4. Climate

(a) The northeastern part of Brazilian Highlands receives very less rainfall.

• Brazil receives moisture-laden winds from the South Atlantic Ocean, namely the South-East Trade winds.
• The Great Escarpment and the Brazilian Highlands act as an obstruction to these winds coming from the sea.
• This causes heavy orographic rainfall in the coastal region. However, after crossing the highlands, the moisture content of these winds reduces drastically.
• As a result, the region to the leeward side of the highlands (the northeastern part) becomes a rain-shadow region, receiving minimal rainfall. This area is known as the 'Drought Quadrilateral'.

(b) Snowfall doesn't always occur in Brazil.

• Brazil is primarily a tropical country, with the equator passing through its northern part and the Tropic of Capricorn passing through its southern part.
• Due to this latitudinal extent, the average temperatures remain generally high throughout the year, especially in the northern and central regions.
• Because of the high temperatures, water vapour condenses into rain, not snow. Snowfall occurs only rarely, at higher places in the southern states of Santa Catarina, Parana and Rio Grande do Sul.

(c) Convectional type of rainfall is not prominent in India.

• Convectional rainfall is a characteristic feature of the equatorial regions where intense solar heating causes air to rise vertically every afternoon, leading to daily rainfall.
• India is located to the north of the equator and largely falls within the tropical and sub-tropical zones, missing the daily intense equatorial heating required for prominent convectional rain.
• Instead, India's climate is dominated by the 'monsoon' winds. The Indian Ocean and the Himalayan ranges exert a great influence on India's climate, causing mainly orographic rainfall during the monsoon season.

(d) Tropical cyclones occur rarely in Brazil.

• In the coastal regions near the equator in Brazil, the differences in temperatures are negligible.
• The winds in this equatorial region move primarily in the vertical direction.
• Furthermore, the convergence zone of the trade winds is very weak in this area.
• Because these atmospheric conditions are not favorable for the formation of cyclonic depressions, tropical cyclones rarely visit the coasts of Brazil.

(e) There is not much difference in the range of temperature in Manaus.

• Manaus is located in the Amazon River basin, very close to the equator.
• Due to its equatorial location, the region receives almost perpendicular sunrays throughout the year, keeping the average temperature constantly high (around 25°C to 28°C).
• The area also experiences frequent convectional rainfall and has dense tropical rainforests, which maintain high humidity.
• The constant high heat and high humidity prevent extreme fluctuations between daytime and nighttime temperatures, leading to a very low range of temperature.

(f) India receives precipitation from the North-East Monsoon winds too.

• After the South-West Monsoon winds reach the Himalayas, they are obstructed and begin their retreat journey.
• During the Retreating Monsoon season, these winds blow from the north-east towards the Indian Ocean.
• As they blow over the Bay of Bengal, they pick up moisture.
• When these moisture-laden North-East winds strike the eastern coast of the Indian Peninsula (especially Tamil Nadu), they cause precipitation.

(a) Describe in brief the changes occurring in the climatic conditions of India while going from south to north.

• Temperature: As we move from south to north, the average temperature gradually decreases. The southern part, being closer to the equator, experiences higher temperatures throughout the year. The northern parts have an extreme climate. In winter, temperatures fall far below freezing point in places like Drass and Kargil in the Himalayas.
• Rainfall: The southern peninsula and coastal regions receive heavy rainfall due to the obstruction of the South-West monsoon winds by the Western and Eastern Ghats. As the winds move further north towards the central plains and the north-west (like Rajasthan), their moisture capacity decreases, leading to lower rainfall.
• Seasons: The southern part experiences a more equable, hot climate year-round with less distinct seasonal variation. The north experiences distinct hot summers and severe cold winters.

(b) Explain the importance of the Himalayas and the Indian Ocean with respect to the climate of India.

• Indian Ocean: High temperatures in summers develop a low-pressure area over the Punjab plains and the Thar desert. This attracts moisture-laden winds from the high-pressure region in the Indian Ocean, which bring the vital South-West Monsoon rainfall to the Indian mainland.
• Himalayas (Barrier to Cold Winds): The towering Himalayan ranges obstruct the extremely cold winds blowing from the north, preventing the Indian subcontinent from experiencing severe freezing temperatures.
• Himalayas (Orographic Rain): The Himalayas obstruct the advancing South-West Monsoon winds, forcing them to rise and causing heavy orographic rainfall in the northern and northeastern parts of India. After striking the Himalayas, these winds begin their retreating journey.

(c) Discuss the factors affecting the climate of Brazil.

• Latitudinal Extent: The equator passes through northern Brazil, making it hot and humid (Amazon basin averages 25°C-28°C). The Tropic of Capricorn passes through the south, giving it a more temperate climate.
• Trade Winds: Brazil's climate is heavily influenced by rainfall brought by the South-East and North-East Trade winds from the Atlantic Ocean.
• The Great Escarpment: The escarpments along the eastern coast obstruct the sea winds, causing heavy orographic rainfall in the coastal areas.
• Rain Shadow Region: Beyond the escarpments, the effect of the winds reduces drastically, creating a rain shadow area in the northeast known as the 'Drought Quadrilateral' where rainfall is minimal.
• Ocean Currents and Cyclones: Near the equator, vertical wind movement and a weak convergence zone mean that tropical cyclones rarely affect the Brazilian coast.

(d) Compare the climates of Brazil and India.