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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

Exciting open day and Albert Einstein program at Boyden Observatory

2005-05-06

National Science Week, which will be held from 7-14 May 2005, is an annual country-wide celebration of science, led by the Department of Science and Technology. The department selected a proposal by the Boyden Science Centre to coordinate a week of activities in the Bloemfontein area as one of the many projects in the country.

The project for Bloemfontein and surrounding areas will be delivered though a collaboration between the National Museum in Bloemfontein and the University of the Free State (UFS), including the Research Institute for Education Planning, the Department of Physics and other departments in the Faculty of Natural and Agricultural Sciences.

The purpose of National Science Week is:

to create awareness of the important role that science play in people’s daily lives;
to encourage our youth to consider studying and improving their performance in mathematics and science; and
to attract more of our youth into science, engineering and technology (SET) careers.

World Year of Physics and Albert Einstein Program at Boyden Observatory

The International Union of Pure and Applied Physics (IUPAP) declared the year 2005 as the World Year of Physics (WYP). In recognition of this declaration, the great contribution of Physics to the development of technology, and its importance in our everyday lives will be featured strongly during the National Science Week 2005.

On Saturday 7 May 2005 there will be a public programme at Boyden Observatory from 15:30 as a contribution to the World Year of Physics. The programme will be presented in collaboration with the Bloemfontein branch of the Astronomical Society of Southern Africa and will include short presentations on astronomy, space exploration and the sun.

The main presentation will be at 19:00 the evening on the life and work of Albert Einstein. The programme will also include observing sessions through telescopes of objects like the sun, Jupiter and Saturn. There will also be an exhibit on Albert Einstein. Attendance is free but booking is required. For bookings, phone 051-4012561.

Public lecture programme:

Next week the following exciting public lectures will be presented as part of the Science Week activities:

Monday 9 May 2005

National Museum:

A discussion on Apocalypse Then: the greatest mass extinction of all time. The lecture will be presented by Dr Jennifer Botha, Paleontologist at the National Museum.
Bookings: 051-4479609 (entrance is free).

UFS campus:

All lectures at Kine 2, Medical Faculty, UFS campus. Follow directions from the DF Malherbe Road entrance.
Bookings: 051-4012561 (entrance is free).

Tuesday 10 May 2005:

A discussion on the Tsunami disaster of 26 December 2004 at 19:30 (UFS campus, Kine 2 Medical Faculty).

Wednesday 11 May 2005:

A discussion on Is there life out there? at 19:30 (UFS campus, Kine 2 Medical Faculty).

Friday 13 May 2005:

A discussion on Hunting Black Holes at 19:30 (UFS campus, Kine 2 Medical Faculty). The lecture will be presented by Dr Phil Charles, Director: South African Astronomical Observatory.

Science awareness day at the National museum

The science week will be concluded on Saturday 14 May 2005 with a special Science Awareness Day at the National Museum, Aliwal Street, Bloemfontein.

The excellent exhibits at the museum will be supplemented with activities, career information and video shows. The duration of the programme will be from 10:00-16:00. For enquiries, please call 051-4479609.

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

6 May 2005

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