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Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa
Dissertation (MSc)--University of Pretoria, 2016.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2016
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| _version_ | 1867613724511043584 |
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| access_status_str | Open Access |
| author2 | Landman, Willem Adolf |
| author_browse | Landman, Willem Adolf |
| author_facet | Landman, Willem Adolf |
| collection | Thesis |
| dc_rights_str_mv | © 2016 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc)--University of Pretoria, 2016. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/57261 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:40:42.021Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/57261 Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa Landman, Willem Adolf kelebogile.mathole@weathersa.co.za Ndarana, Thando Mathole, Kelebogile UCTD Dissertation (MSc)--University of Pretoria, 2016. Seasonal climate prediction of rainfall and temperature in South Africa (SA) during summer is mainly related to the variability of El Niño Southern Oscillation (ENSO) besides other forcings from local surrounding oceans. However, the predictive skill is low whenever ENSO is dormant; therefore rainfall and temperature forecast become uncertain over the region. The study then aims to investigate the possible importance of proper representation of stratospheric processes in climate prediction models. These stratospheric processes include mainly ozone and green-house gases. A comparison of trends in lower stratospheric temperatures and summer zonal wind fields in 27 years of the National Centre for Environmental Prediction (NCEP) of the Department of Energy (DOE) Reanalysis II data and output from hindcast simulations using an ocean-atmosphere general circulation model (OAGCM) is conducted. Lower stratospheric ozone in the OAGCM is relaxed towards the observed climatology and increasing greenhouse gas concentrations are neglected. In reanalysis lower stratospheric ozone fields are better represented than in the OAGCM. The lower stratospheric/upper tropospheric cooling in the polar cap during spring (shown by previous studies as a result of lower ozone depletion) appears in reanalysis but not in the OAGCM. The corresponding summer tropospheric response also differs between datasets. Moreover, in reanalysis a statistically significant poleward trend of the summer jet position is found. However, contrary to this, no such trend is found in OAGCM. Furthermore, the dynamics of the stratosphere is analyzed using wave activity. The lack of wave activity in the model as opposed to observations further suggests that the dynamical coupling which is essential for proper simulation of the stratosphere is compromised. Lastly, the statistical forecasting system using winds and temperature during spring when the stratosphere is actively coupled also suggest potential predictability of summer rainfall over South Africa, particularly wet conditions when the tropospheric eddy-driven jet is shifted towards the poles. tm2016 Geography, Geoinformatics and Meteorology MSc Unrestricted 2016-10-14T07:32:56Z 2016-10-14T07:32:56Z 2016-09-01 2016 Dissertation Mathole, K 2016, Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/57261> S2016 http://hdl.handle.net/2263/57261 en © 2016 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa |
| title | Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa |
| title_full | Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa |
| title_fullStr | Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa |
| title_full_unstemmed | Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa |
| title_short | Impact of lower stratospheric dynamics on the predictability of summer rainfall over South Africa |
| title_sort | impact of lower stratospheric dynamics on the predictability of summer rainfall over south africa |
| topic | UCTD |
| url | http://hdl.handle.net/2263/57261 |