Final answer:
In the equatorial climate region, the small diurnal temperature range is due to high humidity, cloud cover, and the consistent angle of direct sunlight, which leads to stable temperatures throughout the day and night.
Step-by-step explanation:
In the equatorial climate region, the yearly average temperature is around 26°C due to the high incidence of direct sunlight. However, it is characterized by a small diurnal temperature range, typically around 3°C. This is because the vast amount of vegetation and water vapor present in the equatorial regions absorbs and re-radiates heat, which minimizes temperature fluctuations between day and night. The energy from the sun warms the earth's surface during the day, but due to the specific characteristics of the equator, including cloud cover and humidity, the temperature does not drop significantly at night.
Directly related to the latitude and the consistent angle of the sun's rays at the equator, there is less variation in temperature. Additionally, the equatorial region tends to have considerable cloud cover that can trap heat during the night, further limiting the diurnal temperature range.