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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

Consumer Science at the UFS awards three PhDs
2015-07-08

Dr Gloria Seiphetlheng, Dr Natasha Cronje, Dr Ismari van der Merwe and Prof Hester Steyn.
Photo: Leonie Bolleurs

For the first time in its history, the Department of Consumer Science in the Faculty of Natural and Agricultural Sciences at the University of the Free State (UFS) earned three doctorates at one graduation ceremony this year. This week three PhDs were awarded to Ismari van der Merwe, Natasha Cronje, and Gloria Seiphetlheng at the Winter Graduation that took place on the Bloemfontein Campus.

Electrochemically-activated water is widely used in the food and other industries, due to its excellent environment-friendly properties. However, it is not used in the textile industry yet, because too little research has been done to determine the possible positive and negative impact it may have on textiles.

With the thesis, The evaluation of catholyte treatment on the colour and tensile properties of dyed cotton, polyester and polyamide 6,6 fabrics,  Dr Cronje, a lecturer in the UFS’s Department of Consumer Science, and Dr Seiphetlheng from the Serowe College of Education in Botswana,  provided major new information with the thesis, Anolyte as an alternative bleach for cotton fabrics. This information is essential when considering the application of catholytes and anolytes in the textile industry.

Electrochemically-activated water divides water in catholytes and anolytes. The anolyte part is used as a disinfectant and bleach. It is not really suitable for domestic use, as it can cause colour loss in coloured textile products. However, it can be used in the hospitality industry where white sheets, towels, etc., are used and washed on a regular basis.

The catholyte part of the water has properties similar to washing powder. It can also be used in the textile industry as washing liquid.

According to Prof Hester Steyn, Head of the Department of Consumer Science and supervisor of all three PhD candidates, this electrochemically-activated water is also very eco-friendly. “It has a short shelf life. If the electrochemically-activated water isn’t utilised, it returns to normal water that wouldn’t harm the environment. No water is therefore lost, and no waste products are released that would contaminate the environment,” she says.

Dr Van der Merwe’s research focused on Degumming Gonometa postica cocoons using environmentally conscious methods. A lecturer in the Department of Consumer Science, she demonstrated that simple and environmentally-friendly methods can be used with great success to procure wild silk from the cocoons of the Gonometa postica worms living in the camel thorn trees found in the Northern Cape and Namibia.

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