CBSE Class 9 Social Science: Climate NCERT Solutions

Solution: The correct answer is (iii) Mawsynram. Mawsynram, located in the state of Meghalaya, India, receives the highest average annual rainfall in the world. This is primarily due to its geographical location, which is situated on the crest of the southern part of the Khasi hills, directly facing the Bay of Bengal monsoon winds.

Solution: The correct answer is (iii) Loo. The Loo is a strong, hot, dry, and dusty wind that blows across the northern plains of India during the summer months, typically from May to June. It originates in the Thar Desert and can cause heatstroke due to its high temperatures.

Solution: The correct answer is (ii) Western disturbances. These are extra-tropical storms that originate in the Mediterranean region and travel eastwards, bringing light rainfall and snow to the northwestern parts of India during the winter season.

Solution: The correct answer is (b) Early June. The Southwest Monsoon, which is the primary source of rainfall for India, typically begins its advance into the southern parts of the country around the first week of June and gradually covers the rest of the country by mid-July.

Solution: The correct answer is (c) Cool days and cold nights. During the cold weather season, which generally lasts from December to February, the days are typically cool, and the nights are cold across most parts of India, with temperatures often dropping significantly, especially in the northern plains and hilly regions.

Solution: The climate of India is affected by several controls, including:

1. Latitude: India is located in the tropics, with the Tropic of Cancer passing through the middle of the country, influencing temperature patterns.
2. Altitude: The Himalayas in the north significantly influence the climate by acting as a barrier to cold winds and affecting monsoon patterns.
3. Distance from the Sea: Coastal areas experience moderate climates, while interior regions have extreme temperatures due to the moderating effect of the sea.
4. Pressure and Winds: The pressure conditions over the Indian subcontinent and the surrounding oceans, along with the prevailing winds (like the Southwest Monsoon), are crucial determinants of rainfall and temperature.
5. Relief Features: The physical features, such as mountains and plateaus, influence the distribution of rainfall and temperature.
6. Ocean Currents: While less significant than other factors, ocean currents can have a minor influence on coastal climates.

Solution: India has a monsoon type of climate primarily due to the differential heating of land and sea, and the seasonal reversal of winds. The presence of the Himalayas in the north and the vast Indian Ocean to the south create unique pressure conditions. During summer, the land heats up more than the ocean, creating low pressure over the subcontinent, attracting moisture-laden winds from the Indian Ocean (Southwest Monsoon). In winter, the land cools down more than the ocean, creating high pressure over land and low pressure over the ocean, leading to winds blowing from land to sea, resulting in a dry season.

Solution: The northwestern part of India, particularly the desert regions of Rajasthan (like Jaisalmer and Bikaner), experiences the highest diurnal range of temperature. This is because these areas have arid or semi-arid conditions with clear skies and low humidity. The land heats up rapidly during the day due to intense solar radiation and cools down quickly at night due to the absence of cloud cover and moisture, leading to significant temperature differences between day and night.

Solution: The Southwest Monsoon winds account for the rainfall along the Malabar coast. As these moisture-laden winds blow from the Arabian Sea towards the Indian subcontinent, they strike the Western Ghats, which run parallel to the coast. The winds are forced to rise, cool, and condense, leading to heavy orographic rainfall on the windward side of the Ghats, which includes the Malabar coast.

Solution: Jet streams are fast-flowing, narrow air currents in the Earth's atmosphere, typically found at high altitudes (around 9-12 km above sea level). They blow from west to east. Jet streams significantly affect India's climate in two main ways:

1. Winter: The՚Subtropical Westerly Jet՚ stream blows over peninsular India during winter. It is responsible for bringing the Western Disturbances, which cause much-needed winter rainfall in the northwestern parts of the country.
2. Summer: The՚Tropical Easterly Jet՚ stream forms over the Indian peninsula during summer. This jet stream is crucial for the onset and strengthening of the Southwest Monsoon, driving the monsoon winds towards India and influencing the distribution of rainfall.

Solution:

Monsoons are defined as seasonal winds that experience a sudden reversal in direction during the year. They are characterized by a distinct wet season (summer monsoon) and a dry season (winter monsoon), driven by differential heating of land and sea.

A "break" in monsoon refers to a phenomenon where the monsoon rainfall becomes irregular and is interrupted by periods of dry spells. During these breaks, the monsoon trough tends to shift northwards, leading to reduced rainfall or no rainfall in many parts of the country, while some areas might experience heavy rainfall due to other weather systems.

Solution: The monsoon is considered a unifying bond in India because it affects the entire subcontinent in a similar way, despite regional variations. The arrival of the monsoon brings life-giving rain, which is crucial for agriculture, the backbone of the Indian economy. The shared experience of the monsoon's arrival, its intensity, and its eventual withdrawal creates a sense of commonality and interdependence across diverse regions and cultures of India. The monsoon's influence on festivals, livelihoods, and the overall rhythm of life fosters a collective identity and a sense of unity among the people.