Key Takeaways
- • Singapore's air quality returned to moderate levels (PSI 81–99) across all five regions as of 11pm on September 30, following a peak of 134 earlier in the day and a season-high of 164 on September 29 in the central region.
- • The central region recorded a new seasonal high of 164 PSI on September 29 at 10am, surpassing the previous peak of 154 set on September 15, marking the first breach into the unhealthy band (101–200) in two weeks.
- • Hourly PM2.5 readings normalized to the standard band (18–37 micrograms per cubic meter) by 11pm on September 30, down from elevated levels of 74–142 recorded during the haze event, indicating particulate matter concentrations returned to safe operational levels.
- • All five regions entered the unhealthy PSI range simultaneously on September 29, the second instance this season following September 15, triggering National Environment Agency (NEA) advisories recommending outdoor activity reduction during the affected period.
- • The air quality improvement aligns with weather pattern shifts, including regional showers over Singapore and surrounding areas, which contributed to the dispersion of transboundary smoke haze originating from southern Sumatra wildfires.
Summary
Singapore experienced a significant air quality deterioration event on September 29 before conditions normalized by September 30. The 24-hour Pollutant Standards Index (PSI) readings across all regions returned to moderate levels (51–100 band) by 11pm on September 30, marking recovery from the season's most severe air quality breach to date.
The haze event peaked on September 29 when the central region recorded a PSI of 164 at 10am, establishing a new seasonal high and surpassing the previous peak of 154 recorded on September 15. Earlier on September 30, the central and western regions had reached 134 before improving to 99 by late evening. All five regions simultaneously entered the unhealthy range (PSI 101–200) on September 29, prompting the National Environment Agency to advise the public to reduce outdoor activities—a concurrent regional impact not recorded since September 15.
The underlying air quality metric, hourly PM2.5 (fine particulate matter), exhibited parallel recovery. During peak haze hours, PM2.5 readings spiked across all regions to between 74 and 142 micrograms per cubic meter, with the central region recording 142. By 11pm on September 30, all regions normalized to 18–37 micrograms per cubic meter, remaining well within the standard band and below the elevated threshold of 56–150. The NEA differentiates between metrics for operational planning: the 24-hour PSI rolling average guides next-day activity planning, while hourly PM2.5 readings inform immediate decisions.
The transboundary haze originated from wildfires in southern Sumatra, with regional meteorological monitoring indicating that showers over Singapore and surrounding areas contributed to smoke dispersion. This weather pattern shift facilitated the rapid transition from unhealthy to moderate air quality within 36 hours, preventing sustained periods of hazardous conditions typical of severe regional haze events.
The haze event peaked on September 29 when the central region recorded a PSI of 164 at 10am, establishing a new seasonal high and surpassing the previous peak of 154 recorded on September 15. Earlier on September 30, the central and western regions had reached 134 before improving to 99 by late evening. All five regions simultaneously entered the unhealthy range (PSI 101–200) on September 29, prompting the National Environment Agency to advise the public to reduce outdoor activities—a concurrent regional impact not recorded since September 15.
The underlying air quality metric, hourly PM2.5 (fine particulate matter), exhibited parallel recovery. During peak haze hours, PM2.5 readings spiked across all regions to between 74 and 142 micrograms per cubic meter, with the central region recording 142. By 11pm on September 30, all regions normalized to 18–37 micrograms per cubic meter, remaining well within the standard band and below the elevated threshold of 56–150. The NEA differentiates between metrics for operational planning: the 24-hour PSI rolling average guides next-day activity planning, while hourly PM2.5 readings inform immediate decisions.
The transboundary haze originated from wildfires in southern Sumatra, with regional meteorological monitoring indicating that showers over Singapore and surrounding areas contributed to smoke dispersion. This weather pattern shift facilitated the rapid transition from unhealthy to moderate air quality within 36 hours, preventing sustained periods of hazardous conditions typical of severe regional haze events.
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