21 May 2021
Discrete fluffy white clouds. When I photographed this field of rapeseed in Ohio I was struck that all the clouds are flat on the bottom. Why?
They look as if they are laid on a glass ceiling. The bottoms are at the same altitude. Here’s a similar sky in Australia.
These fair weather clouds are Cumulus humilis, “humble” clouds that are flat and wide.
If the rising air is strong enough they grow upward to become Cumulus mediocris …
… and taller into Cumulus congestus which can end a fair weather day.
All of them have flat bottoms at the same altitude because …
The flat bottom of cumulus clouds defines the exact height at which a critical combination of temperature and air pressure causes water vapor within the rising current to condense into a visible cloud.
— Chicago Tribune, Ask Tom about weather, 19 July 2015
The bottoms show where the dewpoint is.
A NOTE about the yellow field: Rapeseed (Brassica napus), in the mustard family, is grown for its oil-rich seeds. Cultivars with very low eruric acid become canola oil. “Rapeseed is the third-largest source of vegetable oil and second-largest source of protein meal in the world,” according to Wikipedia.
(photo by Kate St. John)
We were visiting our son in Saskatchewan. The fields of canola (rapeseed) were SPECTACULAR for miles. Thank you for the cloud tutorial. I have never quite mastered cloud recognition. Enjoy your day as I daily enjoy your site.
The bottoms of those clouds define the “lifting condensation level”. That is the meteorological term for the altitude at which water vapor begins to condense.