Hazy skies due to change in wind direction

SINGAPORE — The air quality around the island dipped yesterday, with the three-hour Pollutant Standards Index (PSI) hitting 92 in the early afternoon, but conditions are expected to improve.

The three-hour PSI climbed hourly from 52 at 9am, reaching 63 at 11am, 80 at noon, and 91 at 1pm.

It peaked at 92 at 2pm — with the 24-hour PSI between 65 and 75 — before improving steadily, falling to 76 at 4pm and 72 at 5pm. By 7pm, the three-hour PSI reading was 69, and the 24-hour PSI was between 69 and 73.

A PSI reading ranging from 51 to 100 is moderate, while anything from 101 and 200 is considered unhealthy.

In response to TODAY’s queries, the National Environment Agency (NEA) said there had been reports of a burning smell in some parts of Singapore.

“The hazy conditions are due to a change in the prevailing winds to blow from the south-west, and this could have brought in some haze from the fires in central Sumatra.”

It added that conditions would improve as winds were forecast to blow from the south later yesterday.

Last week, the NEA said slightly hazy conditions could be expected on a few days, particularly in the early morning, because of the accumulation of particulate matter under light wind conditions.

Two weeks ago, the Meteorological Service also noted that sporadic hot-spot activities with smoke plumes had been seen recently in Sumatra, which could affect Singapore, depending on factors such as wind direction and rainfall.

The previous time the 24-hour PSI reading entered the unhealthy range was on Nov 3 last year, when it peaked at 120. The three-hour PSI reading on that day peaked at 116.

In 2013, Singapore suffered one of its most serious haze episodes, when the three-hour PSI peaked at 401 on June 21.