An index for tropical temperate troughs over southern Africa

Ratna, Satyaban B.; Behera, Swadhin K.; Ratnam, J. V.; Takahashi, Kazutaka; Yamagata, Toshio

doi:10.1007/s00382-012-1540-8

Cited by 49 publications

(53 citation statements)

References 40 publications

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“…Figure (a) and (b) displays a similar NW–SE oriented anomaly patterns in SAT max and relative humidity which is reminiscent of TTT formation extending southeast from the Angola Low towards the southeast coast of South Africa (Hart et al , ; Macron et al , ). During TTT events, convection over the continent is linked to the transients in the mid‐latitudes identified by the presence of convective cloud‐bands elongated along NW–SE direction (Todd et al , ; Hart et al , ; Ratna et al , ). The negative impact of the deep convective clouds on the vertical structure of temperature is demonstrated in Figure (d) which is more prominent below 700 mb between about 16° and 28°S.…”

Section: Resultsmentioning

confidence: 99%

ENSO–Kalahari Desert linkages on southern Africa summer surface air temperature variability

Manatsa

Reason

2016

Intl Journal of Climatology

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In this work, we use observational and reanalysis data to demonstrate the prominent role which is played by the Kalahari Desert in the modulation of the maximum surface air temperature (SATmax) over southern Africa during austral summer. It is not only the El Niño Southern Oscillation (ENSO) related modification of the middle and upper troposphere but the coupling to the desert surface through cloud development mechanisms which contribute immensely to the SATmax extremes. This is achieved through the convective cloud enhancement mechanisms linked to the tropical temperate troughs and suppression processes forced by the Botswana Upper High during La Niña and El Niño events, respectively. However, significant ENSO impact on the regional SATmax is restricted to the setting in of the Indian Ocean basin‐wide sea surface temperature (SST) mode in December. This SST mode is unique and specifically characterizes the distinctive nature of the canonical version of the ENSO extremes. In this regard, the prominent anomalous warming and cooling of SATmax is predominantly explained by the canonical El Niño and La Niña events, respectively. On the other hand, ENSO ‘modoki’ cases appear not only to have notably reduced impacts on SATmax but have effects which are opposite in sign relative to their canonical ENSO counterparts. Therefore, factors which modulate ENSO characteristics, be they natural or anthropogenic, should have strong implications on the environment, water resource availability and societies of southern Africa.

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Section: Resultsmentioning

confidence: 99%

ENSO–Kalahari Desert linkages on southern Africa summer surface air temperature variability

Manatsa

Reason

2016

Intl Journal of Climatology

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“…A large proportion of southern African rainfall is associated with TTT systems (Harrison 1984), particularly heavy rainfall (Hart et al 2013). TTTs are therefore a good target for evaluation in terms of impact relevance and might also be an indicator of the credibility of modeled regional dynamics: the location and character of tropical convection, storm tracks, subtropical highs, and the Angola low might all influence the formation of TTCBs (Todd et al 2004;Fauchereau et al 2009;Hart et al 2010;Ratna et al 2013;Macron et al 2014).…”

Section: Pan-africanmentioning

confidence: 99%

Evaluating Climate Models with an African Lens

James

Washington

Abiodun

et al. 2018

Bulletin of the American Meteorological Society

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“…The Mascarene high brings a huge amount of moisture from the southern Indian Ocean over southern Africa, which helps develop the South Indian convergence zone (Cook 2000) during austral summer (DecemberFebruary, hereafter the season is defined in the Southern Hemisphere) and causes most of the annual rainfall over southern Africa via synoptic-scale rainfall systems called the tropical-temperate trough (Harrison 1984;Todd and Washington 1999;Todd et al 2004;Ratna et al 2013). As shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Local SST Impacts on the Summertime Mascarene High Variability

et al. 2015

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The interannual variations in the summertime Mascarene high have great impacts on the southern African climate as well as the sea surface temperature (SST) in the southern Indian Ocean. A set of coupled general circulation model (CGCM) experiments are performed to examine a role of the interannual SST variability in the southern Indian Ocean on the summertime Mascarene high variability. The dominant interannual variability in the summertime Mascarene high shows the strengthening (weakening) in its southern part throughout the austral summer (December-February). However, in the experiment where the interannual SST variability in the southern Indian Ocean is suppressed, the strengthening (weakening) of the Mascarene high in its southern part does not persist until February. Also, the Mascarene high variability and its associated SST anomalies in December and January are found to increase (decrease) the southern African rainfall via more (less) moisture supply from the southern Indian Ocean. The Mascarene high variability is actually associated with a meridional dipole of positive and negative SST anomalies, which in turn produces that of the meridional SST gradient anomaly. This causes a southward (northward) shift of the storm tracks and hence the westerly jet, favoring the strengthening (weakening) of the Mascarene high in its southern part. This local ocean-atmosphere feedback effectively operates in February, when the meridional dipole of the SST anomalies reaches the maximum. These results provide new insight into the important role of the local SST variability in the summertime Mascarene high variability and hence the southern African climate.

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An index for tropical temperate troughs over southern Africa

Cited by 49 publications

References 40 publications

ENSO–Kalahari Desert linkages on southern Africa summer surface air temperature variability

ENSO–Kalahari Desert linkages on southern Africa summer surface air temperature variability

Evaluating Climate Models with an African Lens

Local SST Impacts on the Summertime Mascarene High Variability

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