'Blocked' jetstream to blame for freak weather in Russia and Pakistan, say scientists
By Niall Firth
Last updated at 11:36 AM on 12th August 2010
A massive heatwave in Russia and the current devastating floods in Pakistan could be linked by the unusual behaviour of the jetstream, scientists believe.
一大型的熱浪在俄羅斯和目前毀滅性的洪災在巴基斯坦，可能與急流的不正常行為有關，科學家相信。
The jetstream is the high-altitude wind that circles the globe from west to east and normally pushes a series of wet but mild Atlantic lows across Britain.
急流是高海拔的風，由西向東在地球盤旋，通常推動一系列的濕但溫和的大西洋低氣壓區橫過英國。
But meteorologists who study the phenomenon say that it is producing unusual holding patterns which keep weather systems in one place and produce freak conditions.
但研究那現象的氣象學家說，它是在生產不尋常的把持模式，那保持天氣系統在一個地方和產生畸型的情况。
A satellite map which shows the intense heat that has built up over Russia after the jetstream has been held up due to Rossby waves一衛星地圖顯示強烈的熱量，已在俄羅斯上空建立，在急流已被 Rossby波把持後
The jetstream is being held by the Rossby waves that normally produce its distinctive wave-like pattern.
These powerful spinning wind currents are caused by the Earth’s shape and rotation and push the jet stream from east to west at high altitudes.
Now scientists believe that Rossby waves are acting against the jetstream’s usual pattern, holding it in place, according to a report in New Scientist.
Since mid-July, when it would normally be moving eastwards the jetstream has been held in one place as strong Rossby waves push against it.
When the jet stream is held in one place it traps the weather systems that are caught between its meanders. Warm air is sucked north to the ‘peaks’ while cold air travels to the ‘troughs’.
Professor Mike Blackburn of the University of Reading believes that a blocked jetstream could be behind a heatwave in Japan which killed 60 and the sudden end to warm weather in the UK.
A satellite image from this afternoon shows smoke from wildfires burning in Russia. The red dots indicate active fires. Scientists believe the jetstream could be to blame一張今天下午的衛星圖像顯示，煙霧來自俄羅斯野火燃燒，紅點表示活躍火災。科學家相信可責怪急流
Pakistani flood survivors evacuate a flooded area in Bssera village near Muzaffargarh today巴基斯坦水災生存者今天撤離一淹沒災區，穆紮法爾格爾附近的Bssera村莊
In Pakistan, the blocking event took place at the same time as the summer monsoon, with tragic consequences.
Floods triggered by heavy monsoon rain over much of Pakistan began nearly two weeks ago and have killed around 1,600 people and forced more than two million from their homes.
Many survivors from flooded villages have lost their stores of food as well as crops and livestock and are surviving on relief handouts.
In Russia, the immobile jetstream pulled in hot air from Africa creating stifling conditions and horrendous smog in Moscow.
Hundreds of wildfires have been burning across three time zones. Prime Minister Vladimir Putin yesterday boarded a fire-fighting plane to dump water on blazes close to Moscow, where the smoke has caused thick smog
Scientists are still unclear as to the cause of ‘blocking events’ although there have been some research that linked them to low solar activity.
A graph for 24 - 30th July which shows a succession of meanders along the jet stream, with a northward meander (ridge of high pressure) over the Atlantic, a southward meander (trough of low pressure) over Europe. Here the jet splits, around a large 'blocking' anticyclone over western Russia. On the eastern side of this anticyclone, air moves into the southward meander (trough) close to Pakistan from quite far north一張7月 24 - 30日的圖，顯示一曲折河流的延續沿著急流，在大西洋上空有一向北的蜿蜒（高壓脊），一向南的蜿蜒（槽的低壓）在歐洲上空。在這裡射流分裂，圍繞一大的'堵塞'反氣旋在俄羅斯西部上空。在這反氣旋的東邊，空氣移入向南的蜿蜒（槽），從遠北靠近巴基斯坦
A graph from the same period over a number of years shows what scientists would normally expect over this period with calmer winds and fewer 'trapped' weather patterns一張圖來自同一年期數字，顯示科學家通常會在期間期望什麼，有較平靜的風和較少'被困的天氣模式
http://www.dailymail.co.uk/sciencetech/article-1302225/Blocked-jetstream-blame-freak-weather-Russia-Pakistan.html
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