New tools will help predict haze better, say experts

Mr Jared Lee, 18, playing football on a hazy day last month when the PSI read 95. Climate scientist Matthias Roth says the index should be modified to consider the PM2.5 particles to better reflect the haze's health impact.
Mr Jared Lee, 18, playing football on a hazy day last month when the PSI read 95. Climate scientist Matthias Roth says the index should be modified to consider the PM2.5 particles to better reflect the haze's health impact.ST PHOTO: MARK CHEONG

New satellite feeds, ground instruments can aid Singapore in preparing for it

New satellite feeds that the Government will soon tap, combined with ground instruments, can help Singapore to better predict haze, said experts.

But this may take years and may require Indonesia's co-operation. In the short term, the authorities should consider installing more advanced sensors here and modify the air pollution index to better monitor and reflect the haze's health impact.

Scientists gave these assessments when The Straits Times asked them how Singapore could better prepare for the haze.

Last month, raging fires in Indonesia led to the worst haze in Singapore's history.

On Monday, Minister for the Environment and Water Resources Vivian Balakrishnan said Singapore will tap new satellite feeds by 2015 to provide early haze alerts, but scientists said this could be easier said than done.

Satellites look at the ground in different ways, and cross different places at different times, said Assistant Professor Jason Cohen from the National University of Singapore (NUS). He specialises in climate change computer models and is researching the haze.

For example, the Modis satellite passes over the region several times a day and can "see" several thousand kilometres at once, but its cameras' observations can be blocked by clouds. It may also mistake thick smoke for a cloud.

The Calipso satellite shines a laser beam that can cut through most clouds to pick up images. The thicker the smoke, the more energy is removed from the beam returned to the satellite.

But the beam's thinness means its horizontal visual range is at most 1km, and the satellite passes over the region more slowly.

Both satellites are operated by the US National Aeronautics and Space Administration (Nasa). The National Environment Agency (NEA) uses data from several satellites including Modis ones and Nanyang Technological University's X-Sat satellite.

"If you want to integrate information from different satellites to come up with a prediction, you must have a computer program that can cover different scales in space and time, and different physical and chemistry data collected by the satellites. It's very challenging," said Dr Cohen.

Dr Santo Salinas, a senior research scientist at the NUS Centre for Remote Imaging, Sensing and Processing, said having data from more ground instruments in the region would help scientists track how pollutants spread. This will lead to better forecasting systems.

"There has to be a holistic approach combining satellite remote sensing, on-site sampling and measurements and numerical modelling."

Defence Minister Ng Eng Hen, who heads an inter-ministerial task force to tackle the haze, said that under a previous agreement, Singapore was willing to fund better meteorological instruments in Indonesia to get an early sense of the winds, but it has to respect Indonesia's territorial rights.

Singapore also needs to invest in more advanced instruments that can give more information about the chemical composition of particles and toxic gases in the haze in real time, said Dr Erik Velasco, a research scientist at the Singapore-MIT Alliance for Research and Technology.

This will allow scientists and the authorities to better analyse and gauge the health impact of the pollution, he said.

Historical records and maps showing how the pollution is distributed here should also be made publicly available.

"Similar to other international monitoring networks, these data and maps will provide even more information to Singaporean society, and help the authorities to better design measures to take in future haze episodes."

Besides more studies, the NEA can also consider updating the air pollution index here, said climate scientist Matthias Roth, deputy head of geography at NUS.

The Pollutant Standards Index (PSI) does not accurately reflect the danger of small, toxic particles called PM2.5, he said.

This was why the US replaced the PSI in 1999 with the Air Quality Index.

"Two emissions sources may generate the same PSI, but one could have a higher fraction of PM2.5 than the other, resulting in a more serious impact on health."

During the recent haze crisis, the NEA issued stricter health warnings when the PM2.5 levels were high, even though the PSI would have triggered a lower warning level.

"This was prudent, but to avoid confusion, it would be better to have an air quality indicator which considers PM2.5 as the US is doing, for example," said Dr Roth.

zengkun@sph.com.sg