Category: Geography

With the El Nino phenomenon expected to have an impact on the Indian monsoon this year, there is growing confidence about the emergence of a positive Indian Ocean Dipole (IOD) and its ability to counteract El Nino’s consequences. The Indian Ocean Dipole (IOD), a weaker ocean-atmosphere interaction in the Indian Ocean, has had minimal repercussions in the past but has the potential to mitigate the negative effects of El Nino, particularly in nearby regions.

The Indian Ocean Dipole (IOD) and El Nino are now inactive

IOD:

• The IOD is now in a state of neutrality. This means that there is no considerable temperature difference around the equator between the western and eastern sides of the Indian Ocean.
• However, international climate models indicate that a positive IOD event may occur in the next months.
• According to the India Meteorological Department (IMD), there is an 80% possibility of a positive IOD during the June-August 2023 season. A positive IOD would have ramifications for weather patterns in the Indian Ocean region.

El Nino:

• This year, El Nino has already established itself in the Pacific Ocean. El Nino occurs when the prevailing wind systems weaken, resulting in less warm water displacement in the eastern Pacific.
• This unusual warming of the eastern Pacific has the potential to affect global weather patterns, especially the Indian monsoon. El Nino’s presence raises concerns about its potential impact on Indian monsoon rains.

The interaction between the El Nino Southern Oscillation (ENSO) and the IOD Triggering Mechanism:

• ENSO occurrences, particularly El Nino, can cause a positive IOD to develop in the Indian Ocean.
• External Drivers: While external influences like as ENSO can cause IOD events in some situations, there is evidence that IOD events can also occur as a result of local circulations or subsurface processes in the equatorial Indian Ocean.
• Internal Dynamics: Even when sparked by external forces, IOD events evolve and mature predominantly through internal dynamics. They have the potential to live independently and influence weather patterns in the Indian Ocean region.
• Influence on IOD: During El Nino, the Pacific side of Indonesia is cooler than usual, which influences the Indian Ocean side, resulting in the formation of a positive IOD.
• Mutual Interaction: When both occurrences are strong, the circulation patterns of IOD and ENSO can have an impact on each other. The interaction of the two events can have an effect on the intensity and duration of each occurrence.
• Positive IOD occurrences are frequently related with El Nino, whilst negative IOD events are sometimes associated with La Nina. This link, however, is not absolute, and IOD events can occur independently or with alternative associations depending on the circumstances.
• Strong IOD and ENSO occurrences can have combined effects on weather patterns because their circulation patterns interact and influence one another.

The effects of the Indian Ocean Dipole Rainfall Distribution:

• The IOD has a substantial impact on rainfall patterns in the Indian Ocean region. During a positive IOD, convection and rainfall rise along the African coastline and over the Indian subcontinent. A negative IOD, on the other hand, results in reduced rainfall in these areas.
• Drought and Floods: Positive IOD events can provide above-average rainfall to impacted areas, alleviating drought and replenishing water resources. However, increasing rainfall can cause flooding and other water-related calamities in some locations.
• Agricultural Productivity: IOD has ramifications for agriculture since it impacts rainfall availability and distribution. Positive IOD events can boost agricultural output in impacted areas, however negative IOD events can result in lower crop yields and agricultural issues.
• Fisheries: IOD has an impact on marine ecosystem productivity. Increased upwelling of nutrient-rich waters occurs during positive IOD, which encourages higher fish stocks and improves fisheries. Negative IOD, on the other hand, can disrupt the marine food chain and have an influence on fish populations.
• IOD influences sea surface temperatures, and sustained positive IOD events can contribute to higher sea surface temperatures in impacted areas. This can cause coral bleaching, which harms coral reefs and marine biodiversity.
• Indian Monsoon: The intensity and spread of the Indian monsoon rainfall can be influenced by IOD. Positive IOD events are typically connected with increased monsoon rainfall over the Indian subcontinent, whereas negative IOD events might result in decreased monsoon rainfall.
• Weather Extremes: IOD can contribute to the occurrence of extreme weather events in the Indian Ocean region, such as heatwaves, storms, and tropical cyclones.
• Economic and social consequences: The effects of IOD on rainfall, agriculture, fisheries, and other industries have immediate economic and social consequences. These consequences can have an influence on livelihoods, water availability, food security, and overall economic development in the impacted areas.

