Detailed Study Notes on Climate of India

Climate of India

Introduction to Climate

  • Natural Environment Elements: Three basic elements:
    • Landforms
    • Drainage
    • Atmospheric conditions (the main focus of this chapter)
  • Importance of Climate: Understanding climate explains:
    • Why to wear certain clothes in December (woollens) or in May (light attire).
    • The rainy season in June-July.

Definition of Climate and Weather

  • Climate:
    • Refers to the sum total of weather conditions and variations over a large area for a long period (usually more than thirty years).
  • Weather:
    • Refers to the state of the atmosphere over a specific area at any given time.
  • Common Weather-Climate Elements:
    • Temperature
    • Atmospheric Pressure
    • Wind
    • Humidity
    • Precipitation
  • Observations: Weather can fluctuate day-to-day, but patterns emerge over weeks/months resulting in recognized seasons.

Climatic Regions and Characteristics

  • Climate of India is classified as a 'monsoon' type, primarily in the south and southeast of Asia.
  • Regional Variations: There are significant variations in temperature and precipitation across different regions and seasons.
Temperature Variation

  • Regional Example Variations:

    • Temperature in Rajasthan can peak at 50°C;
    • Jammu and Kashmir can drop to -45°C in winter nights.
    • Thiruvananthapuram averages about 22°C.

  • Day-Night Temperature Differences:

    • Thar Desert: Day temperature can reach 50°C; at night, it may drop to around 15°C.
    • Andaman and Nicobar Islands/Kerala: Minimal day-night temperature variation.
Precipitation Variation
  • Precipitation forms include rain and snow, varying widely in amount and distribution:
    • Annual Precipitation Extremes:
    • Over 400 cm in Meghalaya.
    • Less than 10 cm in Ladakh and Western Rajasthan.
    • Monsoon Season: June to September rains are fundamental for most of India, while Tamil Nadu often receives rain in October-November.
  • Temperature and Rainfall: Coastal areas typically experience less temperature contrast compared to the interior regions.

Climatic Controls

Key Controls of Climate (6 in total)
  1. Latitude
  2. Altitude
  3. Pressure and Wind Systems
  4. Distance from the Sea (Continentality)
  5. Ocean Currents
  6. Relief Features
  • Each of these factors plays a crucial role in defining the climate across different regions.

Factors Affecting India's Climate

1. Latitude
  • The Tropic of Cancer runs through the middle of India:
    • Southern half in the tropical region, northern half in subtropical region.
    • Solar energy varies with latitude; thus, temperature decreases towards the poles.
2. Altitude
  • Himalayan mountains restrict cold winds, leading to milder winters in India compared to Central Asia.
3. Pressure and Winds
  • Indian weather is affected by pressure systems:
    • High-pressure during winter in the northern region.
    • Low-pressure develops in summer over northern India leading to summer monsoon wind reversal.
4. Distance from the Sea (Continentality)
  • The sea moderates climate; locations farther away experience extreme temperatures (hot summers and cold winters).
5. Ocean Currents
  • Coastal climates are influenced by warm or cold currents affecting temperatures.
6. Relief Features
  • Relief influences rainfall patterns:
    • High mountains serve as barriers and modify wind movement.
    • Leeward sides of mountains tend to be drier.

Seasonal Weather Patterns

Cold Weather Season (Winter)
  • Begins mid-November, lasts until February (colder months: December and January).
    • Northeastern winds dominate, leading to dry and cool conditions.
    • Cyclonic disturbances cause winter rains, significant for Rabi crops.
Hot Weather Season (Summer)
  • March to May sees escalating temperatures.
    • Recorded temperatures in March: 38°C in Deccan Plateau; April: Approximately 42°C in Gujarat; May: Can reach 45°C in Northwestern India.
    • Loo: Strong, dry winds common in northern India causing adverse effects if exposed.
Rainy Season (Advancing Monsoon)
  • Starts in early June with low-pressure areas forming over northern India.
    • Southwest monsoon winds bring moisture leading to heavy rainfall.
    • Mawsynram, the wettest place, receives exceptionally high rainfall.
    • Variability in rainfall affects agricultural cycles and can lead to droughts or floods.
Post-Monsoon/Retreating Season
  • October-November marks the transition from rainy to winter climates.
    • Cyclonic depressions can bring significant rainfall, especially on eastern coasts and cause destructive cyclones.

Distribution of Rainfall

  • Western coast and northeastern India receive over 400 cm of rainfall, while western Rajasthan and parts of Gujarat may receive under 60 cm.
  • Snowfall: Restricted to Himalayan regions.
  • Annual rainfall variability is high, leading to droughts in some areas while causing floods in others.

Conclusion

  • Monsoons bind the Indian landscape, affecting not just weather but the agricultural calendar and overall lifestyle of its people, driven by the uncertainties and variations in rainfall patterns.

Exercise Section

  1. Select correct answers from provided options regarding rainfall and weather characteristics.
  2. Briefly answer questions relating to the described weather phenomena across regions.