El-Nino effect and cyclones

El Nino

• El Niño is the name given to the occasional development of warm ocean surface waters along the coast of Ecuador and Peru.
• When this warming occurs the usual upwelling of cold, nutrient rich deep ocean water is significantly
• El Niño normally occurs around Christmasand usually lasts for a few weeks to a few months.
• Sometimes an extremely warm event can develop that lasts for much longer time periods. In the 1990s, strong El Niños developed in 1991 and lasted until 1995, and from fall 1997 to spring 1998.

Normal Conditions

• In a normal year, a surface low pressuredevelops in the region of northern Australia and Indonesia and a high pressure system over the coast of Peru. As a result, the trade winds over the Pacific Ocean move strongly from east to west.
• The easterly flow of the trade winds carries warm surface waters westward, bringing convective storms (thunderstorms)to Indonesia and coastal Australia. Along the coast of Peru, cold bottom cold nutrient rich water wells up to the surface to replace the warm water that is pulled to the west.

Walker circulation (Occurs during Normal Years)

• The Walker circulation (walker cell) is caused by the pressure gradient force that results from a high pressure system over the eastern Pacific ocean, and a low pressure system over Indonesia.

This cross-section of the Pacific Ocean, along the equator, illustrates the pattern of atmospheric circulation typically found at the equatorial Pacific. Note the position of the thermocline.

• Thermocline== Noun a temperature gradient in a lake or other body of water, separating layers at different temperatures.
• The Walker cell is indirectly related to upwelling off the coasts of Peru and Ecuador. This brings nutrient-rich cold water to the surface, increasing fishing stocks.

During El Nino year

• In an El Niño year, air pressure drops over large areas of the central Pacific and along the coast of South America.
• The normal low pressure system is replaced by a weak high in the western Pacific (the southern oscillation). This change in pressure pattern causes the trade winds to be reduced == Weak Walker Cell. Sometimes Walker Cell might even get reversed.
• This reduction allows the equatorial counter current (current along doldrums)to accumulate warm ocean water along the coastlines of Peru and Ecuador.
• This accumulation of warm water causes the thermocline to drop in the eastern part of Pacific Ocean which cuts off the upwelling of cold deep ocean wateralong the coast of Peru.
• Climatically, the development of an El Niño brings drought to the western Pacific, rains to the equatorial coast of South America, and convective storms and hurricanes to the central Pacific.

This cross-section of the Pacific Ocean, along the equator, illustrates the pattern of atmospheric circulation that causes the formation of the El Niño.

• In the image above, we can see the presence of a strong El Niño event (October, 1997).

Effects of El Nino

• The warmer waters had a devastating effect on marine lifeexisting off the coast of Peru and Ecuador.
• Fish catches off the coast of South America were lower than in the normal year (Because there is no upwelling).
• Severe droughts occur in Australia, Indonesia, India and southern Africa.
• Heavy rains in California, Ecuador, and the Gulf of Mexico.

Normal Conditions

Eastern Pacific == Coast of Peru and Ecuador == Cold Ocean Water == Good for Fishing.

Western Pacific == Indonesia and Australia == Warm Ocean Water == Plenty of rains.

El Nino Condition

Eastern Pacific == Coast of Peru and Ecuador == Warm Ocean Water == Fishing Industry takes a hit.

Western Pacific == Indonesia and Australia == Cold Ocean Water == Drought.

How El Nino impacts monsoon rainfall in India

• El Nino and Indian monsoon are inversely related.
• The most prominent droughts in India – six of them – since 1871 have been El Nino droughts, including the recent ones in 2002 and 2009
• However, not all El Nino years led to a drought in India. For instance, 1997/98 was a strong El Nino year but there was no drought (Because of IOD).
• On the other hand, a moderate El Nino in 2002 resulted in one of the worst droughts.
• El Nino directly impacts India’s agrarian economy as it tends to lower the production of summer crops such as rice, sugarcane, Cotton and oilseeds.
• The ultimate impact is seen in the form of high Inflation and low gross domestic product Growth as agriculture contributes around 14 per cent to the Indian economy.

