Class 9 Geography Chapter 1 Question Answers - Contemporary India - I

Q1: Distinguish between weather and climate.
Ans: The difference between weather and climate is a measure of time.

• Weather refers to the atmospheric conditions of a specific place over a short period of time, usually 24 hours.
• Climate refers to the average atmospheric conditions over a relatively long period of time, usually 30 years.
• Weather can change from hour to hour and day to day, but climate represents the long-term patterns and trends of temperature, precipitation, humidity, and other atmospheric factors.

Q2: What are western cyclonic disturbances?
Ans: Western cyclonic disturbances are weather phenomena that occur during the winter months and are brought in by westerly flow from the Mediterranean region. These disturbances usually influence the weather of the north and northwestern regions of India. They are characterized by the movement of low-pressure systems in the upper troposphere and are associated with cloudiness, rain, and sometimes snowfall in the northern parts of India.

Q3: What is known as the Southern Oscillation or SO? Mention the feature connected with it.
Ans: The Southern Oscillation (SO) refers to the periodic change in pressure conditions over the southern oceans, particularly the tropical eastern South Pacific Ocean and the tropical eastern Indian Ocean. It is characterized by the reversal of pressure conditions, where the eastern Pacific experiences lower pressure compared to the eastern Indian Ocean. This phenomenon is connected with the El Niño-Southern Oscillation (ENSO), where warm ocean currents replace cold currents along the Peruvian coast, leading to changes in global weather patterns.

Q4: Withdrawal of the monsoon is a gradual process. Explain.
Ans: The withdrawal of the monsoon is a gradual process that begins in the northwestern states of India by early September. By mid-October, it withdraws completely from the northern half of the peninsula. The withdrawal from the southern half of the peninsula is fairly rapid, and by early December, the monsoon has withdrawn from the rest of the country. This gradual retreat is influenced by the movement of the monsoon trough and the changing pressure systems.

Q5: The breaks in the monsoon are related to the movement of the monsoon trough. Explain.
Ans: The breaks in the monsoon are related to the movement of the monsoon trough, which is an elongated low-pressure area in the lower troposphere. The axis of the monsoon trough can shift northward or southward, influencing the spatial distribution of rainfall. When the trough's axis lies over the plains, there is good rainfall in those areas. However, when the axis shifts closer to the Himalayas, dry spells occur in the plains, while rainfall increases in the mountainous catchment areas of the Himalayan rivers.

Q6: How do the frequency and intensity of tropical depressions determine the amount and duration of monsoon rains?
Ans: Tropical depressions, which form over the Bay of Bengal, play a significant role in the monsoon rains. These depressions follow the axis of the monsoon trough and bring moisture-laden winds from the ocean. The frequency and intensity of these depressions can influence the amount and duration of monsoon rains. More frequent and intense depressions can lead to heavy rainfall, while their absence or weaker formation can result in dry spells and drought conditions during the monsoon season.

Q7: Give a brief description of the distribution of rainfall in India.
Ans: The distribution of rainfall in India is uneven:

• Western coast and northeastern India receive over 400 cm of rainfall annually.
• Rainfall is less than 60 cm in western Rajasthan, parts of Gujarat, Haryana, and Punjab.
• The interior of the Deccan plateau and the east of the Sahyadris also receive low rainfall.
• Some areas, like Leh in Jammu and Kashmir, receive low precipitation.
• The rest of the country receives moderate rainfall, with snowfall occurring mainly in the Himalayan region.

Q8: What do you mean by the southwest monsoon? Explain in brief.
Ans: The southwest monsoon refers to the seasonal wind pattern that brings moist air from the Indian Ocean to the Indian subcontinent during the summer months. The intense heating of the Thar Desert and adjoining areas leads to the formation of a low-pressure area, drawing moisture-laden winds from the ocean. These winds are blocked by the Himalayas, causing them to rise, cool, and condense, leading to precipitation. The south-west monsoon is responsible for the majority of India's rainfall.

Q9: What is known as the North East Monsoon or Retreating Monsoon? Explain in brief.
Ans: The North East Monsoon, also known as the Retreating Monsoon, occurs around September when the northern landmass of the Indian subcontinent begins to cool rapidly. Cold winds from the Himalayas and Indo-Gangetic Plain sweep down towards the Indian Ocean south of the Deccan peninsula. This wind pattern brings rainfall to the southeastern coast of India, particularly Tamil Nadu, during the retreating monsoon period.

Q10: What are the characteristic features of retreating monsoon?
Ans:
Following are the characteristics features of retreating monsoon:

• During October-November, with the apparent movement of the sun towards the south, the monsoon trough or the low-pressure trough over the northern plains becomes weaker. This is gradually replaced by a high-pressure system. The southwest monsoon winds weaken and start withdrawing gradually. By the beginning of October, the monsoon withdraws from the northern plains.
• The months of October-November are a period of transition from hot-rainy season to dry winter conditions. The retreat of the monsoon is marked by clear skies and a rise in temperature.
• While day temperatures are high, nights are cool and pleasant. The land is still moist. Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive
• during the day. In the second half of October, the mercury begins to fall rapidly in northern India.
• The low-pressure conditions over north-western India get transferred to the Bay of Bengal by early November. This shift is associated with the occurrence of cyclonic depressions, which originate over the Andaman Sea. These cyclones generally cross the eastern coasts of India and cause heavy and widespread rain.

