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1) C 

2) D 

3) B 

4) A

There are seven pressure belts on the earth’s surface.

 They are : 

1. The equatorial low-pressure belt. (1) 

2. The sub-tropical high pressure belts. (2) 

3. The sub-polar low pressure belts. (2) 

4. The polar high pressure belts. (2)

C) Stratosphere

Depending upon the wind speed, their features, their directions, the way they occur, winds are classified into three types. 

A) Planetary winds – present on the planet as a whole through out the year, that blow continuously and regularly. 

B) Seasonal winds – Restricted to regions or seasonal in character like monsoons. 

C) Local winds – These blow due to local variation in the temperature and pressure, and influence a very small area.

• Water vapour in the atmosphere attracts dust particles and condense as droplets. 
• These droplets in millions and millions together appear like clouds.
• Clouds are different types based on their forms and heights. 
• For examples, Cirrus clouds (at higher level), Cumulus clouds (at middle level), Stratus (at lower level) and nimbus (rain bearing and vertical clouds).

• The moist air is forced to rise over mountain. 
• It gives heavy precipitation on the windward side. 
• After that the air, which is devoid of moisture blows over leeward side. 
• It does not give rain there. So this dry region is known as ‘rain-shadow’ region.

Cyclonic rain is associated with a depression or a low pressure. This type of rainfall takes place where air masses of different temperatures and humidity meet. The cyclonic rainfall is most common in the temperate region. The rainfall caused with a cyclone or a depression is known as cyclonic rainfall.

Cyclones Can be classified into 

1. Tropical cyclones 

2. Temperate cyclones 

3. Extra Tropical cyclones.

• Because they are formed due to the diffetential heating of land and sea.
• Due to heavy rain, strong wind & large storm. 
• The destruction depends mainly on its intensity, its size and its location,
• After the cyclone the devastation continuesv

The cooling of saturated air mass is an important cause for rainfall. The cooling process takes place in different ways. Major causes are:

• The warm and moist air rises upward by vertical convection currents. 
• Air is also forced to ascend over mountain ranges. 
• The warm air rises over cold air.
• There should be sufficient humidity in the air. 
• Condensation should be taken place.

When the ascending air may reach the mountain summit and descends On the leeward side, it is warmed by compression during its descent, and thus becomes drier and drier. The part of land over which this dry wind blows, it known as the rain shadow area. This influence of the mountain barrier is called the rain shadow effect.

• Early warning systems are needed to be installed by the government. 
• Government should inform people in advance about the possibility of disasters like cyclones. 
• Government shall provide people with longterm security like strong roads, safe pucca houses for people of low land areas. 
• Food, water and medical emergency teams should be kept ready whenever there is a forecast of cyclone. 
• Close cooperation between people, Non Governmental organizations and Government organizations are essential to mitigate cyclone affects.

Tropical cyclones in India is known as Cyclones

The term cyclone is a Greek word meaning “coil of a snake”. Cyclones are centres of low pressure where, winds from the surrounding high pressure area converge towards the centre in a spiral form. Due to the rotation of the earth, the cyclonic winds in the northern hemisphere move in anti clock wise direction, where as they move in clockwise direction in the southern hemisphere. Cyclones can be classified into

Tropical cyclones, Temperate cyclones and Extra tropical cyclones . Tropical cyclones: Tropical cyclones develop in the Inter tropical convergence zone [ITCZ], They are formed due to the differential heating of land and sea. Tropical cyclones are known as ‘cyclones’ in Indian ocean, ‘typhoons’ in the western pacific ocean, ‘hurricanes’ in the Atlantic and eastern Pacific ocean, ‘baguios’ in Phillipines and ‘willy willy’ in Australia. Tropical cyclones often cause heavy .loss of life and property on the coasts and become weak after reaching the landmasses.

Temperate cyclones: Temperate cyclones are formed along a front where hot and cold air masses meet in mid-latitudes between 35° and 65°N and S. Temperate cyclones do not become weak like the tropical cyclones on reaching the land. Temperate cyclone commonly occurs over the North Atlantic Ocean, North West Europe, Mediterranean basin. Mediterranean basin’s temperate cyclones extend up to Russia and India in winter. In India it is as called western disturbances.

Extra tropical cyclones: Extra tropical cyclones occur in the latitudes between 30° and 60° in both the.hemispheres. They are also called as midlatitude cyclones. They collect energy from temperature differences which are found in higher latitudes. Extra tropical cyclones produce mild showers to heavy gales, thunderstorms, blizzards, and tornadoes.

Orographic rainfall occurs due to ascent of air over mountain slopes. Orographic rain is heavy on the windward slope of the mountain. The slope of the mountain facing the wind is called “Wind ward side” while the opposite slope is called “leeward side” After crossing over the mountain, the air begin to descend along the leeward slope. It gets heated and becomes dry.

Antitrade winds in the southern hemisphere are known as Westerlies.

