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SA now experiencing half-year summers

12 October 2020 | Story Leonie Bolleurs | Photo Supplied

Although several international studies have used temperature metrics to statistically classify their seasonal divisions, a study in which Adriaan van der Walt was involved, would be the first known publication in a South African context using temperature as classification metric.

Gone are the days when we as South Africans would experience a three-month spring season, easing into summer, and then cooling off for three months before we hit winter.

Adriaan van der Walt, Lecturer in the Department of Geography at the University of the Free State (UFS), focuses his research on biometeorology (a specialist discipline exploring the role and climate change in physical and human environments) as well as climatology and geographic information systems.

He recently published an article: ‘Statistical classification of South African seasonal divisions on the basis of daily temperature data’ in the South African Journal of Science.

In this study, which Van der Walt undertook with Jennifer Fitchett, a colleague from the University of the Witwatersrand, data on daily maximum and minimum temperatures was collected from 35 meteorological stations of the South African Weather Service, covering the period between 1980 and 2015.

They went to great lengths to ensure that they had a complete set of data before presenting it to demonstrate seasonal brackets.

First for South Africa

Their statistical seasonal brackets indicate that South Africans now experience longer summers (from October to March), autumn in April and May, winter from June to August, and spring in September.

Although considerable work has been done using rainfall to determine seasonality in Southern Africa, Van der Walt believes that these methods did not work well as there are too many inconsistencies in this approach, as identified by Roffe et al. (2019, South African Geographical Journal). To make matters more complicated – as a semi-arid region, and with desert conditions along the west coast – some regions do not have enough rainfall to use as a classifier.

Temperature, on the other hand, worked well in this study. “Temperature, by contrast, is a continuous variable, and in Southern Africa has sufficient seasonal variation to allow for successful classification,” says Van der Walt.

He continues: “Although several international studies used temperature metrics to statistically classify their seasonal divisions, this study would be the first known publication in a South African context using temperature as classification metric.”

Van der Walt says what we understand as seasons largely relates to phenology – the appearance of blossoms in spring, the colouration and fall of leaves in autumn, and the migration of birds as a few examples. “These phenological shifts are more sensitive to temperature than other climatic variables.”

Seasonal brackets

According to Van der Walt, they believe that a clearly defined and communicated method should be used in defining seasons, rather than just assigning months to seasons.

“One of the most important arguments of our work is that one needs to critically consider breaks in seasons, rather than arbitrarily placing months into seasons, and so we welcome any alternate approaches,” he says.

A number of sectors apply the temperature-based division to their benefit. “For example, in the tourism sector it is becoming increasingly important to align advertising with the season most climatically suitable for tourism,” says Van der Walt.

Temperature-based division is also used to develop adaptive strategies to monitor seasonal changes in temperature under climate change. However, Van der Walt points out that each sector will have its own way of defining seasons. “Seasonal boundaries should nevertheless be clearly communicated with the logic behind them,” he says.

News Archive

Twee broers lewer intreerede

2004-06-10

‘n Unieke geleentheid sal homself môre, 9 Junie 2004, voordoen wanneer twee broers - proff Francois en Janse Tolmie - tydens dieselfde geleentheid hul intreeredes aan die Universiteit van die Vrystaat (UV) sal lewer.

Prof Francois Tolmie is verbonde aan die UV se Departement Nuwe Testament en die onderwerp van sy lesing is Die impak van die metodologie op die verstaan van die Nuwe Testament. Prof Janse Tolmie, sy jonger broer, is verbonde aan die UV se Departement Rekenaarwetenskap en Informatika en die onderwerp van sy lesing is Die rol van inligtingstegnologie in kennisbestuur.

Hoewel die studievelde vér verwyderd staan, klop die twee broers se missies wat betref die terugploeg van die verworwe vakkennis ten bate van die gemeenskap. Prof Francois Tolmie is nóú betrokke by dowes en Prof Janse Tolmie tap weer kunsmatige intelligensie ten bate van die mediese wetenskap en geestesgesondheid.

Prof Francois Tolmie verwerf die grade BA, BA Honneurs (Grieks), MA (Grieks), B Th en M Th almal cum laude aan die UV. In 1992 verwerf hy 'n D Th (Nuwe Testament) en in 2004 'n Ph D (Grieks) aan dieselfde universiteit. Na sy militêre diens as kapelaan in Walvisbaai aanvaar hy 'n beroep na die NG-gemeente Walvisbaai. Hy begin sy akademiese loopbaan op 1 April 1990 as senior lektor in die Departement Nuwe Testament en word in 1999 tot medeprofessor en in 2003 tot professor bevorder.

Sy navorsingspesialiteit is die Johannesevangelie en die Brief aan die Galasiërs. Hy is tesourier van die Nuwe Testamentiese Werksgemeenskap van Suid-Afrika, lid van die Society of Biblical Literature en die Studiorum Novi Testamenti Societas, redakteur van Acta Theologica en assistent-redakteur van Neotestamentica. Hy het reeds 34 artikels in geakkrediteerde tydskrifte gepubliseer, asook drie populêr-wetenskaplike boeke en talle bydraes in populêr-wetenskaplike boeke. Hy het twee akademiese boeke in die buiteland gepubliseer - onderskeidelik in Nederland en in die VSA. Later vanjaar verskyn 'n derde akademiese boek in Duitsland. Hy is ook een van die vertalers van die Afrikaanse Bybel vir Dowes.

Prof Janse Tolmie verwerf die grade B Sc, B Sc (Hons) en M Sc (Cum Laude) in Rekenaarwetenskap aan die UV.

Hy is vanaf 1989 betrokke by die UV en was ook ’n dosent aan die Militêre Akademie in Saldanhabaai in 1990/91 en het klas gegee by DePaul Universiteit in Chicago in 2002.

In 1992 is hy vir ses maande gesekondeer na ’n patologiese firma, Van Drimmelen en Vennote, in Johannesburg vir die ontwikkeling van kennisgebaseerde sagteware. Met hierdie projek word hy een van slegs ’n handjievol navorsers in die wêreld wat daarin kon slaag om ’n mediese kundigheidstelsel te ontwikkel wat werklik gebruik word.

Hy verwerf sy Ph D in 1994 en in 1994/95 doen hy navorsing aan die Besigheidskool van Carleton Universiteit in Ottawa, Kanada. Hy word in 1997 bevorder tot mede-professor en in 2003 tot volprofessor. Vanaf 2003 tree hy op as departementele voorsitter van die UV se Departement Rekenaarwetenskap en Informatika.

Hy het meer as 30 publikasies al die lig laat sien, insluitend verskeie internasionale kongresbydraes en artikels in geakkrediteerde joernale. Hy was ook vir 2 siklusse geëvalueer by die NRF. Sy portfolio sluit in die ontwikkeling van sagteware of prototipes vir groot maatskappye soos Van Drimmelen en Vennote en Bayer Diagnostics (VSA). Sy privaatbesigheid fokus op die ontwikkeling van nismarksagteware vir tersiêre instellings. Die sagteware word tans gebruik deur afdelings aan verskeie universiteite in Suid-Afrika.

Die geleentheid vind om 19:00 in die CR Swart-ouditorium op die kampus plaas.

MEDIAVERKLARING

Uitgereik deur: Lacea Loader
Mediaverteenwoordiger
Tel: (051) 401-2584
Sel: 083 645 2454
E-pos: loaderl.stg@mail.uovs.ac.za

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