Model simulations of rainfall over southern Africa and its eastern escarpment

Dedekind, Zane; Engelbrecht, François; Merwe, Jacobus Van der

doi:10.4314/wsa.v42i1.13

Cited by 34 publications

(20 citation statements)

References 45 publications

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“…1b). This high-pressure cell creates a blocking effect over the continent, which stops moisture advection inland over the majority of South Africa during winter (Dedekind et al, 2016), except for in the winter rainfall zone (WRZ), where the westerlies bring rainfall. During summer, the high-pressure cell shifts to the south, and the Angola and Kalahari low-pressure cells dominate the continent, enabling monsoonal systems (tropical easterlies) to penetrate southern Africa, bringing rainfall to the summer rainfall zone (SRZ; Fig.…”

Section: Regional Settingmentioning

confidence: 99%

Late Quaternary climate variability at Mfabeni peatland, eastern South Africa

et al. 2019

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Abstract. The scarcity of continuous, terrestrial, palaeoenvironmental records in eastern South Africa leaves the evolution of late Quaternary climate and its driving mechanisms uncertain. Here we use a ∼7 m long core from Mfabeni peatland (KwaZulu-Natal, South Africa) to reconstruct climate variability for the last 32 000 years (cal ka BP). We infer past vegetation and hydrological variability using stable carbon (δ13Cwax) and hydrogen isotopes (δDwax) of plant-wax n-alkanes and use Paq to reconstruct water table changes. Our results indicate that late Quaternary climate in eastern South Africa did not respond directly to orbital forcing or to changes in sea-surface temperatures (SSTs) in the western Indian Ocean. We attribute the arid conditions evidenced at Mfabeni during the Last Glacial Maximum (LGM) to low SSTs and an equatorward displacement of (i) the Southern Hemisphere westerlies, (ii) the subtropical high-pressure cell, and (iii) the South Indian Ocean Convergence Zone (SIOCZ), which we infer was linked to increased Antarctic sea-ice extent. The northerly location of the high-pressure cell and the SIOCZ inhibited moisture advection inland and pushed the rain-bearing cloud band north of Mfabeni, respectively. The increased humidity at Mfabeni between 19 and 14 cal kyr BP likely resulted from a southward retreat of the westerlies, the high-pressure cell, and the SIOCZ, consistent with a decrease in Antarctic sea-ice extent. Between 14 and 5 cal kyr BP, when the westerlies, the high-pressure cell, and the SIOCZ were in their southernmost position, local insolation became the dominant control, leading to stronger atmospheric convection and an enhanced tropical easterly monsoon. Generally drier conditions persisted during the past ca. 5 cal ka BP, probably resulting from an equatorward return of the westerlies, the high-pressure cell, and the SIOCZ. Higher SSTs and heightened El Niño–Southern Oscillation (ENSO) activity may have played a role in enhancing climatic variability during the past ca. 5 cal ka BP. Our findings highlight the influence of the latitudinal position of the westerlies, the high-pressure cell, and the SIOCZ in driving climatological and environmental changes in eastern South Africa.

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Section: Regional Settingmentioning

confidence: 99%

Late Quaternary climate variability at Mfabeni peatland, eastern South Africa

et al. 2019

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“…Large protected areas in these savannas, like Kruger, are important for the preservation of large-scale intact environments and the conservation of diverse wildlife assemblages and extensive wilderness qualities (Cantú-Salazar and Gaston, 2010). SA has a highly variable climate and pronounced rainfall seasonality, driven predominantly by sea surface temperatures, the effects of the El Niño-Southern Oscillation (ENSO) -both its warm (El Niño) and cool (La Niña) phases and the Intertropical Convergence Zone (ITCZ) (Philippon et al, 2014;Dedekind et al, 2016;Favre et al, 2016). The displacement of ITCZ to the south of the equator during the austral summer produces the South Indian Convergence Zone which restricts most of SA to a summer rainfall region (Dedekind et al, 2016).…”

Section: Study Areamentioning

confidence: 99%

“…SA has a highly variable climate and pronounced rainfall seasonality, driven predominantly by sea surface temperatures, the effects of the El Niño-Southern Oscillation (ENSO) -both its warm (El Niño) and cool (La Niña) phases and the Intertropical Convergence Zone (ITCZ) (Philippon et al, 2014;Dedekind et al, 2016;Favre et al, 2016). The displacement of ITCZ to the south of the equator during the austral summer produces the South Indian Convergence Zone which restricts most of SA to a summer rainfall region (Dedekind et al, 2016). Kruger falls within a semi-arid zone which spans much of the central and northeastern parts of SA (Rutherford and Westfall, 1986;Trabucco and Zomer, 2009).…”

