What is Monsoon ?
* Due to land and sea breezes world experience 'seasonal winds'.
* Seasonal wind is known as Monsoon.
* Tropical Monsoon : On-shore wet monsoons on lands during summer and off-shore dry monsoon in the winter.
* Monsoon is seasonal winds which change in direction with change in season.
* In summer sea to land breezes and in winter land to sea breezes appears.
Origin of Word 'Monsoon' :
* The word monsoon has been derived from Arabic word Mausin. Mausin means season.
* Seasonal winds best develop in Indian subcontinent (in Asia - Southern Asia and South East Asia).
* Word Mausim pronounced as 'Mausam' in India and neighbouring countries.
* Sometimes weather of Indian subcontinent is unpredictable, because of it in layman language - kya mausam hai ! (What is Monsoon !).
Characteristics of Indian Monsoon (Indian Mausam) :
Annually, India experience for seasonal division but Indian monsoon occur in two divisions, they are -
1. The Southwest Monsoon Season : Most of the rainfall in India received from Southwest monsoon, which occurs in June to September. Winds move from southwest to north-east.
2. The Retreating Monsoon Season : Appear Clear skies, cool and dry season in the months of October and November are known as retreating monsoon. WinsW move from north-east to southwest.
* Formation of Southwest Monsoon :
+ Intense heating of land mass of Indian subcontinent (especially Tibetan plateau) during summer.
+ Formation of high pressure belt in the South Indian Ocean (east to north-east of Medagascar in Summer).
+ Formation of Southwest Monsoon in mid-June to September.
+ Heavy rainfall in Indian subcontinent.
* Influence Southwest Monsoon :
+ Orographic features.
+ The hot and dry season (march to mid-June) due to this low pressure created on Indian-subcontinent.
+ Subtropical jet stream (from west to east).
+ Tropical Easterly Jet stream (African Jet stream).
+ Formation of Indian Ocean Dipole.
+ Shifting of Inter Tropical Convergence Zone (ITCZ).
* Formation of Retreating Monsoon :
+ Rainfall decreasing after second week of September.
+ Rainy season gradually moving towards southward after mid September is known as retreating monsoon.
+ First withdrawal of Southwest monsoons in Punjab plain.
+ The skies are clear cool and dry season.
+ This will lead to form North East monsoon.
* Altitude : Temperature decrease with increasing height.
* Physiography : Himalaya protect from cold wave of Siberia. Most of the rainfall in India is Orographic.
* Western Disturbance : It cause rainfall mainly in Punjab, Haryana, western UP in winter.
* Pressure and Winds : It influence the Indians monsoon.
Some Primary Factors that affects Indian Monsoon :
* Latitude : India is region of tropical and subtropical part.* Altitude : Temperature decrease with increasing height.
* Physiography : Himalaya protect from cold wave of Siberia. Most of the rainfall in India is Orographic.
* Western Disturbance : It cause rainfall mainly in Punjab, Haryana, western UP in winter.
* Pressure and Winds : It influence the Indians monsoon.
Theory of Origin and Growth of Indian Monsoon :
* The origin of monsoon is still not well known.
The theory regarding origin and growth of monsoon have classify in Two types -
1. Classical Theory
2. Modern Theory
1. Classical Theory of Indian Monsoons :
+ Monsoon are mentioned in old scriptures like the Rig Veda as well as writing of Buddhist and Greek scholars.
+ The first credit for scientific study goes to Arab scholar Al-Masudi (a trader) in 10th century A.D.
+ Arab trader use the sea route to carry out trade with India and monsoon pattern were of prime importance for them.
+ He gave an account of the the reversal ocean currents and the monsoon winds over the North Indian Ocean.
His theory is based on Thermal concepts.
Summer Monsoon :
+ In summer the sun appear vertically over the Tropic of Cancer resulting in high temperature and low pressure in Central Asia.
+ The high pressure over Arabian Sea and Bay of Bengal. Hence winds flowed from Ocean towards landmass in summer.
+ This flow of winds bring heavy down pour to the Indian subcontinent.
Winter Monsoon :
+ In winter Sun appear vertically over the Tropic of Capricorn.
+ High pressure form over land and low pressure over ocean.
+ Winds will blow from land to sea.
Limitations : The monsoons do not develop equally everywhere on earth and the thermal concept of Halley fail to explain the difficulties of Monsoon such as the sudden burst of monsoons, delay in on set of monsoons sometimes, etc.
* Role of Himalaya - Himalaya act as mechanical barrier to the sub-tropical westerly Jet stream.
* Over ITCZ - cumulus nimbus cloud form and heavy rainfall.
* Shifting of ITCZ due to intense heating of Tibetan Plateau.
* El-Nino - It create drought like conditions in Indian subcontinent.
* La-Nina - appear flood like conditions in Indian subcontinent.
* Role of Indian Ocean Dipole.
* More than 60% of Indian agriculture depending on monsoons.
* Regional variations in monsoons help in growing diversity of crops.
* Differences in monsoons in India is reflected in vast variety of food, clothes and house types.
* Monsoon rain helps recharge dams, lake, and reservoirs.
* They help in generate hydro-electric power.
* To relief for drought area.
* Grow water intensive crops.
Limitations -
* It may be double edged sword problems like drought or flood.
* Extreme climate resulted as crop failure.
* Damage of crops - Farmer commit suicide e.g. in Maharashtra, MP, Telengana.
* Famine & starvation.
* Simultaneously presence of Southwest monsoon and western disturbances can cause cloudburst e.g. Kedarnath.
* Monsoon break can also cause heavy flooding in the rivers.
