Blamey_et_al_2018_submission.pdf (5.43 MB)
The role of regional circulation features in regulating El Nin~o climate impacts over southern Africa: a comparison of the 2015/16 drought with previous events
journal contribution
posted on 2023-06-09, 12:52 authored by R C Blamey, Seshu Kolusu, P Mahalela, Martin ToddMartin Todd, C J C ReasonExtremely dry conditions were experienced across most of southern Africa during the austral summer (October-March) of 2015/16, associated with one of the strongest observed El Niño events in the Pacific. Dry conditions peaked in the early austral summer months (October-December) producing the most intense drought in the 116 year historical record, as measured by the intensity of the Standardized Precipitation Index across all spatial scales up to the sub-continental. We estimate the return period of this extreme early summer drought to be greater than 200 years. The interior and eastern parts of South Africa were particularly hard-hit with station data showing rainfall totals being at their lowest since at least 1950. The early summer dry conditions make the 2015/16 event atypical compared to past El Niño events of similar magnitude. We find that key regional circulation patterns, influenced by planetary scale processes, play an important role in modulating the spatial and temporal evolution of the summer rainfall during these El Niño events. Specifically, (i) the Angola Low and the South Indian Ocean High, two dominant low level circulation features that drive moisture convergence to support convective precipitation in the region, were anomalously weakened in early austral summer of 2015/16 resulting in less moisture being transported over the continent, and (ii) the mid-level Botswana High was stronger than in previous El Niño years further producing unfavourable conditions for rainfall through stronger subsidence in the mid- to upper levels over southern Africa.
Funding
GROFUTURES: Groundwater Futures in Sub-Saharan Africa; G1702; NERC-NATURAL ENVIRONMENT RESEARCH COUNCIL; NE/M008207/1
DRiSL: The Drought Risk Finance Science Laboratory; G2314; NERC-NATURAL ENVIRONMENT RESEARCH COUNCIL; NE/R014272/1
Uncertainty reduction in Models For Understanding deveLopment Applications (UMFULA); G1671; NERC-NATURAL ENVIRONMENT RESEARCH COUNCIL; NE/M020258/1
Towards Forecast-based Preparedness Action (ForPAc): Probabilistic forecasts information for defensible preparedness decision-making and action; G2043; NERC-NATURAL ENVIRONMENT RESEARCH COUNCIL; NE/P000673/1
History
Publication status
- Published
File Version
- Accepted version
Journal
International Journal of ClimatologyISSN
1097-0088Publisher
Royal Meteorological SocietyExternal DOI
Issue
11Volume
38Page range
4276-4295Department affiliated with
- Geography Publications
Research groups affiliated with
- Sussex Sustainability Research Programme Publications
Full text available
- Yes
Peer reviewed?
- Yes
Legacy Posted Date
2018-04-16First Open Access (FOA) Date
2019-07-13First Compliant Deposit (FCD) Date
2018-04-16Usage metrics
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