Convection is the process by which surface-heated air rises (less dense) while cooler upper-level air descends to replace it. It generates vertically developing clouds: cumulus, cumulus congestus, and cumulonimbus.
Types
Free convection occurs when surface heating alone is sufficient (summer afternoons). Forced convection is triggered by fronts, orography, or surface convergence. Convective precipitation (showers, storms) is distinguished from stratiform (continuous rain) by being intense, localised, and short-lived.