Seasonal to Decadal Prediction of Southern African Climate and Its Links with Variability of the Atlantic Ocean

Reason, C. J. C.; Landman, Willem A.; Tennant, Warren

doi:10.1175/bams-87-7-941

Cited by 182 publications

(184 citation statements)

References 48 publications

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“…Therefore, the fact that there is no simple relationship between interannual rainfall variability in Zimbabwe rainfall and the IODZM suggests that other low frequency climate processes are also at play. These may include modes of the Atlantic Ocean, sub-tropical and extra-tropical variability as described by Reason (2001); Reason et al (2006) and Mulenga et al, 2003;and Washington and Todd 1999, respectively. However, it is quite possible that the relationship of the positive IODZM and more intense droughts is supreme, as the mode is linked to virtually all extreme droughts and as much as two-thirds of the severe droughts.…”

Section: Discussionmentioning

confidence: 99%

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

Manatsa

Chingombe

Matarira

2008

Intl Journal of Climatology

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A comparative study of the impact of the anomalous positive Indian Ocean SST gradient, referred to as the Indian Ocean Dipole/Zonal Mode (IODZM), and El Niño-Southern Oscillation (ENSO) on Zimbabwe seasonal rainfall variability for the period 1940-1999, is documented. Composite techniques together with simple and partial correlation analyses are employed to segregate the unique association related to IODZM/ENSO with respect to the Zimbabwe seasonal rainfall.The analysis reveals that the IODZM impact on the country's summer rainfall is overwhelming as compared to that of ENSO when the two are in competition. The IODZM influence remains high (significant above 99% confidence level), even after the influence of ENSO has been removed, while that of ENSO collapses to insignificance (even at 90% confidence level) when the IODZM contribution is eliminated. The relationship between ENSO and Zimbabwe seasonal rainfall seems to be sustained through El Niño occurring in the presence of positive IODZM events. However, when the co-occurring positive IODZM and El Niño events are removed from the analysis, it is apparently clear that ENSO has little to do with the country's rainfall variability. On the other hand, positive IODZM is mostly associated with the rainfall deficits, whether or not it co-occurs with El Niño. However, the co-occurrence of the two events does not necessarily suggest that El Niño influences droughts through the positive IODZM events. The El Niño event components during co-occurrence seem to be unrelated (at least linearly) to the droughts, while the positive IODZM events display a relatively strong relationship that is significant above the 95% confidence level. It thus becomes important to extend the study of this nature to cover the whole of southern Africa, so that the extent of the impact of the phenomena can be realized over the whole region.

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Section: Discussionmentioning

confidence: 99%

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

Manatsa

Chingombe

Matarira

2008

Intl Journal of Climatology

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“…At the climate variability time scale, while the effects of ENSO are less consistent in southern Africa, Pohl et al, [10] Reason et al [11] and Landman and Beraki [12] show that seasonal scale climate variability over southern Africa is variably predictable and in some cases (particularly in the north-east) strongly associated with the ENSO state. Lazenby et al [13] have considered the prediction skill of temperature variability at the seasonal time scale for various time frames (in months) and various lead times and show the utility (and current limitations) of these predictabilities in respect of health applications.…”

Section: Climate Variability and Change In Southern Africamentioning

confidence: 98%

Climate change is catchy – but when will it really hurt?

Sweijd¹,

Wright²,

Westwood³

et al. 2015

S Afr Med J

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“…Node 12, the synoptic forcing is not as favourable as in Node 4, but local conditions are favourable for the development of thundershowers, as the surface temperatures are higher and the atmosphere is Composite maps for every node of the mean 850 hPa geopotential heights (shaded), 700 hPa moisture flux (arrows), 500 hPa geopotential heights (black contours) and southern subcontinent (Reason et al 2006). The 500 hPa high pressure centre is in the same location at the 700 hPa high, but with very weak geopotential gradients over South Africa.…”

Section: Early Summer Heavy Rainfallmentioning

confidence: 99%

A heavy rainfall sounding climatology over Gauteng, South Africa, using self-organising maps

Dyson

2015

Clim Dyn

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The daily weather at a particular place is largely influenced by the synoptic circulation and thermodynamic profile of the atmosphere. Heavy rainfall occurs from a particular subset of synoptic and thermodynamic states. Baseline climatologies provide objective information on heavy rainfall-producing circulation patterns and thermodynamic variables. This is how climatologically large or extreme values associated with heavy rainfall are identified. The aim of this research is to provide a heavy rainfall sounding climatology in austral summer over Gauteng, South Africa, using self-organising maps (SOMs).The results show that the SOM captures the intra-seasonal variability of heavy rainfall soundings by clearly distinguishing between the atmospheric conditions on early summer (October to December) and late summer (January to March) heavy rainfall days. Conditions associated with heavy early summer rainfall are large vertical wind shear and conditional instability, while the atmosphere is drier and cooler than when heavy rainfall occurs in late summer. Late summer heavy rainfall conditions are higher convective instability and small vertical wind shear values. The SOM climatology shows that some heavy rainfall days occur in both early and late summer when large-scale synoptic weather systems cause strong near-surface moisture flux and large values of wind shear. On these days, both the conditional and convective instability of the atmosphere are low and heavy rainfall results from the strong synoptic forcing. In contrast, heavy rainfall also occurs on days when synoptic circulation is not very favourable and the air is relatively dry, but the atmosphere is unstable with warm surface conditions and heavy 2 rainfall develops from local favourable conditions. The SOM climatology provides guidelines to critical values of sounding-derived parameters for all these scenarios.

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Seasonal to Decadal Prediction of Southern African Climate and Its Links with Variability of the Atlantic Ocean

Cited by 182 publications

References 48 publications

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

Climate change is catchy – but when will it really hurt?

A heavy rainfall sounding climatology over Gauteng, South Africa, using self-organising maps

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