Why is it rainy in winter in Sichuan Basin and rainy in West Sichuan Plateau?

The main influence is the cold air from the northern mainland, which has been greatly weakened after a long journey over mountains and mountains. After climbing the rugged Guizhou Plateau, the airflow is very slow. After contact with the warm air originally left in Guizhou, the two sides were evenly matched and deadlocked for a long time, resulting in continuous rain.