Expect wetter, cooler weather this summer

Last year was one of the hottest on record for South Africa since 1951, an average of 1.1°C warmer than between 1981 and 2010.

Warmer weather brought with it persistent dry conditions, with the western part of South Africa receiving less than 50% of its normal rainfall. This forms part of the country’s seven-year drought, which spelt disaster for many farming regions in the Northern and Eastern Cape, the South African Weather Service revealed in its annual state of the climate findings.

The country is experiencing a weak La Niña effect where cool waters build up in the eastern Pacific.

This means colder ocean surface temperatures, less water evaporation and widespread rainfall in some parts of the world.

In East Africa, for example, La Niña usually leads to dry spells, but in southern Africa, it brings about cooler temperatures and more regular rainy spells.

The opposite of La Niña is the El Niño phenomenon, where warm water builds in the eastern Pacific. This warms the atmosphere and can cause water temperatures to increase by up to 6°C.

According to the National Aeronautics and Space Administration earth observatory, El Niño and La Niña cycles rotate every three to seven years.

Storm Report SA said models suggest a moderate or even strong La Niña season for South Africa.

Graphic: Costa Makola

What does this mean for SA?

Dr Johan Malherbe from the Agricultural Research Council Institute for Soil, Climate and Water said that although La Niña was not a guarantee that more rainfall would be experienced, some parts of the country were predicted to benefit from cooler, wetter conditions.

“Because there is a positive relationship between La Niña and summer rain, most of the summer rainfall region is expected to receive normal to above-normal rain during the coming season, according to seasonal forecast models.

“Given the very strong dependence of South African agriculture on rain, wetter and cooler summers, as associated with La Niña, usually bodes well for food production.”

Although these conditions can harm the maturation of crops and harbour fungal pathogens, those who lived through the last few years’ scorching temperatures and droughts, such as the Northern and Eastern Cape, will welcome a rainy
summer season.

Encouragingly, the International Research Institute for Climate and Society weather models suggest above-normal rainfall for the Northern and Eastern Cape in November, December and January, according to Storm Report SA.

The SA Weather Service said prolonged droughts adversely affect many sectors, but notably the agricultural industry, as this results in little to no significant crop production and farm workers being laid off.

Farming and rainfall

The weather service reported in its seasonal climate watch that even weak La Niña conditions should provide above-normal rainfall for parts of the country, especially in the northeast. This would also bring below-normal maximum temperatures.

Chief economist for the Agricultural Business Chamber Wandile Sihlobo said early predictions for the 2020-21  agricultural season are encouraging.

“It is plausible to assume that the central and western regions of South Africa would possibly receive rain early enough to keep up with the typical planting schedule for summer crops.”

And a good rainy season is essential for food security, Malherbe said.

Much of the country’s maize is produced locally under drylands cultivation and consumers live off what is produced in summer. A good harvest, therefore, means less need to import maize to satisfy local demand.

Sihlobo said good rains would also secure farmers’ financial conditions, especially those who have taken a knock due to drought.

“This would be an improvement for not only field crop and horticulture farmers, but also for the livestock sector,  which would benefit from improved grazing veld conditions and available supply of grains,” Sihlobo said.

All indications point to South Africa experiencing “another good agricultural season in 2020-21 because of the  expected higher rainfall”.

And, thanks to La Niña conditions, albeit weak, the summer crop season could start in its traditional period, which is in October, as opposed to it being delayed, Sihlobo added.

If forecasts are correct, Storm Report SA said the peak of this season’s La Niña will be between November and  January. La Niña is expected to weaken in autumn next year.

Malherbe was optimistic that La Niña conditions could interrupt prolonged drought conditions that have been plaguing regions such as the Eastern and Northern Cape for years.

The nature of  El Niño and La Niña is not yet fully understood.

“The relationship between La Niña and rainfall over South Africa weakens and strengthens at a decadal (10-year period) scale over South Africa,” he explains.

However, it is impossible to relate these changes to climate change, “as it is certainly, at least to some extent, related to the slowly varying nature of the global climate system impacting the subtropical regions – where we
are located”.

Data from the Agricultural Research Council shows the difference in rainfall in different parts of prominent farming regions in the country, notably the Eastern and Northern Cape, Free State and the North West, over the last 10 years. In 2010, the Eastern Cape received a total rainfall amount of 2 075mm. This year, 1 196mm of rain has fallen in the province so far.

In the Northern Cape, 626mm of rain fell in 2010 and this year it has recorded just 383mm.

In 2010, the North West received 2 137mm of rain, but this year just 821mm has fallen so far.

And in the Free State, a total of 2 427mm of rain fell in 2010, while in 2020 the province had 1 310mm.

South African Weather Service data from its Annual State of the Climate for 2019 shows that last year, East London’s highest daily temperature since 1951 was 43.3°C. Port Elizabeth’s was 40.7°C.

In the Northern Cape, which the weather service said had experienced intermittent spells of extremely low rainfall since 2013, Upington’s highest daily temperature since 1951 was 45.3°C. Last year, Upington received just 24 days of rain. In other words, the town got just less than a months’ worth of rain.

Including 2013, the Northern Cape has experienced four years of consistently low rain.

The Eastern Cape’s last above-normal rain year was in 2011.

– nicas@citizen.co.za

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