Definition: Measure of the degree of hotness or coldness of a body (Physical definition)
Variation: Temperature changes place to place and region to region.
Examples:
Barmer: Has temperatures up to 48-50°C in summer.
Pahalgam (Kashmir): Maintains around 22°C on the same day.
Dras (a mountainous region of Kashmir): Temperature drops to -40°C in winters.
Kerala: A southern state with tropical climate - hot and wet, receives heavy rainfall from southwest monsoons, and it's near the Equator.
Northern States (like Punjab, Delhi): Have continental climate - very cold winters and very hot summers.
Climate
Definition: Average of weather conditions over a long period for a specific area or region.
Weather vs Season vs Climate:
Weather: Day-to-day atmospheric conditions.
Season: Longer period phenomena (e.g., summer, monsoon).
Climate: Long-term average of weather conditions.
Factors Affecting Climate in India
Himalayas
Role: Climatic barrier preventing cold Siberian winds from entering India and trapping rain-bearing winds.
Monsoon Winds
Origin: Arabic word 'Mawsim', meaning seasonal reversal of winds.
Summer Monsoon:
Low pressure over central India, high pressure over Indian Ocean.
Winds blow from ocean to land, bringing heavy rainfall, notably starting at Kerala in June.
Divides into Arabian Sea branch and Bay of Bengal branch - both essential for Indian rains.
Latitude
Role: Influence of the Tropic of Cancer, dividing India into temperate zone (north) and tropical zone (south).
Effect: Tropical zones experience extreme temperatures and wet conditions.
Relief (Landforms)
Role: Mountains (Western Ghats) cause orographic rainfall leading to high rainfall on windward side and rain-shadow on leeward side.
Example: Western Ghats receiving heavy rain, Rajasthan remaining dry due to Aravalli range's alignment.
Altitude
Rule: Higher elevation means cooler temperatures (Lapse rate: temperature drops by 1°C for every 166 meters ascent).
Examples: Hill stations like Nainital, Shimla are cooler in summers.
Proximity to the Sea
Influence: Coastal areas experience moderate climate (equitable) due to maritime influence.
Examples: Mumbai, Chennai vs continental climates in inland cities like Varanasi.
Western Disturbances
Origin: Low-pressure systems originating from the Mediterranean Sea, affect North India during winters causing sudden rainfall and snow in Jammu and Kashmir.
Effect: Bring short spells of rain and snow during winters.
Jet Streams
Definition: Fast blowing cold winds in the upper atmosphere, especially stratosphere, influencing weather patterns including rainfall concentration in certain areas (e.g., Meghalaya hills).
El Nino
Definition: A warm ocean current affecting surface temperatures and monsoon patterns, often reducing rainfall in India leading to droughts.
Impact: Change in sea surface temperature, affects Indian monsoons drastically.
Local Winds
Loo: Hot and dry winds in Northern India during summers.
Nor'westers (Kal Baisakhi, Bordoisila): Storms bringing rain & thunderstorms in Assam, West Bengal, facilitating agriculture.
Mango Showers: Pre-monsoon showers aiding in the ripening of mangoes in Kerala and Karnataka, known as 'Cherry Blossoms' when beneficial for tea and coffee.
Seasons in India
Summer (Hot and Dry)
Months: March to May
Characteristics: High temperatures, occurrence of local winds like Loo.
South-West Monsoon (Hot and Wet)
Months: June to September
Characteristics: Heavy rainfall, South-West monsoons starting in Kerala.
Retreating Monsoon (Season of Transition)
Months: October to November
Characteristics: North-East monsoons, high humidity, known as 'October Heat'.
Winter (Cold and Dry)
Months: December to February
Characteristics: Low temperatures, low humidity, occurrence of Western Disturbances.
Rainfall in India
Types: Orographic (due to mountains) is common, while cyclonic and convectional are less frequent.
Distribution: Uneven, varies seasonally and geographically.
Impact: Monsoon dependence makes Indian agriculture vulnerable to rainfall variability.
Conclusion
Climate of India highly influenced by its diverse geography, latitude, and interaction of various atmospheric phenomena.
Understanding these factors is crucial for grasping India's weather patterns and preparing for its climatic variations.