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  • 1
    Online Resource
    Online Resource
    Atmospheric and Climatic Drivers of Tide Gauge Sea Level Variability along the East and South Coast of South Africa
    MDPI AG ; 2021
    In:  Journal of Marine Science and Engineering Vol. 9, No. 9 ( 2021-08-26), p. 924-
    Details
    In: Journal of Marine Science and Engineering, MDPI AG, Vol. 9, No. 9 ( 2021-08-26), p. 924-
    Abstract: Atmospheric forcing and climate modes of variability on various timescales are important drivers of sea level variability. However, the influence of such drivers on sea level variability along the South African east and south coast has not yet been adequately investigated. Here, we determine the timescales of sea level variability and their relationships with various drivers. Empirical Mode Decomposition (EMD) was applied to seven tide gauge records and potential forcing data for this purpose. The oscillatory modes identified by the EMD were summed to obtain physically more meaningful timescales—specifically, the sub-annual (less than 18 months) and interannual (greater than two years) scales. On the sub-annual scale, sea level responds to regional zonal and meridional winds associated with mesoscale and synoptic weather disturbances. Ekman dynamics resulting from variability in sea level pressure and alongshore winds are important for the coastal sea level on this timescale. On interannual timescales, there were connections with ENSO, the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM), although the results are not consistent across all the tide gauge stations and are not particularly strong. In general, El Niño and positive IOD events are coincident with high coastal sea levels and vice versa, whereas there appears to be an inverse relationship between SAM phase and sea level.
    Type of Medium: Online Resource
    ISSN: 2077-1312
    URL: Article
    DOI: 10.3390/jmse9090924
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2738390-8
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  • 2
    Online Resource
    Online Resource
    Role of ocean mesoscale structures in shaping the Angola-Low pressure system and the southern Africa rainfall
    Springer Science and Business Media LLC ; 2020
    In:  Climate Dynamics Vol. 54, No. 7-8 ( 2020-04), p. 3685-3704
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 54, No. 7-8 ( 2020-04), p. 3685-3704
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-020-05199-1
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    The influence of southeastern African river valley jets on regional rainfall
    Springer Science and Business Media LLC ; 2021
    In:  Climate Dynamics Vol. 57, No. 9-10 ( 2021-11), p. 2905-2920
    Details
    In: Climate Dynamics, Springer Science and Business Media LLC, Vol. 57, No. 9-10 ( 2021-11), p. 2905-2920
    Type of Medium: Online Resource
    ISSN: 0930-7575 , 1432-0894
    URL: Article
    DOI: 10.1007/s00382-021-05846-1
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 382992-3
    detail.hit.zdb_id: 1471747-5
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    April 2022 Floods over East Coast South Africa: Interactions between a Mesoscale Convective System and a Coastal Meso-Low
    MDPI AG ; 2022
    In:  Atmosphere Vol. 14, No. 1 ( 2022-12-30), p. 78-
    Details
    In: Atmosphere, MDPI AG, Vol. 14, No. 1 ( 2022-12-30), p. 78-
    Abstract: Extreme rainfall occurred over the South African east coast during 10–12 April 2022, leading to over 500 deaths and massive damage. This study seeks to understand a key feature, namely the progression of the rainfall maxima from the northern KwaZulu-Natal (KZN) coast during the night of 10–11 April by ~550 km to the Eastern Cape coast about 48 h later. The large-scale circulation was dominated by a cut-off low over the South African interior with a strong ridging anticyclone southeast of the country in the South Indian Ocean. Satellite, rain gauge, and ERA5 reanalysis are used to show that the timing and location of the heaviest rainfall are closely tied to, firstly, the formation of a Mesoscale Convective System (MCS) at ~0300UTC April 11 on the northern KZN coast which tracked south and then offshore, and secondly, a meso-trough which formed a coastal meso-low by ~2100 UTC April 11. The meso-low tracked south over the warm waters of the Agulhas Current before strengthening into Subtropical Depression Issa. Mesoscale interaction between the MCS and coastal meso-low determined the positioning and timing of the strongest onshore low-level jet, moisture convergence and uplift, and hence the progression of the heavy rainfall down the coast. Such mesoscale interaction has not previously been documented in southern Africa or the Southern Hemisphere.
