Abstract
Lines of discontinuity in the atmosphere are classified into 4 types, that is, passive front, warm front, cold front and active front. If the motions of warm air mass and cold air mass are passive, such the front is called passive front. If warm air, mass moves rapidly, the front is called warm front, if cold air mass moves rapidly, cold front, and if both warm and cold air masses move rapidly, active front. And the character of these fronts are researched.