Q11: Describe briefly what you know about the onset of monsoon and its withdrawal.
Ans:

• The climate of India is described as the monsoon type. The monsoons are not steady winds but are pulsating in nature, affected by different atmospheric conditions encountered by it, on its way over the warm tropical seas. The duration of the monsoon is between 100—120 days from early June to mid-September.
• The monsoon generally arrives at the southern tip of the Indian peninsula by the first week of June. Subsequently, it proceeds into two—the Arabian Sea branch and the Bay of Bengal branch.
• The Arabian Sea branch reaches Mumbai about ten days later, on approximately the 10th of June. This is a fairly rapid advance. The Bay of Bengal branch also advances rapidly and arrives in Assam in the first week of June. The lofty mountains cause the monsoon winds to deflect towards the west over the Ganga plains.
• By mid-June, the Arabian Sea branch of the monsoon arrives over Saurashtra-Kuchchh and the central part of the country.
• The Arabian Sea and the Bay of Bengal branches of the monsoon merge over the northwestern part of the Ganga plains and cause rainfall. By mid-July, the monsoon reaches Himachal Pradesh
• and the rest of the country.
• The withdrawal of the monsoon begins in the north-western states of India by early September. By mid-October, it withdraws completely from the northern half of the peninsula. 

Q12: What are the factors that affect India’s climate? Describe them.
Ans:
The factors affecting the climate of India are—latitude, altitude pressure and winds. Here is a brief description of these factors:

• Latitude: India’s climate has characteristics of tropical as well as sub-tropical climates. The Tropic of Cancer passes through the middle of the country. Almost half of the country, lying south of the Tropic of Cancer, belongs to the tropical area. All the remaining area, north of the Tropic, lies in the sub-tropics.
• Altitudes: The Himalayas prevent the cold winds from Central Asia from entering the subcontinent. It is because of these mountains that this sub-continent experiences comparatively milder winters than Central Asia.
• Pressure and winds: The pressure and wind conditions over India are unique. During winter, there is a high-pressure area north of the Himalayas. Cold, dry winds blow from this region to the low-pressure areas over the oceans to the south. In summer, a low-pressure area develops over interior Asia as well as over northwestern India. This causes a complete reversal of the direction of winds during summer.

Air moves from the high-pressure area over the southern Indian Ocean, in a south-easterly direction, crosses the equator, and turns right towards the low-pressure areas over the Indian subcontinent. These are known as the southwest monsoon winds, which bring widespread rainfall over the mainland of India. The upper air circulation, western cyclonic disturbances and tropical cyclones also affect India’s climate.

Q13: Give a brief description of the controls that affect India's climate.
Ans:
There are six major controls that affect the climate of India—latitude, altitude, pressure, and wind system, distance from the sea, ocean currents, and relief features. Here is a brief description of all these climatic controls:

• Latitude: Due to the curvature of the earth, the amount of solar energy received varies according to latitude. As a result, air temperature generally decreases from the equator towards the poles.
• Altitude: At higher altitudes, the atmosphere becomes less dense, and temperature decreases. The hills are, therefore, cooler during summer.
• Pressure and wind system: It depends on the latitude and altitude of the place. Thus, it influences the temperature and rainfall pattern.
• Distance from the sea: The sea exerts a moderating influence on climate. As the distance from the sea increases, its moderating influence decreases, and people experience extreme weather conditions.
• Ocean currents: Ocean currents, along with onshore winds, affect the climate of the coastal areas. For example, any coastal area with warm or cold currents flowing past it will be warmed or cooled if the winds are onshore.
• Relief: It also determines the climate of a plane. High mountains act as barriers to cold or hot winds; they may also cause precipitation if they are high enough and lie in the path of rain-bearing winds. The leeward side of the mountains remains relatively dry.

Q14: State the factors that help in understanding the mechanism of monsoon.
Ans:
The following factors help us understand the mechanism of monsoon:

• The differential heating and cooling of land and water creates low pressure on India's landmass while the seas around experience comparatively high pressure.
• The shift of the position of the Inter Tropical Convergence Zone (ITCZ) over the Ganga plain in summer. This is the equatorial trough normally positioned about 5°N of the equator. It is also known as the monsoon trough during the monsoon season.
• The presence of the high-pressure area, east of Madagascar, approximately 20°S over the Indian Ocean. The intensity and position of this high-pressure area affects the Indian monsoon.
• The Tibetan plateau gets intensely heated during summer, which results in strong vertical air currents and the formation of low pressure over the plateau at about 9 km above sea level.
• The movement of the westerly jet stream to the north of the Himalayas and the presence of the tropical easterly jet stream over the Indian peninsula during summer.
• The changes in pressure conditions over the southern oceans also affect the monsoons.

Q15: Differentiate between southwest monsoon and northeast monsoon.
Ans:

• The south-west summer monsoons occur from July through September. The Thar Desert and adjoining areas of the northern and central Indian subcontinent heat up considerably during the hot summers.
• This causes a low-pressure area over the northern and central Indian sub-continent. To fill this void, the moisture-laden winds from the Indian Ocean rush into the subcontinent.
• These winds, rich in moisture, are drawn towards the Himalayas, which block the winds passing into Central Asia and force them to rise. As the clouds rise, their temperature drops and precipitation occurs. Some areas of the subcontinent receive up to 10,000 mm of rain annually.