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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

International Association of Hydrogeologists strengthens ties with IGS
2015-03-31

 

From the left are: Prof Neil Heideman, Dean of the Faculty of Natural and Agricultural Sciences, Mr Shammy Puri, secretary-general of the International Association of Hydrogeologists, and Prof Danie Vermeulen, Director of the Institute for Groundwater Studies.
Photo: Supplied

The Institute for Groundwater Studies (IGS) is in the process of establishing a SADC Groundwater Management Institute, sponsored by the World Bank. To coincide with this process, the IGS received a visit from Mr Shammy Puri, the secretary-general of the International Association of Hydrogeologists (IAH).

“The aim of the visit was to further cooperation between the IAH and IGS regarding transboundary aquifers in the SADC region,” said Prof Danie Vermeulen, Director at the IGS.

The International Association of Hydrogeologists (IAH/AIH) is a scientific and educational charitable organisation for scientists, engineers, water managers, and other professionals working in the fields of groundwater resource planning, management, and protection.  The IAH is the leading international society for the science and practice of hydrogeology, and is a globally recognised information source and facilitator for the transfer of groundwater knowledge.

Mr Shammy Puri was elected Secretary-General of IAH in 2008, and chaired the Commission on Transboundary Aquifer Resources Management (TARM) from 1998 to 2011.

During his visit, Mr Puri also presented lectures to the postgraduate students at the Institute on Transboundary Aquifers. He was also invited by the Dean of the Faculty of Natural and Agricultural Sciences, Prof Neil Heideman, to present the faculty prestige lecture later this year.

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