Wind, Storms and Cyclones

IMPORTANT TERMS

 

Anemometer                A device used to measure wind speed.

Wind Vane                   An instrument used to determine the direction of the moving wind.

Water Spout                Tornadoes that are formed over the seas are called Water Spouts.

Wind                            The movement of air in the atmosphere is known as wind.

Typhoon                      In the Eastern Hemisphere, a cyclone is known as typhoon.

Natural Calamity           A physical phenomenon which causes damage to life and property

 

AIR PRESSURE

 

• The pressure exerted by air is known as air pressure.
• The atmospheric pressure decreases, as we go higher because at higher altitudes the gravitational pull is lesser. The lesser air above the higher altitude also exerts lesser pressure. Higher the altitude, lower the pressure.
• Temperature also affects the atmospheric pressure as it causes the air to change its density. Higher the temperature, higher the pressure.

 

Properties of Air

• Air always moves from an area of high pressure to an area of low pressure.
• Air expands on heating and occupies more space. When the air occupies more space, it becomes lighter. Warm air is lighter than cooler air.
• Air contracts on cooling.
• Air exerts pressure in all directions.

 

MONSOON WINDS

 

Monsoon winds are seasonal winds which blow from the Indian Ocean to the Indian subcontinent during summers. In summers, the land close to the equator becomes very hot as compared to the ocean. The air over the land gets heated and rises. The cooler wind from over the ocean blows towards the land. These are called monsoon winds. They are rain-bearing winds as they carry water. They are also known as summer monsoon winds. These winds are generated from southwest direction in summers.

During winter, uneven heating of land and water, generate winds from northeast colder lands. These are known as winter monsoon winds. These winds do not carry much water.

 

THUNDERSTORMS

 

Thunderstorms are a combination of thunder, lightning and heavy rainfall.

Hot and humid conditions are highly favourable for the development of a thunderstorm.

The rise in temperature produces strong winds. These winds carry water droplets upwards, where they freeze and fall down again. During a thunderstorm, air currents move upwards and water droplets move down. These movements cause development of charges. The accumulation of charges produces streaks of bright light and sound, which is known as lightning.

 

CYCLONES

Cyclones are huge revolving storms caused by winds blowing around a central area of low atmospheric pressure.

Hurricane, typhoon and tropical storms are the other names for a cyclone. The different names generally indicate where the storm took place.

The region near the equator receives the maximum heat of the Sun. The warm moist water of the oceans near the equator heats up the atmosphere over it. Warm air rises and cool air takes its place which results in creating a low pressure area. Under certain weather conditions storms can develop into cyclones.

Cyclones can be tracked and predicted accurately with the help of modern instruments such as weather satellites and weather radar. A cyclone warning is issued 24 hours in advance for the general public.

The East coast of India is more vulnerable to cyclones as compared to the West coast in terms of intensity and frequency of cyclones.

Damage caused by a cyclone

Cyclones can be highly destructive. The effects of cyclones include heavy rains and strong winds. Cyclones can destroy buildings, vehicles, bridges etc. People living near coastal areas get affected during cyclones.

During a cyclone, the seawater enters the low-lying coastal areas and continuous heavy rainfall also causes flood situation.

The communication system such as telephone services, cell-phones services and television are disrupted during cyclones.

TORNADOES

A tornado is a violently rotating column of air that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. A tornado is a spinning storm that is typically shaped like a funnel. The narrow end of a tornado is towards the land.

Tornadoes are different from cyclones as they are formed mostly on land. Unlike cyclones, they are usually narrow and rarely do they move beyond 20 km. A tornado reaches from a cloud to the ground as a vertical column of air.

Tornado sucks dust, debris and all the objects which come in its path. Tornadoes generally do not occur in India but their occurrence is common in USA and Canada.

SAFETY MEASURES DURING A STORM

• The people living near the coastal region should move to a safer place to deal with the situation created by a cyclone.
• Fishermen should not venture into the sea if a cyclone warning has been issued.
• Food, water and medicines should be stored in advance.
• One should not ignore the warnings issued by the meteorological department.
• One should keep all the emergency numbers.

 

INTERESTING FACTS

• Hurricanes have led to the death of around 2 million people over the last 200 years.
• On an average, about 87 cyclones come every year worldwide.
• The word cyclone comes from an old Greek story about a race of one eyed giants called 'Cyclops'.
• There are nearly 500,000 lightning strikes during a monsoon.
• A tornado can last from a few seconds to more than an hour. On an average, they remain for about 10 minutes.
• Every second, a large hurricane releases the energy of 10 atomic bombs.
• India’s very first monsoon forecast was made on 4th June 1886. From 1871 till 2006, monsoon has been normal 94 times, while there were 23 drought years.