aajqta
Age: 44 
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qta, Pakistan
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Wind is air in motion:
The chief cause of wind is difference in atmosphere
pressure. One of the main reasons for differences in
pressure is unequal heating of the air. From the high
pressure belts the air flows outwards to the regions of
low pressure. Owing to the rotation of the earth, the winds
do not blow due north and south, but are deflected. In
this deflection they obey Ferrel’s Law which states, “Any
moving body on the earth surface including a current of
air, tends to be deflected, the deflection being to the right
in the northern hemisphere and to the left in southern
hemisphere.” Land and seabreezed are local winds caused
by the unequal heating of land and water. During the day
the land becomes very much hotter than the sea, with the
result that there is marked low pressure over the land.
Thus the air over the sea flows rapidly loses heat, but the
sea remains warm for a longer time. Thus at night, heavy
cool air blows from the land to take the place of warm air
rising over the sea. The monsoon or seasonal winds may
be regarded as land and sea breezes on a large scale, in
which the time-frame is a year instead of a day. This
phenomenon is to be found in south-east Asia, but is
especially marked in the subcontinent of India. A cyclone
is a portion of the atmosphere in which the pressure is
lowest in the centre. The winds blow inwards in anticlockwise
direction in the Northern Hemisphere. In the
© THE RAMAN’S BOOKS
Southern Hemisphere cyclonic winds blow in a
clockwise
direction in accordance with Ferrel’s Law. An anticyclone
is a portion of the atmosphere in which the pressure is
highest in the centre. The winds blow outwards in a
clockwise direction in the Northern Hemisphere and in
an anti-clockwise direction in the Southern Hemisphere.
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