The correct option is 2 only.
Explanation
The heating and cooling of the atmosphere occur through four primary mechanisms: radiation, conduction, convection, and advection. While radiation involves the absorption of energy, the other mechanisms describe how heat is transferred and redistributed within the atmospheric layers.
Statement-wise Analysis
- Statement 1 is Incorrect. Conduction is the process of heat transfer that occurs when two bodies of unequal temperature are in direct contact. In the atmosphere, conduction heats only the layer of air directly touching the earth's surface. The transfer of heat through the horizontal movement of air is termed advection.
- Statement 2 is Correct. Convection is the process of vertical heating of the atmosphere. When the air in contact with the earth heats up, it expands, becomes lighter, and rises in the form of currents. This vertical movement transports heat from the lower layers to the upper layers of the atmosphere.
- Statement 3 is Incorrect. Advection plays a critical role in weather variations. In middle latitudes, most of the diurnal (daily) variation in weather is caused by advection alone. For example, in tropical regions like northern India during summer, local winds known as 'Loo' are the outcome of the advection process.
Key Takeaway
Conduction involves heat transfer through contact; Convection involves vertical heat transfer through rising air currents; and Advection involves horizontal heat transfer through wind movement.