以Comment on one greatest invention or discovery in 21century

以Comment on one greatest invention or discovery in 21century 为要求的 大学水平英语作文 300字

THE explosive eruption of Eyjafjallajokull,an Icelandic volcano,wreaked havoc on air travel over the North Atlantic for several weeks this spring.The very existence of the ash cloud thrown into the sky was bad enough.But an inability to predict the cloud’s behaviour made matters worse.In particular,sudden changes in its height made the job of flying safely above it a tricky one.
Now a team of researchers at the British and Icelandic Meteorological Offices,led by Alec Bennett,may have found a way round the problem of predicting the height of volcanic ash clouds like that created by Eyjafjallajokull.As they report in Environmental Research Letters,the lightning the ash generates tells all.
Volcanic-ash clouds contain a lot of static electricity.This is eventually discharged as bolts of lightning.The details,however,are obscure,so Dr Bennett and his colleagues decided to take advantage of ATDnet,a British long-range lightning-location network,to look at the phenomenon in more detail.
ATDnet is an arrangement of 11 sensors scattered across Eurasia,one of which is in Iceland.It is designed to detect the low-frequency radio pulses emitted by lightning strikes.Such pulses can travel thousands of kilometres,which means they are frequently picked up by more than one of ATDnet’s sensors.When that happens,triangulation allows the system to locate the original bolt with precision.Using ATDnet,Dr Bennett and his colleagues were able to identify 790 bolts which had descended from the ash cloud created by Eyjafjallajokull.They combined these findings with radar information on the height of the cloud to work out if there was any connection between the two.
There was.When the cloud’s maximum altitude was less than 5km (3 miles),ATDnet detected no lightning from it.The number of strikes went up as the maximum altitude increased.Sudden changes in altitude also pushed the strike-rate up.More than 20 bolts an hour indicated a rapid rise of more than 1km.
In the case of Eyjafjallajokull,the watchful eye of Icelandic radar meant the cloud’s behaviour was reasonably well understood,even at the time.But radar can be blinded by bad weather,and not all volcanoes are within range of suitable equipment.Next time a volcano threatens the air lanes,then,Dr Bennett’s method may provide valuable illumination of what is happening,and thus enable airliners to steer safely through what might otherwise ground them.