Grace Chua Straits Times 6 Nov 12;
MORE built-up space means the city centre is staying warmer at night, according to research by a Singapore scientist.
And the effect is spreading to previously less-developed areas that are now urbanising, such as Tampines, Punggol and Pasir Ris.
It could even affect rainfall over the city, said National University of Singapore atmospheric science expert Matthias Roth, who conducted the study. His work - a review of research from the past four decades - is not yet published but likely to appear in a scientific journal early next year.
The urban heat island effect refers to hard, flat surfaces such as streets and buildings becoming hotter during the day and staying warmer at night than forested areas.
Human activity, such as cars being driven and heat from air-conditioning vents, also contributes to the effect, said Associate Professor Roth.
Greater urbanisation in downtown Singapore means that in the last 40 years, the difference in night-time temperatures between the city centre and undeveloped areas has doubled.
Today, urban areas can be up to 7 deg C hotter at night than rural areas such as Lim Chu Kang, compared to 40 years ago, when the difference was about 3.5 deg C. That is under windless conditions. If there are strong winds or rain, the gap is smaller.
This is the first time temperature differences in areas have been quantified for Singapore, said Prof Roth. He added that study also helps put current research into context.
Average night-time temperatures have also gone up, according to Meteorological Service statistics. From 1982 to 1991, night temperatures measured 26.3 deg C. From 1992 to 2001, it was 26.6 deg C, followed by 26.8 deg C, from 2002 to 2011. As nights get warmer, people are more likely to sleep with the air-con on, thus increasing energy and fossil fuel use, said Prof Roth.
Average daytime temperatures are up as well. From 1982 to 1991, it was 28.6 deg C. Between 2002 and 2011, it rose to 29.1 deg C.
Urbanisation can affect rainfall patterns in ways that are still being studied, said Prof Roth. For example, higher temperatures create more updraft, which may lead to the formation of more clouds.
Now, Prof Roth is carrying out a more detailed study of how urban heat islands in Singapore vary by place and season.
But he said that simply "keeping a few trees here and there" may not help to mitigate the effect. "You need medium-sized parks and nature areas," he said.
Natural ventilation is also very important for Singapore, he added. For instance, void decks allow natural ventilation at ground level as the wind can flow through.
