Physics of Cyclones

         Cyclones are the most violent storms on earth. They are also called hurricanes, typhoons and willy willies depending upon their locations on earth. Geographically these all storms are called tropical cyclones. Tropical regions receive vertically and direct sunrays whereas polar regions receive slanting sunrays. Wind movements are determine by high pressure and low pressure system. Winds always move from high pressure to low pressure areas. The differences in atmospheric pressure create pressure gradient causes the wind to move. Low pressure occurs where land or ocean is warm and high pressure occurs where land or ocean is cool. That’s why winds blow from polar region (cool land) to equator (warm land).

     Another factor which is important in the formation of cyclones is CORIOLIS FORCE. Due to the rotation of earth, a force is generated and it acts perpendicular to the direction of motion and to the axis of rotation. Earth is spherical and it moves from west to east and also, earth is much wider at the equator than at the poles. So, if anything has to be come straight from the poles to the equator it gets deflected towards right in northern hemisphere and towards left in southern hemisphere. Such deflection is caused by coriolis force.

At the centre of every cyclone there is region of low pressure called eye of cyclone. As air moves from high pressure to low pressure which means outer region of cyclone consists of cool air which surrounds low pressure area of cyclone. Warm and moist air rises from the surface of ocean. As it rises, to fill its place cool air rushes to this low pressure region. Now this air becomes warm and moist and this rises too and hence warm air continues to rise. Temperature drops at high altitude, so warm air cools off to form clouds. Now coriolis force comes into factor, as air deflected to right in northern hemisphere but it got attracted to eye of storm (low pressure region) this makes it swirl in anticlockwise direction. Similarly in southern hemisphere due to bending in left side it swirl in clockwise direction.

Cyclones normally occur on the ocean surface due to continuous supply of moisture. When it hits the land, moisture supply cut off and storm dissipates.