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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

UFS Autumn Graduation inspires perseverance
2015-04-20

 

Louzanne Coetzee and her guide dog, Oakley after she received her degree at the UFS’s Autumn Graduation.
Photo: Gerhardus Bosch

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Autumn has seen the UFS’s first graduation ceremonies of the year on the Bloemfontein Campus. From 14 to 17 April 2015, a total of 3 660 graduates were rewarded for their hard work while top speakers addressed them in the Callie Human Centre.

UFS Chancellor, Dr Khotso Mokhele, commented the more than 250 students who passed their degrees with distinctions at the autumn graduation.

Prof Soodyall, a Medical Scientist at the South African Institute for Medical Research as well as  Principal Medical Scientist for the National Health Laboratory Service, and Director for the Human Genome Diversity and Disease Research Unit at the University of Witwatersrand delivered the first motivational message of the April Graduation. The group of graduates in the Faculty of Natural and Agricultural Sciences listened as she shared her story with them.
 
"My own career – with no grand design or script – steered me into conducting genetic research on human populations from sub-Saharan Africa with a focus on a better understanding of human evolution, and to reconstruct the prehistory of African populations. While giving graduates a glimpse on how her career progressed, Prof Soodyall said: "I share these stories with you to give you some reassurance that you do not need feel that you have to figure out every minute detail of where to from here. Things fall into place with hard work, dedication, and dreams.

The developed world is forging ahead with interventions, so the gap between the developed world and the developing world continues to grow bigger. Prof Soodyall said: “You have the unenviable opportunity to think strategically, and to use the modern tools in your respective fields to make significant advances to transform our society, and to contribute to making it a better place for all. We need to embrace the current challenges, and build networks and bridges across disciplines to close the gaps, to work beyond the cultural barriers, and to ensure equity in access to health, water, education, etc, for all, as we would wish these things for ourselves and our families.

Read the full story of the Autumn Graduation 2015

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