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Introduction

  • The word monsoon originated from “Mausim” which means “Weather”
  • Monsoon can be defined as a wind that operates at a level of 20 kilometers from the earth’s surface. It can be characterized by the wind reversal according to seasonal change at regular intervals
  • There are an array of factors that heavily influence the monsoons. These rains only cover the South part of the world, including countries like Sri Lanka, India, Bhutan, Bangladesh, and Southeast Asia
  • There are various factors that influence the climate of India. One of which is Indian monsoons. The continental nature provided by the Himalayas can be recognized by dry air, land winds, rainfall scanty, and diurnal range. At the same time, the tropical character is contributed by the Indian Ocean to the Indian climate. Along with the monsoons, the Indian climate is majorly influenced by two more factors due to frequent rainfalls and damp air
  • When compared to the rest of Asia, there is a considerable difference in the Indian monsoon system

Classical Theory of Indian Monsoon

  • As per the Classical Theory, the leading cause of the difference in the Indian monsoonal order is the heating of the sea and the land when the sun faces the north
  • Factors affecting Indian monsoon are responsible for the robust development of monsoons are their size as the adjacent seas, and the Indian subcontinent is highly vast. Meteorological significance is the second on the list
  • The Himalayas have high mountain chains, which add borders to the subcontinent and acts as a motor as well as breaks at the same time
  • Hydrodynamic effects were caused by the mighty Himalayas that characterize precipitation in India
  • According to the thermal concept, the sun shifts northward, especially after the Spring Equinox. Due to this, the tropics and the sub-tropics acquire high solar radiation
  • Its effects are pretty evident on the Indian subcontinent and are often seen in extreme heat conditions in the northern plains
  • From the adjoining areas, the wind is attracted by the low-pressure zones. Though it started slow, it reached its peak during May and June. Along with the process and helping this pull of wind patterns is the development of a few high-pressure centers in the Indian Ocean, Arabian Sea, and over Australia (it is the winter season)
  • The winds that are prevalent to the south are the southeast trade winds blowing from the southeast to the northwest. Due to the regular earth rotation, the shift in the wind occurs. During monsoons, the southwest monsoons are initially the southeast trade winds coming from the northeast
  • During this time, the ITCZ or the Inter-Tropical Convergence Zone starts to move towards the north. This is the theoretical line where the Southern Hemisphere’s southeast trade winds and the Northern Hemisphere’s northeast trade winds meet. The southwest winds blow ABOVE THE Indian Ocean
  • During this trip, these winds carry a lot of moisture to the extent that when they reach India, they are full and over-saturated, which leads to southwest monsoons. Since these winds carry huge amounts of moisture, the windward side experiences heavy rainfall 

Why is there no Precipitation in Western Rajasthan and Kutch?

  • Since the areas like Kutch and Western Rajasthan do not have any mountain barrier, there is no way to trap the advancing winds. Due to the north-south axis of the Aravallis, there is no way they can block these monsoon currents and uplift them
  • As the desert conditions already prevail in western Rajasthan and Kutch, conditions like these are suitable for precipitation

Bay of Bengal Branch

  • When the monsoon currents reach Myanmar’s Coast in the Arabian Sea branch, Myanmar’s West Coast Mountains and India’s the Western Ghats receive adequate rainfall
  • The rain takes place when the northern branch strikes the Khasi Hills in Meghalaya. Over the years, it is recorded, Mawsynram, a place located on the southern slopes of the Khasi hills, receives the highest annual rainfall around the world due to its peculiar location
  • The place is surrounded by Khasi, Garo, and Jaintia hills from all three sides except a narrow gap for the rain-bearing winds to enter, which leads to heavy rainfall. Shillong is only 40 km away from the Khasi hills and receives an average of only 140 cm of rain in the months of June and September
  • The other current of the Bay of Bengal leads to rainfall on the northern plains. After reaching the Bengal delta, it travels in the southeast to northwest direction due to the influence of the Himalayas
  • The westerly disturbances can be defined when the northern plains rainfall is served by cyclonic depression; it is referred to as “Westerly Disturbances” 
  • The rainfall intensity slows down from north to south and east to west in the northern plains. The decrease in westwards is proportional to the increasing distance from the source of the moisture; as the distance between the mountains increases, the intensity of the rainfall from north to south decreases. These mountains are responsible for holding the moisture-packed winds leading to adequate moisture in plains