El Nino’s Effects on the Indian Monsoon

• Weakening Monsoon Winds: The trade winds that blow from the east across the Indian Ocean diminish during El Nino. These winds are in charge of transporting moisture-laden air to the Indian subcontinent, facilitating monsoon rainfall. Weakening winds restrict the supply of moisture, resulting in less rainfall.
• Delayed Onset: El Nino might cause the Indian monsoon to arrive later than usual. The monsoon season typically begins in June in India, although during El Nino years, the arrival of the monsoon may be delayed, resulting in a late start to the rainy season.
• El Nino events cause below-average rainfall in India due to reduced moisture transport and altered atmospheric circulation. Regional variations exist, with central and northern regions more susceptible to below-average rainfall, while southern areas may experience near-normal or above-normal rainfall.
• El Nino-induced rainfall deficiency causes drought, affecting agriculture, water availability, and livelihoods. Increased temperatures during monsoon season in India cause heatwaves, health risks, and impacts human well-being.

Conclusion

The Indian Ocean Current (IOD) has limited ability to counter El Nino’s effects, but a positive IOD event could be expected in the coming months. Past strong IOD events have shown IOD’s potential in compensating for monsoon rainfall deficits.

Source: https://indianexpress.com/article/explained/explained-climate/indian-ocean-dipole-what-is-it-how-it-can-limit-el-nino-effects-8689360/

• For people living north of the Equator, the summer solstice, often known as the longest day of the year, comes on June 21st.
• This article delves into the meaning of the summer solstice, the causes for its existence, and the affects it has on various parts of the world.

What exactly is the Summer Solstice?

• The summer solstice occurs when the Earth’s axial tilt is greatest inclined towards the Sun.
• It happens every year on or around June 21st in the Northern Hemisphere.
• The Sun takes its highest and longest trip across the sky at the summer solstice.
• As a result, the daytime hours are prolonged, making it the longest day of the year.

Summer Solstice Influencing Factors

• The Axial Tilt of the Earth: The Earth’s axis is tilted at an angle of around 23.5 degrees relative to its orbit around the Sun.
• The summer solstice occurs when the Sun is directly over the Tropic of Cancer, which is located at 23.5 degrees north latitude.
• Seasonal Changes: Because of the tilt of the Earth’s axis, various latitudes receive varied quantities of sunlight throughout the year.

The Distribution of Sunlight in the Hemispheres

• The Northern Hemisphere receives the most sunlight during the summer solstice, which occurs on June 20, 21, or 22.
• The Southern Hemisphere, on the other hand, experiences its highest sunshine on the winter solstice, which falls on December 21, 22, or 23.

Celebrations and Cultural Importance

• Throughout history, the summer solstice has had cultural and religious significance in numerous civilizations.
• This celestial event is frequently commemorated through festivals and ceremonies, symbolising the triumph of light and fertility.
• Festivals, bonfires, music, dancing, and outdoor activities are held all around the world to commemorate the summer solstice.
• The Summer Solstice Stonehenge Festival in England and the Midnight Sun Festival in Norway are two notable festivities.

Source: https://economictimes.indiatimes.com/news/international/us/why-jun-21-is-years-longest-day-what-is-summer-solstice/articleshow/101166962.cms

• Monsoon Delay: Any discussion of the Indian monsoon delay these days must include mention of the El Nino phenomenon.
• El Nino’s unexpected rise: This year’s monsoon is also moving under the shadow of an El Nino in the Pacific.

El Nino and La Nina: What You Need to Know

• The El Nino and La Nina phases of the El Nino-Southern Oscillation (ENSO) cycle are diametrically opposed.
• ENSO is a naturally occurring occurrence in the equatorial Pacific that involves the interplay of the ocean and atmosphere.

A full comparison between El Nino and La Nina is provided below:

	El Nino	La Nina
Definition	Warmer-than-normal sea surface temperatures	Cooler-than-normal sea surface temperatures
Frequency	Every two to seven years	Every two to seven years
Duration	Several months to a year or more	Several months to a year or more
Impact on winds	Weakens trade winds, leading to changes in patterns	Strengthens trade winds, leading to changes in patterns
Impact on rains	Reduces rainfall and can cause droughts	Increases rainfall and can cause flooding
Impact on temp.	Warmer-than-average temperatures	Colder-than-average temperatures
Global effects	Droughts in Asia and Africa, floods in Americas	Floods in Asia and Africa, droughts in South America