    Type of Medium: Online Resource
    ISSN: 2073-4433
    URL: Article
    DOI: 10.3390/atmos14010078
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2605928-9
    SSG: 23
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  • 5
    Online Resource
    Online Resource
    Relationships between NDVI , river discharge and climate in the Okavango River Basin region
    Wiley ; 2022
    In:  International Journal of Climatology Vol. 42, No. 2 ( 2022-02), p. 691-713
    Details
    In: International Journal of Climatology, Wiley, Vol. 42, No. 2 ( 2022-02), p. 691-713
    Abstract: The Okavango River Basin (ORB) is a highly sensitive and biodiverse region in southern Africa whose climate, vegetation and river discharge characteristics are not well understood. This study investigated relationships between rainfall, temperature, Normalized Difference Vegetation Index (NDVI) and river discharge over the region as well as their trends and interannual variability. It is found that spatial patterns of NDVI are closely related to those of rainfall, but less so with temperature at monthly and seasonal time scales. The relationships between NDVI and rainfall/temperature differ north of 18.9°S where rainfall is higher than to its south. Typically, there are lags of 1–2‐months between NDVI and either rainfall or temperature. Also, there are large areas across the region that show significant warming trends in all seasons as well as wetting (mainly in the north). This increasing trend in surface temperature may act to worsen the impacts of extreme events such as severe drought and fire in the region. There is also pronounced interannual variability with significant correlations found with El Niño‐Southern Oscillation (ENSO), the subtropical South Indian Ocean Dipole and the Botswana High for rainfall and temperature, and for NDVI with ENSO. For the Southern Annular Mode, significant correlations were found with rainfall and temperature only in December and April. On longer time scales, focus was also placed on the wet 2006–2013 period relative to much drier 1999–2005 epoch for October–December. The wetter conditions during 2006–2013 appear related to La Niña Modoki conditions and warmer sea surface temperature near Angola as well as regional circulation differences.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    URL: Article
    DOI: 10.1002/joc.v42.2
    DOI: 10.1002/joc.7267
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Coupled Climate Model Simulation of Tropical–Extratropical Cloud Bands over Southern Africa
    American Meteorological Society ; 2020
    In:  Journal of Climate Vol. 33, No. 19 ( 2020-10-01), p. 8579-8602
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 33, No. 19 ( 2020-10-01), p. 8579-8602
    Abstract: There are increasing efforts to use climate model output for adaptation planning, but meanwhile there is often limited understanding of how models represent regional climate. Here we analyze the simulation in global coupled climate models of a key rainfall-generating mechanism over southern Africa: tropical temperate troughs (TTTs). An image-processing algorithm is applied to outgoing longwave radiation data from satellites and models to create TTT event sets. All models investigated produce TTTs with similar circulation features to observed. However, there are large differences among models in the number, intensity, and preferred longitude of events. Five groups of models are identified. The first group generates too few TTTs, and relatively dry conditions over southern Africa compared to other models. A second group generates more TTTs and wet biases. The contrast between these two groups suggests that the number of TTTs could explain intermodel variations in climatological rainfall. However, there is a third group of models that simulate up to 92% more TTTs than observed, but do not have large rainfall biases, as each TTT event is relatively weak. Finally, there are a further two groups that concentrate TTTs over the subcontinent or the ocean, respectively. These distinctions between models are associated with the amount of convective activity in the Congo Basin, the magnitude of moisture fluxes into southern Africa, and the degree of zonal asymmetry in upper-level westerly flow. Model development focused on tropical convection and the representation of orography is needed for improved simulation of TTTs, and therefore southern African rainfall.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    URL: Article
    DOI: 10.1175/JCLI-D-19-0731.1
    DOI: 10.1175/JCLI-D-19-0731.s1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 7
    Online Resource
    Online Resource
    A Climatology of Dryline‐Related Convection on the Western Plateau of Subtropical Southern Africa
    American Geophysical Union (AGU) ; 2023
    In:  Journal of Geophysical Research: Atmospheres Vol. 128, No. 18 ( 2023-09-27)
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 128, No. 18 ( 2023-09-27)
    Abstract: Lightning data is used to determine how frequently drylines are associated with thunderstorms on the western plateau of southern Africa Seventy‐six percent of drylines were convective during the austral summers of 2010–2021 Moisture pathways shift south from the Zambezi to the Limpopo River Valley between early and late summer
    Type of Medium: Online Resource
    ISSN: 2169-897X , 2169-8996
    URL: Article
    DOI: 10.1029/2023JD038966
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2023
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 2969341-X
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Diversity and Ranking of ENSO Impacts along the Eastern Seaboard of Subtropical Southern Africa
    MDPI AG ; 2023
    In:  Atmosphere Vol. 14, No. 6 ( 2023-06-17), p. 1042-
    Details
    In: Atmosphere, MDPI AG, Vol. 14, No. 6 ( 2023-06-17), p. 1042-
    Abstract: El Niño–Southern Oscillation (ENSO) is the dominant mode of interannual climate variability over southern Africa during the summer half of the year. It is widely accepted that El Niño (La Niña) core summers (December–February) are typically warmer and drier (cooler and wetter) than average over the region. Although it is recognized that the ENSO impacts are nonlinear and not all events result in the expected impact, little or no work has been carried out to systematically explore the diversity and ranking of these impacts. Here, parameter-space bubble plots involving various rainfall and temperature metrics are used to study how such impacts vary over the eastern seaboard of subtropical southern Africa to determine the ENSO events with the strongest impacts, and to identify the most anomalous ENSO cases. Comparison of neutral summers experiencing the strongest droughts/floods with ENSO impacts is also performed. These metrics are designed to be applicable to the interests of farmers and other user groups. It is found that 1987/1988 (2017/2018) was the most unusual El Niño (La Niña) and neutral 1981/1982 had a severe drought, worse than occurs during most El Niños. These unusual cases are explained in terms of regional circulation and SST anomalies. Implications of the results for seasonal forecasting and for farmers are discussed.
