19.3. Cyclonic or Frontal Rainfall

Cyclones have low pressure at the centre, surrounded by high pressure. When wind from all directions blow towards centre, air masses of different characteristics meet creating fronts. The warm air being the lighter, rises above the cold air. The rising warm air cools and condensation takes place, causing rainfall.

This type of rainfall is associated with temperate and tropical cyclones. Since the lifting of warm air along the warm front of the temperate cyclone is slow and gradual, the condensation is also slow and gradual. Thus the precipitation occurs in the form of drizzle3, It is widespread and continues for a longer duration. Most of the rainfall in the temperate region is received through frontal or cyclonic rains.

The tropical cyclone, regionally known as typhoons, hurricanes, tornadoes, etc., yield heavy downpour in China, Japan, Southeast Asia, India, USA, etc.

3 When the drops of rain are very small, it is called drizzle.