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NCERT Class 9 Geography | Chapter 4 | Climate


Chapters :

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NCERT Class 9 Geography | Chapter 4 | Climate





Introduction :


  • Growing demands for water from rivers, driven by domestic, municipal, industrial, and agricultural needs, impact water quality.

  • Increased water extraction diminishes river volume, exacerbating the issue.

  • Untreated sewage and industrial effluents worsen water quality, diminishing the self-cleansing capacity of rivers.

  • Urbanization and industrialization contribute to pollution, impeding natural dilution processes.

  • Various action plans have been initiated to tackle rising river pollution.

  • River pollution has adverse effects on human health, leading to various illnesses.

  • Life without access to fresh water can have severe consequences for communities.

  • A classroom debate can be organized to explore different perspectives and solutions regarding river pollution and its consequences.




Regarding India's climate...


  • India's climate is primarily characterized as the "monsoon" type, prevalent in South and Southeast Asia.

  • Despite a general pattern, there are significant regional variations in temperature and precipitation across the country.

  • Temperature variations range from extreme heat in the Rajasthan desert to milder climates in places like Pahalgam in Jammu and Kashmir.

  • Precipitation also varies greatly, from heavy snowfall in the Himalayas to monsoon rains in other regions.

  • Annual precipitation ranges from over 400 cm in Meghalaya to less than 10 cm in Ladakh and western Rajasthan.

  • Coastal areas generally experience less temperature variation compared to interior regions.

  • These climate variations influence aspects of people's lives, including their food, clothing, and housing choices.



Climatic Controls:


  • Six major controls of climate:

    • Latitude

    • Altitude

    • Pressure and wind system

    • Distance from the sea (continentality)

    • Ocean currents

    • Relief features


  • Solar energy received varies with latitude due to the earth's curvature, leading to temperature variations from equator to poles.

  • Higher altitudes experience lower air density and temperature, making hills cooler during summers.

  • Pressure and wind systems are influenced by latitude and altitude, impacting temperature and rainfall patterns.

  • Proximity to the sea moderates climate, with increasing distance leading to more extreme weather conditions (continentality).

  • Ocean currents and onshore winds affect coastal climate, with warm or cold currents influencing temperature.

  • Relief features, such as mountains, act as barriers to winds and can cause precipitation if high enough and in the path of rain-bearing winds.

  • The leeward side of mountains tends to be drier compared to the windward side.



Factors affecting India’s climate:


  • Latitude:

    • Tropic of Cancer divides India, with south experiencing tropical climate and north subtropical.

  • Altitude:

    • Himalayas block cold winds, giving India milder winters.

  • Pressure and Winds:

    • India's climate is influenced by pressure, winds, and cyclonic disturbances.

  • Northeast winds bring little rain, while Southwest Monsoon winds bring widespread rainfall in summer.



The seasons : 


  • Monsoon Climate:

    • Characterized by distinct seasonal changes, particularly noticeable in interior regions.

    • Coastal areas experience less temperature variation but varied rainfall patterns.

    • Four Main Seasons in India:

      • Cold Weather Season (Winter):

      • Begins mid-November and lasts till February.

      • North experiences colder temperatures, with frost and snowfall in Himalayas.

      • Northeast trade winds prevail, bringing dry weather with occasional rains on Tamil Nadu coast.

      • Hot Weather Season (Summer):

        • March to May marks hot weather season.

        • Rising temperatures and falling air pressure in north.

        • Loo winds bring hot, dry gusts in northwestern India, dust storms, and localized thunderstorms.

      • Advancing Monsoon (Rainy Season):

        • Early June sees intensifying low-pressure conditions attracting southwest monsoon winds.

        • Southwest monsoon brings heavy rainfall, varying across regions with wet and dry spells

      • Retreating Monsoon (Transition Season):

        • October-November transition from rainy to dry conditions.

        • Monsoon withdraws, marked by clear skies, rising temperatures, and occasional cyclonic depressions in the Bay of Bengal.


Distribution of rainfall :

  • Rainfall Distribution in India:

    • Parts of western coast and northeastern India receive over 400 cm of rainfall annually.

    • Conversely, rainfall is less than 60 cm in western Rajasthan, Gujarat, Haryana, Punjab, interior Deccan plateau, and east of Sahyadris.

    • Low precipitation areas include Leh in Jammu and Kashmir.

    • Factors for Low Rainfall:

      • These regions receive low rainfall due to various factors such as rain shadow effect, distance from sea, and topographical features.

    • Variability:

      • Annual rainfall highly variable, especially in regions of low rainfall like Rajasthan, Gujarat, and leeward side of Western Ghats.

      • High variability leads to floods in high rainfall areas and droughts in low rainfall regions.



Monsoon as a unifying bond... 


  • Himalayas shield northern India from cold winds, maintaining higher temperatures compared to similar latitudes.

  • Peninsular plateau, surrounded by sea, enjoys moderate temperatures.

  • Despite moderating factors, temperature variations exist.

  • Monsoon brings rhythmic seasons, uncertainties, and uneven rain distribution.

  • Monsoon is crucial for agriculture, shaping landscape, animal and plant life, and people's lives.





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