North-East Monsoons or Retreating

  • The northwest low-pressure center travels to the equatorial region at the end of September. The anticyclonic conditions restore the cyclonic conditions. This is why the winds start to blow away from the northern region
  • At this point, the sun moves to the south of the equator. Here the winds that are blowing from northeast to the southwest are the winds that dominate the sub-continental landscape
  • These conditions are known as the retreating monsoons, which start from October and continue till mid-December. After mid-December, India witnessed zero monsoons
  • These monsoons carry moisture with them which gets released in some parts of Odisha, Karnataka, and Tamil Nadu in the months of October and November. During these months, the southward Coast receives ample rainfall

Winter Rainfall due to Western Disturbance

  • The stable and dry winds residing on the subcontinent do not cause precipitation as there is no moisture present. Inside, these winds lead to dry weather. However, there are certain areas in the north that receive rainfall even during winters
  • The north-western parts of India, Punjab and Ganga plains are invaded by shallow cyclonic disturbances moving from west to east and having their origin in the Mediterranean Sea. These are called “Westerly Disturbances,” which cross West Asia and Afghanistan before they reach India. These disturbances come with cloudiness as well as rising temperature in the front and cold wind in the rear
  • Due to westerly disturbances, places like Kashmir, Punjab, and Uttar Pradesh experience 2.5 centimeters of rainfall during winters. These rains are suitable for the Rabi crop

El Nino/La Nina (ENSO) and Monsoons

  • The temperature of the sea plays a significant role in global weather. These heavily influence the 2 phases of the climate cycle, including La Nina and El Nino/Southern Oscillation
  • When the temperature of the sea surface changes drastically, it refers to La Nina and El Nino/Southern Oscillation
  • This alters more than half of the planet’s climate, which changes the weather patterns
  • The El Nino phenomenon can be defined as a warm ocean current flowing from the Peruvian Coast every 2 to 5 years rather than the cold Peruvian current. Since the water of the Pacific is warmer, it might affect the winds in various ways. This takes place only when the wind pattern is abnormal
  • As the Warmer surface waters increase, it leads to adequate precipitation (sometimes above the natural level) in South America and gives rise to drought conditions in Australia and Indonesia
  • Due to this wind pattern, the weather changes its course. The winters are warmer, and there’s not enough rainfall. In many cases, it also brings the condition of drought
  • La Nina or the opposite of an El Nino. This condition appears when the water in the Pacific is way colder, and winds start to blow strongly
  • Together, El Nino and La Nina are an integral part of the ocean’s atmosphere system, referred to as the ENSO cycle or the El NinoSouthern Oscillation
  • El Nino shows adverse effects on the weather and mostly favors tropical storms and eastern Pacific hurricanes
  • It recorded untimely rainfall in Chile, Ecuador, and Peru, which takes place due to the change in the climatic conditions
  • El Nino minimizes the uplift of the ocean’s nutrient content from the bottom and the upwelling of cold water. This upsets seabirds and marine life. Also, the fishing industry has witnessed its effects
  • El Nino drought can affect India, southern Africa, Australia, the Pacific Islands, and Southeast Asia. Countries depending upon agriculture are highly affected
  • WHO highlighted the major EI Nino health issues, including the rapid rise in borne diseases, especially in South and Central America. Also, the prevalence of malaria in India is linked to El Nino
  • El Nino adversely affects the monsoons. As the wind pattern changes, the rainfall declines, leading to weak monsoon winds that often lead to drought conditions. These conditions are highly harmful to India, where people heavily depend on the agriculture industry

Conclusion

India gets around 70 percent of its annual rainfall in the monsoon season, which also affects the yield of some key kharif or summer crops like rice, pulses and oilseeds such as soybeans respectively. Farmers start planting these crops with the arrival of monsoon rains in June.The most prominent of the world’s monsoon systems is Indian Monsoon, which primarily affects India and its surrounding water bodies. It blows from the northeast during cooler months and reverses its direction to blow from the southwest during the warmest months of the year.