0 a type of stratus (= flat grey cloud) formed in a wide thick layer at a low level and usually carrying rain -- 乱层云（低空的一种平坦的暗灰色层云，云层厚、面积大，多携带雨水）
Nimbostratus usually has a thickness of about 2000 m.
Nimbostratus and some cumulus in this family usually only achieve comparatively moderate vertical extent.
Nimbostratus can have multiple associations as low, middle, or multi-tage depending on the criteria used by various authorities.
Of the latter, "upward-growing" cumulus mediocris produces only isolated light showers, while "downward growing" nimbostratus is capable of heavier, more extensive precipitation.
The occurrence of cumulonimbus and nimbostratus together is uncommon, and usually only nimbostratus is found at a warm front.
Downward-growing nimbostratus can be as thick as most upward-growing vertical cumulus, but its horizontal extent tends to be even greater.
Lightning from an embedded cumulonimbus cloud may interact with the nimbostratus but only in the immediate area around it.
The cloud layer achieves significant vertical extent as it lowers and changes into nimbostratus.
