Climate of India

 Climate of India

image sources:https://en.wikipedia.org/wiki/Climate_of_India#/media/File:India_climatic_zone_map_en.svg

India’s climate is affected by two seasonal winds — 

• the northeast monsoon and 
• the south-west monsoon. 

The north-east monsoon commonly known as the winter monsoon blows from land to sea whereas the south-west monsoon known as the summer monsoon blows from sea to land after crossing the Indian Ocean, the Arabian Sea, and the Bay of Bengal. 

The southwest monsoon brings most of the rainfall during the year to the country. 

Tropical location, the presence of the Himalayas, and the Indian Ocean define the special characteristics of the Indian climate, but, it's broadly the tropical monsoon type. The region to the South of the Tropic of Cancer experiences a tropical climate, whereas the region of the North of the Tropic of Cancer experiences a warm temperate climate.

The Northern Himalayan Range separates India from the rest of India and hence, protects India from the bitterly cold and dry winds of Central Asia during winter. Moreover, it acts as a physical barrier for the rain-bearing South-West monsoon.

India's large size also has a significant impact on its climatic pattern, the areas near to the sea experience maritime climate, whereas the areas away from the sea experience continental climate.

Monsoon is the most dominating factor of Indian climate; it is the seasonal wind circulation, which completely reverses their directions of flow with the change in season.

The South-West summer monsoon from the Arabian Sea and the Bay of Bengal bring rainfall to the entire country. Besides, the North-East winter monsoon, traveling from land to sea causes rainfall along the Coromandal coast after getting moisture from the Bay of Bengal.

The Arabian branch of the monsoon is more powerful than the Bay of Bengal branch. The onset of monsoon takes place first in Andaman and Nicobar Island and in Kerala coast in the Mainland of India.

The tropical cyclones generated in the Arabian" Sea and Bay of Bengal during the South-West monsoon and the retreating monsoon seasons, influence the weather conditions of Peninsular India. The Eastern coast is more prone to tropical cyclone as the number of depressions originated in the Bay of Bengal is more as compared to that of in the Arabian Sea. On the Western coast, Gujarat and the Northern part of Maharashtra are more affected as compared to the Southern part. But during the period of El-Nino, the Modoki Western coast gets more cyclones than the eastern coast in India and during the El-Nino period, the Eastern coast gets unusually more cyclones.

Areas of very high rainfall:  

Areas receiving 200 cm and above rainfall include North-East of India and the Western coast from Thiruvananthapuram to Mumbai.

Areas of high rainfall:  

The areas receiving 100-200 cm include the Eastern slopes of Western Ghats, major parts of Northern Plain, and the East coast.

Areas of low rainfall: 

The areas receiving rainfall between 50-100 cm include a large part of Gujarat, Eastern Rajasthan, etc.

Areas of very low rainfall:  

Areas receiving rainfall below 50 cm, include arid and semi-arid areas of Western Rajasthan, Kutch, and most of the region of Ladakh, Jammu, and Kashmir.

• Indian Monsoons
• El Nino
• La Nina

Driving Mechanism

• The term monsoon has been derived from the Arabic word mausin or from the Malayan word monsin meaning ‘season’.
• Monsoons are seasonal winds (Rhythmic wind movements) (Periodic Winds) that reverse their direction with the change of season.
• The monsoon is a double system of seasonal winds – They flow from sea to land during the summer and from land to sea during winter.
• Some scholars tend to treat the monsoon winds as land and sea breeze on a large scale.
• Monsoons are peculiar to the Indian Subcontinent, South East Asia, parts of Central Western Africa, etc.
• They are more pronounced in the Indian Subcontinent compared to any other region.
• Indian Monsoons are Convection cells on a very large scale.
• They are periodic or secondary winds which seasonal reversal in wind direction.
• India receives southwest monsoon winds in summer and northeast monsoon winds in winter.
• South-west monsoons are formed due to the intense low-pressure system formed over the Tibetan plateau.
• North-east monsoons are associated with high-pressure cells over Tibetan and Siberian plateaus.
• South-west monsoons bring intense rainfall to most of the regions in India and north-east monsoons bring rainfall to the mainly south-eastern coast of India (Southern coast of Seem Andhra and the coast of Tamil Nadu.).
• Countries like India, Indonesia, Bangladesh, Myanmar, etc. receive most of the annual rainfall during the southwest monsoon season whereas southeast China, Japan, etc., during northeast rainfall season.

