Attributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising maps
The Southwestern Cape (SWC) region in South Africa experienced a severe rainfall deficit between 2015–2017. The resulting drought caused the City of Cape Town to almost run out of water during the summer of 2017–2018. Using the self-organising maps approach, we identify and classify the synoptic cir...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/ace26f |
| _version_ | 1797747316978876416 |
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| author | Romaric C Odoulami Piotr Wolski Mark New |
| author_facet | Romaric C Odoulami Piotr Wolski Mark New |
| author_sort | Romaric C Odoulami |
| collection | DOAJ |
| description | The Southwestern Cape (SWC) region in South Africa experienced a severe rainfall deficit between 2015–2017. The resulting drought caused the City of Cape Town to almost run out of water during the summer of 2017–2018. Using the self-organising maps approach, we identify and classify the synoptic circulation states over Southern Africa known to influence the local climate in the SWC into three groups (dry, intermediate, and wet circulation types) using large ensembles of climate model simulations with anthropogenic forcing and natural forcing. We then assessed the influence of anthropogenic climate change on the likelihood of these circulation types and associated rainfall amounts over the SWC during the drought. Our findings suggest that during the drought, the frequency of dry (wet) circulation types increases (decreases) across all models under anthropogenic forcing relative to the natural forcing. While there was no clear direction in the associated rainfall change in the dry circulation types, rainfall decreased across most models in wet nodes. All models agree that anthropogenic climate change has increased the likelihood of dry circulation types (median probability ratio (PR): 0.93–0.96) and decreased that of wet circulation types (median PR: 1.01 and 1.12), indicating a shift towards lesser (more) wet (dry) synoptic circulation states and associated rainfall during the drought. The long-term climatology also depicts similar patterns indicating the drought may result from long-term changes in the frequency of wet circulations and their associated rainfall. This study further explains the anthropogenic influence on the dynamic (synoptic circulation states) and thermodynamic (rainfall) factors that influenced the SWC 2015–2017 drought. |
| first_indexed | 2024-03-12T15:49:03Z |
| format | Article |
| id | doaj.art-88d600916fa6469885006e3b0497cbdb |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T15:49:03Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-88d600916fa6469885006e3b0497cbdb2023-08-09T15:17:49ZengIOP PublishingEnvironmental Research Letters1748-93262023-01-0118707404310.1088/1748-9326/ace26fAttributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising mapsRomaric C Odoulami0https://orcid.org/0000-0001-8228-1608Piotr Wolski1https://orcid.org/0000-0002-6120-6593Mark New2https://orcid.org/0000-0001-6082-8879African Climate and Development Initiative, University of Cape Town , Cape Town, South AfricaClimate System Analysis Group, University of Cape Town , Cape Town, South AfricaAfrican Climate and Development Initiative, University of Cape Town , Cape Town, South Africa; School of International Development, University of East Anglia , Norwich NR47TJ, United KingdomThe Southwestern Cape (SWC) region in South Africa experienced a severe rainfall deficit between 2015–2017. The resulting drought caused the City of Cape Town to almost run out of water during the summer of 2017–2018. Using the self-organising maps approach, we identify and classify the synoptic circulation states over Southern Africa known to influence the local climate in the SWC into three groups (dry, intermediate, and wet circulation types) using large ensembles of climate model simulations with anthropogenic forcing and natural forcing. We then assessed the influence of anthropogenic climate change on the likelihood of these circulation types and associated rainfall amounts over the SWC during the drought. Our findings suggest that during the drought, the frequency of dry (wet) circulation types increases (decreases) across all models under anthropogenic forcing relative to the natural forcing. While there was no clear direction in the associated rainfall change in the dry circulation types, rainfall decreased across most models in wet nodes. All models agree that anthropogenic climate change has increased the likelihood of dry circulation types (median probability ratio (PR): 0.93–0.96) and decreased that of wet circulation types (median PR: 1.01 and 1.12), indicating a shift towards lesser (more) wet (dry) synoptic circulation states and associated rainfall during the drought. The long-term climatology also depicts similar patterns indicating the drought may result from long-term changes in the frequency of wet circulations and their associated rainfall. This study further explains the anthropogenic influence on the dynamic (synoptic circulation states) and thermodynamic (rainfall) factors that influenced the SWC 2015–2017 drought.https://doi.org/10.1088/1748-9326/ace26fattributionCape Town ‘Day Zero’ droughtself-organising mapscirculationsynoptic driverswinter rainfall |
| spellingShingle | Romaric C Odoulami Piotr Wolski Mark New Attributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising maps Environmental Research Letters attribution Cape Town ‘Day Zero’ drought self-organising maps circulation synoptic drivers winter rainfall |
| title | Attributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising maps |
| title_full | Attributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising maps |
| title_fullStr | Attributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising maps |
| title_full_unstemmed | Attributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising maps |
| title_short | Attributing the driving mechanisms of the 2015–2017 drought in the Western Cape (South Africa) using self-organising maps |
| title_sort | attributing the driving mechanisms of the 2015 2017 drought in the western cape south africa using self organising maps |
| topic | attribution Cape Town ‘Day Zero’ drought self-organising maps circulation synoptic drivers winter rainfall |
| url | https://doi.org/10.1088/1748-9326/ace26f |
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