A Singapore weekend pans out in vibrant colours

Singapore residents were treated to a vibrant display of sunset colours as the weekend kicked off.

Netizens posted images of bright orange streaks and wavy clouds across the sky last evening from places such as HarbourFront, Ang Mo Kio and Pasir Ris.

Facebook user Valerie VC said the clouds resembled the famous Northern Lights.

Another netizen, Mr Steven Lim, said he decided to chase the sunset at West Coast on his way home from work as he noticed that the weather was good. "Mr Sun is good to me to allow me to take many nice photos," he wrote.

Weather and climate scientist Koh Tieh Yong from the Singapore University of Social Sciences said the spectacular sunset was typical of a sunny day, and the air was relatively free of pollutants across the island.

"Under such clean conditions, sunlight is scattered by air molecules in a process known as Rayleigh scattering. This causes the sky to be reddish at low angles near the direction of the setting sun and to slowly turn orange, yellow, green and finally blue at higher and higher angles," said Associate Professor Koh.

He noted that the clouds in the photos are also indicative of the fine weather. "The ice crystals and water droplets which make up these clouds scatter the intense red-orange sunlight incident at low angles, thus rendering them a brilliant warm hue," he said.

The Straits Times understands that the clouds are likely to be high-altitude cirrus clouds, which stretch across the sky in delicate white filaments. They consist almost entirely of ice crystals, which give them their wispy or feathery appearance.

The presence of cirrus clouds generally means a lack of low-or medium-level clouds to obscure the high-altitude ones, and are therefore a sign of good weather.