R. D. Diab

University of KwaZulu-Natal

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Jean‐Luc Baray

Observatoire de Physique du Globe de Clermont-Ferrand

Anne M. Thompson

Goddard Space Flight Center

F. Sokolic

University of KwaZulu-Natal

Hassan Benchérif

Laboratoire de l'Atmosphère et des Cyclones

R. A. Preston‐Whyte

University of KwaZulu-Natal

Béatrice Morel

Laboratoire de l'Atmosphère et des Cyclones

Mark Zunckel

Umkhuseli Innovation and Research Management

Jimmy Leclair de Bellevue

Centre National de la Recherche Scientifique

S. Baldy

Laboratoire de l'Atmosphère et des Cyclones

J. Combrink

University of KwaZulu-Natal

Cooperative Institutions

University of KwaZulu-Natal

Centre National de la Recherche Scientifique

Laboratoire de l'Atmosphère et des Cyclones

Météo-France

Observatoire des Sciences de l'Univers de la Réunion

University of the Witwatersrand

Council for Scientific and Industrial Research

Écologie Marine Tropicale des Océans Pacifique et Indien

Université Toulouse III - Paul Sabatier

University of Cape Town

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Temperature Climatology and Trend Estimates of The Lower Troposphere - Upper Stratosphere Region As Observed At A Southern Subtropical Latitude, Durban, South Africa

EGS General Assembly Conference Abstracts (2002)

Hassan Benchérif Thierry Portafaix Béatrice Morel R. D. Diab P. Keckhut

Middle latitudes

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Citations (0)

Vertical ozone distribution over southern Africa and adjacent oceans during SAFARI‐92

Journal of Geophysical Research Atmospheres (1996)

R. D. Diab Anne M. Thompson Mark Zunckel G. J. R. Coetzee J. Combrink

A set of four ozonesonde stations located at Ascension Island, Brazzaville, Okaukuejo, and Irene, operational during the TRACE A and SAFARI‐92 experiments has provided an opportunity to investigate the vertical distribution of ozone over southern Africa and adjacent oceans. All stations display a springtime maximum in tropospheric ozone. Enhanced tropospheric ozone, which occurs between June and September at Brazzaville and between July and October at Ascension Island, is linked to dry season biomass burning. The influence of tropical biomass burning is delayed until September at Okaukuejo when a sharp increase in tropospheric ozone is experienced. The biomass burning influence at Irene is less because of its more southerly location. A general tropospheric enhancement is observed at all stations. It is manifest as an enriched layer in the upper troposphere at Okaukuejo (9–12 km) and Brazzaville (11–14 km) and in the lower troposphere (2–8 km) at Ascension Island. At Ascension Island lower tropospheric ozone values are about 20 parts per billion by volume greater than elsewhere and the tropospheric component here accounts for about 18% of the total column ozone. A series of tethersonde soundings conducted at hourly intervals at Okaukuejo revealed ozone to be well mixed in the lower boundary layer during the day, but to display marked vertical stratification at night.

Tropospheric ozone

Trace gas

10.1029/96jd01267

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Citations (67)

OZONE MAXIMA OFF THE EAST COAST OF SOUTH AFRICA: THE ROLE OF BIOMASS BURNING

Clean Air Journal (1994)

Yogan Pillay R. D. Diab F. Sokolic

Maxima

10.17159/caj/1994/9/1.7115

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Citations (5)

Simulations of stratospheric to tropospheric transport during the tropical cyclone Marlene event

Atmospheric Environment (2007)

Jimmy Leclair de Bellevue Jean‐Luc Baray S. Baldy G. Ancellet R. D. Diab

Tropospheric ozone

Atlantic hurricane

10.1016/j.atmosenv.2007.04.040

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Citations (43)

Inter-annual variability of temperature in the upper troposphere and lower stratosphere at Durban

South African Journal of Science (2003)

Ashokabose Moorgawa Hassan Benchérif R. D. Diab S. Sarcia M.M. Michaelis

We have investigated the inter-annual variability of temperature in the upper troposphere and lower stratosphere over Durban for the 20-year period from 1980 to 1999. A spectral analysis of morning and afternoon temperatures at tour heights (10, 12, 16 and 18 km) revealed a number of oscillations which could be associated with the annual cycle, the Quasi-biennial Oscillation (QBO) and the El Nino/Southern Oscillation (ENSO). The annual and OBO (27 months) cycles were present at 10, 16 and 18 km, with the former being dominant. Peaks at ∼2.7,4 and 6.7 years were also detected and were linked to ENSO cycles. By contrast, these cycles were either absent or not well developed (in the case of the annual cycle) at a height of 12 km. Possible reasons for this lack of consistency were sought, with the presence of the jet stream at 12 km being a likely explanation.

