CLIMATE - Q&A

EXERCISE

1. Choose the right answer from the four alternatives given below.

(i) Which one of the following places receives the highest rainfall in the world?
(a) Silchar
(b) Mawsynram
(c) Cherrapunji
(d) Guwahati

Answer: (b) Mawsynram

Explanation: Mawsynram, located in the southern ranges of the Khasi Hills in Meghalaya, receives the highest average annual rainfall in the world due to its funnel-shaped hills that trap moisture-laden winds.

(ii) The wind blowing in the northern plains in summers is known as:
(a) Kaal Baisakhi
(b) Loo
(c) Trade Winds
(d) None of the above

Answer: (b) Loo

Explanation: 'Loo' are strong, gusty, hot, dry winds blowing during the day over the north and northwestern India during summer. Exposure to them can cause heatstroke.

(iii) Which one of the following causes rainfall during winters in north-western part of India?
(a) Cyclonic depression
(b) Retreating monsoon
(c) Western cyclonic disturbances
(d) Southwest monsoon

Answer: (c) Western cyclonic disturbances

Explanation: These low-pressure systems originate over the Mediterranean Sea and Western Asia. They move into India along with the westerly flow and cause winter rains in the plains and snowfall in the mountains.

(iv) Monsoon arrives in India approximately in:
(a) Early May
(b) Early July
(c) Early June
(d) Early August

Answer: (c) Early June

Explanation: The south-west monsoon typically reaches the southern tip of the Indian peninsula (Kerala) by the first week of June.

(v) Which one of the following characterises the cold weather season in India?
(a) Warm days and warm nights
(b) Warm days and cold nights
(c) Cool days and cold nights
(d) Cold days and warm nights

Answer: (b) Warm days and cold nights

Explanation: During the cold weather season (winter) in Northern India, the sky is generally clear, which allows for solar heating during the day (making them warm) but rapid heat loss at night (making them cold).

2. Answer the following questions briefly.

(i) What are the controls affecting the climate of India?

Answer: The six major controls affecting the climate of India are:
1. Latitude: The Tropic of Cancer passes through the middle of the country.
2. Altitude: India has mountains to the north and coastal areas.
3. Pressure and Wind System: Governed by surface winds, upper air circulation, and cyclones.
4. Distance from the Sea (Continentality): Coastal areas have equable climate; interiors have extreme.
5. Ocean Currents: Affect coastal climate.
6. Relief Features: High mountains act as barriers to winds.

(ii) Why does India have a monsoon type of climate?

Answer: India has a monsoon type of climate because its climate is strongly influenced by the monsoon winds. The seasonal reversal of wind direction—blowing from the sea to land in summer (bringing rain) and land to sea in winter (dry)—dominates the weather patterns. This is caused by the differential heating of the land and the Indian Ocean.

(iii) Which part of India does experience the highest diurnal range of temperature and why?

Answer: The Northwestern part of India (Thar Desert/Rajasthan) experiences the highest diurnal (daily) range of temperature.
Reason:
1. Sand: The sandy soil heats up very quickly during the day and cools down very quickly at night.
2. Lack of Cloud Cover: Clear skies allow maximum solar radiation during the day and rapid escape of heat at night.
3. Continentality: It is far from the moderating influence of the sea.
Example: Day temperatures can hit 50°C and drop to 15°C the same night.

(iv) Which winds account for rainfall along the Malabar coast?

Answer: The South-West Monsoon winds account for rainfall along the Malabar coast (Kerala). These winds strike the Western Ghats first, causing heavy orographic rainfall.

(v) Define monsoons. What do you understand by "break" in monsoon?

Answer:
Monsoon: Derived from the Arabic word 'Mausim', it refers to the seasonal reversal in the wind direction during a year.
Break in Monsoon: The monsoon rains take place in wet spells of a few days duration interspersed with rainless intervals. These dry spells are known as "breaks" in the monsoon. They occur due to the movement of the monsoon trough.

(vi) Why is the monsoon considered a unifying bond?

Answer: The monsoon is considered a unifying bond because:
1. Agricultural Calendar: The entire agricultural cycle of India revolves around the arrival and distribution of monsoon rain.
2. Life and Festivals: Many Indian festivals (like harvest festivals) are related to the agricultural cycle and seasons.
3. Water Resource: It binds the whole country by providing water to rivers, which are the lifelines of the people.
4. Rhythm of Life: The yearning for the rain is common across the diverse landscape of India.

3. Why does the rainfall decrease from the east to the west in Northern India?

Answer: Rainfall decreases from east to west in Northern India because:
1. Source of Moisture: The Bay of Bengal branch of the Southwest Monsoon enters India from the east.
2. Progressive Loss of Moisture: As these winds move westwards up the Ganga valley, they shed their moisture causing rainfall. By the time they reach the northwest (Delhi, Rajasthan), they hold very little moisture, resulting in lower rainfall.

4. Give reasons as to why.

(i) Seasonal reversal of wind direction takes place over the Indian subcontinent?

Answer: This happens due to the differential heating and cooling of land and water.
Summer: A low-pressure area develops over the interior of the Asian continent (land), while high pressure exists over the Indian Ocean. Winds blow from high pressure (sea) to low pressure (land).
Winter: The land cools down faster, creating a high-pressure area north of the Himalayas. The ocean remains warmer (low pressure). Winds blow from land to sea.

(ii) The bulk of rainfall in India is concentrated over a few months.

Answer: This is because the rainfall is mainly driven by the South-West Monsoon winds. These winds blow only during the summer season (June to September). Once the monsoon trough shifts and the winds reverse (Retreating Monsoon), the rainy season ends for most of the country.

(iii) The Tamil Nadu coast receives winter rainfall.