El Nino Southern Oscillation [ENSO]

• The formation of an El Niño [Circulation of Water]is linked with Pacific Ocean circulation pattern known as the southern oscillation [circulation of Atmospheric Pressure]
• Southern Oscillation, in Oceanography and Climatology, is a coherent inter-annual fluctuation of atmospheric pressureover the tropical Indo-Pacific region.
• El Nino and Southern Oscillation coincide most of the times hence their combination is called ENSO – El Nino Southern Oscillation.

Only El Nino == [Warm water in Eastern Pacific + Cold water in Western Pacific].

Only SO == [Low Pressure over Eastern Pacific + High Pressure over Western Pacific]

ENSO = [Warm water in Eastern Pacific + Low Pressure over Eastern Pacific] + [Cold water in Western Pacific + High Pressure over Western Pacific].

Southern Oscillation Index and Indian Monsoons

• SO is a see-saw pattern of meteorological changes observed between the Eastern Pacific and Western Pacific.
• When the pressure was high over equatorial Eastern Pacific, it was low over the equatorial Western Pacific and vice versa.
• The pattern of low and high pressures gives rise to vertical circulation along the equator with its rising limb over low pressure area and descending limb over high pressure area. This is known as Walker Circulation.
• The location of low pressure and hence the rising limb over Western Pacific is considered to be conductive to good monsoon rainfall in India.
• Its shifting eastwardfrom its normal position, such as in El Nino years, reduces monsoon rainfall in India.
• Due to the close association between an El Nino (E.N.) and the Southern Oscillation SO the two are jointly referred to as an ENSO event.
• The periodicity of SO is not fixed and its period varies from two to five years.
• Southern Oscillation Index (SOD) is used to measure the intensity of the Southern Oscillation.
• This is the difference in pressure between Tahiti in French Polynesia(Central Pacific), representing the Central Pacific Ocean and Port Darwin, in northern Australia representing the Eastern Pacific Ocean.
• The positive and negative values of the SOI i.e. Tahiti minus the Port Darwin pressure are pointers towards good or bad rainfall in India.

Indian Ocean Dipole effect (Not every El Nino year is same in India)

• Although ENSO was statistically effective in explaining several past droughts in India, in the recent decades the ENSO-Monsoon relationship seemed to weaken in the Indian subcontinent. For e.g. the 1997, strong ENSO failed to cause drought in India.
• However, it was later discovered that just like ENSO was an event in the Pacific Ocean, a similar seesaw ocean-Atmosphere system in the Indian Ocean was also at play. It was discovered in 1999 and named the Indian Ocean Dipole (IOD).
• The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperature between two areas(or poles, hence a dipole) – a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia.
• IOD develops in the equatorial region of Indian Ocean from April to May peaking in October.
• With a positive IODwinds over the Indian Ocean blow from east to west (from Bay of Bengal towards Arabian Sea). This results in the Arabian Sea (western Indian Ocean near African Coast) being much warmer and eastern Indian Ocean around Indonesia becoming colder and dry.
• In the negative dipole year (negative IOD), reverse happens making Indonesia much warmer and rainier.
• It was demonstrated that a positive IOD index often negated the effect of ENSO, resulting in increased Monsoon rains in several ENSO years like the 1983, 1994 and 1997.
• Further, it was shown that the two poles of the IOD – the eastern pole (around Indonesia) and the western pole (off the African coast) were independently and cumulatively affecting the quantity of rains for the Monsoon in the Indian subcontinent.
• Similar to ENSO, the atmospheric component of the IOD was later discovered and named as Equatorial Indian Ocean Oscillation [EQUINOO][Oscillation of warm water and atmospheric pressure between Bay of Bengal and Arabian Sea].

Impact on IOD on Cyclonogeneis in Northern Indian Ocean

• Positive IOD (Arabian Sea warmer than Bay of Bengal) results in more Cyclones-2/”>Cyclones than usual in Arabian Sea.
• Negative IOD results in stronger than usual cyclonogenesis (Formation of Tropical Cyclones) in Bay of Bengal. Cyclonogenesis in Arabian Sea is suppressed.

