Haze and Rain Making

Wednesday’s Post quotes Chiang Mai’s Vice Governor indicating pollution levels of PM 10 cancer causing particles in Chiang Mai, resulting from forest burning, were not of concern. Readings taken Tuesday at a school in the centre of town at 86 microgrammes per cubic metre of air seem to confirm this.

Readers wondering why “safe” pollution levels seem to apply in Chiang Mai, while in neighboring Mae Hong Sorn province the air is carcinogenic, might like to know that on Monday afternoon a violent ,smog clearing, thunderstorm with torrential rain and gale force winds hit just 10 kilometres north of Chiang Mai, town allowing blue sky to appear.

Cloud Seeding

1. Aircraft or artillery spray chemicals (often silver iodide or dry ice) into clouds to encourage tiny vapour droplets to coalesce
2. Droplets of supercooled water (liquid below freezing) coalesce into snow and melt as they fall
3. Heat released as the droplets freeze boosts updrafts, which pull more moist air into the cloud

[Taken from the following BBC article – Thai king aims high over drought]

The day before, a Sunday morning, when our normally well informed Vice Governor may not have been on duty, the government liason officer on the smoke pollution problem informed a citizens meeting that the PM 10 level was 140, 20 above the “safe” level. Later that day three fires were set on nearby Doi Suthep and two helicopters worked for two hours to douse the flames, the smoke from the blaze presumably worsening the problem.

By Wednesday two days after the rain, visibility and presumably pollution levels, had returned to their normal toxic levels.

On Tuesday, during a brief trip north to Fang I saw blackened roadsides and fires burning along the Ping River Gorge and on Doi Luang Chang Dao, just as they had the previous week, but no sign of red shirted firemen or helicopters fighting fires there.

Now it is suggested that artificial rain making may ease the problem. Perhaps our officials need to apply a bit of statistical accuracy in their reporting to higher authority. If they do so they will perhaps admit that rain making, when it works at all, works to move precipitation a few minutes of longitude, robbing say Tak to pay Chiang Mai.

Forest fire brings great public health and environmental costs and if we are to take it seriously we need to get our heads out of the clouds and many feet on the ground where the arsonists are at work.