CBSE Class 9 Geography Chapter 4 – Climate
Download PDF 💾➥ Climate refers to the sum total of weather conditions and variations over a large area for a long period of time (more than thirty years).
➥ Weather refers to the state of the atmosphere over an area at any point in time.
➯ The elements of weather and climate are the same,
i.e., temperature, atmospheric pressure, wind, humidity, and precipitation.
⇨ On the basis of the monthly atmospheric conditions, the year is divided into seasons such as:
- Winter
- Summer
- Rainy Seasons
Climatic Controls
➥ The climate of any place depends on the following factors:
- Latitude: The amount of solar energy received varies according to latitude due to the curvature of the earth. Air temperature generally decreases from the equator towards the poles.
- Altitude: The atmosphere becomes less dense, and temperature decreases with higher altitude. This is why hills are cooler during summer.
- Pressure and Wind System: The pressure and wind system of an area depend on its latitude and altitude, influencing temperature and rainfall patterns.
- Distance from the Sea: The sea moderates climate. As the distance from the sea increases, people experience extreme weather conditions, known as continentality (e.g., very hot summers and very cold winters).
- Ocean Currents: Ocean currents and onshore winds affect coastal climate. Warm or cold currents regulate the temperatures of coastal areas.
- Relief Features: Relief features like mountains act as barriers to winds, cause precipitation, and influence the climate of a region.
Factors Affecting India’s Climate
- Latitude: The Tropic of Cancer divides the country, giving it tropical and subtropical climate characteristics.
- Altitude: India’s northern mountains cause milder winters compared to central Asia.
- Pressure and Winds: Atmospheric conditions such as pressure, surface winds, upper air circulation, and cyclones govern India's weather.
The Indian Monsoon
➥The Indian climate is heavily influenced by monsoons.
➥ The seasonal reversal of wind systems is known as "monsoon." Key factors include:
- Heating and cooling differences between land and water creating pressure differences.
- Position of the Inter-Tropical Convergence Zone (ITCZ).
- High-pressure areas near Madagascar affecting wind flows.
- Heating of the Tibetan plateau during summer causing low-pressure zones.
- Jet streams influencing monsoon patterns.
The Onset of the Monsoon and Withdrawal
➥ The monsoon lasts from early June to mid-September.
➥ Its arrival and retreat follow this pattern:
- First week of June: Southern tip of India.
- Mid-June: Arabian Sea and Bay of Bengal branches merge over northern plains.
- By July: Monsoon covers the entire country.
- Withdrawal: Starts in September from the northwest, completes by December across the country.
The Seasons
➥ India experiences four main seasons:
- The Cold Weather Season (Winter): Mid-November to February; clear skies, low temperatures, and low humidity.
- The Hot Weather Season (Summer): March to May; rising temperatures and hot winds like 'loo.'
- Advancing Monsoon (Rainy Season): June to September; heavy rainfall and humid conditions.
- Retreating Monsoon (Transition Season): October to November; clear skies and rising temperatures during the day.
Distribution of Rainfall
- Western coast and northeastern India receive over 400 cm annually.
- Western Rajasthan and parts of Gujarat receive less than 60 cm.
- Snowfall is restricted to the Himalayan region.
Monsoon as a Unifying Bond
➥ The monsoon acts as a unifying bond for India by providing water for agriculture and influencing the cultural and economic rhythms of the country.
- Agricultural Dependence: Indian agriculture is heavily reliant on monsoon rains.
- Cultural Significance: Monsoon impacts festivals, literature, and traditions.
- Economic Role: Water resources for irrigation, hydroelectric power, and industry depend on monsoon patterns.
- Geographical Unity: The monsoon system influences the entire subcontinent, connecting diverse regions.
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