Convection
Topic: Solar Radiation, Heat Balance and Temperature · NCERT: Class 11, Ch 8 "Solar Radiation, Heat Balance and Temperature"
Meaning
Convection is the upward movement of heat in rising currents of air. Air warmed at the ground becomes lighter and rises. Cooler air sinks to take its place. This happens only in the troposphere, the lowest layer of the atmosphere. As the rising air cools, its water vapour condenses (turns into tiny water drops). This builds tall cumulus clouds (puffy, heaped clouds) and can bring heavy afternoon showers, called convectional rain.
Example
In April and May, the land in West Bengal and nearby states heats up strongly. Rising warm, moist air builds tall clouds and evening thunderstorms called Kalbaisakhi (also called nor'westers).
Don't confuse with
- Advection: advection moves heat sideways with the wind. Convection moves heat upward.