Climate

• 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 of time
• Elements of weather and climate include temperature, atmospheric pressure, wind, humidity, and precipitation
• India has a monsoon type of climate, found mainly in the south and southeast of Asia
• Latitude:

  • Tropic of Cancer passes through the middle of India
  • Almost half of the country lies in the tropical area, while the remaining area lies in the subtropics
• Altitude:

  • Mountains in the north with an average height of about 6,000 meters
  • Coastal areas with maximum elevation of about 30 meters
  • Himalayas prevent cold winds from Central Asia, leading to milder winters in India compared to central Asia
• Pressure and Winds:

  • Atmospheric conditions in India are governed by pressure and surface winds, upper air circulation, westerly cyclonic disturbances, and tropical cyclones
  • India lies in the region of north easterly winds
• Relief:

  • High mountains act as barriers for cold or hot winds
  • Leeward side of mountains remains relatively dry
• Monsoon refers to the seasonal reversal in wind direction during a year
• Four main seasons in India: cold weather season, hot weather season, advancing monsoon, and retreating monsoon with regional variations
• Cold Weather Season (Winter):

  • Begins from mid-November in northern India and lasts till February
  • Coldest months in the northern part of India are December and January
• • Feeble high-pressure region develops in the northern part of the country, with winds moving through the Ganga valley from the west and northwest
  • Inflow of cyclonic disturbances from the west and northwest brings winter rains over the plains and snowfall in the mountains
• Cold Weather Season (Winter):

  • Begins from mid-November in northern India and stays till February
  • December and January are the coldest months in the northern part of India
  • Temperature decreases from south to north
  • Average temperature in Chennai is between 24°–25° Celsius, while in the northern plains it ranges between 10°C and 15° Celsius
  • Days are warm and nights are cold
  • Frost is common in the north and higher slopes of the Himalayas experience snowfall
  • Northeast trade winds prevail, leading to a dry season in most parts of the country
• Hot Weather Season (Summer):

  • From March to May
  • Rising temperature and falling air pressure in the northern part of the country
  • Development of an elongated low-pressure area from the Thar Desert to Patna and Chotanagpur plateau
  • 'Loo' winds are strong, gusty, hot, dry winds in north and northwestern India
  • Dust storms common in May, bringing temporary relief
  • Season for localised thunderstorms, hail, and 'Kaal Baisakhi' storms in West Bengal
  • Pre-monsoon showers in Kerala and Karnataka, known as 'mango showers'
• Advancing Monsoon (The Rainy Season):

  • By early June, low-pressure condition intensifies over the northern plains
  • South-east trade winds bring abundant moisture as the south-west monsoon
  • Monsoon winds cover the country in about a month
  • Heavy rainfall on the windward side of the Western Ghats
  • Maximum rainfall in the north-eastern part of the country
  • Mawsynram in the Khasi Hills receives the highest average rainfall in the world
  • Breaks in monsoon related to the movement of the monsoon trough
  • Tropical depressions influence the amount and duration of monsoon rains
• Retreating/Post Monsoons (The Transition Season):

  • October-November transition from hot rainy season to dry winter conditions
  • Monsoon withdraws from the Northern Plains by early October
  • Clear skies and rise in temperatures
  • Low-pressure conditions over northwestern India transfer to the Bay of Bengal
  • Cyclonic depressions originate over the Andaman Sea, causing heavy rain
  • Distribution of rainfall varies across different regions in India
• The Peninsular plateau, under the influence of the sea from three sides, has moderate temperatures
• Day temperatures are high, nights are cool and pleasant, and the land is still moist
• High temperature and humidity lead to oppressive weather during the day, known as 'October heat'
• Climate refers to the sum total of weather conditions and variations over a large area for a long period of time
• The climate of India is described as the monsoon type
• Weather refers to the state of the atmosphere over an area at any point of time
• The word monsoon is derived from the Arabic word mausim which literally means season
• The Tropic of Cancer passes through the middle of the country from the Rann of Kuchchh in the west to Mizoram in the east
• India lies in the region of southwest winds
• As the distance from the sea increases, its moderating influence decreases and the people experience extreme weather conditions. This condition is known as continental climate
• An apparent force caused by the earth’s rotation is Coriolis force
• January and February are the coldest months in the northern part of India
• The total amount of winter rainfall locally known as 'Mahawat'
• A striking feature of the hot weather season is the Loo (strong, gusty, hot, dry winds)
• The monsoon rains take place only for a few days at a time. They are interspersed with rainless intervals. These are called 'breaks in the monsoon'
• Monsoon arrives in India approximately in early June
• Pre-monsoon showers especially, in Kerala and Karnataka are often referred to as 'Mango showers'
• Mawsynram in the southern ranges of the Khasi Hills receives the highest average rainfall in the world