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12 October 2020 | Story Leonie Bolleurs | Photo Supplied
Adriaan van der Walt
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

Inaugural lecture focuses on the Apostle Paul’s recognition of the divinity of Christ
2005-02-16

Prof Pieter Verster from the Department of Missiology at the University of the Free State (UFS) will deliver his inaugural lecture on Wednesday 23 February 2005 at 19:00 in the CR Swart Auditorium on campus.

The topic of the lecture is Die begronding van die sending by Paulus in die lig van sy erkenning van die godheid van Christus.

Pieter Verster started his theological training in 1973 at the UFS and continued it at the University of Pretoria (UP). He obtained the degrees BA (cl) from the UFS in 1976; BA Hons (Greek cl) from the UP in 1979; MA (Greek) from the UFS in 2000;

a BD (cl) from the UP in 1979; a Post-graduate Diploma in Theology (cl) from the UP in 1980; a DD (Missiology and Religion Studies) from the UP in 1985 and a DD (Dogmatics and Ethics) from the UP in 1989.

He was honoured for academic excellence (UFS 1975), overall excellence (UP 1979) and research excellence (UFS 2004). He has visited various overseas universities and institutions in the Netherlands , Switzerland , Germany and the USA ,.

Prof Verster has also published various articles in academic journals and his books include Wie het die waarheid beet? for which he received the CUM/RSG writers’ competition prize in 1996. He has also published short stories in Tydskrif vir Letterkunde and Dolos and poems in inter alia Literator and Litnet.

Media release
Issued by: Lacea Loader
Media Representative
Tel: (051) 401-2584
Cell: 083 645 2454
E-mail: loaderl.stg@mail.uovs.ac.za
16 February 2005

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