India's Climate: Factors and Seasons

• India's climate, landscape, and environment influence its vegetation and wildlife.

Factors Influencing India's Climate

• India has a tropical monsoon climate in most areas.
• Latitude places India in tropical and sub-tropical heat zones.
• Lower latitudes are warmer, while higher latitudes have warm summers but cold winters.
• Higher mountain ranges and plateaus experience lower temperatures and varying rainfall compared to low-lying plains.
• Mountain ranges affect wind and rainfall directions.
• The Himalayas act as a barrier to cold Asian winds and prevent monsoon winds from leaving the country.
• Coastal climates are defined by sea and land breezes, leading to equable conditions.
• Areas far from the sea experience extreme climatic conditions.
• Seasonal winds combine with land characteristics to create temperature and rainfall conditions typical of monsoons.

Cycle of Seasons

• India has four seasons: summer, monsoon, retreating monsoon, and winter.

Summer

• Temperatures rise from 30°C in March to over 40°C in May.
• By mid-June, the sun is vertically over the Tropic of Cancer, causing hot summers in north-western and central India, exceeding 50°C in the Great Indian Desert.
• Coastal India has lower temperatures (around 30°C) due to cool sea breezes.
• Hilly areas experience low temperatures due to the increase in height.
• Hot winds rise, creating low pressure over land, while cooler seas develop higher pressure.
• Loo is a hot, dry wind in the Northern Plains, common in Punjab, Haryana, Uttar Pradesh, and Bihar, often causing dust storms.
• Local thunderstorms include mango showers in Kerala (helping mango ripening), Kalbaisakhi in West Bengal (beneficial for tea, jute, and rice), and Bardolichheerha in Assam.

Monsoon

• The word 'monsoon' comes from the Arabic 'mausim' for 'season' and lasts from mid-June to September.
• Low pressure over North-west India draws winds from high-pressure areas over the seas.
• Monsoon winds, originating in the Southern Hemisphere and the Indian Ocean, absorb moisture and become rain-bearing.
• These winds bring violent thunderstorms and heavy downpours to coastal India.
• The sky is often cloudy, with brief sunshine spells between rains.
• Two main branches of the south-west monsoon winds exist: the Arabian Sea branch and the Bay of Bengal branch.
• The Arabian Sea branch brings rain to the west coast and parts of Gujarat.
• The Bay of Bengal branch splits: one moves towards eastern India, Myanmar, and Bangladesh; the other travels up the Northern Plains.
• Monsoon winds bring less rain to the interior and are almost dry by western Rajasthan.
• The west coast and Gangetic Delta receive over 200 cm of rain, while interior areas get 50-100 cm, and the Great Indian Desert gets only 25 cm.
• Cherrapunji was once the wettest place, with a record of 2,250 cm in 1861.
• Mawsynram now records the highest rainfall at 1,187 cm. annually.
• Windward slopes receive heavy rain, while leeward slopes are dry, creating a rainshadow area.

Retreating Monsoon

• By late September, rainfall decreases, and the sun moves towards the Southern Hemisphere.
• The weather becomes clearer and cooler by October.
• Dry winds blow from land to sea.
• Northern Plains' temperatures decrease as the sun is no longer directly over the Tropic of Cancer.
• The south-west monsoon winds withdraw in stages.

Winter

• By December, the sun is vertically over the Tropic of Capricorn.
• Winter begins in late November and continues until late February; the weather is generally cold and dry.
• Winter temperatures range from 10°C to 22°C in most areas.
• The Northern Plains and Great Indian Desert get extremely cold.
• Southern India has higher temperatures due to surrounding seas.
• Mountain areas in the north, north-west, and north-east record the lowest temperatures, often below freezing.
• High pressure develops over land, while low pressure develops over the seas, causing winds to move from land to sea.
• North-east monsoons, blowing over land, do not bring rainfall to most of India, but after gathering moisture over the Bay of Bengal, they bring rain to the east coast, especially Tamil Nadu.
• Some westerly disturbances from the Mediterranean bring scattered showers to north-western India and snowfall to areas in Jammu and Kashmir, Himachal Pradesh, and Uttarakhand.
• Cyclones in the Bay of Bengal affect the east coast and Bangladesh.
• Seasonal climatic patterns significantly impact daily lives, and influence local flora and fauna.

Vegetation of India

• Forests provide natural cover to animals, while animal waste nourishes forests.
• Natural vegetation develops without human interference.
• India has five major types of natural vegetation.