El Nino and La Nina

The Sea surface temperatures play a major role in global weather which influences two extreme phases of a naturally occurring climate cycle. I.e., El Nino/Southern Oscillation and La Nina. Both terms refer to large-scale changes in sea-surface temperature across the eastern tropical Pacific and the most powerful phenomenon of the Earth. These are best known for altering the climate across more than half of the planet that also impact weather patterns.

• El Nino and La Nina are complex weather patterns resulting from variations in ocean temperatures in the Equatorial Pacific Region. They are opposite phases of what is known as the El Nino-Southern Oscillation (ENSO) cycle.
  
  
• The ENSO cycle describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific.
• El Nino and La Nina episodes typically last nine to 12 months, but some prolonged events may last for years.
• El Nino is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean.
• It is the “warm phase” of a larger phenomenon called the El Nino-Southern Oscillation (ENSO).
• It occurs more frequently than La Nina.
• La Nina, the “cool phase” of ENSO, is a pattern that describes the unusual cooling of the tropical eastern Pacific.
• La Nina events may last between one and three years, unlike El Nino, which usually lasts no more than a year.
• Both phenomena tend to peak during the Northern Hemisphere winter.

El Nino and La Nina

El Nino and La Nina are complex weather patterns resulting from variations in ocean temperatures in the Equatorial Pacific Region. They are opposite phases of what is known as the El Nino-Southern Oscillation (ENSO) cycle.

• The ENSO cycle describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific.
• El Nino and La Nina episodes typically last nine to 12 months, but some prolonged events may last for years.

• El Nino is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean.
• It is the “warm phase” of a larger phenomenon called the El Nino-Southern Oscillation (ENSO).
• It occurs more frequently than La Nina.
• La Nina, the “cool phase” of ENSO, is a pattern that describes the unusual cooling of the tropical eastern Pacific.
• La Nina events may last between one and three years, unlike El Nino, which usually lasts no more than a year.
• Both phenomena tend to peak during the Northern Hemisphere winter.

El Nino

El Nino was first recognized by Peruvian fishermen off the coast of Peru as the appearance of unusually warm water.

• The Spanish immigrants called it El Nino, meaning “the little boy” in Spanish.
• El Nino soon came to describe irregular and intense climate changes rather than just the warming of coastal surface waters.
• The El Nino event is not a regular cycle, they are not predictable and occur irregularly at two- to seven-year intervals.
• The climatologists determined that El Nino occurs simultaneously with the Southern Oscillation.
• The Southern Oscillation is a change in air pressure over the tropical Pacific Ocean.
• When coastal waters become warmer in the eastern tropical Pacific (El Nino), the atmospheric pressure above the ocean decreases.
• Climatologists define these linked phenomena as El Nino-Southern Oscillation (ENSO).

Monitoring El Nino and La Nina

Scientists, governments, and non-governmental organizations (NGOs) collect data about El Nino using a number of technologies such as scientific buoys.

• A buoy is a type of object that floats in water and is used in the middle of the seas as locators or as warning points for ships. They are generally bright (fluorescent) in color.
• These buoys measure ocean and air temperatures, currents, winds, and humidity.
• The buoys transmit data daily to researchers and forecasters around the world enabling scientists to more accurately predict El Nino and visualize its development and impact around the globe.
• The Oceanic Nino Index (ONI) is used to measure deviations from normal sea surface temperatures.
  
  
• The intensity of El Nino events varies from weak temperature increases (about 4-5° F) with only moderate local effects on weather and climate to very strong increases (14-18° F) associated with worldwide climatic changes.

Impact of El Nino

In order to understand the concept of El Nino, it’s important to be familiar with non-El Nino conditions in the Pacific Ocean.

