20 April 2010 While eruptions from the Icelandic volcano that have disrupted global air travel have recently ejected less ash, that could change at any time, the United Nations World Meteorological Organization (WMO) warned today.
The current high pressure system with weak winds does not help to disperse the ash cloud, but a stronger low pressure system is expected over Iceland towards the end of the week, changing the winds and pushing the cloud towards the Arctic, with accompanying rains resulting in a degree of “wash out” of ash at lower levels, it added.
Regarding public health, the ash has no effect except in the immediate vicinity of the volcano in Iceland, according to the UN World Health Organization (WHO).
The WMO said the plume from Eyjafjallajokull volcano was now reaching less than 3,000 metres, with its whiteness suggesting it contains mainly steam and little ash. “However, the volcano is liable to revert to explosive eruptions at any time,” it added.
The fine ash injected into higher levels of the atmosphere, above 6,000 metres, will remain there for some time, as these small particles can only be effectively removed by thunderstorms which are not expected for the next few days. The particles are slowly descending to lower levels, with measurements showing most ash is now between the Earth’s surface and 3,000 metres.
The fine particles, if sucked into a jet engine, can erode and destroy fan blades, eventually leading to the engine stalling. They can also ‘blind’ by sandblasting the windscreen, requiring an instrument landing, and damage the fuselage.
The WMO is working in close cooperation with the UN International Civil Aviation Organization (ICAO), which runs nine Volcanic Ash Advisory Centres (VAAC) in various regions that issue meteorological warns for aircraft.
As for public health, WHO environmental epidemiologist Carlos Dora told a news briefing in Geneva that the very coarse particles near the volcano in Iceland caused a lot of irritation and people had to take precautions, including using goggles and masks and remaining indoors as much as possible.
In the rest of Europe, the pollution has not arrived at ground level, he said. There is a very good network of air quality monitoring at ground level in European cities, and so far the range has been within the normal, with no concern for health in European countries.
It is very possible that the plume will disperse in the air without there being any concentration at ground level, he added.
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