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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

Inaugural lecture focuses on Plant Pathology
2005-08-16

Prof Neal Mc Laren, from the University of the Free State’s (UFS) Department of Plant Pathology, will deliver his inaugural lecture on Wednesday 17 August 2005 at 19:00 in the CR Swart Auditorium on campus.

The topic of the lecture is Beyond the pathogen:  revisited”.

Prof Mc Laren obtained his B Sc, B Sc (Hons) and M Sc (Agric) at the University of Natal and    Ph D (Plant Pathology) from the University of Pretoria.  In 1977 he was appointed as a research technician at the former Department of Agricultural Technical Services, was promoted to professional officer in 1983 and in 1995 to specialist scientist at the Agricultural Research Council.  In 2003 he was appointed as Associate Professor Extraordinary in the Department of Plant Sciences at the UFS and in 2005 as a full-time Professor of Plant Pathology. 

Prof Mc Laren has published 32 papers in accredited scientific journals or refereed proceedings which include two feature articles.  He also has three book chapters to his credit.  He has presented 35 local and 18 international conference papers and has been an invited/keynote speaker on a number of occasions.  He has published 26 popular articles, co-supervised several post-graduate students and been an examiner of a number of dissertations/theses.   He has acted as referee for numerous journal articles and was associate editor for African Plant Protection. In 1998 he received the ARC-President’s Award and in 1999, an award from the Sorghum Producers Organisation of the USA for outstanding research.

Prof Mc Laren’s principle area of interest has been diseases of sorghum with emphasis on ergot, damping-off and seedling blights, root rots and grain molds.  In addition, root rots of maize and more recently, soybean rust have received attention.  He has a particular interest in quantitative epidemiology.  

For any enquiries, please contact Ms Joan Nel at (051) 401-9301.

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

16 August 2005
 

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