Question

Define Heat budget. Explain the processes involved in the heat budget of the earth.

Answer 1

Instructions:

• Give definition of heat budget.(1M)
• Explain the processes of absorption and emission of solar radiation in five steps.(3M)
• Explain the heat budget with numbers.(1M)

Solution:
The heat budget is the balance between insolation and terrestrial radiation.

We can break the heat budget of the earth into 5 steps:-

• Step 1- The arrival and reflection of solar radiation towards and from the earth's atmosphere.
• Step 2- The absorption of solar radiation by the earth’s atmosphere.
• Step 3- The absorption and emission of solar radiation by the earth’s surface.
• Step 4- The additional absorption of emitted solar radiation by the atmosphere.
• Step 5- The emission of solar radiation by the atmosphere, back to outer space.

The heat budget is as follows:-

Let us assume, the total solar radiation= 100 units

Step 1:
Solar radiation entering earth’s atmosphere= 65 units

Step 2:
Solar radiation absorbed by atmosphere= 14 units
Remaining solar radiation moving towards earth surface= 65 units - 14 units = 51 units

Step 3:
Solar radiation absorbed by earth’s surface= 51 units
Solar radiation emitted by earth’s surface= 51 units

Step 4:
Solar radiation again absorbed by atmosphere= 34 units
Remaining solar radiation leaving= 51 units - 34 units = 17 units
Total solar radiation absorbed by atmosphere= 14 units + 34 units = 48 units

Step 5:
Solar radiation emitted by atmosphere= 48 units
Total solar radiation leaving earth= 17 units + 48 units = 65 units

Therefore,

The solar radiation entering earth’s atmosphere= 65 units
The solar radiation leaving earth= 65 units