This is because the winds normally vary widely between the near-surface and the upper atmosphere, home to the eastward-flowing jet stream.

这是因为风通常从近地高度和高空大气层之间变化很大，进入高层后会并入向东流动的气流中。

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The sinking air is also carried along the surface to the equator, where it rises again, strengthening the already-powerful western winds in the upper atmosphere in the tropics.

下沉到海水表面的空气也会顺流而下到赤道附近，在那里它又变强，加强热带地区高空大气的西风。

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And upper-atmosphere winds in the hurricane region are affected by conditions in distant oceans, especially in the north Atlantic and the tropical Pacific.

而飓风区的高层大气气流又受遥远海洋特别是北大西洋和热太平洋的影响。

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The upper level winds are still transporting that down towards the U.K.and northwest Europe.

VOA: standard.2010.04.17

"I think we're going to get the upper level winds carrying that ash down for a few more days yet until the upper wind patterns change which will probably not happen until the time frame Thursday-Saturday.

VOA: standard.2010.04.17

Weather forecasters have said that recent rising temperatures and strong winds in the area have made it more dangerous as upper layers of snow are more likely to become detached, Italian media report.

BBC: Italy avalanche kills two in Fiemme Valley