Section: Study Areamentioning

confidence: 99%

Long‐term rainfall regression surfaces for the Kruger National Park, South Africa: a spatio‐temporal review of patterns from 1981 to 2015

MacFadyen

Zambatis

Teeffelen

et al. 2018

Intl Journal of Climatology

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ABSTRACT:As an important bottom-up driver of ecosystem processes, rainfall is intrinsically linked to the dynamics of vegetation and species distributions through its effects on soil moisture content and surface water availability. Rainfall effects are thus spatially and temporally specific to different environmental role-players. Knowledge of its spatio-temporal pattern is therefore essential to understanding natural ecosystem flux and potential climate change effects. Climate change poses a serious threat to protected areas in particular, as they are often isolated in fragmented landscapes and confined within hard park boundaries. In consequence, a species' natural movement response to resulting climate-induced niche shifts is often obstructed. Long-term, accurate and consistent climate monitoring data are therefore important resources for managers in large protected areas like the Kruger National Park (Kruger). In this article we model local rainfall measurements as a function of global rainfall surfaces, elevation and distance to the ocean using a generalized additive mixed effects model to produce fine-scale (1 km 2 ) monthly rainfall surfaces from July 1981 to June 2015. Results show a clear seasonal cycle nested within an oscillating multi-decadal trend. Most noticeably, seasonality is shifting both temporally and spatially as rainfall moves outside of the typical dry/wet periods and areas. In addition, high-rainfall seasons are generally receiving more rainfall while low-rainfall seasons are receiving less. Northwestern regions of the park are experiencing more extreme annual rainfall differences, while far northern and southern regions show greater seasonality changes. The well-described north-south and east-west rainfall gradient is still visible but the spatial complexity of this pattern is more pronounced than expected. Taken together, we show that Kruger's spatio-temporal rainfall patterns are changing significantly in the short to medium term. The resulting raster data set is made freely available to promote holistic ecosystem studies and support longer-term climate change research (http:// dataknp.sanparks.org/sanparks/).

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“…African rainfall variability is mostly related to the ENSO indices [11,12]. Like tropics, Southern Africa regions have high climate variation and hence susceptible to droughts and floods [13][14][15].…”

Section: Rainfall-altitude Relationshipmentioning

confidence: 99%

Development and Application of Conceptual Rainfall-Altitude Regression Model: The Case of Matahara Area (Ethiopia)

Dinka¹

2019

Topics in Hydrometerology

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Rainfall data available, in tropical regions with undulating topography, may provide a valuable information for water resource development as well as for predicting and preventing natural disasters. But in developing countries like Ethiopia, rain gauge stations are sparsely populated, and rainfall data are the limiting factor. Hence, estimation of rainfall is extremely important. The current paper deals with the development of a rainfall-altitude relationship for Matahara area, Awash Basin of Ethiopia. A conceptual rainfall-altitude regression model was formulated and its performance evaluated. The relationship between monthly rainfall totals and gauge elevation over Matahara region (including Lake Basaka catchment) was examined using the conceptual regression model (ordinary least square). The regression parameters were identified and estimated and then used to map the spatial rainfall for Lake Basaka catchment in ArcGIS. The regression analysis showed a strong positive correlation (r = 0.85) between the long-term average monthly rainfall and altitude of the region. It is shown that the rate of increase of rainfall with altitude is in the range of 0.020 mm/h at Matahara to 0.067 at Welenchiti, with average value of 0.0475 mm/m/month. The best fit (R 2 = 0.9187, p = 0.015) was obtained between observed and estimated rainfall depths for all the stations with total standard error of 12.97 mm. The high R 2 reveals that the developed equation is acceptable for the area at 98.5% (p > 0.015) confidence limit. The performance of the developed model is found to be within reasonable accuracy, which is limited by the elevation difference and distance from the base station. Therefore, the spatial and temporal structures of rainfall distribution (daily, monthly or annual) for Matahara region (including Basaka Lake catchment) can be determined from the available records of rainfall data at the Matahara Research Station (Merti) meteorological station with acceptable reliability. In general, the performance of the developed model is found to be within reasonable accuracy, which is limited by the elevation difference and distance from the base station.

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Model simulations of rainfall over southern Africa and its eastern escarpment

Cited by 34 publications

References 45 publications

Late Quaternary climate variability at Mfabeni peatland, eastern South Africa

Late Quaternary climate variability at Mfabeni peatland, eastern South Africa

Long‐term rainfall regression surfaces for the Kruger National Park, South Africa: a spatio‐temporal review of patterns from 1981 to 2015

Development and Application of Conceptual Rainfall-Altitude Regression Model: The Case of Matahara Area (Ethiopia)

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