The correct option is 1 only
Explanation
The Earth maintains its temperature through a heat balance, where the amount of heat received from the Sun (insolation) equals the amount lost to space (terrestrial radiation). Assuming the total incoming insolation is 100 units, 35 units are reflected (albedo) and 65 units are absorbed (14 by the atmosphere and 51 by the Earth's surface). The Earth radiates these 51 units back as terrestrial radiation.
Statement-wise Analysis:
- Statement 1 is Correct: Out of the 51 units of terrestrial radiation emitted by the Earth's surface, 17 units pass directly through the atmosphere and are radiated into space. This occurs through specific spectral ranges known as "atmospheric windows."
- Statement 2 is Incorrect: The atmosphere absorbs 34 units of the terrestrial radiation (not 48). These 34 units are absorbed via direct absorption (6 units), convection/turbulence (9 units), and latent heat of condensation (19 units). The figure of 48 units refers to the total radiation emitted by the atmosphere to space, which is the sum of the 14 units absorbed from incoming solar radiation and the 34 units absorbed from terrestrial radiation.
- Statement 3 is Incorrect: The atmosphere does not absorb terrestrial radiation solely through conduction. In fact, conduction plays a very minor role, limited to the air layer in direct contact with the surface. The primary modes of heat transfer from the surface to the atmosphere are longwave radiation, convection, and the release of latent heat of condensation.
Key Takeaway:
The 51 units of terrestrial radiation are returned to space in two parts: 17 units directly and 34 units via the atmosphere (which eventually radiates them out along with the 14 units it absorbed from the sun).