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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

Four modernised controlled environment cabinets inaugurated

2006-07-27

Photographed in a controlled environment cabinet were at the back from the left: Mr Adriaan Hugo (head of the UFS Electronics and Mechanisation Division), Prof Herman van Schalkwyk (Dean: Faculty of Natural and Agricultural Sciences at the UFS) and Prof Koos Terblans (lecturer at the UFS Department of Physics). In front is Mr Koos Uys (engineering consultant from Experto Designa who helped with the cooling systems of the cabinets).
Photo: Leonie Bolleurs

Different look for research in controlled circumstances at the UFS

Research in controlled circumstances at the University of the Free State (UFS) turned a new page today with the inauguration of four modernised controlled environment cabinets of the Department of Soil, Crop and Climate Sciences.

“The controlled environment cabinets, which are situated next to the glass houses on the eastern side of the Agriculture Building on the Main Campus in Bloemfontein, were installed in the early 1980’s. The cabinets, used for research purposes in controlled circumstances by the UFS for many years, became dysfunctional and needed to be repaired and put into use again,” said Prof Herman van Schalkwyk, Dean: Faculty of Natural and Agricultural Sciences at the UFS.

“The cabinets are used by the agronomics, horticulture and soil science divisions of the Department of Soil, Crop and Climate Sciences to control factors such as the temperature, the intensity and quality of light, synthesis and humidity. This is done 24 hours a day, with hourly intervals,” said Prof Van Schalkwyk.

The cabinets are ideally suited to determine the joint and separate effects of these factors on the growth of plants. The adaptability of plants to climate can also be investigated under controlled circumstances. All of this leads to a better understanding of the growth and development process of plants, more specifically that of agricultural crops.

“The effect of these environmental factors on the effectiveness of insect killers such as fungus killers, insecticide and weed killers can also be investigated and can help to explain the damage that is sometimes experienced, or even prevent the damage if the research is timeously,” said Prof Van Schalkwyk.

A new cabinet can cost between R2-3 million, depending on the degree of sophistication. “Although controlled environment cabinets have been used for agricultural research for a long time, it has become costly to maintain them and even more impossible to purchase new ones,” said Prof Van Schalkwyk.

According to Prof Van Schalkwyk the cabinets were re-built by die UFS Electronics and Mechanisation Division. Some of the mechanisms were also replaced and computerised.

“The re-building and mechanisation of the cabinets were funded by the faculty and because the work was done by our own staff, an amount of about R1 million was saved. The maintenance costs will now be lower as the cabinets are specifically tailor made for our research needs,” said Prof Van Schalkwyk.

Where all monitoring was done manually in the past, the cabinets can now be controlled with a computer. This programme was designed by Prof Koos Terblans from the UFS Department of Physics.

According to Prof Van Schalkwyk the modernisation of the cabinets is part of the faculty’s larger strategy to get its instruments and apparatus up to world standards. “With this project we have proved that we can find a solution for a problem ourselves and that there are ways to get old apparatus functional again,” said Prof Van Schalkwyk.

Media release
Issued by: Lacea Loader
Media Representative
Tel: (051) 401-2584
Cell: 083 645 2454
E-mail: loaderl.stg@mail.uovs.ac.za
26 July 2006

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