Impact of the Agulhas Current on storm development

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dc.contributor.advisorRouault, Mathieu
dc.contributor.authorO'Connor, Jason
dc.date.accessioned2020-12-30T10:18:01Z
dc.date.available2020-12-30T10:18:01Z
dc.date.issued2020
dc.description.abstractA high-resolution atmospheric model (WRF) is used to investigate the impact of the Agulhas Current on synoptic storm development. A sensitivity experiment is conducted to analyse the influence of the Agulhas Current's sea surface temperature (SST) on rain producing, synoptic scale weather features. Two model configurations: Control (CTL) and Smooth (SMTH) are analysed to understand the effect of the Agulhas Current's SST and high latent heat fluxes on storms that develop or track over the Current. The two configurations are identical except that the SMTH simulation has the SST signature of the Agulhas reduced by smoothing out the strong SST gradients associated with the Current. This results in the Agulhas Current core having SSTs reduced by roughly 1.5°C in the SMTH configuration. Consequently, lower (100 - 150 W.m¯²) latent heat fluxes are also simulated at the Current core's location in the SMTH run. Using daily South Africa Weather Service synoptic charts from 2001 - 2005, when the model output is available, two hundred (200) synoptic scale storms are found to track over the Current. Using the TRMM 3B42 3-hourly 0.25 x 0.25° precipitation rain rate product, 70 (of the 200) are found to have produced rainfall. Five model variables are used as proxies for the storm intensity of these 70 storms. Ten storms are found to show storm intensification when passing over the Current. In the CTL simulation, of these ten storms, ten show lower 850mb geopotential heights (m), nine show higher surface wind speeds (m.sˉ¹), seven show higher rain rates (mm.hrˉ¹), eight show higher Eddy Kinetic Energy (EKE) (m².sˉ²) and nine show greater upward moisture flux at the surface (g.mˉ².sˉ¹) compared to the SMTH run once each storm has propagated over the Current. Model output analysis shows sustained or dissipating storm intensity of the other 60 storms while passing over the Current. Nonetheless, these results provide a strong case for the influence of the Agulhas Current on the intensification of synoptic scale, rain producing events.
dc.identifier.apacitationO'Connor, J. (2020). <i>Impact of the Agulhas Current on storm development</i>. (Master Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/32473en_ZA
dc.identifier.chicagocitationO'Connor, Jason. <i>"Impact of the Agulhas Current on storm development."</i> Master Thesis., University of Cape Town, 2020. http://hdl.handle.net/11427/32473en_ZA
dc.identifier.citationO'Connor, J. 2020. Impact of the Agulhas Current on storm development. Master Thesis. University of Cape Town. http://hdl.handle.net/11427/32473en_ZA
dc.identifier.ris TY - Master Thesis AU - O'Connor, Jason AB - A high-resolution atmospheric model (WRF) is used to investigate the impact of the Agulhas Current on synoptic storm development. A sensitivity experiment is conducted to analyse the influence of the Agulhas Current's sea surface temperature (SST) on rain producing, synoptic scale weather features. Two model configurations: Control (CTL) and Smooth (SMTH) are analysed to understand the effect of the Agulhas Current's SST and high latent heat fluxes on storms that develop or track over the Current. The two configurations are identical except that the SMTH simulation has the SST signature of the Agulhas reduced by smoothing out the strong SST gradients associated with the Current. This results in the Agulhas Current core having SSTs reduced by roughly 1.5°C in the SMTH configuration. Consequently, lower (100 - 150 W.m¯²) latent heat fluxes are also simulated at the Current core's location in the SMTH run. Using daily South Africa Weather Service synoptic charts from 2001 - 2005, when the model output is available, two hundred (200) synoptic scale storms are found to track over the Current. Using the TRMM 3B42 3-hourly 0.25 x 0.25° precipitation rain rate product, 70 (of the 200) are found to have produced rainfall. Five model variables are used as proxies for the storm intensity of these 70 storms. Ten storms are found to show storm intensification when passing over the Current. In the CTL simulation, of these ten storms, ten show lower 850mb geopotential heights (m), nine show higher surface wind speeds (m.sˉ¹), seven show higher rain rates (mm.hrˉ¹), eight show higher Eddy Kinetic Energy (EKE) (m².sˉ²) and nine show greater upward moisture flux at the surface (g.mˉ².sˉ¹) compared to the SMTH run once each storm has propagated over the Current. Model output analysis shows sustained or dissipating storm intensity of the other 60 storms while passing over the Current. Nonetheless, these results provide a strong case for the influence of the Agulhas Current on the intensification of synoptic scale, rain producing events. DA - 2020 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PY - 2020 T1 - Impact of the Agulhas Current on storm development TI - Impact of the Agulhas Current on storm development UR - http://hdl.handle.net/11427/32473 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/32473
dc.identifier.vancouvercitationO'Connor J. Impact of the Agulhas Current on storm development. [Master Thesis]. University of Cape Town, 2020 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/32473en_ZA
dc.language.isoeng
dc.publisherUniversity of Cape Town
dc.publisher.departmentDepartment of Oceanography
dc.publisher.facultyFaculty of Science
dc.subject.otherOceanography
dc.subject.otherApplied Ocean Sciences
dc.titleImpact of the Agulhas Current on storm development
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMSc
uct.type.publicationResearch
uct.type.resourceMaster Thesis
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