山风

yè wǎn shí kōng qì biàn lěng biàn zhòng chéng wéi xià jiàng qì liú suǒ yǐ chuī shān fēng

夜晚时空气变冷变重，成为下降气流，所以吹山风。

At night, the air becomes cold and heavy, becoming a downdraft, so the mountain wind blows.