Notes Class 11 Chapter 4 Geography Maharashtra Board

Climatic Regions

Introduction to Climatic Regions

Climatic regions are areas distinguished by their common natural features of geography, geology, and climate. These regions, also called Natural Regions, are homogeneous ecosystems where climate influences flora, fauna, soils, and human activities such as food habits, clothing, housing, and occupations. The climate of a region is determined by long-term observations (e.g., 30 years) of weather trends, including temperature, precipitation, and humidity. The atmosphere, one of the five spheres (atmosphere, lithosphere, hydrosphere, biosphere, magnetosphere), is primarily responsible for climate and weather.

Key Questions

• Why do skin color, food, clothing, and housing vary globally? Climate influences human physiology, agriculture, and lifestyle.
• Why are flora and fauna region-specific? Geographical and climatic factors like soil and water availability restrict their distribution.
• Human activities influenced by climate: Most activities (e.g., agriculture, clothing) are climate-dependent, but some (e.g., indoor activities like coding) may be less affected.

Classification of Climatic Regions

Climatic regions are classified based on latitudinal location, as latitude determines insolation (solar energy received) and atmospheric circulation. During the 19th and early 20th centuries, geographers prioritized climate for defining macro-regions. The regions are divided into:

1. Low-Latitude Regions (0°-30° N/S)
2. Mid-Latitude Regions (30°-60° N/S)
3. High-Latitude Regions (60°-90° N/S)
4. High-Altitude Regions (mountainous areas)

Why Climatic Regions are Called Natural Regions?

A natural region is a geographic unit with uniform natural features (geography, geology, climate). The flora and fauna are shaped by soil, water, and climate, forming distinct ecosystems.

Detailed Notes on Climatic Regions

A) Low-Latitude Regions

1) Equatorial Rainforests

• Geographical Distribution: 5°-10° N and S (Amazon Basin, Congo Basin, Central America’s east coast, Madagascar, Malaysia, Indonesia, Philippines, Papua New Guinea).
• Climatic Characteristics:
  • Constant high temperatures (~27°C).
  • Heavy convectional rainfall (2500-3000 mm), evenly distributed.
  • High cloud cover and humidity.
  • No distinct dry season, though some months have less rain (15-20 days).
• Related Features:
  • Dense, three-layered rainforests with tall hardwood trees.
  • High biodiversity (climbing/jumping animals, reptiles).
  • Iron-rich soils; chemical weathering dominates.
  • Tribal inhabitants in dense forests.
• Geographical Explanation:
  • Located near the equator, where the Sun’s noon rays are nearly vertical, ensuring consistent insolation.
  • Days and nights are of equal length; no distinct summer/winter.
  • The Inter-Tropical Convergence Zone (ITCZ), where trade winds converge, causes low pressure and heavy daily rainfall due to convectional currents.
• Key Questions:
  • Annual temperature range: Minimal (~1-2°C) due to constant insolation.
  • In India: Found in Andaman and Nicobar Islands, parts of Western Ghats.

2) Tropical Monsoon Climate

• Geographical Distribution: 10°-30° N and S (SW India, SE Asia, SW Africa, NE/SE Brazil, northern Australia, parts of Japan).
• Climatic Characteristics:
  • Summer temperatures: 27-32°C; winter: 15-24°C.
  • Rainfall: 250-2500 mm, mostly in summer (orographic in India); one or more months with <6 cm rainfall.
  • High annual temperature range.
  • Summer onshore and winter offshore winds due to ITCZ shifts.
• Related Features:
  • Vegetation ranges from jungles to thorn forests.
  • Large herbivores (e.g., deer) and carnivores (e.g., tigers).
  • Iron-rich soils in high-rainfall zones.
  • Paddy rice agriculture dominant.
• Geographical Explanation:
  • Distinct wet (summer) and dry (winter) seasons due to seasonal monsoon winds.
  • Differential heating of land and sea creates low pressure on land in summer, attracting moisture-laden southwest winds. In winter, dry northeast winds prevail.
  • ITCZ shifts north (20°-25°N) in summer and south in winter, driving rainfall patterns.
• Key Questions:
  • Weathering: Chemical weathering due to high rainfall and humidity.