* Today's, IMD collects weather data like temperature, humidity, wind and precipitation through 679 automatic weather station, 550 surface Observatories, 43 radiosonde or weather balloons, 24 radars and three satellites.
* Indian Meteorological Department (IMD) predicted Southwest monsoon season (June to September) rainfall for the country as a whole in two stages. The first stage forecast is issued in April and 2nd stage forecost is issued in June.
According to Ministry of Earth Science Indian southwest monsoon in 2020 -
Southwest monsoon seasonal rainfall over the country likely to be normal.
In 2020, Conditions are favourable for further advance of Southwest Monsoon.
* Quantitatively, the monsoon seasonal (June to September) rainfall is likely to be 96% of the Long Period Average (LPA) with a model error of plus-minus 5%. The LPA of the season rainfall over the country as a whole for the period 1951-2000 is 89 cm.
* Weak El Nino conditions likely to prevail during the monsoon season with reduced intensity in the later part of the season.
* Strengthening of westerlies and increase in convective clouds, the Southwest monsoon has for the advancing in parts of South Bay of Bengal.
* Low pressure area over Westcentral Arabian Sea. It can move towards northwest northwest near South Oman & east Yemen coast in few days.
* Warning to fisherman.
The sea surface temperature (SST) conditions over the Pacific (El Nino/La Nina) and Indian Ocean (Indian Ocean Dipole-IOD) which are known to have a strong influence on Indian monsoon has been continuously monitored.
+ Monsoon are mentioned in old scriptures like the Rig Veda as well as writing of Buddhist and Greek scholars.
+ The first credit for scientific study goes to Arab scholar Al-Masudi (a trader) in 10th century A.D.
+ Arab trader use the sea route to carry out trade with India and monsoon pattern were of prime importance for them.
+ He gave an account of the the reversal ocean currents and the monsoon winds over the North Indian Ocean.
Classical Theory of Indian Monsoons : Sir Edmund Halley's Theory :
He gave Indian Monsoon theory in 1686.His theory is based on Thermal concepts.
Summer Monsoon :
+ In summer the sun appear vertically over the Tropic of Cancer resulting in high temperature and low pressure in Central Asia.
+ The high pressure over Arabian Sea and Bay of Bengal. Hence winds flowed from Ocean towards landmass in summer.
+ This flow of winds bring heavy down pour to the Indian subcontinent.
Winter Monsoon :
+ In winter Sun appear vertically over the Tropic of Capricorn.
+ High pressure form over land and low pressure over ocean.
+ Winds will blow from land to sea.
Limitations : The monsoons do not develop equally everywhere on earth and the thermal concept of Halley fail to explain the difficulties of Monsoon such as the sudden burst of monsoons, delay in on set of monsoons sometimes, etc.
Modern Theory of Indian Monsoons :
* Role of Inter Tropical Convergence Zone (ITCZ) - It meeting zone of southeast trade winds and northeast trade winds near the equator.* Role of Himalaya - Himalaya act as mechanical barrier to the sub-tropical westerly Jet stream.
* Over ITCZ - cumulus nimbus cloud form and heavy rainfall.
* Shifting of ITCZ due to intense heating of Tibetan Plateau.
* El-Nino - It create drought like conditions in Indian subcontinent.
* La-Nina - appear flood like conditions in Indian subcontinent.
* Role of Indian Ocean Dipole.
Impact of Monsoons on Life in India :
Benefits -* More than 60% of Indian agriculture depending on monsoons.
* Regional variations in monsoons help in growing diversity of crops.
* Differences in monsoons in India is reflected in vast variety of food, clothes and house types.
* Monsoon rain helps recharge dams, lake, and reservoirs.
* They help in generate hydro-electric power.
* To relief for drought area.
* Grow water intensive crops.
Limitations -
* It may be double edged sword problems like drought or flood.
* Extreme climate resulted as crop failure.
* Damage of crops - Farmer commit suicide e.g. in Maharashtra, MP, Telengana.
* Famine & starvation.
* Simultaneously presence of Southwest monsoon and western disturbances can cause cloudburst e.g. Kedarnath.
* Monsoon break can also cause heavy flooding in the rivers.
Weather Forecasts in India :
* Before the era of computer or technology IMD's (Indian Meteorological Department) forecasts depended only on snow cover. Lesser cover meant a better monsoon.* Today's, IMD collects weather data like temperature, humidity, wind and precipitation through 679 automatic weather station, 550 surface Observatories, 43 radiosonde or weather balloons, 24 radars and three satellites.
* Indian Meteorological Department (IMD) predicted Southwest monsoon season (June to September) rainfall for the country as a whole in two stages. The first stage forecast is issued in April and 2nd stage forecost is issued in June.
According to Ministry of Earth Science Indian southwest monsoon in 2020 -
Southwest monsoon seasonal rainfall over the country likely to be normal.
In 2020, Conditions are favourable for further advance of Southwest Monsoon.
* Quantitatively, the monsoon seasonal (June to September) rainfall is likely to be 96% of the Long Period Average (LPA) with a model error of plus-minus 5%. The LPA of the season rainfall over the country as a whole for the period 1951-2000 is 89 cm.
* Weak El Nino conditions likely to prevail during the monsoon season with reduced intensity in the later part of the season.
* Strengthening of westerlies and increase in convective clouds, the Southwest monsoon has for the advancing in parts of South Bay of Bengal.
* Low pressure area over Westcentral Arabian Sea. It can move towards northwest northwest near South Oman & east Yemen coast in few days.
* Warning to fisherman.
The sea surface temperature (SST) conditions over the Pacific (El Nino/La Nina) and Indian Ocean (Indian Ocean Dipole-IOD) which are known to have a strong influence on Indian monsoon has been continuously monitored.
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