Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa
ABSTRACT The seasonal and interannual variability of the mid‐tropospheric Botswana High and its relationships with various characteristics of rainfall and temperature over southern Africa are examined. This High typically forms in August and then strengthens and moves southward over southern Africa...
Published in: | International Journal of Climatology |
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crwiley:10.1002/joc.5022 2024-09-15T17:47:15+00:00 Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa Driver, P. Reason, C. J. C. National Research Foundation 2017 http://dx.doi.org/10.1002/joc.5022 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.5022 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.5022 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor International Journal of Climatology volume 37, issue S1, page 570-581 ISSN 0899-8418 1097-0088 journal-article 2017 crwiley https://doi.org/10.1002/joc.5022 2024-08-01T04:23:43Z ABSTRACT The seasonal and interannual variability of the mid‐tropospheric Botswana High and its relationships with various characteristics of rainfall and temperature over southern Africa are examined. This High typically forms in August and then strengthens and moves southward over southern Africa during the spring and summer. It also expands in zonal extent so that by March it is part of an anticyclonic ridge extending from the South Atlantic Convergence Zone eastwards over this ocean, across southern Africa and to the western Indian Ocean, with its greatest intensity in February. Its position is always to the south and southeast of the region of heavy precipitation across tropical southern Africa associated with the Inter Tropical Convergence Zone ( ITCZ ) and its meridional arm that passes through the eastern Congo Basin. Substantial interannual variability exists in the strength of the Botswana High. While the High is typically stronger (weaker) during El Niño (La Niña) events, there are also a number of neutral El Niño Southern Oscillation (ENSO) summers with large anomalies in the Botswana High. Neutral summers with an anomalously weak Botswana High are also characterized by a cyclonic anomaly extending from Angola south to the Antarctic and an anticyclonic anomaly over the South West Indian Ocean. These circulation patterns favour the development of tropical extratropical cloud bands, the main synoptic summer rainfall producing system, and the inflow of more moisture from the Indian Ocean towards the source of the cloud bands and hence increased rainfall. Roughly, the reverse circulation anomalies occur during neutral summers with anomalously large values of the Botswana High. Relationships are also found between the Botswana High and dry spell frequency, maximum temperature, diurnal temperature range and the number of days with extreme temperatures during the summer. Article in Journal/Newspaper Antarc* Antarctic Wiley Online Library International Journal of Climatology 37 S1 570 581 |
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Open Polar |
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Wiley Online Library |
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crwiley |
language |
English |
description |
ABSTRACT The seasonal and interannual variability of the mid‐tropospheric Botswana High and its relationships with various characteristics of rainfall and temperature over southern Africa are examined. This High typically forms in August and then strengthens and moves southward over southern Africa during the spring and summer. It also expands in zonal extent so that by March it is part of an anticyclonic ridge extending from the South Atlantic Convergence Zone eastwards over this ocean, across southern Africa and to the western Indian Ocean, with its greatest intensity in February. Its position is always to the south and southeast of the region of heavy precipitation across tropical southern Africa associated with the Inter Tropical Convergence Zone ( ITCZ ) and its meridional arm that passes through the eastern Congo Basin. Substantial interannual variability exists in the strength of the Botswana High. While the High is typically stronger (weaker) during El Niño (La Niña) events, there are also a number of neutral El Niño Southern Oscillation (ENSO) summers with large anomalies in the Botswana High. Neutral summers with an anomalously weak Botswana High are also characterized by a cyclonic anomaly extending from Angola south to the Antarctic and an anticyclonic anomaly over the South West Indian Ocean. These circulation patterns favour the development of tropical extratropical cloud bands, the main synoptic summer rainfall producing system, and the inflow of more moisture from the Indian Ocean towards the source of the cloud bands and hence increased rainfall. Roughly, the reverse circulation anomalies occur during neutral summers with anomalously large values of the Botswana High. Relationships are also found between the Botswana High and dry spell frequency, maximum temperature, diurnal temperature range and the number of days with extreme temperatures during the summer. |
author2 |
National Research Foundation |
format |
Article in Journal/Newspaper |
author |
Driver, P. Reason, C. J. C. |
spellingShingle |
Driver, P. Reason, C. J. C. Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa |
author_facet |
Driver, P. Reason, C. J. C. |
author_sort |
Driver, P. |
title |
Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa |
title_short |
Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa |
title_full |
Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa |
title_fullStr |
Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa |
title_full_unstemmed |
Variability in the Botswana High and its relationships with rainfall and temperature characteristics over southern Africa |
title_sort |
variability in the botswana high and its relationships with rainfall and temperature characteristics over southern africa |
publisher |
Wiley |
publishDate |
2017 |
url |
http://dx.doi.org/10.1002/joc.5022 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.5022 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.5022 |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
International Journal of Climatology volume 37, issue S1, page 570-581 ISSN 0899-8418 1097-0088 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/joc.5022 |
container_title |
International Journal of Climatology |
container_volume |
37 |
container_issue |
S1 |
container_start_page |
570 |
op_container_end_page |
581 |
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1810496185872416768 |