Traditional Culture Encyclopedia - Weather inquiry - Why is the weather here in Lanzhou so different from that in Liujiaxia?

Why is the weather here in Lanzhou so different from that in Liujiaxia?

Lanzhou is seriously polluted, and the river valley topography leads to pollutant discharge, which is gray in winter and even in other seasons.

Liujiaxia is close to Lanzhou, and the weather is actually very close.

It's just that there's no pollution, so it's always sunny and it feels much better than Lanzhou.