Answer: The Tamil Nadu coast receives rainfall during winter (October-November) because:
1. Retreating Monsoon: The Northeast trade winds blow from land to sea. However, while crossing the Bay of Bengal, they pick up moisture and shed it on the Coromandel Coast (Tamil Nadu).
2. Tropical Cyclones: Depressions originating in the Andaman Sea often hit this coast during this season.

(iv) The delta region of the eastern coast is frequently struck by cyclones.

Answer: This is because the low-pressure conditions over Northwestern India transfer to the Bay of Bengal by early November. This shift creates cyclonic depressions over the Andaman Sea. These cyclones move west/northwest and cross the eastern coast, hitting the deltas of Godavari, Krishna, and Kaveri.

(v) Parts of Rajasthan, Gujarat and the leeward side of the Western Ghats are drought-prone.

Answer:
1. Rajasthan/Gujarat: The Arabian Sea branch of the monsoon blows parallel to the Aravali range, so the mountains do not block the wind to cause rain. Also, the air is very hot, which reduces relative humidity.
2. Leeward side of Western Ghats: As the monsoon winds climb the Western Ghats, they cool and rain on the windward side. When they cross over to the leeward side (Deccan Plateau), they descend, get warmed up, and become dry (Rain Shadow Effect).

5. Describe the regional variations in the climatic conditions of India with the help of suitable examples.

Answer: India has vast regional variations in climate:
1. Temperature Variations:
- Summer: Parts of the Rajasthan desert can reach 50°C, while Pahalgam in Kashmir is around 20°C.
- Winter: Drass (Kashmir) can drop to -45°C, while Thiruvananthapuram (Kerala) remains at a pleasant 22°C.
- Diurnal Range: The Thar desert has a wide day-night difference (Day 50°C, Night 15°C), while Kerala has hardly any difference.

2. Precipitation Variations:
- Form: Snowfall in the upper Himalayas, rain in the rest of India.
- Amount: Meghalaya receives over 400 cm of rain, while Ladakh and Western Rajasthan receive less than 10 cm.
- Season: Most of India receives rain in June-September (SW Monsoon), but Tamil Nadu gets rain in October-November (Retreating Monsoon).

6. Discuss the mechanism of monsoons.

Answer: The mechanism of the monsoon is understood by the following factors:
1. Differential Heating: Land heats/cools faster than the sea, creating low pressure over the Indian landmass and high pressure over the seas.
2. ITCZ Shift: The Inter-Tropical Convergence Zone (ITCZ) shifts north over the Ganga plain in summer (monsoon trough), attracting winds.
3. High Pressure Area (Madagascar): A high-pressure zone east of Madagascar pushes winds towards the Indian low pressure.
4. Tibetan Plateau: It gets intensely heated, creating vertical air currents and low pressure at high altitude.
5. Jet Streams: The westerly jet stream moves north of the Himalayas, and the tropical easterly jet stream moves over the Indian peninsula, driving the monsoon.

7. Give an account of weather conditions and characteristics of the cold season.

Answer:
Duration: Mid-November to February.
Temperature: Coldest months are December and January. Temperature decreases from South (warm) to North (cold). Frost is common in the North.
Winds: Northeast trade winds prevail (Land to Sea), keeping the weather dry.
Rainfall:
- Generally dry.
- Tamil Nadu gets rain from these winds (Sea to Land path).
- Northern Plains get light winter rain ('Mahawat') from Western Cyclonic Disturbances, which is good for Rabi crops.
Features: Clear skies, low temperatures, low humidity, and feeble winds.

8. Give the characteristics and effects of the monsoon rainfall in India.

Answer:
Characteristics:
1. Seasonal: Concentrated in 3-4 months (June-Sept).
2. Variable: It is erratic; some years cause floods, others droughts.
3. Uneven Distribution: Heavy rain in Northeast/West Coast; scanty in Rajasthan/Leh.
4. Pulsating Nature: Occurs in wet spells and dry breaks.

Effects:
1. Agriculture: Success of crops depends on timely and adequate monsoon.
2. Economy: A good monsoon boosts the economy; a failure leads to inflation and distress.
3. Disasters: Heavy rains cause devastating floods (e.g., Assam, Bihar), while weak monsoons cause famines.

MAP SKILLS

On an outline map of India, show the following.
(i) Areas receiving rainfall over 400 cm.
(ii) Areas receiving less than 20 cm of rainfall.
(iii) The direction of the south-west monsoon over India.

Answer: (Self-Activity. Description for plotting provided)
(i) Over 400 cm: Western coast of India (Konkan and Malabar coasts), and North-Eastern India (Meghalaya, Assam, Arunachal Pradesh).
(ii) Less than 20 cm: Western Rajasthan (Thar Desert), Northern parts of Kashmir (Ladakh).
(iii) Direction:
- Arabian Sea Branch: Arrows entering from the southwest towards the Western Ghats and curving towards North India.
- Bay of Bengal Branch: Arrows entering from the south/southeast towards Northeast India and turning west up the Ganga valley.

PROJECT/ACTIVITY

(Based on Table I in the chapter)

1. Name two rainiest stations.

Answer: Mumbai and Shillong (Based on typical data, these have the highest annual rainfall figures in the list).

2. Name two driest stations.

Answer: Leh and Jodhpur (Leh is a cold desert, Jodhpur is in the arid region).

3. Two stations with most equable climate.

Answer: Thiruvananthapuram and Chennai (Coastal stations have low annual temperature range).

4. Two stations with most extreme climate.

Answer: Leh and Delhi (or Jodhpur). They have high variation between summer and winter temperatures.

5. Two stations influenced by retreating monsoons.

Answer: Chennai and Bengaluru (Chennai receives peak rain in Oct-Nov-Dec).