Numerical simulation of a mesoscale convective system over the east coast of South Africa

Blamey, Ross C.; Reason, C. J. C.

doi:10.1111/j.1600-0870.2008.00366.x

Cited by 41 publications

(33 citation statements)

References 82 publications

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“…Other studies have similarly concluded that this current is a notably influential feature on South African weather patterns as it affects the summer rainfall and severe weather events in the region (e.g. Jury et al 1993;Crimp and Mason 1999;Reason and Mulenga 1999;Reason 2001;Rouault et al 2002;Singleton and Reason 2006;Blamey and Reason 2009). …”

Section: Discussion and Concluding Remarksmentioning

confidence: 93%

A climatology of potential severe convective environments across South Africa

et al. 2016

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Section: Discussion and Concluding Remarksmentioning

confidence: 93%

A climatology of potential severe convective environments across South Africa

et al. 2016

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“…Nevertheless, the heaviest rainfall of these three events was recorded in case I, where QG forcing was weak, implying the role of convective overturning. Spatial inhomogeneities in the magnitude of the rainfall for all cases (e.g., the extreme precipitation over Mozambique during case III) suggests phenomenon such as mesoscale convective systems (e.g., Blamey and Reason 2009) may be embedded in TE cloud bands, at least over South Africa. Indeed, De Coning et al (1998) found the tropical root of a TTT on 12 February 1996 to be a mesoscale convective vortex centered near the Angola low.…”

Section: Discussionmentioning

confidence: 98%

Tropical–Extratropical Interactions over Southern Africa: Three Cases of Heavy Summer Season Rainfall

Hart

Reason

Fauchereau

2010

Monthly Weather Review

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The synoptic evolution of three tropical-extratropical (TE) interactions, each responsible for extreme rainfall events over southern Africa, is discussed in detail. Along with the consideration of previously studied events, common features of these heavy rainfall producing tropical temperate troughs (TTTs) over southern Africa are discussed. It is found that 2 days prior to an event, northeasterly moisture transports across Botswana, set up by the Angola low, are diverted farther south into the semiarid region of subtropical southern Africa. The TTTs reach full maturity as a TE cloud band, rooted in the central subcontinent, which is triggered by upper-level divergence along the leading edge of an upper-tropospheric westerly wave trough. Convection and rainfall within the cloud band is supported by poleward moisture transports with subtropical air rising as it leaves the continent and joins the midlatitude westerly flow. It is shown that these systems fit within a theoretical framework describing similar TE interactions found globally.Uplift forcing for the extreme rainfall of each event is investigated. Unsurprisingly, quasigeostrophic uplift is found to dominate in the midlatitudes with convective processes strongest in the subtropics. Rainfall in the semiarid interior of South Africa appears to be a result of quasigeostrophically triggered convection.Investigation of TTT formation in the context of planetary waves shows that early development is sometimes associated with previous anticyclonic wave breaking south of the subcontinent, with full maturity of TTTs occurring as a potential vorticity trough approaches the continent from the west. Sensitivity to upstream wave perturbations and effects on anticyclonic wave breaking in the South Indian Ocean are also observed.

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“…In summary, the steep topography of the eastern escarpment is known for creating problems for climate models as rainfall totals are generally overestimated (Joubert et al, 1999;Engelbrecht et al, 2002;Giorgi, 2005;Christensen et al, 2007;Liang et al, 2008;Engelbrecht et al, 2009;Nikulin et al, 2012;Jury, 2012;Sylla et al, 2012;Hernandez-Diaz et al, 2013). The purpose of this paper is to evaluate the performance of the variable-resolution atmospheric model CCAM in representing rainfall totals over STA and in particular the eastern escarpment region of South Africa and Lesotho.…”

Section: Rainfall Modellingmentioning

confidence: 99%

Model simulations of rainfall over southern Africa and its eastern escarpment

Dedekind¹,

Engelbrecht²,

Merwe³

2016

WSA

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Rainfall simulations over southern and tropical Africa in the form of low-resolution Atmospheric Model Intercomparison Project (AMIP) simulations and higher resolution National Centre for Environmental Prediction (NCEP) reanalysis downscalings are presented and evaluated in this paper. The model used is the conformal-cubic atmospheric model (CCAM), a variable-resolution global atmospheric model. The simulations are evaluated with regards to rainfall totals, spatial distribution, seasonality and inter-annual variability. Since both Global Circulation Models (GCMs) and Regional Climate Models (RCMs) are known to have relatively large biases and shortcomings in simulating rainfall over the steep eastern escarpment of southern Africa and in particular Lesotho, the paper has a focus on evaluating model performance over these regions. It is shown that in the reanalysis simulations the model realistically represents the seasonal cycle in rainfall. However, the AMIP simulations are prone to the model overestimating rainfall totals in spring. The spatial distribution of rainfall is simulated realistically; however rainfall totals are significantly overestimated over the escarpment areas of both southern Africa and East Africa. When nudged within the observed circulation patterns of the reanalysis data, the model is capable of realistically simulating inter-annual rainfall variability over the eastern parts of southern Africa.

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Numerical simulation of a mesoscale convective system over the east coast of South Africa

Abstract: identified that the development of the MCS and the heavy nocturnal precipitation was due to a combination of the continuous moisture supply into the region, a conditionally unstable atmosphere, and uplift due to low level convergence and the local topography.11

Cited by 41 publications

References 82 publications

A climatology of potential severe convective environments across South Africa

A climatology of potential severe convective environments across South Africa

Tropical–Extratropical Interactions over Southern Africa: Three Cases of Heavy Summer Season Rainfall

Model simulations of rainfall over southern Africa and its eastern escarpment

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