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local winds which develop due to differen- immense damage. An anticyclone is a high-
tial heating of land and sea in the coastal pressure area surrounded by low pressure.
areas. Cyclones and anticyclones are Gentle winds blow out in all directions from
variable winds. A cyclone is an area of low the centre. They bring fine weather and
pressure surrounded by high pressure. clear skies. Cyclones are common in tropical
Winds blow in a spiral manner at great regions. They are called by different names
speed towards the low-pressure centre. They in different countries.
are accompanied by heavy rains and cause

CASE STUDY south-east India causing record breaking surge
The Odisha Cyclone 29th October, 1999 was 26 feet. It struck the coast of Odisha, crops

The super cyclone of Odisha on 29th October, were destroyed and an additional 90 million trees
1999 is called the biggest of that century. About were either uprooted or had snapped.
10 million people as well as domestic animals Approximately 275,000 homes were destroyed
leaving 1.67 millions people homeless. A total of
had perished in the cyclone.
10,000 people died and hundreds went missing
A tropical depression formed over the Malay
and thousand were injured.
Peninsula on October 25. It moved to the north-
west and became a tropical storm on October Relief
26. It continued to strengthen into a cyclone on Timely warning of the cyclone made it possible
the 27th. On 28th October, it became a severe to evacuate thousands of families. The Indian
cyclone with a speed of 260 km per hour. It hit Red Cross Society immediately responded with
India for over 36 hours in the state as a 260 emergency relief. The State government, the
km/hr cyclone which caused death and extreme Army, the Air Force and several NGOs extended
damage in its path of destruction. help and operated for three months and rehabili-
tation programs extended to much beyond six
Impact
months.
The cyclone caused heavy torrential rain over
Moisture used to measure

Water vapour is an important part of the atmo- humidity is called a
sphere. Its presence in the air determines the hygrometer. What
moisture content and is called ‘humidity’. The happens to the water
humidity level varies from place-to-place and vapour present in the
time-to-time, depending upon the temperature air?
conditions. When presence of water vapour in At a given tempera-
the air is more, the humidity level is high. This is ture, the capacity of air
directly linked to temperature conditions. If to hold moisture is Hygrometer
temperature is high, rate of evaporation will be limited. When the air holds maximum water
high and so will be the humidity factor. In case of vapour, it is said to be saturated. The tempera-
low temperature, the capacity of air to hold ture at which air gets saturated is known as ‘dew
moisture will be less and therefore, the humidity point’.
level will be low. When the air is full of water As the temperature of saturated air falls, the
vapour, we call it a ‘humid day’. The instrument water vapour in it condenses forming droplets of

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