Std 9 Geography · Chapter 5

5. Precipitation

Complete solutions to the Exercise. Maharashtra State Board (Balbharati), Grade 9 Geography.

Exercise

1Identify the precipitation type with the help of the description given:

(a) It is the main source of the water that you use. Sometimes it is torrential and sometimes continuous. Most of the agriculture in India is dependent on it. — Rainfall
(b) It seems as if water droplets are floating in the atmosphere. In London, one cannot see the Sun till the afternoon during winters because of this phenomenon. — Fog
(c) It never precipitates like this in equatorial areas. Precipitation in the solid form sometimes causes damage to the crops. — Hailstones (Hail)
(d) A white cotton like layer spreads on the earth's surface. Because of this form of precipitation, the State of Jammu and Kashmir has to change its capital in winters. In Maharashtra, it does not precipitate like this. — Snowfall

2Look at the following pictures and identify the correct rainfall type.

Figure (A): Convectional rainfall
Figure (B): Orographic rainfall
Figure (C): Cyclonic rainfall

3Look at the figures above and answer the following questions:

(1) In fig B, on which side of the mountain is it raining more?

In Figure B, it is raining more on the windward side of the mountain (the side facing the moisture-laden winds coming from the water body).

(2) Shade the rain shadow region in fig B and name it.

This is a diagram-based activity. You need to shade the right side of the mountain in Figure B (the side opposite to where the wind is coming from, where rainfall is very sparse) and label it as the Rain Shadow Area or Leeward Side.

(3) What is the difference between A and C?

Figure A represents Convectional rainfall, which occurs mainly due to intense heating of the earth's surface causing air to rise vertically in a continuous convection current. It is highly localized, occurs almost daily in the afternoons, and is accompanied by lightning and thunder.
Figure C represents Cyclonic rainfall, which occurs when a low-pressure center is formed and surrounding air spirals inwards and upwards. It covers a much more extensive area and is accompanied by stormy winds.

(4) Stormy winds and floods are associated with which rainfall type?

Stormy winds and floods are associated with Cyclonic rainfall.

(5) What type of rainfall occurs in Singapore?

As Singapore is located very close to the equator, it experiences Convectional rainfall.

4Identify the odd man out:

(1) Orographic rainfall, acid rain, cyclonic rainfall, convectional rainfall. — Acid rain (It is a result of pollution, whereas the others are natural types of rainfall).
(2) Snowfall, rainfall, hailstones, dew. — Dew (It forms on the earth's surface via condensation, whereas the others precipitate or fall from the clouds).
(3) Thermometer, rain gauge, anemometer, measuring jar. — Measuring jar (It is just an accessory component, whereas the others are complete standalone meteorological instruments).

5Answer in brief:

(1) In what ways does precipitation occur on the earth?

Precipitation occurs on the earth when water falls in the solid or liquid state from the clouds to the ground. The major forms of precipitation are:

Rainfall: Water vapour condenses into water droplets that grow heavy and fall to the ground.
Snowfall: When the temperature drops below the freezing point, water vapour directly turns into solid snowflakes (sublimation) and falls to the ground.
Hailstones: Upward vertical winds push condensing water droplets to high altitudes where they solidify into concentric layers of ice and fall as hailstones.

(2) Comment on the rainfall occuring in the rain shadow area.

A rain shadow area is formed on the leeward side of a mountain range. When moisture-laden winds cross a mountain, they drop most of their moisture on the windward side as orographic rainfall. As these winds descend on the leeward side, their temperature increases, which in turn increases their moisture-holding capacity. As a result, the amount of water vapour available for condensation is extremely low, leading to highly reduced or very sparse rainfall in this area.

(3) Which type of rainfall occurs in most of the world? Why?

Orographic rainfall occurs in most parts of the world. This is because high mountain ranges and elevated landforms are present across almost all continents globally. Whenever moisture-laden winds coming from seas or lakes encounter these natural mountainous barriers, they are forced to rise, leading to condensation and orographic rainfall.

(4) If condensation occurs closer to the earth's surface, what types of forms become visible?

When condensation or solidification of water vapour occurs near or at the earth's surface, three main forms become visible:

Fog: Microscopic water particles float in the air near the surface when temperature reduces and humidity increases.
Dew: Water vapour condenses into tiny water droplets that stick to the surfaces of cold objects near the ground.
Frost: If the temperature of the air falls below 0°C, the dew drops stuck to cold surfaces freeze into solid ice particles known as frost.

(5) What precautions should be taken while measuring rainfall?

The following precautions should be taken while measuring rainfall using a rain gauge:

The rain gauge must be placed in an open ground so that rainwater can be collected without any obstruction from trees or buildings.
It should be kept on a flat mount that is approximately 30 cm high to prevent surface water from splashing into the funnel.
In areas of heavy rainfall, readings must be taken frequently (e.g., every three hours) to prevent the measuring bottle from overflowing.

6Distinguish between

(1) Dew and frost

Dew	Frost
Dew is formed when moisture-laden air comes in contact with cold objects, causing vapour to condense into tiny liquid water droplets.	Frost is formed when the temperature drops below 0°C and water vapour or dew droplets freeze into solid ice particles.
It forms when the surface temperature is above the freezing point but below the dew point.	It forms when the surface temperature drops below the freezing point (0°C).
It looks like tiny drops of water sticking to grass leaves, glass, or cold surfaces.	It looks like a thin, white coating of ice crystals on surfaces.
Dew provides moisture to crops and is generally beneficial in dry seasons.	Frost is often harmful to agricultural crops and can cause accidents if spread on roads.

(2) Snow and hail

Snow	Hail
Formed when water vapour turns directly into solid snowflakes (sublimation) due to temperatures below the freezing point.	Formed when strong upward vertical winds push condensing water droplets to high altitudes, freezing them into concentric layers of solid ice.
Snow is friable, soft, and initially opaque.	Hail is hard, heavy, and consists of solid ice pellets.
Occurs mainly in high latitudinal and temperate regions during winters.	Occurs mainly in summers in tropical and temperate zones due to intense localized heating.
It accumulates in layers and slowly melts to provide a steady source of water.	It falls rapidly due to gravity, often severely destroying standing crops and causing loss of property.

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