Quasi-biennial oscillation

Annual cycle

Jet stream

Oscillation (cell signaling)

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Air quality and climate change co-benefits for the industrial sector in Durban, South Africa

Energy Policy (2011)

Tirusha Thambiran R. D. Diab

Energy Sector

10.1016/j.enpol.2011.08.027

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Citations (20)

THERMO-TOPOGRAPHICALLY INDUCED WINDS IN THE BOUNDARY LAYER OVER THE ETOSHA PAN

South African Geographical Journal (1994)

R. A. Preston‐Whyte R. D. Diab F. Sokolic

ABSTRACT Boundary layer winds over the Etosha Pan at Okaukuejo reveal a diurnal oscillation. Wind direction is characteristically northeast by day and south by night. Daytime winds appear to be synoptically forced, being part of the easterly airflow around the continental high, while the nocturnal airflow appears to be the result of thermo-topographical forcing between the higher standing plateau to the south and west of Okaukuejo and the Etosha Pan. The diurnal wind variation is suppressed by synoptic forcing when the high over the sub-continent strengthens or when a mid-latitude trough moves westward across the sub-continent.

Forcing (mathematics)

Trough (economics)

Diurnal temperature variation

10.1080/03736245.1994.9713576

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Citations (8)

An unusual stratospheric ozone decrease in the Southern Hemisphere subtropics linked to isentropic air-mass transport as observed over Irene (25.5° S, 28.1° E) in mid-May 2002

Atmospheric chemistry and physics (2006)

N. Semane Hassan Benchérif Béatrice Morel Alain Hauchecorne R. D. Diab

Abstract. A prominent ozone minimum of less than 240 Dobson Units (DU) was observed over Irene (25.5° S, 28.1° E), a subtropical site in the Southern Hemisphere, by the Total Ozone Mapping Spectrometer (TOMS) during May 2002 with an extremely low ozone value of less than 219 DU recorded on 12 May, as compared to the climatological mean value of 249 DU for May between 1999 and 2005. In this study, the vertical structure of this ozone minimum is examined using ozonesonde measurements performed over Irene on 15 May 2002, when the total ozone (as given by TOMS) was about 226 DU. It is shown that this ozone minimum is of Antarctic polar origin with a low-ozone layer in the middle stratosphere above 625 K (where the climatological ozone gradient points equatorward), and is of tropical origin with a low-ozone layer in the lower stratosphere between the 400-K and 450-K isentropic levels (where the climatological ozone gradient is reversed). The upper and lower depleted parts of the ozonesonde profile for 15 May are then respectively attributed to equatorward and poleward transport of low-ozone air toward the subtropics in the Southern Hemisphere. The tropical air moving over Irene and the polar one passing over the same area associated with enhanced planetary-wave activity are successfully simulated using the high-resolution advection contour model of Ertel's potential vorticity MIMOSA. The unusual distribution of ozone over Irene during May 2002 in the middle stratosphere is connected to the anomalously pre-conditioned structure of the polar vortex at that time of the year. The winter stratospheric wave driving leading to the ozone minimum is investigated by means of the Eliassen-Palm flux computed from the European Center for Medium-range Weather Forecasts (ECMWF) ERA40 re-analyses.

Ozone Depletion

10.5194/acp-6-1927-2006

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Citations (33)

WIND ENERGY POTENTIAL IN THE CAPE COASTAL BELT

South African Geographical Journal (1989)

Mark R. Jury R. D. Diab

ABSTRACT Climatological records have indicated that the coastal zone of the Cape Province experiences sustained wind speeds suitable for wind energy conversion systems (7 m s−1 at 10 m). The seasonal, synoptic and diurnal cycles within the prevailing coast- parallel winds are outlined from climatological data. Screening of the coastal zone for high wind power and suitable land usage leads to a focus on three particular sites: Cape Columbine, Cape Agulhas and Cape St Francis. On the west coast at Cape Columbine the stronger winds are from the south, while on the south coast the highest winds may be either from the east (summer) or west (winter). Mesoscale wind surveys conducted at these three sites under various synoptic weather conditions over the 1982–1983 period are reported. Small areas of wind acceleration are identified and appear to be confined to the sides of smooth low ridges within 10 km of the coast. These observations are compared with predictions from a two-dimensional numerical model. The matching of power availability with electricity demand offers hope that wind energy conversion will constitute a viable alternative energy resource in the next century.

Cape

Global wind patterns

Prevailing winds

East coast

Sea breeze

10.1080/03736245.1989.9713498

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Citations (6)

WIND CHARACTERISTICS AND BLOWOUT FORMATION NEAR MABIBI, NORTHERN KWAZULU-NATAL

South African Geographical Journal (2004)

Andrew Green Gerald G. Garland R. D. Diab

ABSTRACT Although blowouts in sand dunes have been extensively studied elsewhere, little is known about those within the Holocene dune fields of the Maputaland coastal margin in KwaZulu-Natal, on the east coast of South Africa. Research in this paper involved measuring, describing and analysing wind flow patterns at a single blowout near Mabibi and related the results to the wind dynamics. From this, a preliminary hypothesis of blowout formation was made. Topographic steering through both the logarithmic spiral form of the bay adjacent to the blowout and the morphology of the dune had a significant influence on wind patterns in both pre-and post-frontal wind conditions. As the blowout widens, further channelling accelerated a jet around the headland, which would ultimately result in complete breakthrough of the dune, leaving a small isolated residual dune fragment, cut off by a mobile arc of sand. The paper concluded that such blowouts are characteristically formed under highly negative beach budgets, and that blowout formation along this coast is more likely at sites in the proximity of rocky headlands.

Headland

Global wind patterns

Prevailing winds

10.1080/03736245.2004.9713814

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Citations (4)