Uneven heating of surface leads to lumpy clouds

If you observe some of the scattered clouds that often form on a sunny afternoon, you often notice that the clouds are relatively flat at the bottoms, but very lumpy at the tops. Uneven heating of the surface by the sun is one of the main reasons for the lumpy tops. Different surfaces absorb different amounts of sunlight. Dark surfaces, such as asphalt, absorb more of the sun's heat than lighter surfaces. The more energy absorbed by the surface, the hotter it becomes and the more it heats the air above it. The more the air is heated, the more unstable it becomes. As a result, warmer air pockets rise faster than cooler ones. Cloud bases tend to form near the lifted condensation level (LCL), which is the lowest altitude in which the air becomes saturated. All air pockets do not necessarily reach saturation at the LCL, but enough do so that enough moisture condenses into clouds to make the cloud bottoms relatively flat. The faster-moving air pockets tend to rise higher than the slower ones. As a result, the faster ones continue to cool as they rise and condense out more moisture, which creates the lumps that you see on the tops of clouds.

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