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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

NRF grants of millions for Kovsie professors
2013-05-20

 

Prof Martin Ntwaeaborwa (left) and Prof Bennie Viljoen
20 May 2013


Two professors received research grants from the National Research Foundation (NRF). The money will be used for the purchase of equipment to add more value to their research and take the university further in specific research fields.

Prof Martin Ntwaeaborwa from the Department of Physics has received a R10 million award, following a successful application to the National Nanotechnology Equipment Programme (NNEP) of the NRF for a high-resolution field emission scanning electron microscope (SEM) with integrated cathodoluminescence (CL) and energy dispersive X-ray spectrometers (EDS).

Prof Bennie Viljoen from the Department of Microbial, Biochemical and Food Biotechnology has also been awarded R1,171 million, following a successful application to the Research Infrastructure Support Programme (RISP) for the purchase of a LECO CHN628 Series Elemental Analyser with a Sulphur add-on module.

Prof Ntwaeaborwa says the SEM-CL-EDS’ state-of-the art equipment combines three different techniques in one and it is capable of analysing a variety of materials ranging from bulk to individual nanoparticles. This combination is the first of its kind in Africa. This equipment is specifically designed for nanotechnology and can analyse particles as small as 5nm in diameter, a scale which the old tungsten SEM at the Centre of Microscopy cannot achieve.

The equipment will be used to simultaneously analyse the shapes and sizes of submicron particles, chemical composition and cathodoluminescence properties of materials. The SEM-CL-EDS is a multi-user facility and it will be used for multi- and interdisciplinary research involving physics, chemistry, materials science, life sciences and geological sciences. It will be housed at the Centre of Microscopy.
“I have no doubt that this equipment is going to give our university a great leap forward in research in the fields of electron microscopy and cathodoluminescence,” Prof Ntwaeaborwa said.

Prof Viljoen says the analyser is used to determine nitrogen, carbon/nitrogen, and carbon/hydrogen/nitrogen in organic matrices. The instrument utilises a combustion technique and provides a result within 4,5 minutes for all the elements being determined. In addition to the above, the machine also offers a sulphur add-on module which provides sulphur analysis for any element combination. The CHN 628 S module is specifically designed to determine the sulphur content in a wide variety of organic materials such as coal and fuel oils, as well as some inorganic materials such as soil, cement and limestone.

The necessity of environmental protection has stimulated the development of various methods, allowing the determination of different pollutants in the natural environment, including methods for determining inorganic nitrogen ions, carbon and sulphur. Many of the methods used so far have proven insufficiently sensitive, selective or inaccurate. The availability of the LECO analyser in a research programme on environmental pollution/ food security will facilitate accurate and rapid quantification of these elements. Ions in water, waste water, air, food products and other complex matrix samples have become a major problem and studies are showing that these pollutants are likely to cause severe declines in native plant communities and eventually food security.

“With the addition of the analyser, we will be able to identify these polluted areas, including air, water and land pollution, in an attempt to enhance food security,” Viljoen said. “Excess levels of nitrogen and phosphorous wreaking havoc on human health and food security, will be investigated.”

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