S'pore can expect frequent heatwaves in coming years: Experts

Singapore is less vulnerable to the warming climate caused by large-scale, high-pressure systems. ST PHOTO: CHONG JUN LIANG

SINGAPORE - Singapore will not experience the weather phenomena causing deadly heatwaves in Europe and China this month but it can expect frequent heatwaves in the coming years, experts said on Wednesday (July 20).

Located in the equatorial region, Singapore is less vulnerable to the warming climate caused by large-scale, high-pressure systems such as those over Europe and East Asia, said Assistant Professor Wang Jingyu from the National Institute of Education, who studies land-atmosphere interaction, as well as regional and global climate modelling and application.

"The main reason for the heatwaves that prevail is the abnormal expansion and intensification of high-pressure systems," he said.

As Singapore is situated next to the equator, the island is not directly affected by temperate or subtropical anti-cyclones, which triggered heatwaves in India, said Associate Professor Koh Tieh Yong, a weather and climate scientist from the Singapore University of Social Science.

Temperate regions such as Europe and North-east Asia experience heatwaves when high-pressure systems, known as anti-cyclones, descend over them, said Prof Koh.

These anti-cyclones that originate over the North Atlantic Ocean, Tibetan Plateau or North Pacific Ocean have winds that bring hot air from subtropical deserts and the tropics to the temperate regions in summer, he said.

But Singapore can still experience heatwaves caused by drier weather.

Responding to queries from The Straits Times, the Meteorological Service Singapore (MSS), under the National Environment Agency, said Singapore is more vulnerable to a heatwave when there is a strong El Nino - the abnormal warming of sea surface temperatures in the central equatorial Pacific Ocean.

Singapore's last heatwave in 2016 was triggered by El Nino, which led to the hottest year here since temperature records started in 1929.

Prolonged dry and warm weather can also be triggered by a strong positive Indian Ocean Dipole event, MSS said. This refers to warmer sea surface temperatures in the western Indian Ocean. The phenomenon has induced weather extremes such as the 2019 Australian bushfires and African floods.

Climate change is a common denominator that will worsen warming globally.

The heatwave sweeping across Europe is largely due to the Azores High - a slow-moving, semi-permanent high-pressure cell - usually located off Spain, said Professor Matthias Roth from the Department of Geography at the National University of Singapore.

Temperatures have surged past 40 deg C in countries such as Britain and Spain due to the high-pressure system, which is extremely strong this year. More of such occurrences can be expected in the future.

The "extremely large" Azores High is becoming more frequent - from once every 10 years in the pre-industrial period to once every four years in the 21st century, said Prof Wang.

As greenhouse gases warm the climate, more anti-cyclones such as the Azores High are projected to reach further north across temperate regions in Europe, Asia or North America, said Prof Koh.

In Singapore, stronger El Ninos caused by climate change can result in higher-than-normal temperatures.

Said Prof Koh: "Under climate change scenarios, more models show stronger El Ninos than not.

"This spells drier and hotter weather in Singapore during El Nino years in future, sometimes being intense enough to constitute heatwaves."

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