With temperatures rising and the dry season setting in, Indonesia has taken the pre-emptive step of cloud seeding to induce rain in a bid to keep haze under control.
The country's forest fires give rise to haze that has posed a persistent environmental problem not only for its people but also for its neighbours Malaysia and Singapore.
President Joko Widodo issued an ultimatum to all stakeholders last November to resolve the issue of forest fires, especially in Sumatra's Riau province.
Starting this week, a Casa C-295 aircraft loaded with about four tonnes of salt has been deployed to fly over Central Sumatra to search for clouds to seed.
"This week, the weather is very dry and the clouds are small so they are not conducive for cloud-seeding. This is part of a cycle... Next week, we should get good results," Dr Heru Widodo, head of the weather modification team at the Indonesian agency for the assessment and application of technology, told The Straits Times.
"The clouds good for seeding are those that look like cauliflower," Kompas daily quoted Mr Sutrisno, a flight scientist who goes by one name, as saying.
The pre-emptive move in Riau comes as Sumatra is seeing higher temperatures because of the El Nino effect, which can bring drought to Asia and wetter and cooler summers to parts of North America.
In the past three days, the temperature in Riau has reached 34 deg C, up from the normal range of 32 to 33 deg C, according to Ms Yesi Christy, an analyst at the weather agency in Pekanbaru, the provincial capital of Riau.
It will only get hotter in the coming weeks, she told The Straits Times.
Medan, the provincial capital of North Sumatra, recorded a high of 36 deg C, the Jakarta Post reported, citing a local weather agency official.
"This is already categorised as extreme because the normal temperature for these regions never exceeded 35 deg C," said Ms Lestari Purba, an analyst at the weather agency in Medan.
In June 2013, the worst haze in years shrouded Sumatra as well as Malaysia and Singapore, where air pollution shot to record high levels. In Pekanbaru, the temperature hit 37 deg C, the highest in more than 40 years.
The Riau region has just entered the dry season and is set to see minimum rainfall through next month and August, according to Ms Yesi, of the meteorology, climatology and geophysics office in Pekanbaru.
Indonesia expects the dry weather to continue until December.
Annual cross-border air pollution caused by uncontrolled land clearing in Indonesian plantations has been a source of unhappiness among Indonesia's neighbours, until Jakarta ratified the 2002 ASEAN Agreement on Transboundary Haze Pollution last September.
Under the agreement, countries have to co-operate in taking measures to prevent, monitor and mitigate the haze by controlling the sources of fires, in exchanging information and technology, and in helping one another manage outbreaks.
This article was first published on June 24, 2015.
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