Why is the temperature low in the valley and high on the hillside during the day? Isn't the lower the altitude, the higher the temperature?

The phenomenon described in the topic is contrary to the general temperature distribution law, so it is necessary to consider the different topographic characteristics of valleys and hillsides and their influence on temperature.

First of all, we know that the lower the altitude, the higher the temperature, because the ground is the main energy source of the atmosphere.

Secondly, the valley topography is blocked by hills on both sides, which makes the valley bottom lack of sunshine, and at the same time, the valley bottom has a large surface area, which can absorb and store a lot of solar radiation energy. Therefore, the valley terrain receives less solar radiation during the day and the temperature is relatively low.

On the contrary, the hillside has high topography, abundant sunshine, small surface area and less solar radiation energy absorbed and stored. Therefore, the hillside terrain receives more solar radiation during the day and the temperature is relatively high.

To sum up, although the lower the altitude, the higher the temperature is a universal law, but under certain terrain conditions, such as valleys and hillsides, the opposite may happen. Therefore, it is necessary to analyze specific problems.