The El Niño Modoki

• El Niño Modoki is a coupled ocean-atmosphere phenomenon in the tropical Pacific.
• It is different from another coupled phenomenon in the tropical Pacific namely, El Niño.
• Conventional El Niño is characterized by strong anomalous warming in the eastern equatorial Pacific.
• Whereas, El Niño Modoki is associated with strong anomalous warming in the central tropical Pacific and cooling in the eastern and western tropical Pacific(see figure below).

El Niño Modoki Impacts

• The El Niño Modoki phenomenon is characterized by the anomalously warm central equatorial Pacific flanked by anomalously cool regions in both west and east.
• Such zonal gradients result in anomalous two-cell Walker Circulationover the tropical Pacific, with a wet region in the central Pacific.

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The El Niño–Southern Oscillation (ENSO) is a Climate pattern that occurs across the tropical Pacific Ocean every few years. It is characterized by changes in sea surface temperature, atmospheric pressure, and winds. El Niño and La Niña are the two phases of ENSO, and they can have a significant impact on weather patterns around the world.

El Niño is a warming of the waters in the eastern tropical Pacific Ocean. It occurs when trade winds weaken, allowing warm water to build up in the region. El Niño can cause changes in weather patterns around the world, including droughts in some areas and floods in others.

La Niña is a cooling of the waters in the eastern tropical Pacific Ocean. It occurs when trade winds strengthen, pushing warm water away from the coast and allowing cold water to upwell. La Niña can also cause changes in weather patterns around the world, including floods in some areas and droughts in others.

The Southern Oscillation Index (SOI) is a measure of the pressure difference between the western and eastern tropical Pacific Ocean. The SOI is used to track the El Niño–Southern Oscillation. When the SOI is positive, it indicates El Niño conditions. When the SOI is negative, it indicates La Niña conditions.

Tropical cyclones are intense storms that form over warm waters in the tropics. They are known by different names in different parts of the world, including hurricanes, typhoons, and cyclones. Tropical cyclones are fueled by warm, moist air that rises from the ocean surface. As the air rises, it cools and condenses, forming clouds and rain. The strong winds that circle the storm are caused by the difference in pressure between the center of the storm and the surrounding area.

Tropical cyclones can cause extensive damage to coastal areas. The strong winds can damage buildings and Infrastructure-2/”>INFRASTRUCTURE, and the heavy rains can cause flooding. Tropical cyclones can also cause deaths and injuries.

Storm surge is a rise in sea level that occurs when a Tropical Cyclone makes landfall. Storm surge is caused by the strong winds of the storm pushing water towards the coast. Storm surge can be several meters high, and it can cause extensive damage to coastal areas.

Flooding is a common hazard associated with tropical cyclones. The heavy rains that fall during a tropical cyclone can cause rivers and streams to overflow their banks, flooding low-lying areas. Flooding can also occur when storm surge inundates coastal areas.

Landslides are another hazard associated with tropical cyclones. The heavy rains that fall during a tropical cyclone can cause Soil to become saturated and unstable. This can lead to landslides, which can damage or destroy buildings and infrastructure.

Tsunamis are large waves that are caused by Earthquakes or volcanic eruptions. Tsunamis can travel at speeds of up to 800 kilometers per hour, and they can cause extensive damage when they reach land.

Drought is a period of time when there is an abnormally low amount of rainfall. Droughts can cause a number of problems, including crop failures, water shortages, and wildfires.

Heat waves are periods of time when the temperature is much higher than normal. Heat waves can cause a number of problems, including heat stroke, dehydration, and death.

Wildfires are uncontrolled fires that spread through forests, grasslands, and other areas. Wildfires can cause a number of problems, including damage to property, loss of life, and Air Pollution.

Disease outbreaks can occur during and after natural disasters. This is because natural disasters can disrupt water supplies, sanitation systems, and healthcare Services. This can make people more susceptible to diseases, such as cholera, typhoid, and malaria.

