"Smog is still detected today, but the visibility is better," Ahmad Agus, an official at the BMKG station in Pekanbaru, remarked here on Tuesday.
Agus pointed to visibility on Monday having reached four to five kilometers after rain fell in the region. However, on early Tuesday, it had dropped again to lie in the range of 700 meters to a kilometer.
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In Rengat, Indragiri Hulu District, the visibility had reached one kilometer; while in Dumai City, it had reached two kilometers, and some one kilometer in Pelalawan District.
The PM10 Pollutant Standards Index (PSI) in Pekanbaru had dropped to 160-180 after earlier rising to 700, an improvement from the hazardous to unhealthy level.
However, on Tuesday morning, the PSI reading climbed to 234, almost reaching the level of very unhealthy.
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"It means that rainfall significantly reduced the smog, although it only fell in some areas," he stated.
According to the BMKG, the Terra and Aqua satellites had detected 39 hotspots indicative of forest fires in Riau at 6 a.m. local time. Most hotspots were observed in Rokan Hilir District, reaching 19; followed by 10 in Indragiri Hilir; six in Dumai City; three in Bengkalis District; and one hotspot in Meranti Islands.
Of these hotspots, 27 are believed to be land and forest fires, including 13 detected in Rokan Hilir, eight in Indragiri Hilir, four in Dumai, and two in Bengkalis. Related news: Terra, Aqua satellites identify 1,182 forest fire hotspots in Sumatra