The winds blowing alternatively during day and night from the sea and the land near the coasts are known as ‘Sea Breeze’ and ‘Land Breeze’ respectively. These are the best developed local winds near the coastal regions. They affect only a narrow strip of land along the coast. During the day time, the land gets heated more quickly than the adjacent sea. So the air is heated and raised upwards to produce a low pressure region.

The pressure at sea is comparatively high. The warm air of the land being light rises up allowing the air from sea to enter in. Such incoming air from the sea is called‘Sea breeze’. The sea breezes continue during the day time. At night the land looses its temperature quickly due to rapid radiation and a high pressure is developed. As the seawater is still retaining temperature the air is lighter and rises upward

(B) The equatorial doldrums

The flow of air from land to sea is called land breeze and the flow of air from sea to land is called Sea breeze.

There are three major types of planetary winds. They are Trade winds, Anti trade winds and Polar winds.

The distribution of atmospheric pressure on the earth’s surfaces most uneven. The horizontal movement of air, parallel to the earth’s surface is knows as ‘winds’.

The vertical movement is called “air current”. The wind and currents are interrelated and forms a system of air circulation through out world and play an important role in the distribution of temperature and humidity in the atmosphere.

The result of the earth’s rotation, a body moving in any direction over surface of the earth will tend to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This law is known as “Ferrell’s law”. It mainly concerned with the movement of air. 

(c) cyclones

Air flows from high pressure to low pressure due to horizontal differences. This horizontal movement of air is called wind whereas the vertical movement of air is called air currents. 

Quickly rising ocean water levels associated with hurricanes that can cause widespread flooding.

Linked ocean and atmospheric events that have worldwide effects, characterized by warming of water in the topical pacific from around the International Date Line to the coast of Peru.

(a) Trade winds: 

1. Trade winds blow from the subtropical high pressure belt to the Equatorial low pressure belt in both the hemispheres. 

2. They blow with great regularity, force and in a constant direction throughout the year. They are very helpful to the traders.

(b) Roaring forties: 1. Westerlies are the permanent winds. 

2. They blow from South West to North East in the Northern hemisphere and North West to South East in the Southern hemisphere. 

3. The velocity of westerlies become so vigourous and fast to be called Roaring forties at 40°.

Hygrometer is an instrument that measures the water vapour content (humidity) of the air.

(C) Exosphere

Exosphere is the upper most layer of the atmosphere. This is the highest layer. Very little is known about it.

In troposphere the life is present. The suitable conditions that make life possible in the troposphere are : 

1. The troposphere is the lower most layer of the atmosphere. 

2. It contains about 75% of the total gaseous mass of the atmosphere and practically all the moisture and dust particles. 

3. The entire weather phenomenon happens in this sphere. 

4. Condensation, evaporation, precipitation, rainfall, cyclones etc., occur in this layer.

Exosphere is also known as‘Magnetosphere’.

If the humidity is low in our atmosphere, our skin becomes dry during winter. This also leads to chapped lips.

1. (e) 

2. (d) 

3. (a) 

4. (b) 

5. (c) 

6. (g) 

7. (f)

The scientific study of the atmosphere and its physical processes is called ‘Meteorology’.

‘Anemometer’ is used to measure the speed of winds.

The average weather condition of a place for a long period like 30- 33years is known as climate.

Temperature, pressure, wind, humidity and precipitation are called the elements of weather.

If the atmosphere has 100% relative humidity, it is known as saturation level.

(B) Troposphere

Condensation is a reverse process of evaporation. The transformation of gaseous form of water vapour into solid or liquid form is called condensation. This is caused by the loss of heat.

When relative humidity exceeds 100 per cent the excess of water vapour present in the atmosphere gets condensed and forms as minute droplets of water.

Rain gauge is used to measure the amount of Rainfall.

The line joining the places of equal amount of water vapor is called ‘Isohygric’ line.

Acloud of dust, smoke, salt or other particles that reduces visibility close to the Earth’s surface. A haze is said to exist when visibility is less than 1.25 miles but more than 0.6 mile (1km).

The atmospheric condition of a place at a given time is known as weather.

The line drawn on maps joining places having the same air temperature are called Isotherms. They are drawn after reducing the temperature to mean sea level to eliminate the variation caused by altitude. The horizontal distribution of temperature is shown with the help of isotherms.

• Isotherms run east-west and are parallel to the latitudes. 
• Isotherms take sudden deviation near coasts indicating contrasting temperature conditions between land and water bodies. 
• Spacing of isotherms indicates latitudinal thermal gradient or steepness of temperature change or intensity of temperature variation. 
• There is a seasonal difference in spacing of isotherms. Generally they are closer in the month of January while they are widely apart in the month of July. 
• The isothermal lines have east-west trend following the latitudes. 
• The ocean currents also influence and deviate the trend of isotherms.

With condensation, the droplets get heavy and fall to the ground as precipitation in the form of rain, snow, hail etc.