3) Tropical Savannah Climate

• Geographical Distribution: 10°-20° N and S (parts of India’s peninsular plateau, Maharashtra’s rain-shadow zone, Telangana, Karnataka, Mizoram, south-central Africa, llanos of Venezuela, Campos of Brazil).
• Climatic Characteristics:
  • Distinct wet summers (~35°C) and dry winters (~24°C).
  • Rainfall: 250-1000 mm, influenced by alternating ITCZ and subtropical highs.
• Related Features:
  • Tall, thick grasses (e.g., elephant grass) with scattered drought-resistant trees.
  • Large herbivores, carnivores, and scavengers.
  • Grazing and animal husbandry dominant.
• Geographical Explanation:
  • Peripheral to rainforests, influenced by ITCZ in summer (wet) and subtropical highs in winter (dry).
  • High insolation due to near-overhead Sun rays.
• Key Questions:
  • Agricultural crops: Millets, sorghum, cotton.
  • Longitudes not specified: Distribution is determined by latitudinal wind/pressure belts, not specific longitudes.

4) Tropical Deserts (Arid Climate)

• Geographical Distribution: 20°-30° N and S (Gujarat, Rajasthan, SW Haryana, Iran, interior Asia, coastal Chile, Peru, SW Africa, interior Mexico, Baja California, North Africa, Namibia, parts of the US).
• Climatic Characteristics:
  • Summer: 30-45°C; winter: 20-25°C.
  • Highest diurnal temperature range.
  • Precipitation: <200 mm, low/no humidity.
  • Windy conditions due to subtropical high-pressure belts.
• Related Features:
  • Xerophytic vegetation (e.g., cacti).
  • Small, nocturnal burrowing animals.
  • Nomadic tribes (e.g., Bedouins in Sahara, Bushmen in Kalahari).
  • Saline soils; agriculture near oases.
• Geographical Explanation:
  • Deserts form due to subtropical high-pressure belts, continental interiors, rain-shadow effects, or cold ocean currents (e.g., Benguela for Kalahari, Humboldt for Atacama).
  • Dry air and clear skies cause extreme diurnal temperature ranges.
• Key Questions:
  • Weathering: Physical weathering due to temperature extremes and low moisture.

B) Mid-Latitude Regions

1) Mediterranean Climate

• Geographical Distribution: 30°-40° N and S (Central California, Mediterranean Sea borders, Cape Town, Southern/SW Australia, central Chile).
• Climatic Characteristics:
  • Mild, moist winters (~10-14°C); warm, dry summers (~21-27°C).
  • Winter rainfall: 500-1000 mm.
  • Foggy coasts, high summer diurnal range.
  • Subtropical highs in summer, westerlies in winter.
• Related Features:
  • Scrub, evergreen forests with hard, leathery leaves; coniferous vegetation at higher altitudes.
  • Winter-sown grains, olives, grapes, citrus fruits.
  • Tourism and cinema industries (e.g., California).
• Geographical Explanation:
  • Summers are dry due to subtropical highs; winters are wet due to westerly winds bringing moisture.
  • Moderate climate compared to low-latitude regions.
• Key Questions:
  • Olive oil use in Europe: Mediterranean climate supports olive cultivation, a staple in cooking.

2) China Type (Humid Subtropical) Climate

• Geographical Distribution: 20°-40° N and S, east coasts (SE USA, SE South America, coastal SE South Africa, eastern Australia, eastern Asia from South China to southern Japan, Easter Island in Chile).
• Climatic Characteristics:
  • Warmest months >10°C; coldest: 0-18°C.
  • High humidity, hot summers, frost in winter.
  • Year-round rainfall (600-2500 mm), decreasing inland.
  • Cyclonic storms in winter, convectional showers in summer.
• Related Features:
  • Mixed forests, grasslands, pines at higher altitudes.
  • Crops: rice, wheat, corn, cotton, tobacco, sugarcane, citrus fruits.
• Geographical Explanation:
  • Located on eastern continental margins, unlike Mediterranean’s western margins.
  • Rainfall throughout the year, with tropical storms (hurricanes, typhoons) in summer.
• Key Questions:
  • Agricultural productivity: Fertile soils, adequate rainfall, and long growing seasons support diverse crops.

