Some important terms

1. Frost– A state in freezing, frozen dew.
2. Loo– Strong, gusty, hot, dry winds blowing during the day over the north and northwestern India.
3. Mango showers– Pre-monsoon showers in Kerala and Karnataka help in the ripening of mangoes earlier, known as monsoon showers.
4. Trough– A large vacuum in between of the Himalayas and the peninsular plateau, the plains.
5. Leeward– Rain shadow area.

Climate: 

• Climate refers to the sum total of weather conditions and variations over a large area for a long period of time. (More than 30 years).It is the sum total of weather conditions for the larger area. Eg: for a country.
• Climate is a long-term pattern of temperature, humidity, wind, and precipitation. Climate is dependent on a combination of factors like the orbit around the sun, the tilt of the earth’s axis, and the presence of oceans and land masses.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).India has a ‘monsoon’ type of climate. It experiences several kinds of regional climatic variations. While there is hardly 20cm of rainfall annually in the western parts of Rajasthan and Gujarat, Assam and Arunachal Pradesh receive more than 250cm of rainfall. During winters, the night temperature may fall below −45°C, while on the same night, Thiruvananthapuram may experience a temperature of 45°C. These variations have resulted in different lifestyles of the people.

Weather:

• It refers to the state of the atmosphere over an area at any point in time.It is the total of weather conditions for the limited area. Eg: for a city
• Weather is a short-term condition of the atmosphere in a particular place at a particular time. Weather is dependent on temperature, humidity, wind speed, and direction. Weather can change quickly and influence the high and low pressure system.

Elements of Weather and Climate:
→ Temperature
→ Atmospheric pressure
→ Wind
→ Humidity
→ Precipitation

India has monsoon type climate.

Temperature and precipitation vary from place to place and season to season

• In summer, the temperature reaches 50°C in some parts of Rajasthan while it is 20°C in Jammu and Kashmir.
• On a winter night, the temperature in Jammu and Kashmir is minus 45°C whereas it is 22°C in Thiruvananthapuram.
• The annual precipitation in Meghalaya is more than 400 cm while it is less than 10 cm in parts of Rajasthan and Jammu and Kashmir.
• Most of the parts of the country receive rainfall from June to September whereas Tamilnadu receives rainfall during October and November.
• Coastal areas do nor experience much variations in climate conditions.

Climatic Controls
There are six major controls of the climate of any place. They are:
→ Latitude
→ Altitude
→ Pressure and wind system
→ Distance from the sea (continentality)
→ Ocean currents
→ Relief features

They are latitude, altitude, pressure and wind system, distance from the sea, ocean currents be relief features.

1. 1. Latitude– Due to the curvature (curve) of the earth, solar energy received varies according to the latitude.
   2. Altitude– Temperature decreases with higher altitude (height)
   3. Wind System and Pressure- They affect the climate of any place.
   4. Distance from the sea – The places near the sea have a moderate climate and the places away from the sea have an extreme climate (continentality type of climate)
   5. Ocean Currents – The onshore winds affect the climate of coastal areas.
   6. Relief Features – High Mountains act as barriers for cold or hot winds.

 

Climate Influences:

Six key factors determine a region’s climate:

1. Latitude: Temperature changes from the equator to the poles due to sunlight variations.
2. Altitude: Higher elevations have cooler temperatures due to thinner air.
3. Pressure and Winds: Climate depends on location’s altitude and latitude, impacting temperature and rainfall.
4. Distance from the Sea: Proximity to the sea moderates climate; inland areas have more extreme weather.
5. Ocean Currents: Coastal climates are affected by onshore winds and nearby warm or cold ocean currents.
6. Geography and Relief: Land features, such as mountains and valleys, shape climate by blocking winds and affecting rainfall. High mountains may bring rain if tall and in the wind path, while the leeward side stays dry, impacting temperature and wind patterns.

These six factors collectively shape regional climates, making each area unique in its weather patterns.

Factors Affecting India’s Climate:

1. Latitude:
   • The Tropic of Cancer passes through the middle of the country. Half of the country lying south of the Tropic of Cancer, belongs to the tropical area.India spans from the Tropic of Cancer in the south to the subtropics in the north, resulting in a blend of tropical and subtropical climates.
   • The Tropic of Cancer passes through the middle of the country. So, in the south of tropic of cancer we have a tropical climate and in the north of Tropic of cancer have a sub-tropical climate.
2. Altitude:
   • The Himalayas prevent the cold winds from Central Asia from entering the subcontinent ,making winter milder as compared to central Asia.Varying altitudes, from high northern mountains to low coastal areas, affect temperature.
   • The Himalayas prevent the cold winds from central Asia from entering India, so we have milder winter.
3. Pressure and Winds:
   1.  Atmospheric conditions that govern climate and associated weather conditions in India are:
      → Pressure and surface winds
      → Upper air circulation

• • • The upper air circulation over warm oceans is called jet stream.
    • These are the high altitude winds in the atmosphere. Their speed varies from 110 km/hr in summer and 184 km/hr in winter.
    • They have located over 27°-30° North Latitude (Westerly) Jetstream
    • The higher level of the atmosphere is dominated by a westerly flow. An important component of this flow is the jet stream.
    • Jet Streams are a narrow belt of high altitude westerly winds in the troposphere (transition between troposphere and stratosphere.

→ Western cyclonic disturbances and tropical cyclones.

• • • The western disturbances, which enter the Indian subcontinent from the west and the northwest during the winter months, originate over the Mediterranean Sea and are brought into India by the westerly jet stream.
      • Tropical cyclones originate over the Bay of Bengal and the Indian ocean.
      • Tropical cyclones occur during the monsoon as well as in October-November, and are part of the easterly flow.

1. 1. India’s climate is shaped by winter north easterly winds and summer Southwest Monsoon winds, driven by pressure variations.
   2. Upper air circulation, including subtropical westerly and easterly jet streams, influences weather patterns and cyclonic disturbances.

These factors create India’s diverse climate conditions, from arid regions to those receiving heavy monsoon rains.

• Jet Streams: They are narrow, high-speed air currents in the Earth’s atmosphere, typically found in the upper levels of the troposphere.
•  Coriolis force: It is an apparent force caused by the Earth’s rotation, which deflects moving objects to the right in the northern hemisphere and to the left in the southern hemisphere.
• Western Cyclonic Disturbances: Western cyclonic disturbances are weather patterns in India during winter. They come from westerly winds from the Mediterranean and affect the north and northwest regions, causing changes in temperature and rainfall. Tropical cyclones: These are intense storms that form over warm ocean waters, typically occurring during the monsoon season and in October-November. They affect coastal regions and can lead to severe weather events, including heavy rainfall and strong winds.