The correct option is 2 and 3 only.
Explanation
The heating of the atmosphere involves four primary processes: radiation (incoming solar and outgoing terrestrial), conduction, convection, and advection. The lower atmosphere is primarily heated by the earth's surface through longwave terrestrial radiation and direct contact mechanisms like conduction and convection.
Statement-wise Analysis
- Statement 1 is Incorrect: Conduction is the process where heat flows from a warmer object to a cooler object when they are in contact. For the atmosphere, the air touching the warm earth is heated by conduction. Standard physical geography texts explicitly state that conduction is important in heating the lower layers of the atmosphere. Therefore, labeling it as the "least important" process for the lower layers is factually incorrect.
- Statement 2 is Correct: Air is a known poor conductor of heat (an insulator). Consequently, the transfer of heat from the land surface to the air in contact with it occurs relatively slowly compared to other modes of heat transfer like convection or radiation.
- Statement 3 is Correct: According to the principles of atmospheric heating, the layer of air immediately in contact with the ground gets heated first. This layer then transfers heat to the adjacent upper layers through contact. This specific layer-to-layer transfer mechanism is defined as conduction, even though convection becomes the dominant force for vertical mixing once the air becomes buoyant.
Key Takeaway
Conduction is the primary mechanism for heating the thin layer of air directly in contact with the earth's surface.
Convection is responsible for the vertical transport of this heat into the upper atmosphere, while
Advection handles horizontal heat transfer.