3) Marine West European Climate

• Geographical Distribution: 45°-65° N and S, western coasts (western USA/Canada, southern Alaska, southern Chile, SE Australia, New Zealand, Western Europe).
• Climatic Characteristics:
  • Mild/cool summers (~20°C); winters ~5°C.
  • Year-round precipitation (500-2500 mm).
  • Heavy cloud cover, high humidity, drizzle, fog, frost.
  • Influenced by westerlies and warm ocean currents (e.g., North Atlantic Drift).
• Related Features:
  • Short green grass, deciduous trees, coniferous forests.
  • Wheat, rye, pasture, grazing animals, coastal fisheries.
• Geographical Explanation:
  • Proximity to seas and warm ocean currents moderates temperatures, ensuring mild winters.
  • Westerlies bring consistent moisture.
• Key Questions:
  • Chile’s recurrence: Its long latitudinal span covers multiple climates (desert, Mediterranean, Marine West European).
  • Fishing development: Coastal location and nutrient-rich waters support fisheries.

C) High-Latitude Regions

1) Taiga (Sub-Arctic) Climate

• Geographical Distribution: 55°-65° N (northern North America from Newfoundland to Alaska, northern Eurasia from Scandinavia to Siberia).
• Climatic Characteristics:
  • Brief cool summers (~15-20°C); bitterly cold winters (<0°C).
  • Precipitation: 300-500 mm (snow in winter).
  • Heavy cloud cover, high humidity, drizzle, fog, frost.
  • Westerlies in summer, polar anticyclones in winter.
• Related Features:
  • Coniferous forests (softwood), acidic soils, poor drainage.
  • Short growing season; experimental vegetables, root crops.
  • Animals with fur; hunting and lumbering.
• Geographical Explanation:
  • Continental location and low temperatures reduce moisture-holding capacity, limiting rainfall.
  • No Southern Hemisphere equivalent due to limited landmasses.
• Key Questions:
  • Temperature range: High (~35-40°C) due to extreme winters.
  • Occupations: Lumbering, hunting.
  • Weathering: Frost action and physical weathering dominate.

2) Tundra Climate

• Geographical Distribution: 65°-90° N (Arctic Ocean borders, North America, Greenland, Eurasia, Antarctic Peninsula, polar islands).
• Climatic Characteristics:
  • Summer ~10°C; winter -20 to -30°C.
  • Precipitation: 300-500 mm (snow), low evaporation.
  • Coastal fog, strong winds, polar anticyclones, permafrost.
• Related Features:
  • Tundra vegetation, swamps during melting.
  • Mineral/oil resources, animals with fur (polar bears, seals).
  • Hunting, fishing; Inuit communities.
• Geographical Explanation:
  • Closer to poles than Taiga, but milder winters due to maritime influence.
  • Oblique Sun rays and long daylight (up to 6 months) have minimal warming effect.
• Key Questions:
  • Mass movement: Frost heaving, solifluction due to permafrost melting.

3) Ice Cap Climate

• Geographical Distribution: Near poles (Antarctica, interior Greenland, frozen Arctic Ocean parts).
• Climatic Characteristics:
  • All months below 0°C; world’s coldest temperatures.
  • Meager precipitation (snow), exceeds evaporation.
  • Year-round polar anticyclones, ice cover.
• Related Features:
  • No vegetation, only sea life/aquatic birds.
  • Scientific exploration (e.g., research stations).
• Geographical Explanation:
  • Minimal insolation due to oblique rays and snow reflection.
  • Polar anticyclones limit precipitation.
• Key Questions:
  • Activities: Scientific research, polar expeditions.
  • Occupations: None; uninhabited except for researchers.

D) High-Altitude Regions

1) Highland (Mountain) Climate

• Geographical Distribution: Higher reaches of mountains (Asia, central Europe, western North/South America).
• Climatic Characteristics:
  • Varies with altitude, location (leeward/windward), orographic rainfall, snowfall at higher elevations.
  • Temperature decreases with altitude.
• Related Features:
  • Coniferous forests at high altitudes; tropical deciduous/evergreen at lower altitudes.
  • Laterite soils, grazing, pastures, terrace cultivation, tourism.
• Geographical Explanation:
  • Topography governs climate; large temperature changes over short distances.
  • Precipitation varies with elevation and windward/leeward location.
• Key Questions:
  • Human activities: Tourism, terrace farming, animal husbandry.
  • High latitudes vs. altitudes: Latitudes affect insolation; altitudes affect temperature and precipitation due to elevation.

Summary Table of Climatic Regions