Smoke from Christchurch fires to continue until the weekend
Levels of air pollution in parts of Christchurch are now approaching those seen in many of Asia's biggest cities, due to the Port Hills fires.
Air quality levels in the city are now at least five times that recommended by the World Health Organisation.
The University of Canterbury's Geography Department took a reading from the top of the geography building in Fendalton this afternoon and found levels of fine particulate matter (PM 2.5) similar to some of Asia's most polluted cities.
The department's reading was 100 micrograms per square metre, a reading confirmed by Environment Canterbury (ECan) this afternoon in Woolston. That means the level easily exceeds 100 closer to the fire.
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The World Health Organisation recommends cities have a level of no more than 20 micrograms of PM 2.5 per metre squared.
As of this afternoon the level of PM 2.5 in central Shanghai was 155.
University of Canterbury geography technician Justin Harrison said the university reading was not as high as it could be because Fendalton was some distance from the fire and the conditions at the top of the building lowered the number.
"The wind's blowing up here, again, that will be dropping the levels down, if we had still, calm conditions then we'd probably see those levels a bit higher as well."
The reason for the smoke is the new north-easterly wind, which is not only keeping the smoke over the city but also fuelling the fire as it increases in intensity.
PhD in fire simulation at the University of Canterbury Daisuke Seto says a further layer of wind higher up in the atmosphere was preventing the smoke from escaping the city.
"The north-earthly breeze is blowing the smoke that way, and the convection takes place and goes up, but then it looks like there's another layer of flow coming from the west, I believe. The convection looks like it's trying to punch through but the fire doesn't look that strong enough to penetrate the inversion layer on top."
The MetService says the prevailing north-easterly will stay in place until at least the weekend.
There's also very little hope of much rain in Christchurch for at least four days.
The MetService predicts there is not much chance of rain until Sunday. Some scattered rain can be expected on Saturday but the city will have to wait until Sunday for a decent downpour.
Harrison had advice for people living in the area:
"If you don't have the opportunity to get away from it, it's worthwhile covering your nose and face if there is thick smoke around, and just keep an eye on the news and health warnings that might be coming out."
The Canterbury District Health Board has advised any residents concerned about the impact of the smoke on their health to contact their GPs first.
Canterbury Medical Officer of Health Dr Alistair Humphrey said for the "vast majority of people" the smoke carried no health risk though could irritate the eyes, nose, throat and airways and cause a tightness of the chest or difficulty breathing.
"In healthy people, most symptoms disappear soon after exposure to smoke ends and do not cause long-term health problems."