I understand that large cumulonimbus clouds may have powerful up and down drafts within and flying through them would be foolhardy. However, I can’t figure out why even the smallest of cumulus clouds cause turbulence when you fly through them. They’re just patches of fog. Why do you bump around so when flying through any clouds? All I can figure is that the air in a cloud, being slightly cooler than the surrounding air, gives a small downward impetus to the craft. But that doesn’t seem to explain all the bumping. SDMB pilots? meterologists?
Cumulous clouds result from turbulence caused by updrafts (thermals) in a moist atmosphere. When the thermal has risen to the point where the moisure condenses, the added heat resulting from the condensation causes the air to rise even faster. So cumulus clouds are bumpy. Large cumulus clouds are really bumpy because a large amount of heat is being released because of their size.
It is probably the location of the clouds more than the clouds themselves. Turbulence can be caused by the geography of the land. The upwind side of a mountain will lift the air as it flows across the mountain, causing turbulence along with the lift, even when there are no clouds in the area. This is where you’ll find many sailplanes soaring for hours. Even over flat land, turbulence can be caused by different surfaces on the land.
Certain clouds are indicative or turbulence, but clouds are really not required for turbulence. I sense that you, like most people, find turbulence unnerving. Next time you experience it, think of the guys who fly out into the eyes of the hurricanes for the national hurricane center. What they experience is severe turbulence, but the aircraft hold together, and they seem ready to do it again next time.
I’ll second D. Simmons, but note that there is no exact correlation between the size of a cumulus cloud and the turbulence therein.
With certain moisture and temperature profiles, large cu can be created by gently rising air. Under other circumstances, strong updrafts can produce small or no clouds. It is fair to say that cumulus that build to serious heights are reliably turbulent.
I agree. However, large clouds are more likely than small ones to allow relatively large temperature differences and densities within the same cloud which gives rise to strong winds in the cloud.