太陽打蔫兒 北半球今年或再現冷冬

A cyclical drop in the sun's radiation can trigger unusually cold winters in parts of North America and Europe, scientists say, a finding that could improve long-range forecasts and help countries prepare for blizzards.

科學家表示，太陽輻射的週期性減弱可能導致北美洲和歐洲部分地區出現異常“冷冬”。這項科學發現可以改進長期天氣預報，幫助各國準備好應對風雪。

Scientists have known for a long time that the sun has an 11-year cycle during which radiation measured by sunspots on the surface reaches a peak then falls. But pinning down a clear link to weather has proved harder.

早前研究發現，太陽的活動週期爲11年，在此期間，以太陽表面黑子爲衡量標準的太陽輻射達到峯年和谷年。但證實太陽活動週期與天氣之間的明確聯繫一直存在困難。

"Our research confirms the observed link between solar variability and regional winter climate," lead author Sarah Ineson of the UK Met Office told the reporters in an email. The study was published in the journal Nature Geoscience on Monday.

研究負責人、英國氣象局的莎拉 伊尼森在電郵中告訴記者：“對已觀測到的太陽活動變化與地區冬季氣候之間的聯繫，研究予以了證實。” 研究結果本週一發表在英國《自然—地球科學》雜誌上。

Her team focused on data from the recent solar minimum during 2008-10, a period of unusual calm for the sun and intense winters in the United States and parts of Europe that shut down air travel and disrupted businesses.

研究小組對最近的一次太陽活動谷年，也就是2008年至2010年的數據進行了分析。這段時間太陽活動出奇平靜，而美國出現極端寒冬，歐洲部分地區還曾關閉機場，這也打亂了經濟活動。

The researchers found that a reduction in ultraviolet(UV) radiation from the sun can affect high-altitude wind patterns in the Northern Hemisphere, triggering cold winters.

研究人員發現，太陽紫外線輻射水平的降低可以影響北半球高緯度的環流形態，導致冷冬。

"While UV levels won't tell us what the day-to-day weather will do, they provide the exciting prospect of improved forecasts for winter conditions for months and even years ahead. These forecasts play an important role in long-term contingency planning," Ineson, a climate scientist, said.

氣候學家伊尼森說：“紫外線水平無法預測每日的天氣狀況，但可以使我們對未來數月甚至數年的冬季氣候預測更加準確。這種預測可以使我們在較長時期內對極端天氣做好準備。”

Ineson and colleagues from the Imperial College London and the University of Oxford used satellite data that more accurately measures UV radiation from the sun and found a much greater variability than previously thought.

伊尼森和來自帝國理工學院以及牛津大學的同事藉助衛星數據，更爲準確地測得太陽紫外線輻射，發現數據波動超過先前預計。

They found that in years of low activity, unusually cold air forms high in the atmosphere over the tropics. This causes a redistribution of heat in the atmosphere, triggering easterly winds that bring freezing weather and snow storms to northern Europe and the United States and milder weather to Canada and the Mediterranean.

他們發現，在太陽活動谷年，異常冷空氣在熱帶高層大氣形成，造成大氣熱量重新分配，引發東風，令歐洲北部和美國遭遇異常低溫和暴風雪，加拿大和地中海地區氣候則變得更爲溫和。

When solar UV radiation is stronger, the opposite occurs.

太陽紫外線進入活動峯年時，情況則相反。

Ineson's team used the data in a complex computer model that simulates long-term weather patterns. The model successfully reproduced what scientists have observed happening in the upper atmosphere during changes in solar radiation.

伊尼森的研究小組利用一個複雜計算機模型得出數據，這種模型可以模擬長期氣候類型。模型成功重現了在太陽輻射變化時，科學家已經在高層大氣觀測到的狀況。

More study was needed, though. A key uncertainty in the experiment lay in the satellite data used, because it spans only a few years. "So questions remain concerning both accuracy and also applicability to other solar cycles," she said.

但這一結論仍需要更多研究來印證。衛星數據中存在一個關鍵的不確定因素，因爲數據只覆蓋了最近幾年。她說：“因此研究結果的準確性和對太陽其他週期的適用性仍有待驗證。”