Impact on India

El Nino	La Nina
Associated with weak monsoons and drought-like conditions in India	Associated with above-normal rainfall and floods in India
Sea surface temperature in the equatorial Pacific Ocean rises above normal levels	Sea surface temperature in the equatorial Pacific Ocean drops below normal levels
Changes in the atmospheric circulation patterns	Changes in the atmospheric circulation patterns
Shift in the location of the jet stream, affecting the strength and direction of the monsoon winds	Increase in the strength of the monsoon winds, bringing more moisture and rainfall to India
Results in reduced rainfall, dry spells, and heatwaves, leading to crop failures and water scarcity	Excessive rainfall can also lead to floods and landslides, causing damage to crops and infrastructure

El Nino and Indian Monsoon

• El Nino and its impact on Indian monsoon: El Nino refers to abnormal warming of surface waters in the equatorial Pacific Ocean, which tends to suppress monsoon rainfall in India.
• El Nino weather patterns Southern Oscillation (ENSO): In the Pacific Ocean, ENSO has three phases: El Nino, La Nina (excessive cooling), and a neutral phase with sea surface temperatures close to long-term averages.
• ENSO includes not just temperature anomalies in sea surface waters, but also atmospheric factors such as changes in sea-level air pressure and wind strength and direction.
• Southern oscillation and the effect of winds: The Southern Oscillation Index monitors the difference in sea-level air pressure between the western and eastern Pacific Oceans, whereas wind patterns play an important influence in ENSO.

El Nino precipitating factors

• Weakening trade winds: When trade winds in the tropical Pacific weaken, it contributes to El Nino by slowing the migration of warm surface waters.
• Changes in ocean current patterns: Changes in ocean current patterns can cause El Nino episodes because they impact the distribution and buildup of warm water in the central and eastern Pacific.
• Changes in atmospheric pressure: Fluctuations in atmospheric pressure patterns disturb the regular circulation associated with trade winds, causing El Nino conditions to develop.
• The presence and behaviour of oceanic Kelvin waves, large-scale waves that transfer warm water eastward, influence the genesis and intensification of El Nino occurrences.
• Interactions with other climatic modes: El Nino can be influenced by interactions and connections with other climate phenomena such as the Indian Ocean Dipole and the Madden-Julian Oscillation, both of which can affect oceanic and atmospheric conditions in the Pacific region.

Measuring the Cycle

(1) Oceanic Nino Index (ONI)

• The oceanic component of the El Nino Southern Oscillation (ENSO) is measured.
• The deviation from average sea surface temperatures in the tropical Pacific Ocean is tracked.
• It assists in quantifying the intensity and length of El Nino and La Nina occurrences.
• A rolling three-month average of sea surface temperature anomalies in certain regions is typically used.

(2) Southern Oscillation Index (SOI)

• ENSO’s atmospheric component is measured.
• The difference in air pressure between Tahiti and Darwin is calculated.
• Positive SOI levels imply that pressure is higher in the eastern Pacific and lower in the western Pacific.
• Negative SOI levels imply that pressure is lower in the eastern Pacific and higher in the western Pacific.
• Reflects the strength and changes in ENSO-related atmospheric circulation patterns.
• The phase and strength of ENSO, as well as its impact on global weather and climate patterns, are assessed.

El Nino’s Economic Impact on Indian Agriculture

• Drought and reduced rainfall: El Nino occurrences frequently result in below-average monsoon rainfall in India, causing drought conditions in various places.
• Crop failure and lower yields: Crop failure or lower yields for major crops such as rice, wheat, pulses, and oilseeds can occur due to a lack of adequate water availability.
• Increased input costs: During El Nino-induced droughts, farmers may need to spend in more irrigation, water management, and supplementary livestock feeding, resulting in higher input costs.
• Price changes: Because of El Nino, crop production may be reduced, causing price swings and potential inflation in food costs.
• Water scarcity and changes in marine habitats can have a severe impact on animal husbandry and fishing activities, hurting the lives of individuals who rely on these industries.
• Rural livelihoods and migration: Economic hardship can have an impact on rural livelihoods, causing more people to migrate from rural to urban regions in pursuit of alternative employment options.

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Source: https://indianexpress.com/article/explained/explained-climate/what-is-el-nino-and-how-it-impacts-the-monsoon-8661546/#:~:text=El%20Nino%2C%20as%20is%20commonly,to%20aid%20rainfall%20over%20India.

• Dnipro River Dam Breach: A Soviet-era Kakhovka Dam on the Dnipro River in southern Ukraine was burst, causing flooding to spread over the battle zone.
• Conflicting Accounts: Ukraine accused Russia of destroying the dam, but Russian officials offered conflicting explanations, pointing to Ukrainian bombardment or previous damage as possible causes.

