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SA now experiencing half-year summers

12 October 2020 | Story Leonie Bolleurs | Photo Supplied

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 to host one of three world summits on crystallography

2014-04-15

Prof André Roodt from the Department of Chemistry at the University of the Free State (UFS), co-unveiled a special plaque in Poznan, Poland, as president of the European Crystallographic Association, with prof Gautam Desiraju, president of the IUCr (front right) and others to commemorate the Nobel prize winner Max von Laue. (Photo's: Milosz Ruszkowski, Grzegorz Dutkiewicz)

Prof André Roodt from the Department of Chemistry at the University of the Free State (UFS), co-unveiled a special plaque in Poznan, Poland, as president of the European Crystallographic Association, to commemorate the Nobel prize winner Max von Laue at a special Laue Symposium organised by prof Mariusz Jaskolski from the A. Mickiewicz University in Poznan.

Max von Laue, who spent his early childhood in Poznan, was the first scientist to diffract X-rays with a crystal.

2014 has been declared by the United Nations as the International Year of Crystallography, and it was recently officially opened at the UNESCO headquarters in Paris, France, by the Secretary-General of the UN, Ban Ki-moon. The International Year of Crystallography celebrates the centennial of the work of Max von Laue and the father and son, William Henry and William Laurence Bragg.

As part of the celebrations, Prof Roodt, president of the European Crystallographic Association, one of the three regional affiliates (Americas, Europe and Africa; Asia and Australasia) of the International Union of Crystallography (IUCr), was invited by the president of the IUCr, Prof Gautam Desiraju, to host one of the three world summits, wherein crystallography is to showcase its achievements and strategise for the future.

The summit and conference will take place on the Bloemfontein Campus of the UFS from 12 to 17 October 2014 and is titled: 'Crystallography as vehicle to promote science in Africa and beyond.' It is an ambitious meeting wherein it is anticipated to bring the French-, English- and Arab-speaking nations of Africa together to strategise how science can be expanded, and to offer possibilities for this as nestled in crystallography. Young and established scientists, and politicians associated with science and science management, are the target audience to be brought together in Bloemfontein.

Dr Thomas Auf der Heyde, acting Director General of the South African Department of Science and Technology (DST), has committed some R500 000 for this effort, while the International Union of Crystallography provided R170 000.

“Crystals and crystallography form an integrated part of our daily lives, form bones and teeth, to medicines and viruses, new catalysts, jewellery, colour pigments, chocolates, electronics, batteries, metal blades in airplane turbines, panels for solar energy and many more. In spite of this, unfortunately, not many people know much about X-ray crystallography, although it is probably one of the greatest innovations of the twentieth century. Determining the structure of the DNA was one of the most significant scientific events of the 20th century. It has helped understand how genetic messages are being passed on between cells inside our body – everything from the way instructions are sent to proteins to fight infections, to how life is reproduced.

“At the UFS, crystallography finds application in Chemistry, Physics, Biology, Mathematics, Geology, Engineering and the Medical fields. Crystallography is used by the Curiosity Rover, analysing the substances and minerals on Mars!

“The UFS’s Departments of Chemistry and Physics, in particular, have advanced instruments and important research thrusts wherein X-ray crystallography has formed a central part for more than 40 years.

“Crystallography has produced some 28 Nobel prize winners over the past 100 years and continues to provide the means for fundamental and applied research,” said Prof Roodt.

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