High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa
Copyright: 2012 Royal Meteorological Society. This is an ABSTRACT ONLY. The definitive version is published in International Journal of Climatology, vol. 33, pp 173-187 Mid-tropospheric closed-lows (cold-core cut-off lows and warm-core tropical lows) are important rain producing weather systems for...
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ftcsir:oai:researchspace.csir.co.za:10204/6651 2023-05-15T18:18:54+02:00 High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa Engelbrecht, CJ Engelbrecht, FA Dyson, LL 2012-01 application/pdf http://hdl.handle.net/10204/6651 http://onlinelibrary.wiley.com/doi/10.1002/joc.3420/pdf en eng Royal Meteorological Society Workflow;10102 C. J. Engelbrecht, F. A. Engelbrecht and L. L. Dyson. 2012. High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa. International Journal of Climatology, vol. 33, pp 173-187 0899-8418 http://onlinelibrary.wiley.com/doi/10.1002/joc.3420/pdf http://hdl.handle.net/10204/6651 Mid-tropospheric closed-lows Southern Africa climate Climate change Tropical cyclones Article 2012 ftcsir 2022-05-19T06:12:00Z Copyright: 2012 Royal Meteorological Society. This is an ABSTRACT ONLY. The definitive version is published in International Journal of Climatology, vol. 33, pp 173-187 Mid-tropospheric closed-lows (cold-core cut-off lows and warm-core tropical lows) are important rain producing weather systems for the southern Africa region. Over South Africa, most wide-spread flood events are caused by these systems. It is therefore important to explore the potential impact of anthropogenic forcing on the occurrence of closed-lows and extreme rainfall events over the region. Coupled global circulation models (CGCMs) can not be directly applied for this purpose because of their relatively low spatial resolution – some form of downscaling is required to adequately resolve these systems and the rainfall they cause. In this study, a variable-resolution atmospheric global circulation model is applied as a regional climate model to simulate closed-low characteristics over southern Africa under current and future forcings. The model is forced with greenhouse gas concentrations according to the A2 SRES scenario and with sea surface temperatures (SSTs) and sea-ice as specified by the CSIRO Mk3 CGCM. The model projects a general decrease in closed-low frequencies over the region, which occurs in association with a general strengthening of the subsiding branch of the Hadley cell. However, the climate-change signal shows variation in time and space and certain sub-regions are projected to experience an increase in closed-low frequencies during certain seasons. A general increase in extreme rainfall events is projected over southern Africa despite the projected decrease in closed-low frequencies. It is deduced that this increase in extreme rainfall events is driven by intense convective rainfall events occurring within more frequently forming tropical-temperate cloud bands. Over Mozambique, extreme rainfall events are projected to increase in association with more frequently occurring closed-lows. Article in Journal/Newspaper Sea ice Council for Scientific and Industrial Research (South Africa): CSIR Research Space |
institution |
Open Polar |
collection |
Council for Scientific and Industrial Research (South Africa): CSIR Research Space |
op_collection_id |
ftcsir |
language |
English |
topic |
Mid-tropospheric closed-lows Southern Africa climate Climate change Tropical cyclones |
spellingShingle |
Mid-tropospheric closed-lows Southern Africa climate Climate change Tropical cyclones Engelbrecht, CJ Engelbrecht, FA Dyson, LL High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa |
topic_facet |
Mid-tropospheric closed-lows Southern Africa climate Climate change Tropical cyclones |
description |
Copyright: 2012 Royal Meteorological Society. This is an ABSTRACT ONLY. The definitive version is published in International Journal of Climatology, vol. 33, pp 173-187 Mid-tropospheric closed-lows (cold-core cut-off lows and warm-core tropical lows) are important rain producing weather systems for the southern Africa region. Over South Africa, most wide-spread flood events are caused by these systems. It is therefore important to explore the potential impact of anthropogenic forcing on the occurrence of closed-lows and extreme rainfall events over the region. Coupled global circulation models (CGCMs) can not be directly applied for this purpose because of their relatively low spatial resolution – some form of downscaling is required to adequately resolve these systems and the rainfall they cause. In this study, a variable-resolution atmospheric global circulation model is applied as a regional climate model to simulate closed-low characteristics over southern Africa under current and future forcings. The model is forced with greenhouse gas concentrations according to the A2 SRES scenario and with sea surface temperatures (SSTs) and sea-ice as specified by the CSIRO Mk3 CGCM. The model projects a general decrease in closed-low frequencies over the region, which occurs in association with a general strengthening of the subsiding branch of the Hadley cell. However, the climate-change signal shows variation in time and space and certain sub-regions are projected to experience an increase in closed-low frequencies during certain seasons. A general increase in extreme rainfall events is projected over southern Africa despite the projected decrease in closed-low frequencies. It is deduced that this increase in extreme rainfall events is driven by intense convective rainfall events occurring within more frequently forming tropical-temperate cloud bands. Over Mozambique, extreme rainfall events are projected to increase in association with more frequently occurring closed-lows. |
format |
Article in Journal/Newspaper |
author |
Engelbrecht, CJ Engelbrecht, FA Dyson, LL |
author_facet |
Engelbrecht, CJ Engelbrecht, FA Dyson, LL |
author_sort |
Engelbrecht, CJ |
title |
High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa |
title_short |
High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa |
title_full |
High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa |
title_fullStr |
High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa |
title_full_unstemmed |
High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa |
title_sort |
high-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern africa |
publisher |
Royal Meteorological Society |
publishDate |
2012 |
url |
http://hdl.handle.net/10204/6651 http://onlinelibrary.wiley.com/doi/10.1002/joc.3420/pdf |
genre |
Sea ice |
genre_facet |
Sea ice |
op_relation |
Workflow;10102 C. J. Engelbrecht, F. A. Engelbrecht and L. L. Dyson. 2012. High-resolution model-projected changes in mid-tropospheric closed-lows and extreme rainfall events over southern Africa. International Journal of Climatology, vol. 33, pp 173-187 0899-8418 http://onlinelibrary.wiley.com/doi/10.1002/joc.3420/pdf http://hdl.handle.net/10204/6651 |
_version_ |
1766195649863221248 |