Geography – Atmospheric processes and global climate change | e-Consult

The Earth's energy budget undergoes significant diurnal (daily) changes due to the Earth's rotation on its axis. These changes are primarily driven by the cycle of sunlight and darkness.

Daytime: During the day, the Earth's surface absorbs solar radiation. The amount of solar radiation received increases as the sun rises and reaches its peak at solar noon. This absorbed energy warms the Earth's surface, leading to an increase in temperature. The atmosphere also warms through conduction and convection, contributing to the overall warming effect.

Nighttime: During the night, the Earth's surface no longer receives direct solar radiation. The Earth's surface then radiates the heat it absorbed during the day as longwave radiation back into space. The rate of longwave radiation emission depends on the temperature difference between the surface and the atmosphere. As the Earth radiates heat, the surface cools down, leading to a decrease in temperature.

Implications for Temperature Variation: The diurnal cycle of energy input and output is the primary cause of daily temperature variations. The warmest temperatures typically occur in the afternoon, after the sun has reached its highest point in the sky, and the coolest temperatures occur in the early morning, before the sun has risen. The magnitude of the diurnal temperature range (the difference between the highest and lowest temperatures) is influenced by factors such as cloud cover, humidity, and surface type. Cloud cover can reduce the amount of solar radiation reaching the surface during the day, leading to lower daytime temperatures. Humidity can moderate temperature changes by increasing the rate of evaporation, which absorbs heat.