Chapter 8, Problem 1TC

To determine

The factors that contribute to the uneven heating of the Earth by the sun.

Answer to Problem 1TC

The factors that contribute to the uneven heating of the Earth by the sun include latitude, seasons, and the time of the day.

Explanation of Solution

The heat budget of the Earth is not balanced in different latitudes even though it is balanced as a whole. The radiation from the sun that strikes the polar latitudes spreads and covers a large area than that strikes at the tropical latitudes. Adjacent to the poles, filtering of sunlight occurs through more atmosphere and they approach the surface at a low angle, and thereby allows reflection.

During the depths of local winter, no solar radiation is received at the Polar Regions. In contrast, sunlight strikes at a more nearly vertical angle at tropical latitudes and as a result, the same amount of sunlight is distributed over a much smaller area. It leads to the striking of more solar energy in tropical regions than the Polar Regions, and mid-latitude areas receive more heat in summer than in winter.

Due to the $23\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.$ tilt of the Earth’s rotational axis relative to the plane of its orbit around the sun, the Northern Hemisphere receives about three times as much solar energy per day in June as it does in December at mid-latitudes. The revolution of the Earth around the sun causes the leaning of the Northern Hemisphere toward the sun in June and away from it in December due to the constant tilt of its rotational axis. As a result, the sun appears higher in the sky in summer and lower in the sky in winter.

In addition, the time of the day is also an important factor. The rotating Earth spins around the polar axis. As a result, sunrise and sunset occur daily. The sunlight in the morning and afternoon is not strong as the midday sunlight.