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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

Three UFS researchers attend cactus pear congress
2017-05-05

Description: Dr de Wit Cactus pear 2 Tags: Dr de Wit Cactus pear 2

Dr Maryna de Wit, one of the
UFS delegation team was appointed
coordinator for Agro-Processing
and Post-Harvest Technology during
the congress

Description: Dr du Toit Cactus Pear 2 Tags: Dr du Toit Cactus Pear 2

Dr Alba du Toit, also one of the members
of the UFS delegation during the
congress at the University of Chile
in Santiago, Chile.
Photos: Supplied





Dr Alba du Toit, a junior lecturer in Consumer Science at the University of the Free State (UFS), presented her research at the recent IX International Congress on Cactus Pear and Cochineal at the University of Chile in Santiago, Chile. The congress was themed, “CAM Crops for a Hotter and Drier World”.

Dr Du Toit, Prof HO de Waal and Dr Maryna de Wit, from the Faculty of Natural and Agricultural Sciences at UFS, attended the five-day conference held between 26 and 30 March 2017.

Congress a platform for networking
The congress, held every three years since 1993, gathers cactus pear researchers, growers and processing managers from Europe, the Americas, Asia and Africa to review current research trends by networking to form new collaborations that could lead to increased efficiency and shared knowledge. They also present new findings and plan for future research.

Great achievements for researchers
Dr Du Toit said: “My research on cactus pears focused on the utilisation of the slimy substance found in the cactus cladodes as a functional ingredient in innovative nutraceutical food products”. Functional foods are foods that promote health or prevent disease through adding or omitting specific ingredients. She also received the International Society of Horticultural Science award for best student oral presentation.

Dr De Wit also presented her research and was appointed coordinator for Agro-Processing and Post-Harvest Technology at the congress.

Dr Herman Fouché, Affiliated Researcher at the Department of Soil-, Crop- and Climate Sciences at UFS, developed “kuilmoes”, a type of silage from pulped cactus pear fruit, mixed with lucerne, in collaboration with Prof de Waal, which was also presented.at the congress.

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