Seasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibia

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dc.contributor.advisorShillington, Franken_ZA
dc.contributor.authorPeard, Kathleen Rhonaen_ZA
dc.date.accessioned2014-08-13T19:52:02Z
dc.date.available2014-08-13T19:52:02Z
dc.date.issued2007en_ZA
dc.descriptionIncludes bibliographical references (p. 101-108).en_ZA
dc.description.abstractThe aim of this study is to examine the variability in the wind regime at diurnal, seasonal, interannual and interdecadal time scales. Meteorological measurements including wind speed, wind direction and air pressure collected at Dias Point Lighthouse (260 38.094'S 150 05.612'E) at hourly to eight-hourly intervals from 1960 to 2006 are analysed. Known instrument changes in the time series are validated where possible. Predominant winds at Lüderitz blow parallel to the South to North alignment of the coast. Ekman divergence in response to longshore, equatorward wind stress drives coastal upwelling at Lüderitz, the main centre of upwelling in the Benguela Current System. Wind stress is proportional to the square of the wind speed parallel to the coast and is a proxy for upwelling. A diurnal intensification of wind speeds occurred in all seasons at Lüderitz with a concomitant change in wind direction from south in the early morning to southwest in the afternoon. Pressure changes over the continent due to daytime heating and night-time cooling of the land underlie this variability. Southwesterly winds predominate throughout the year at Lüderitz. Maximum wind stress occurs in the austral summer with a fourfold decrease in wind stress during the austral winter. Highest wind stress was recorded from November to January and lowest wind stress from May to July. The wind mixing index, a measure of turbulent mixing calculated from total wind speed cubed, follows the same seasonal pattern indicating the predominance of southerly winds. The wind minimum at Lüderitz is caused by weakened pressure gradients due to the latitudinal northwesterly shift in the position of the South Atlantic Anticyclone in winter combined with a pressure increase over the continent.en_ZA
dc.identifier.apacitationPeard, K. R. (2007). <i>Seasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibia</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Oceanography. Retrieved from http://hdl.handle.net/11427/6498en_ZA
dc.identifier.chicagocitationPeard, Kathleen Rhona. <i>"Seasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibia."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Oceanography, 2007. http://hdl.handle.net/11427/6498en_ZA
dc.identifier.citationPeard, K. 2007. Seasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibia. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Peard, Kathleen Rhona AB - The aim of this study is to examine the variability in the wind regime at diurnal, seasonal, interannual and interdecadal time scales. Meteorological measurements including wind speed, wind direction and air pressure collected at Dias Point Lighthouse (260 38.094'S 150 05.612'E) at hourly to eight-hourly intervals from 1960 to 2006 are analysed. Known instrument changes in the time series are validated where possible. Predominant winds at Lüderitz blow parallel to the South to North alignment of the coast. Ekman divergence in response to longshore, equatorward wind stress drives coastal upwelling at Lüderitz, the main centre of upwelling in the Benguela Current System. Wind stress is proportional to the square of the wind speed parallel to the coast and is a proxy for upwelling. A diurnal intensification of wind speeds occurred in all seasons at Lüderitz with a concomitant change in wind direction from south in the early morning to southwest in the afternoon. Pressure changes over the continent due to daytime heating and night-time cooling of the land underlie this variability. Southwesterly winds predominate throughout the year at Lüderitz. Maximum wind stress occurs in the austral summer with a fourfold decrease in wind stress during the austral winter. Highest wind stress was recorded from November to January and lowest wind stress from May to July. The wind mixing index, a measure of turbulent mixing calculated from total wind speed cubed, follows the same seasonal pattern indicating the predominance of southerly winds. The wind minimum at Lüderitz is caused by weakened pressure gradients due to the latitudinal northwesterly shift in the position of the South Atlantic Anticyclone in winter combined with a pressure increase over the continent. DA - 2007 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2007 T1 - Seasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibia TI - Seasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibia UR - http://hdl.handle.net/11427/6498 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/6498
dc.identifier.vancouvercitationPeard KR. Seasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibia. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Oceanography, 2007 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/6498en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Oceanographyen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherOceanographyen_ZA
dc.titleSeasonal and interannual variability of wind-driven upwelling at Lüderitz, Namibiaen_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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