In this battle, both the polar front and the polar front jet stream can also move seasonally.

在这场战斗中，极锋和 极锋急流也可以季节性移动。

But wars -- or mid-latitude cyclones -- can start when cold air and warm air meet on the polar front.

但是，当冷空气和暖空气在极地前沿相遇时，战争——或中纬度气旋——就会开始。