NCERT Class 9 Geography Chapter 3: Drainage Youtube Lecture Handouts

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Watch video lecture on YouTube: NCERT Class 9 Geography Chapter 4: Climate of India NCERT Class 9 Geography Chapter 4: Climate of India
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NCERT Class 9 Geography

Chapter 4: Climate

Terminology

  • Climate – Sum total of weather for 30 years or more

  • Weather – Atmosphere at a given point of time

  • Includes temp., ppt., pr., wind, humidity

  • Monsoon from Arab “mausim” – seasonal reversal in wind direction

  • India – Monsoon land

  • Temp. from Rajasthan (500C) to J&K (-450C)

  • Rainfall – 400 cm in Meghalaya to 10 cm in Ladakh & Raj.

  • Tamil Nadu – winter rains

  • Rain decrease from east to west in north plains

  • Coastal area has less extreme in temperature

Controls of Climate

  • Latitude – Temp. From equator to poles

  • Altitude - Temp. With ht. (higher areas – less dense air) – hills are cooler

  • Pressure & Wind – depend on latitude & altitude, influence temp & rain

  • Distance from Sea – Distance increase – extreme weather - continentally

  • Ocean Currents – Warm & cold current

  • Relief Features – Mts. act as barrier

  • Deserts on western margins of continents in subtropics: Prevailing winds are tropical easterly winds & go dry on reaching western margins.

India – Climatic Controls

  • Latitude – Tropic of Cancer divides in tropics & subtropics

  • Altitude – Himalayas prevent cold wind from C. Asia – mild winters

  • Pressure and surface winds – NE Winds

  • In South deflect right – Coriolis force

  • Ferrel Law – right in NH & left in SH

  • Summer – LP in interior of India

  • SW Monsoon from HP to LP

Image of India - Climatic Controls

Image of India - Climatic Controls

Image of India - Climatic Controls

  • Upper air circulation – Jet Streams – Westerly Flow at 27°-30° north & so called Subtropical westerly - In India – South of Himalayas (except summer)– Year Round and cause western disturbances

  • In summer – move north of Himalayas

  • Tropical easterly jet stream: Over peninsular India at 14°N in summers

  • Western cyclonic disturbances – Occur in Winters

  • Tropical Cyclones – Occur in Monsoons & in Oct-Nov as easterly flow

Monsoons

  • In 200 N & S tropics

  • Differential heating of water and land

  • Shifting of ITCZ (NE & SE winds converge) – In summer at Ganga plain

  • High Pr. East of Madagascar – 200S

  • Heating of Tibetan Plateau

  • Movement of westerly jet in Himalayas & easterly in Peninsula

Southern Oscillations

Image of Southern Oscillation

Image of Southern Oscillation

Image of Southern Oscillation

  • Pr. Diff. over Tahiti (Pacific Ocean, 18°S/149°W) & Darwin, N. Australia (Indian Ocean, 12°30’S/131°E) – Intensity of Monsoon

  • Negative SOI: late monsoon or below average

El- Nino

  • ‘El Nino’ Spanish implies ‘child or baby Christ’: Starts flowing during Christmas

  • Warm Peruvian Coast, instead of cold Peruvian current, every 2 to 5 years

  • Changes in pressure conditions are connected to El Nino

  • Called as ENSO (El Nino Southern Oscillations)

  • In sea-surface temp. & weakening trade winds

  • Cause poor monsoon in India

Monsoon Mechanism

  • Pulsating

  • 100-120 days – June to Sept

  • Initially – Burst of Monsoon (after pre-monsoon showers)

  • At southern tip in June

  • 2 branches – Bay of Bengal (Assam in 1st week of June- deflect to west by Himalayas) & Arabian Sea (reach Mumbai by 10th June)

  • Both branch merge at Ganga Plains by June end

  • Retreat or withdrawal is gradual – starts in Sept in NW India

  • Islands – Monsoon appear in April to May & retreat Dec to Jan

Seasons

  • Cold Weather – Winter – Nov to Feb – frost & snow in North – NE winds (dry) – Winter rain in Tamil Nadu, cyclonic disturbances form N & NW – “Mahawat – winter rain” if small good for Rabi crop

  • Hot Weather – March to May, heat belt shift north, high temp, LP, loo – hot, dry gusty winds, localized storms – Kal Baisakhi in Bengal

  • Pre-Monsoon Showers: Kerala & Karnataka – Mango ripening – Mango showers

  • Advancing Monsoon – SW monsoon – windward side of Western Ghats receive rain, maximum in NE India – Mawsynram (stalagmite & stalactite caves) – has breaks – wet & dry spells - uncertainties

  • Retreating Monsoon – Transition – Clear Sky & temp. Rise – October Heat (high temp & humidity in day) – Cyclonic depression in Andaman sea- affect east coast of India.

Image of Normal Dates of Withdrawal

Image of Normal Dates of Withdrawal

Image of Normal Dates of Withdrawal

Unifying Bond

  • Himalayas – Protect north winds

  • Peninsula – Moderating influence

  • Rhythmic cycle of seasons

  • Water to rivers

  • Agriculture