Why is the temperature difference between day and night greater on sunny days than on cloudy days?

As shown in the figure, this picture shows the daily variation of temperature on a sunny day, a rainy day and a cloudy day in northern China. Curve A in the figure is the diurnal variation of cloudy temperature. Curve b is the daily variation chart of temperature in sunny days. As can be seen from the figure, the temperature difference between day and night is about 18℃ on sunny days and about 10℃ on cloudy days. The temperature difference between day and night in sunny days is greater than that in cloudy days.

The main reasons why the temperature difference between day and night on sunny days is greater than that on cloudy days are: sunny days and partly cloudy air. The reflection and scattering of solar radiation in the atmosphere is weak, and more solar radiation reaches the ground, and more heat is transferred to the air, resulting in higher temperature. The night is clear and the air is a little cloudy. The absorption capacity of the atmosphere to ground radiation is poor, and the atmospheric inverse radiation is weak. A lot of heat is lost into the universe, and less heat is returned to the ground. The heat transferred from the ground to the air is less, the temperature is low, and the temperature difference between day and night is large. It's cloudy during the day and the air is cloudy and thick. The atmosphere has a strong reflection and scattering effect on solar radiation. Less solar radiation reaches the ground, less heat is transferred to the air, and the temperature is lower than that in sunny days. It is cloudy at night, and the atmosphere has strong ability to absorb ground radiation and strong reverse radiation. A large amount of heat can be returned to geothermal energy with less heat loss. The ground transfers more heat to the air, and the temperature is higher than that on a clear night, and the temperature difference between day and night is small.