The Kakhovka Dam

• It was completed in 1956 as part of the Khakhovka hydroelectric power project, and has a height of 30 metres (98 feet) and a length of 3.2 kilometres (2 miles).
• Water Supply: The dam’s reservoir provides water to the Crimean peninsula, which Russia has claimed since 2014, as well as the Zaporizhzhia nuclear power station, which is also under Russian control.
• Reservoir Capacity: The reservoir holds approximately 18 cubic kilometres of water, which is comparable in capacity to Utah’s Great Salt Lake.

Reports on the Dam Breach

• Ukrainian Accusations: Ukraine blamed Russia, claiming the dam was damaged by “Russian terrorists” and accused Russian occupation forces of the crime.
• Russian Claims: Russian-installed officials provided contradictory stories, with some blaming Ukraine for shelling the dam and others claiming the dam broke owing to pre-existing damage and water pressure.

Evacuations and Human Impact

• Potential Flooding: The rise in flood levels poses a considerable risk, with thousands of individuals in the impacted areas potentially affected.
• Evacuations: Evacuation activities began on both sides of the front line to protect civilian safety.
• At Risk Population: Russian-installed officials said 22,000 people in 14 settlements in Ukraine’s southern Kherson region were at risk of flooding, while the Ukrainian Prime Minister said up to 80 settlements were at risk.

Impact on Crimea

• Concerns regarding water levels in the North Crimea Canal, which feeds fresh water to the Crimean peninsula from the Dnipro River, have been raised as a result of the dam break.
• Dependence on the Canal: Crimea relies on the canal for fresh water, and its earlier closure by Ukraine following the 2014 takeover resulted in regional water shortages.
• Potential Consequences: Reduced water levels in the canal could have serious consequences for Crimea’s water supply.

Other hotspots under concern include:

• Zaporizhzhia Nuclear Power Plant Cooling Water Source: The reservoir serves as a source of cooling water for Europe’s largest nuclear power plant.
• Russian Control: The factory is located on the conflict zone’s southern edge, which is currently under Russian control.
• Assurance of Nuclear Safety: The International Atomic Energy Agency declared that there was no immediate threat to nuclear safety at the Zaporizhzhia Nuclear Power Plant, and Russia’s official nuclear energy organisation confirmed that the plant was safe.

Source: https://www.theguardian.com/world/2023/jun/06/visual-guide-collapse-ukraine-nova-kakhovka-dam

The Palghat (Palakkad) Gap, a key corridor in India’s Western Ghats, is discussed in this article. It tells us about the geological genesis of the gap.

What exactly is the Palghat Gap?

• The Palghat Gap is a 40-kilometer-long corridor in the Western Ghats famed for its steep hills that serves as a doorway to Kerala.
• It is a vital link for roads and trains between Coimbatore and Palakkad.
• The Palghat Gap is crossed by the Bharathappuzha River.
• The vegetation in the gap is described as dry evergreen forest, as opposed to the Western Ghats’ tropical rainforests.
• The Palghat Gap marks a unique split in the region’s flora and fauna.

Geological origin of the Palghat Gap

• The Palghat Gap is a geological shear zone running from east to west.
• Shear zones are weak areas in the Earth’s crust that cause tremors in the Coimbatore area on occasion.
• The Palghat Gap formed when the continental shelf changed following the separation of Australia and Africa from the Gondwana landmass.
• India and Madagascar were once connected until volcanic activity caused their separation, with a similar gap in Madagascar known as the Ranotsara Gap.

Ancient history and biogeographic differences

• The biogeographic differences in species found north and south of the Palghat Gap could be linked to an old river or a sea intrusion in the distant past.
• Elephant populations on the Nilgiris side of the gap have mitochondrial DNA that differs from elephant populations in the Anamalai and Periyar sanctuaries.
• DNA research of the White-bellied Shortwing, an endemic bird species, reveals population divergence in the Nilgiris and Anamalai regions.

South of the Palghat Gap, biodiversity

• The southern Western Ghats region, south of the Palghat Gap, has a high species richness and phylogenetic diversity.
• A recent study found over 450 tree species, including 130 million-year-old species like Magnolia champaca.
• The southern Western Ghats’ warm temperature and moist air support a varied spectrum of species, making it an island haven throughout ice ages and droughts.
• In comparison to the northern part, the southern Western Ghats receive more equally distributed rainfall throughout the year.

Source: https://www.thehindu.com/sci-tech/science/a-break-in-the-western-ghats/article66845725.ece#:~:text=Often%20called%20as%20a%20significant,into%20the%20State%20of%20Kerala.