Why is there no such foggy weather in Gansu? What is the main reason for the fog in the central and eastern regions?

In winter, the central and eastern regions are prone to fog due to the reverse radiation of the atmosphere and sufficient water vapor. Moreover, the weather has been relatively stable recently, there is no cold air activity, the air is relatively quiet, and environmental pollution has caused foggy days for half a month.

Gansu is located in the west, and the main reason why fog is not easy to form may be the lack of water vapor conditions.

The answer is unprofessional, hope to adopt.