云洞又称“穿洞云”(hole-punchcloud)，其形成原理至今是个谜，在气象学上仍属于猜测的课题，可能是小区域内冰晶下沉造成的穿洞现象，也有科学家怀疑是飞机经过造成的...
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云的圆形很可能就是人们所称的穿洞云。
The cloud's round shape is likely what is known as a hole-punch cloud.
穿洞云：这幅拍摄西弗吉尼亚乡村地区的图片展示了左上角覆盖上空的云层。
Hole punch clouds: This picture taken of Rural West Virgina shows cloud cover to the top left.
海明斯菲尔德和同事们于2007年在丹佛国际机场附近的一个装备有许多仪器的涡轮螺旋桨飞机上展开云研究后不久就不偏不倚的发现了穿洞云。
Heymsfield and colleagues flew smack-dab into the hole-punch discovery after having conducted a cloud study from a heavily instrumented turboprop plane near Denver International Airport in 2007.
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