• Normally, strong trade winds blow westward across the tropical Pacific, the region of the Pacific Ocean located between the Tropic of Cancer and the Tropic of Capricorn.
• Impact on Ocean: El Nino also impacts ocean temperatures, the speed and strength of ocean currents, the health of coastal fisheries, and local weather from Australia to South America and beyond.
• Increased Rainfall: Convection above warmer surface waters brings increased precipitation.
• Rainfall increases drastically in South America, contributing to coastal flooding and erosion.
• Diseases caused by Floods and Droughts: Diseases thrive in communities devastated by natural hazards such as floods or droughts.
• El Nino-related flooding is associated with increases in cholera, dengue, and malaria in some parts of the world, while drought can lead to wildfires that create respiratory problems.
• Positive impact: It can sometimes have a positive impact too, for example, El Nino reduces the instances of hurricanes in the Atlantic.
• In South America: As El Nino brings rain to South America, it brings droughts to Indonesia and Australia.
• These droughts threaten the region’s water supplies, as reservoirs dry and rivers carry less water. Agriculture, which depends on water for irrigation, is also threatened.
• In Western Pacific: These winds push warm surface water towards the western Pacific, where it borders Asia and Australia.
• Due to the warm trade winds, the sea surface is normally about 0.5 meters higher and 4-5° F warmer in Indonesia than in Ecuador.
• The westward movement of warmer waters causes cooler waters to rise up towards the surface on the coasts of Ecuador, Peru, and Chile. This process is known as upwelling.
• Upwelling elevates cold, nutrient-rich water to the euphotic zone, the upper layer of the ocean.

La Nina

• La Nina means The Little Girl in Spanish. It is also sometimes called El Viejo, anti-El Nino, or simply "a cold event."
• La Nina events represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific.
• It is indicated by sea-surface temperature decreased by more than 0.9℉ for at least five successive three-month seasons.
• La Nina event is observed when the water temperature in the Eastern Pacific gets comparatively colder than normal, as a consequence of which, there is a strong high pressure over the eastern equatorial Pacific.

Impact of La Nina

• Europe: In Europe, El Nino reduces the number of autumnal hurricanes.
• La Nina tends to lead to milder winters in Northern Europe (especially UK) and colder winters in southern/western Europe leading to snow in the Mediterranean region.
• North America: It is continental North America where most of these conditions are felt. The wider effects include:
• Stronger winds along the equatorial region, especially in the Pacific.
• Favorable conditions for hurricanes in the Caribbean and central Atlantic area.
• Greater instances of tornados in various states of the US.
• South America: La Nina causes drought in the South American countries of Peru and Ecuador.
• It usually has a positive impact on the fishing industry of western South America.
• Western Pacific: In the western Pacific, La Nina increases the potential for landfall in those areas most vulnerable to their effects, and especially into continental Asia and China.
• It also leads to heavy floods in Australia.
• There are increased temperatures in Western Pacific, Indian Ocean, and off the Somalian coast.

Impact of El Nino and La Nina on Indian Weather

1. El Nino during winter causes warm conditions over the Indian subcontinent and during summer, it leads to dry conditions and deficient monsoon. Whereas La Nina results in better than normal monsoon in India.
2. India experienced deficient rainfall during El Nino years 2002 and 2009 whereas monsoon was normal during El Nino years 1994 and 1997. It means that in about 50 percent of the year with El Nino during summer, India experienced droughts during monsoon.
3. Crops like Paddy, Maize, Groundnut, Guar, Castor, Tur, Moong, and Bajra would suffer due to El Nino.
4. El Nino: Strong El Nino events contribute to weaker monsoons and even droughts in India Southeast Asia.
5. La Nina: The cold air occupies a larger part of India than the El Nino cold air.
6. It usually brings in colder than normal winters in India.
7. La Nina influences the Indian subcontinent by piping in cold air from Siberia and South China, which interacts with the tropical heating to produce a north-south low-pressure system.
8. The cold air of La Nina associated with this north-south through tends to extend much further south into India.
9. This is remarkably different from the more northwest-southeast blast of cold air associated with El Nino.
10. The pressure pattern going north-south means a lesser impact of western disturbances.
11. The cold temperature can go down as far as Tamil Nadu, but may not affect the North East that much.