Chapter 5 - Precipitation
Q1. Identify 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.
Ans: Orographic 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.
Ans: Fog / frost
(c) It never precipitates like this in equatorial areas. Precipitation in the solid form sometimes causes damage to the crops.
Ans: Hailstones
(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.
Ans: Snowflakes
Q2. Look at the following pictures and identify the correct rainfall type.
Ans: Convectional rainfall
Ans: Orographic rainfall
Ans: Cyclonic rainfall
Q 3. Look at the figures above and answer the following questions:
(1) In fig B, on which side of the mountain is it raining more?
Ans: The windward side is receiving more rainfall.
(2) Shade the rain shadow region in fig B and name it.
Ans:
(3) What is the difference between A and C?
Ans: In Figure (A), convectional rainfall is shown. Here the hot air rises upwards and then the air cools and begins to condense and due to continuous condensation rainfall occurs. Here rainfall is accompanied by lightning and thunder.
In Figure (C), cyclonic rainfall is shown. Here the air from surrounding regions comes towards the centre of the cyclone and starts moving upwards. As it rises, the temperature of the air reduces, condensation occurs and rainfall takes place.
(4) Stormy winds and floods are associated with which rainfall type?
Ans: Stormy winds and floods are associated with Cyclonic rainfall.
(5) What type of rainfall occurs in Singapore?
Ans: Cyclonic rainfall occurs in Singapore.
Q 4. Identify the odd man out :
(1) Orographic rainfall, acid rain, cyclonic rainfall, convectional rainfall
Ans: Acid rain
(2) Snowfall, rainfall, hailstones, dew
Ans: Dew
(3) Thermometer, rain gauge, anemometer, measuring jar
Ans: Measuring jar
Q 5. Answer in brief:
(1) In what ways does precipitation occur on the earth?
Ans:
(i) Water falls in a solid or liquid state from the clouds to the ground.
(ii) Snow, hailstones, and rainfall are the major forms of precipitation.
(iii) 70.8% of the earth surface is full of water.
(iv) Different forms of condensation occur due to the water vapour in the atmosphere.
(v) As the atmospheric conditions change, we see changes in the form of condensation.
(vi) On winter mornings, we find dew.
(vii) In areas located at higher altitudes, snowfall occurs while it rains in other places.
(viii) Some places experience hailstones suddenly and face crop destruction.
(2) Comment on the rainfall occuring in the rain shadow area.
Ans:
(i) Winds coming from lakes or seas are moisture-laden.
(ii) They are obstructed by the high mountain ranges that stand in their way.
(iii) They start going uphill along the slopes of the mountains.
(iv) The temperature of these winds drops, condensation occurs, and rainfall takes place.
(v) Thus, because of the obstruction of the mountains, this type of rainfall occurs.
(vi) The windward side of the mountains gets more rain; the amount of vapour in the air reduces after crossing the mountain and the moisture holding capacity of the air increases.
(vii) The leeward side of the mountain receives less rainfall, and hence this area is identified as a rain-shadow area.
(3) Which type of rainfall occurs in most of the world? Why?
Ans:
(i) Orographic rainfall occurs in most parts of the world.
(ii) Convectional rainfall is regional in nature.
(iii) There is a certainty in the convectional rainfall occurring in the equatorial areas.
(iv) Comparatively, the orographic and cyclonic rainfall are less certain.
(v) And therefore, such areas are prone to very heavy rainfall, floods, or droughts frequently.
(4) If condensation occurs closer to the earth’s surface, what types of forms become visible?
Ans:
(i) When the condensation or solidification of the water vapour in the atmosphere occurs near the earth’s surface, then we can see fog, dew, or frost.
(ii) The temperature of the layers of air near the surface of the earth decreases.
(iii) As temperature decreases, water vapour condenses.
(iv) In this process, vapour turns into microscopic water particles that float in the air.
(v) When the density of these droplets in the air increases, fog occurs.
(vi) When moisture-laden air near the earth’s surface comes into contact with very cold objects, condensation of the vapour takes place.
(vii) They turn into very small water droplets.
(viii) These water droplets stick to the surface of the cold objects. This is called dew.
(ix) If the temperature of the air is less than 0°C, the water droplets stuck to the surfaces of cold objects freeze. This frozen water droplet is called frost.
(5) What precautions should be taken while measuring rainfall?
Ans:
(i) Rainfall is an important source of water on planet Earth, and rainfall is formed because of changes in the temperature of the air with water vapour.
(ii) The instrument that is used to measure rainfall is called a rain gauge.
(iii) The funnel, i.e., used for measuring rain, has a specific diameter, and the rain falling into it is collected in a bottle fitted in the gauge.
(iv) The collected water is then measured with the help of a measuring jar.
(v) In areas of heavy rainfall, the reading of the rain gauge should be taken every three hours.
(vi) The measuring jar reads rain in millimetres.
(vii) The gauge has to be kept on open ground on a 30 cm-high flat mount so that the rainwater is collected without obstruction.
Q 6. Distinguish between –
(1) Dew and frost
Ans:
| Dew | Frost |
|---|---|
(i) Dew is water in the form of droplets that stick to the surface of cold objects. | (i) If the temperature of the air is less than 0°C, the water droplets stick to the surface of cold objects, and the water droplet freezes. This frozen water droplet is called Frost. |
(ii) Dew is moisture in the air that settles on plants, etc. in the morning, resulting in water droplets. | (ii) Frost is a coating of minute ice crystals on objects that are exposed to the air. |
(iii) Dew condenses and doesn’t freeze overtime. | (iii) Frost is made from dew, but it freezes overtime. |
(2) Snow and hail
Ans:
| Dew | Frost |
|---|---|
(i) When the temperature in the atmosphere falls below the freezing point, the vapour in the form of gas transforms into solid particles. This is called snow. | (i) When there is a lot of heat on the earth’s surface, the air flows upward, where condensation of water vapour takes place, droplets of water solidify, and hailstones are formed. |
(ii) Snowfall occurs in high latitudinal regions. | (ii) The phenomenon of hailstones does not occur at high latitudes. |
(iii) Snowfall occurs in temperate regions. | (iii) Hailstones occur in tropical regions. |
(iv) The atmospheric temperature drops to the freezing point. | (iv) The atmospheric temperature does not drop to the freezing point. |
(v) When snow accumulates on a large scale, the transport and communication systems of that area collapse. | (v) Hailstones cause large-scale destruction to crops and loss of life and property. |