    Type of Medium: Online Resource
    ISSN: 2073-4433
    URL: Article
    DOI: 10.3390/atmos14061042
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2605928-9
    SSG: 23
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  • 9
    Online Resource
    Online Resource
    Drought metrics and temperature extremes over the Okavango River basin, southern Africa, and links with the Botswana high
    Wiley ; 2023
    In:  International Journal of Climatology
    Details
    In: International Journal of Climatology, Wiley
    Abstract: The Okavango River Basin (ORB), including the World Heritage site Okavango Delta, is a region of high biodiversity projected to suffer increased early summer drying under climate change. Little work has been done on drought over this sensitive region. Here, various drought metrics are analysed over the ORB. These include a cumulative drought intensity index, based on the product of maximum temperature anomaly and maximum duration of a dry spell, and the Standardized Precipitation‐Evapotranspiration Index. Strong gradients in dry spell and hot day frequencies shift south over the ORB from August to November as the tropical rain‐belt moves increasingly south of the equator, the Congo Air Boundary declines and the Botswana High strengthens and moves southwestwards. By December, the tropical gradient in dry spell frequencies has vanished while that across the Limpopo River and southern ORB region, where the Botswana High is centred, is prominent. sub‐seasonal analyses highlight October–November 2013–2021 as particularly dry and hot over the Okavango Delta region. This dry and hot epoch appears related to a stronger and southward shifted Botswana High and reduced low‐level moisture convergence. On interannual scales, strong relationships were found with the Botswana High and El Niño‐Southern Oscillation (ENSO). The early summer shows a strong drying‐warming trend, related to a significant strengthening of the Botswana High. These trends, together with the Coupled Model Intercomparison Project Phase 6 projected early summer drying over southern Africa, may impact severely on the sensitive ecosystems of the ORB and on agriculture, with important implications for the management of agricultural activities, water resources and biodiversity.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Article
    DOI: 10.1002/joc.8215
    RVK:
    RA 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 10
    Online Resource
    Online Resource
    Variability in the Mozambique Channel Trough and Impacts on Southeast African Rainfall
    American Meteorological Society ; 2020
    In:  Journal of Climate Vol. 33, No. 2 ( 2020-01-15), p. 749-765
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 33, No. 2 ( 2020-01-15), p. 749-765
    Abstract: The Mozambique Channel trough (MCT) is a cyclonic region prominent in austral summer in the central and southern Mozambique Channel. It first becomes evident in December with a peak in strength in February when the Mozambique Channel is warmest and the Mascarene high (MH) is located farthest southeast in the Indian Ocean basin. The strength and the timing of the mean MCT are linked to that of the cross-equatorial northeasterly monsoon in the tropical western Indian Ocean, which curves as northwesterlies toward northern Madagascar. The interannual variability in the MCT is associated with moist convection over the Mozambique Channel and is modulated by the location of the warm sea surface temperatures in the south Indian Ocean. Variability of the MCT shows a strong relationship with the equatorial westerlies north of Madagascar and the latitudinal extension of the MH. Summers with strong MCT activity are characterized by a prominent cyclonic circulation over the Mozambique Channel, extending to the midlatitudes. These are favorable for the development of tropical–extratropical cloud bands over the southwestern Indian Ocean and trigger an increase in rainfall over the ocean but a decrease over the southern African mainland. Most years with a weak MCT are associated with strong positive south Indian Ocean subtropical dipole events, during which the subcontinent tends to receive more rainfall whereas Madagascar and northern Mozambique are anomalously dry.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    URL: Article
    DOI: 10.1175/JCLI-D-19-0267.1
    DOI: 10.1175/jcli-d-19-0267.s1
    RVK:
    UA 4548
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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