WINDS STORMS AND CYCLONES PRESSURE Pressure symbol p

WINDS, STORMS, AND CYCLONES

PRESSURE Pressure (symbol : p or P) is the ratio of force to the area over which that force is distributed. Pressure is force per unit applied in a direction perpendicular to the surface of an object. Pressure is measured in any unit of force divided by any unit of area.

The increased wind speed is indeed accompanied by a reduced air pressure. Air moves from the region where the air pressure is high to the region where the pressure is low.

THUNDERSTORM Thunderstorms develop in hot , humid tropical areas like India very frequently. The rising temperatures produce strong upward rising winds. These winds carry water droplets upwards, where they freeze , and fall down again. The swift movement of the falling water droplets along with rising air create lightning and sound.

PRECAUTIONS NEEDED TO BE TAKEN WHEN THERE IS A STORM Ø Do not take shelter under an isolated tree. If you are in a forest take shelter under a small tree. Ø Do not take shelter under an umbrella with a metallic end.

ØDo not sit near a window. Open garages, storage sheds. Metal sheds are not safe places to take shelter. ØA car or a bus is a safe place to take shelter. ØIf you are in water , get out and go inside a building.

CYCLONE Before cloud formation, water takes up heat from the atmosphere to change into vapour. When water vapour changes back to liquid form as raindrops, this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in

pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low pressure system with very high speed winds revolving around it. It is this weather condition that we call a cyclone. A cyclone is known by various names. It is called ‘hurricane’ in America. In Japan it is called a ‘typhoon’.

TORNADO A tornado is a dark funnel shaped cloud that reaches from the sky to the ground. Most of the tornadoes are very weak. A violent tornado can travel at speeds of about 300 km/h. Tornadoes may form within cyclones.

ANEMOMETER An anemometer or windmeter is a device used for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind The first known description of an anemometer was given by Leon Battista Alberti around 1450.

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