Front
Topic: Air Masses, Fronts, Cyclones and Thunderstorms · NCERT: Class 11, Ch 9 "Atmospheric Circulation and Weather Systems"
Meaning
A front is the boundary zone where two air masses meet. The two air masses differ in temperature and density (how heavy the air is). They do not mix easily. Instead, the lighter, warmer air is lifted over the heavier, colder air. The lifted air cools, so clouds form and rain or snow falls. Fronts occur mainly in the middle latitudes. Across a front, temperature and pressure change steeply, so weather can change suddenly when one passes.
Example
Over the North Atlantic, cold air from the Arctic meets warm air from the south. The fronts that form there move east over the British Isles, which is why weather in Britain can change from sun to rain within hours.
Don't confuse with
- Air mass: an air mass is a large body of fairly uniform air. A front is only the narrow zone where two different air masses meet.