Humidity and clouds

Today's discussion was a good way for Adam to vent frustration that there isn't enough physics in meteorology . . . or at least we don't take advantage of the physics enough.

One thing we looked at closely was the phenomenon of dew point and relative humidity. We could see this and the relationship between relative humidity and temperature by observing condensation on the outside of an ice filled beaker.

So what is in a cloud? If it were only water in a gas state, there wouldn't be anything to see. The fact that clouds are opaque tells us that they are made of particles of water in liquid and solid states, scattering light in all directions. It makes sense that clouds are more likely to form at higher altitudes, where air is cooler, as the relative humidity goes up (for the same water content) as temperature decreases.