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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

Researchers receive study grant for research into Congo Fever
2015-03-10

UFS researchers will be contributing significantly to the search for a vaccine against the deadly tick-borne disease known as Congo Fever.

Prof Felicity Burt from the Department of Medical Microbiology and Virology was recently awarded a research grant by the National Health Laboratory Service (NHLS) to study candidate vaccines for Crimean-Congo heamorrhagic fever (CCHF) virus and other arboviruses.

Arboviruses are viruses transmitted by mosquitoes, ticks, or other arthropods.

Prof Burt is an internationally-recognised expert on the Crimean-Congo haemorrhagic fever (CCHF). The Crimean-Congo haemorrhagic fever (CCHF) virus is a tick-borne virus that is associated with severe haemorrhagic disease in South Africa and other parts of Africa, Asia, and eastern Europe. Her interests focus on medically significant viruses that are transmitted by ticks and mosquitoes. Her research group is involved in determining the immune responses that are induced by different viral proteins.

Crimean-Congo haemorrhagic fever (CCHF) virus, a tick- borne virus found in Africa, Asia, the Balkans, and eastern Europe, causes severe viral haemorrhagic fever outbreaks.

Although a number of tick species are capable of becoming infected with CCHF virus, ticks of the genus Hyalomma, commonly referred to in SA as the “bont-legged ticks”, are the principal vector. The ticks have distinctive brown and white bands on their legs.

In February 1981, the first case of CCHF was recognised in South Africa (SA). To date, there have been nearly 200 cases of CCHF infection in SA with a 20% fatality rate. The majority of cases occurring in SA were in patients from the Northern Cape and Free State provinces.

“The funding that has been awarded will be used to profile immune responses against CCHF viral proteins, and investigate mechanisms and strategies to enhance these immune responses. We hope that the study will contribute knowledge towards the development of a vaccine against this medically significant virus.”

For more information or enquiries contact news@ufs.ac.za.

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