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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

Vishuis’s fourth Varsity Cup victory about more than rugby
2016-04-15

Description: Vishuis Tags: Vishuis

House Abraham Fischer, a residence from the University of the Free State, is the most successful team in the history of the Varsity Cup. Vishuis beat Patria (Pukke) in the 2016 final of the tournament.
Photo: SASPA
 

For Vishuis, it is about more than just rugby.

This is what Henco Posthumus, captain of House Abraham Fischer’s rugby team, had to say after his team was crowned the national Varsity Cup champions for an incredible fourth time. According to the flyhalf, the title of the leading residence team in the country is “special for the guys”.

Vishuis is the most successful residence team in the history of the tournament. Apart from their four titles, they have played in a total of five Varsity Cup finals.

On 11 April 2016, the residence from the University of the Free State (UFS) launched a great comeback in Stellenbosch to beat Patria (Pukke) by 37-29. This victory ensured that Vishuis was unbeaten in 2016.

Great fighting spirit


The Kovsies started off well against Patria, but were behind 16-29 shortly after break, and had to “delve deep”, according to Posthumus. “To be behind in this way is not what one would prefer. For some reason, we have been in similar situations before, and we know how to make a comeback,” he said.

“We looked one another in the eye and decided that we are not going to lose again in the final.” In last year’s final in Bloemfontein, when Posthumus played at fullback, Vishuis got stuck against Mopanie (Tuks) at the end of the match, and they wanted to prevent this from happening again.

Heymans a hero


According to the Vishuis captain, one of his team’s assistant coaches, Franco (Vaatjie) van der Merwe, spoke harshly to the players when they were behind. The victory was clinched in the dying moments, with the second try of scrumhalf, Ruben Heymans, when the score was 29 points each. Heymans was a star, and the well-deserved Man of the Match.

Posthumus said it is a great privilege to carry the title of Varsity Cup champions. His team has worked hard to reach the top.

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