If we look at the air in the sky in the vicinity of the baiu front, the polar front which forms a border between the winter air and spring or autumn air and the subtropical front which forms the border between the summer air and the spring or autumn air exist close to each other.
また梅雨前線付近の上空の大気を見ると、冬の空気と春・秋の空気の境目となる寒帯前線、春・秋の空気と夏の空気の境目となる亜熱帯前線が接近して存在している。