Tropical Evergreen Rainforests

• They are found in areas with over 200 cm of heavy rainfall, like the western slopes of the Western Ghats and parts of East and North-east India.
• Trees retain leaves throughout the year, remaining green and are known as evergreen forests.
• Hardwood trees are best for making furniture.
• Examples include mahogany, ebony, rubber, and rosewood, as well as bamboo and creepers.
• Evergreen forests also grow in saline coastal waters, forming mangrove thickets and tidal swamp forests.

Mangrove or Tidal Forests

• These forests grow in coastal regions where seawater mixes with fresh water.
• The vegetation is salt-tolerant.
• The sundari tree is commonly found in the Sunderbans, a UNESCO World Heritage Site.
• Mangrove forests are among the most productive and biodiverse wetlands.
• These forests include trees, shrubs, ferns, and palms.
• The largest mangrove forests are the Sunderbans in West Bengal.
• Examples include the Godavari, Mahanadi, Krishna and Kaveri Rivers, and the Andaman and Nicobar Islands.
• They are also located on some slopes of the Western Ghats.
• Freshwater swamp forests are found along the east Himalayan foothills.

Deciduous Monsoon Forests

• The most common natural vegetation in India is found in areas with 100-200 cm of annual rainfall.
• Trees shed leaves during the dry period, hence named deciduous.
• The vegetation becomes green again with the onset of monsoons.
• Examples of trees include teak, sal, shisham, mahua, and sandalwood.
• These forests are mainly found on the leeward slopes of the Western Ghats, the Shiwaliks, the Gangetic Plains, Odisha, Madhya Pradesh, Chhattisgarh, and Jharkhand.

Thorn and Scrub or Dry Forests

• Deciduous forests transition to grasslands and dry forests with less than 100 cm of rainfall.
• Grasslands with stunted trees of acacia and euphorbia grow in areas with 40-100 cm of rainfall.
• Only thorny scrubs and cacti are found in areas with rainfall below 40 cm.
• Practically nothing grows where rainfall is below 25 cm.
• Thorn forests have water-saving adaptations, such as long roots, leathery leaves, stunted growth, prickly thorns, and succulent stems.
• This type of vegetation is called xerophytic, or drought-resistant.
• These forests are found in eastern and western Rajasthan, the central Deccan Plateau, and parts of Gujarat and Madhya Pradesh.
• Kikar, babul and cacti are common, some plants have medicinal value.

Mountain Forests

• Temperature lowers in proportion to height.

Himalayan mountain forests:

• Tropical deciduous forests of mainly sal trees in the lower foothills (up to 1,000 m).
• Subtropical vegetation like walnut, chestnut, maple, elm, ash, birch, and poplar (up to 2,000 m).
• Coniferous trees like pine, cedar, deodar, and silver fir (from 2,000 m to 3,000 m).
• Alpine to sub-alpine grasses, mosses, and lichens (from 3,000 m to 5,000 m).
• The snowline is at 5,000 m, where the subsoil remains frozen, and nothing grows.
• The Himalayan areas (Assam to Kashmir) and higher hills in the Western Ghats have this vegetation type.
• They provide timber, gum, resins, herbs, lac, and honey, aid in soil protection, and are important for flood control.

Wildlife

• Indian forests provide habitat for many animals and birds.
• Human activities (clearing forests, cutting trees, land encroachment, and hunting) have led to species' extinction.
• Wet, dense tropical evergreen forests and deciduous forests of peninsular India, West Bengal, and Assam are home to tigers, elephants, wild buffaloes, wild boar, wolves, foxes, nilgai, hyenas, rhinoceros, deer, sloth bears, langurs, macaques, reptiles, and snakes.
• Grasslands house lions, leopards, deer, and antelope.
• Drier scrub and thorn forests provide habitats for camels and Asiatic wild asses.
• Snow leopards, Himalayan brown bears, blue sheep, and goral live in the higher Himalayan mountains.
• Many birds and insects (parrots, parakeets, wrens, bee-eaters, koels, swallows, sparrows, eagles, kites, vultures, and hawks) are common.
• Wildlife reserves help maintain ecological balance, so all species must be protected.
• The first week of October is observed as Wildlife Week to create general awareness.
• Strict government steps include establishing national parks and wildlife sanctuaries.
• India has 104 national parks, over 550 wildlife sanctuaries, and 51 tiger reserves.
• Project Tiger and Project Rhino protect tigers and rhinoceros.