Solutions-Class-7-Geography-Chapter-5-Winds-Maharashtra Board

When the air expands, it becomes thinner

From high air pressure regions, winds blow towards regions of low air pressure.

In the northern hemisphere, winds blowing towards the equator turn to the west due to the rotation of the earth.

The direction of seasonal winds blowing over the Indian subcontinent during winter is from the north-east to south-west.

The Roaring Forties in the southern hemisphere blow in the areas around 40° S parallel.

These winds are Southwest monsoon winds.

These winds are Polar winds

These winds are Valley breeze.

• Near the equator i.e. in the region up to 5° north and 5° south of the equator, the air pressure variation is considerably very less.
• As its effect, winds do not blow in this region almost all round the year.

Therefore, a belt of calm exists near the equator.

• In the southern hemisphere, the proportion of water (oceans) is comparatively greater. Various landforms causing hurdle in the speed of winds are limited. As its effect, winds blow with high speed in southern hemisphere.
• In the northern hemisphere, the proportion of land (continents) is comparatively greater. Various landforms put restrictions on the speed of winds. As its effect, winds blow with comparatively low speed in northern hemisphere.
• Therefore, the winds coming from the northwest in the southern hemisphere have greater velocities than the winds coming from the southwest in the northern hemisphere.

Monsoon winds are generated due to the uneven heating of land and water in the different seasons.

• During summer, the land remains comparatively hot and the sea-water remains comparatively cool. As its effect, during summer, the air pressure on the land remains low and that on the sea-water remains high. Therefore, the monsoon winds in the summer come from the sea.
• During winter, the land remains comparatively cool and the sea-water remains comparatively hot. As its effect, during winter, the air pressure on the land remains high and that on the sea-water remain low. Therefore, retreating monsoon winds in winter come from land

• In both the Polar Regions, the temperature is below 0° C throughout the year.
• Hence here the air is cold. Therefore, the air pressure is high in polar areas in both hemispheres.

• The earth rotates from the west to the east. The rotation of the earth causes the change in the original direction of the winds.
• Due to earth’s rotation, the winds get deflected towards the right of their original direction in northern hemisphere and towards the left of their original direction in the southern hemisphere.

• Cyclonic winds conditions are created when a low pressure area is surrounded by high pressure areas.
• In these conditions winds start blowing from all directions from the surrounding high pressure areas towards the central low pressure area.

Therefore, the cyclonic winds blow in a circular manner.

Reasons that lead to the formation of cyclones :

• The air pressure in a particular area is low
• The air pressure in surrounding areas is high.

Effects of cyclones :

• Due to cyclones the sky becomes cloudy.
• Cyclonic winds blow heavily with a very high velocity leading to heavy rains.
• Cyclonic winds may prove to be destructive as they may cause loss of property and life near coastal regions.