onset dates over the northern parts of Zambia were observed to occur during strong El Nino seasons and the strength of the observed relationship with Nin03.4 SSTs seems to be stronger for years during the 1980s than those during the 1990s. Early onset dates tend to occur for years with higher than average dry spell frequency in the following DJF season. This suggests that early onset may be a disadvantage in that it often leads to more dry spells during the subsequent peak growing period of the season. DA - 2005 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2005 T1 - An investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy season TI - An investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy season UR - http://hdl.handle.net/11427/4857 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/4857
dc.identifier.vancouvercitationHachigonta SP. An investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy season. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Environmental and Geographical Science, 2005 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/4857en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Environmental and Geographical Scienceen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherEnvironmental and Geographical Scienceen_ZA
dc.titleAn investigation into dry and wet spell characteristics over Zambia and into the onset of the rainy seasonen_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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