Category Archives: Transboundary Haze

The prolonged dry spell experienced in Singapore during late phase of the Northeast Monsoon also affected the surrounding regions and resulted in an increase in hotspot activities in central Sumatra and Malaysia, including southern Johore. The prevailing north-easterly winds then blew the smoke haze from the hotspots in southern Johor towards Singapore on several days from 7 to 15 March. PSI readings hit the Moderate range during this period.

Hotspots and smoke/haze situation on 11 March 2014.

Smoke haze from southern Johore blown towards Singapore.

In the second week of June 2013, hotspot activities escalated in central Sumatra as a result of the relatively dry atmospheric conditions in the region. Westerly winds over the equatorial Indonesia then blew the moderate to dense smoke haze in central Sumatra towards Malaysia and Singapore. Slightly hazy conditions was experienced in Singapore on 13 June 2013, but the condition deteriorated rapidly on 17 – 18 June 2013, with the 24-hr PSI readings breaching the Unhealthy and Very Unhealthy levels within the next few days. The 3-hr PSI reached a record high of 401 on 21 June 2013, and the 24-hr PSI reached a record high of 246 on 22 June 2013, making this the worst transboundary smoke haze occurrence ever experienced in Singapore.

The smoke haze situations on 18 – 19 Jun 2013 were shown in the following NOAA-18 satellite images.

A change in wind direction on 25 June 2013 then brought an end to the haze in Singapore.

The unseasonal westerly winds were partly attributable to the presence of an unusually strong low pressure area to the southwest of Sumatra in Indian Ocean and also to the presence of the two tropical storms near Philippines during the period.

During Southwest Monsoon season in 1997, Southeast Asia experienced one of the worst haze episodes in history.  That year, Indonesia experienced drought conditions brought about by a record-breaking El Nino in 1997-1998, which provided conducive conditions for outbreak of fires. The traditional land clearing activities by farmers then resulted in widespread and prolonged burning of forested land in Sumatra and Kalimantan.  Large areas of smoke haze were blown towards Brunei, Malaysia, Thailand and Singapore between August and October 1997 by the prevailing southeasterly/southwesterly winds.  Air quality in Singapore reached very unhealthy levels and visibility dropped to below 300 m. The hazy conditions improved in November with the onset of the Northeast Monsoon season.

Widespread haze (indicated as yellow shades) shrouded Singapore and the neighbouring countries. On 18^th September, our local 3-hour PSI level hit a peak of 226.

Significantly lower than average rainfall in 1997 across the region including Singapore due to the record-breaking 1997-1998 El Niño phenomenon.