* Solar Radiation: During the day, the sun's radiation heats the ground, which in turn heats the air near the surface. This warm air is less dense and rises, leading to convection. The warmer the surface, the more buoyant the air, and the higher the convection will reach.
* Cooling: At night, the ground cools down by radiating heat into space. This cools the air near the surface. Cooler air is denser and less buoyant, making it harder for it to rise.
Therefore, although there can be some convective activity at night due to other factors like localized heating, the bases of convective clouds are generally higher during the day when the air is warmer and more buoyant.
