ASK THE METEOROLOGIST
“Why are clouds flat on the bottom?”
Lucy G., Mr. Ward’s 6th Grade Class
St. Mary’s School
It’s important to remember that not all clouds are flat on the bottom, but the type we are talking about, and most clouds for that matter, are flat on the bottom. We are going to focus on cumulus clouds, the type of fair-weather clouds that you see on a warm spring or summer day. When they form, an unstable parcel of air rises until it reaches its “level of condensation.”
Air that is warmer than its surroundings will rise, and although it is initially warmer, it cools as its altitude increases. When the temperature of the parcel of air cools to the dew point temperature, water in the air condenses, forming the cloud. The level at which this happens is, as we mentioned, the level of condensation. The flat base of the cloud where this first occurs represents the condensation level.
When air is not very turbulent, or when the winds blow smoothly along the base of a cloud, they appear flat from underneath. When the atmosphere is experience shifting winds, sinking air, or other types of disturbances, clouds may take on a different appearances. Mammatus clouds, which look like bubbles, are caused by sinking air pushing holes in the cloud layer. That’s just one example of clouds that aren’t necessarily flat on the bottom.
Chief Meteorologist Kate McKenna