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Atmosphere-vegetation interactions over South Africa
Bibliography: pages 107-118.
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| Format: | Thesis |
| Language: | English |
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Department of Environmental and Geographical Science
2016
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| _version_ | 1867613143704797184 |
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| access_status_str | Open Access |
| author | Shannon, Debbie Anne |
| author2 | Hewitson, Bruce |
| author_browse | Hewitson, Bruce Shannon, Debbie Anne |
| author_facet | Hewitson, Bruce Shannon, Debbie Anne |
| author_sort | Shannon, Debbie Anne |
| collection | Thesis |
| description | Bibliography: pages 107-118. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/22109 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:31:28.055Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Environmental and Geographical Science |
| publisherStr | Department of Environmental and Geographical Science |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/22109 Atmosphere-vegetation interactions over South Africa Shannon, Debbie Anne Hewitson, Bruce Environmental and Geographical Science Bibliography: pages 107-118. This study examines the sensitivity of the atmospheric circulation to vegetation change over South Africa in the context of the portended global warming. This is achieved using a vegetation model driven by climate change information and subsequently incorporated within a general circulation model (GCM). The stand-alone vegetation model is driven using precipitation, temperature and relative humidity derived from downscaling using artificial neural networks. The vegetation model is then run with perturbed precipitation, temperature and relative humidity from downscaled model data from lxCO₂ and 2xCO₂ GCM simulations. The resultant vegetation perturbation response to climate change is then examined and incorporated into the GCM in order to ascertain the atmospheric sensitivity to vegetation changes. The off-line results of the vegetation model indicate a moderate degree of sensitivity of the vegetation to perturbations in precipitation, temperature and relative humidity. The general trend in response to the CO₂ climate is a westwards and altitudinal shift of lowland vegetation over the eastern part of the country, and a southwards and eastwards shift of the more dryland vegetation in the west. These shifts are in accordance with expected responses, since lowland vegetation responds more to temperature changes and the dryland vegetation to precipitation changes. Nonetheless, the use of the model provides a physically justifiable scenario on which to base the GCM studies, and at a finer resolution than otherwise available. A GCM simulation with the perturbed vegetation was then performed using sea surface temperature boundary conditions for 1980 and compared to an identical GCM run without the perturbation. 1980 was chosen since this year does not represent either a strong El Niño or La Niña year. The atmospheric sensitivity to the vegetation perturbation has been examined in terms of climatic variables such as temperature, precipitation, pressure, specific humidity, horizontal divergence, and sensible and latent heat fluxes. The results show that the atmosphere is quite sensitive to relatively small vegetation changes. Atmospheric response to vegetation perturbations indicates greater sensitivity over the NW and SE regions of southern Africa. The perturbation indicates a reduction in precipitation over the SE interior, related to less moisture feeding in over the interior from the SE Indian Ocean. Wind speed changes over the adjacent ocean were also evident, and are probably related to the changes in the South Atlantic and Indian high pressures. A southwards extension of the Hadley Cell was also suggested, as well as changes in sensible and latent heat fluxes, relating to precipitation and temperature changes. It is suggested that changes may be in response to the general drying out of the country and the associated increase in aridity. This research forms the preliminary investigation for further work incorporating the atmospheric perturbation response back into driving the vegetation model in order to examine the direction of the feedback -- whether this is positive or negative in the longer term. Thus, this study has demonstrated that the atmosphere is significantly sensitive to vegetation changes over South Africa and reinforces the need for improved land surface parameterization schemes and vegetation models in general circulation models. 2016-10-10T14:56:04Z 2016-10-10T14:56:04Z 1997 Master Thesis Masters MSc http://hdl.handle.net/11427/22109 eng application/pdf Department of Environmental and Geographical Science Faculty of Science University of Cape Town |
| spellingShingle | Environmental and Geographical Science Shannon, Debbie Anne Atmosphere-vegetation interactions over South Africa |
| thesis_degree_str | Master's |
| title | Atmosphere-vegetation interactions over South Africa |
| title_full | Atmosphere-vegetation interactions over South Africa |
| title_fullStr | Atmosphere-vegetation interactions over South Africa |
| title_full_unstemmed | Atmosphere-vegetation interactions over South Africa |
| title_short | Atmosphere-vegetation interactions over South Africa |
| title_sort | atmosphere vegetation interactions over south africa |
| topic | Environmental and Geographical Science |
| url | http://hdl.handle.net/11427/22109 |
| work_keys_str_mv | AT shannondebbieanne atmospherevegetationinteractionsoversouthafrica |