The haze that is expected to hit Singapore in the coming months could go on for as long as three months, experts have warned.
This is similar to what the Republic experienced in 1997, they said.
Prolonged hazy skies could happen if a strong El Nino effect sets in, compounded by the already-started illegal land clearing by farmers in Sumatra.
El Nino is a phenomenon which causes severely dry weather and high temperatures in this region.
According to environmental reports, there were more than 3,000 hotspots in Sumatra at the peak of the haze crisis in March alone.
This compared to about 2,700 in June last year.
The next dry season will occur between June and October, and experts are concerned illegal land clearing in Sumatra will result in large-scale fires.
“If they deliberately set fires to clear land, particularly if it’s land being cleared illegally, they are not going to listen to anyone who tells them not to start the fire,” said Mr Faizal Parish, Director of Global Environment Centre, a non-governmental organisation based in Malaysia.
“They won’t take immediate action to put out the fire. The problem (in Sumatra) is the need for active enforcement on the ground.”
Worse, the March fires have not yet been put out completely.
Mr Parish said: “(About) 90 per cent of smoke and haze is coming from peat. Fires can remain burning underground for months and then come back up to the surface during dry periods.
“So, sometimes when there’s rain, the surface fire goes out but is still smouldering on the ground. A few days later, or a week later, the fire can re-emerge again from underground to the surface.”
Mr Parish said the fires deep within the peat smouldered for as long as six months between 1997 and 1998.
That was also the year strong El Nino conditions set in.
How warm a particular stretch of the Pacific Ocean is could provide an indication of an El Nino pattern.
Experts say the sea surface temperatures have to consistently be 0.5 degrees Celsius above a long-term average for an El Nino season to be declared and this part of the Pacific Ocean has been exceeding these thresholds since April.
In Singapore, experts say 1997 was also characterised by the lowest annual rainfall measured in the Republic since 1948.
Assistant Professor Winston Chow from the National University of Singapore’s Geography Department said: “In June, July and August, we should be experiencing South West Monsoon or summer monsoon conditions where wind direction comes from the south or south west.
“You still have rainfall occurring. But what happens during El Nino is that while the wind conditions more or less remain the same, you can expect less rainfall to happen. On top of that, you would expect higher-than-normal temperatures during the season as well.”
Professor Chow said if there are intense fires in Sumatra, the prevailing wind direction would fan the smoke and particulate matter towards Singapore and Peninsular Malaysia.
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