瑞典上空的珍珠云
(原标题: Nacreous Clouds over Sweden)
2025-02-01
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生动而有光泽，飘浮的彩虹色波浪从瑞典北部的天空中掠过。它们被称为珠母云或珍珠母云，非常罕见。但这张摄于1月12日的照片捕捉到了它们令人难忘的样子，当时太阳刚刚低于当地的地平线。极地平流层云的一种，当平流层下层通常无云的异常低温形成冰晶时，它们就形成了。在大约15到25公里的高度，云层仍然是阳光照射的，即使太阳本身隐藏在直射视线之外，云层也会遮挡阳光。
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Vivid and lustrous, wafting iridescent waves of color wash across this skyscape from northern Sweden. Known as nacreous clouds or mother-of-pearl clouds, they are rare. But their unforgettable appearance was captured in this snapshot on January 12 with the Sun just below the local horizon. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers, the clouds diffract the sunlight even when the Sun itself is hidden from direct view.
© Vojan Höfer