Natural disasters can have a significant impact on the economy. This is because they can damage infrastructure, disrupt businesses, and lead to job losses.

Natural disasters can also have a significant impact on people. This is because they can cause death, injury, and displacement. Natural disasters can also have a psychological impact on people, causing Stress, anxiety, and post-traumatic stress disorder.

Natural disasters can also have an environmental impact. This is because they can damage Ecosystems, pollute water supplies, and contribute to Climate Change.

What is a cyclone?

A cyclone is a large, rotating storm with low pressure at its center. The winds around the center of a cyclone blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Cyclones can form over warm ocean waters and can cause heavy rain, flooding, and high winds.

What are the different types of cyclones?

There are many different types of cyclones, but the most common are hurricanes, typhoons, and tropical storms. Hurricanes are the most powerful type of cyclone, with winds of at least 74 miles per hour. Typhoons are similar to hurricanes, but they form in the Pacific Ocean. Tropical storms have winds of at least 39 miles per hour, but they are not as powerful as hurricanes or typhoons.

How do cyclones form?

Cyclones form when warm, moist air rises from the ocean surface. As the air rises, it cools and condenses, forming clouds and rain. The rising air creates an area of low pressure at the surface, which draws in more warm, moist air from the ocean. This cycle of rising air and condensation continues to build the cyclone until it reaches its maximum strength.

What are the effects of cyclones?

Cyclones can cause extensive damage and loss of life. The high winds can damage or destroy buildings, trees, and other structures. The heavy rain can cause flooding, which can damage homes and businesses and make roads impassable. The storm surge, which is a rise in sea level caused by the cyclone, can inundate coastal areas and cause even more damage.

How can we prepare for cyclones?

The best way to prepare for a cyclone is to have a plan in place. This plan should include things like where you will go if you need to evacuate, what supplies you will need, and how you will communicate with your family and friends. You should also make sure that your home is in good condition and that you have a way to protect yourself from the high winds and rain.

What can we do to reduce the risk of cyclones?

There are a few things we can do to reduce the risk of cyclones. One is to reduce our emissions of greenhouse gases, which are causing the Earth’s atmosphere to warm. This warming is making the Oceans warmer, which is creating more conditions that are favorable for cyclone formation. We can also invest in better early warning systems and disaster preparedness measures. This will help us to save lives and reduce the damage caused by cyclones.

1. Which of the following is not a type of cyclone?
   (A) Tropical cyclone
   (B) Extratropical cyclone
   (C) Polar cyclone
   (D) El Niño

2. Which of the following is not a characteristic of a tropical cyclone?
   (A) A low-pressure system
   (B) Strong winds
   (C) Heavy rain
   (D) A warm core

3. Which of the following is not a characteristic of an extratropical cyclone?
   (A) A low-pressure system
   (B) Strong winds
   (C) Heavy rain
   (D) A cold core

4. Which of the following is not a characteristic of a polar cyclone?
   (A) A low-pressure system
   (B) Strong winds
   (C) Heavy snow
   (D) A warm core

5. Which of the following is not a factor that contributes to the formation of a tropical cyclone?
   (A) Warm ocean waters
   (B) High humidity
   (C) A lack of wind shear
   (D) The presence of an El Niño

6. Which of the following is not a factor that contributes to the formation of an extratropical cyclone?
   (A) Warm ocean waters
   (B) High humidity
   (C) A lack of wind shear
   (D) The presence of a cold front

7. Which of the following is not a factor that contributes to the formation of a polar cyclone?
   (A) Cold ocean waters
   (B) Low humidity
   (C) A lack of wind shear
   (D) The presence of a cold front

8. Which of the following is the most destructive type of cyclone?
   (A) Tropical cyclone
   (B) Extratropical cyclone
   (C) Polar cyclone

9. Which of the following is the most common type of cyclone?
   (A) Tropical cyclone
   (B) Extratropical cyclone
   (C) Polar cyclone

10. Which of the following is the least common type of cyclone?
    (A) Tropical cyclone
    (B) Extratropical cyclone
    (C) Polar cyclone