El-Nino & La-Nina

• El Niño is a meteorological phenomenon characterized by the abnormal warming of surface waters in the eastern tropical Pacific Ocean. 
• It occurs more frequently than La Niña.
• Fishermen along the coast of Peru recognize El Niño when they observe unusually warm water conditions. 
• El Niño does not follow a regular or predictable cycle, unlike ocean tides.       

INTRODUCTION

• El Niño was initially observed off the coast of Peru by Peruvian fishermen who noticed the presence of unusually warm water. 
• The term "El Niño," meaning "the little boy" in Spanish, was coined by Spanish immigrants.
• Over time, El Niño expanded beyond its original definition of warming coastal surface waters to signify erratic and extreme climatic changes. 
• These events are not part of a regular cycle; rather, they occur unpredictably at intervals ranging from two to seven years.
• Climate scientists have identified a correlation between El Niño events and the Southern Oscillation, which involves a shift in atmospheric pressure across the tropical Pacific Ocean. 
• Specifically, when the coastal waters of the eastern tropical Pacific warm during El Niño, the air pressure over the ocean decreases. 
• The interconnected processes of El Niño and the Southern Oscillation are collectively referred to as the El Niño-Southern Oscillation (ENSO).

El Niño - Formation

• During an El Niño year, there is a widespread decrease in air pressure across the central Pacific and along the South American coast. 
• In the western Pacific, a weak high-pressure system replaces the typical low-pressure system. 
• This shift in pressure patterns leads to a reduction in the strength of the Walker Cell trade winds and, at times, a reversal of the Walker Cell.
• As a consequence of this atmospheric adjustment, the equatorial countercurrent (current through the doldrums) is allowed to accumulate warm ocean water along the coasts of Peru and Ecuador. 
• The concentration of warm water leads to the descent of the thermocline in the eastern Pacific Ocean, disrupting the upwelling of cold deep ocean water near the coast of Peru.
• El Niño weather patterns result in distinct effects: dry conditions in the western Pacific, increased rainfall along the equatorial coast of South America, and the development of convective storms and hurricanes in the central Pacific region.
• This complex interplay of atmospheric and oceanic phenomena characterizes the formation of El Niño.

El Niño - Impact

El Niño exerts a profound impact on various aspects, influencing ocean temperatures, ocean currents' speed and strength, the well-being of coastal fisheries, and local weather patterns from Australia to South America and beyond.

• Ocean Temperatures and Currents:
  • El Niño disrupts ocean temperatures and alters the speed and strength of ocean currents. Warm surface waters are pushed westward, affecting regions from Asia to Australia.
• Coastal Fisheries and Weather Patterns:
  • Coastal fisheries are affected as El Niño leads to increased precipitation, causing convection above warmer surface waters. This results in dramatic rainfall in South America, contributing to coastal floods and erosion.
• Health Impact and Disease Outbreaks:
  • The extreme weather conditions associated with El Niño, such as flooding and drought, create favorable conditions for the spread of diseases. Outbreaks of cholera, dengue fever, and malaria have been linked to El Niño-related flooding in some regions.
• Wildfires and Respiratory Difficulties:
  • Dry conditions during El Niño can lead to wildfires, causing respiratory difficulties. This phenomenon has been observed in areas where increased dryness contributes to the spread of fires.
• Regional Water Resources and Agriculture:
  • El Niño jeopardises water resources in affected regions as reservoirs dry up, and rivers transport less water. Agriculture, dependent on water for irrigation, faces challenges during El Niño events.
• Indonesia and Australia Weather Disparities:
  • While El Niño brings rain to South America, it causes dryness in Indonesia and Australia. This weather disparity impacts local ecosystems, agriculture, and water availability.
• Sea Surface Height and Temperature Discrepancy:
  • Mild trade winds during El Niño result in a higher sea surface in Indonesia, about 0.5 meters higher and 4-5°F warmer than in Ecuador. This discrepancy affects ocean circulation patterns and influences weather phenomena.
• Upwelling and Nutrient Transport:
  • El Niño disrupts the typical upwelling process, where cold, nutrient-rich water rises to the ocean's surface off the shores of Ecuador, Peru, and Chile. This has implications for marine ecosystems and fisheries.
• Hurricane Frequency in the Atlantic:
  • El Niño lessens the frequency of hurricanes in the Atlantic, showcasing a beneficial effect on hurricane patterns in this region.
  • Understanding the multifaceted impacts of El Niño is essential for anticipating and managing the consequences of these climatic events across diverse geographical regions.
• El Niño - Impacts on India
  • El Niño and the Indian monsoon exhibit an inverse relationship, with El Niño often leading to adverse effects on India's climate and agriculture.
• Historical Droughts:
  • Since 1871, the most notable droughts in India, including six major ones, have coincided with El Niño events. Notable El Niño-induced droughts occurred in 2002 and 2009.
• Variable Drought Outcomes:
  • While El Niño is often associated with droughts in India, not all El Niño years result in such conditions. For instance, the significant El Niño event in 1997/98 did not lead to a drought, and this variability is attributed to the influence of the Indian Ocean Dipole.
• 2002 Drought Impact:
  • A mild El Niño in 2002 had a severe impact, resulting in one of the worst droughts on record in India. This underscores the variable nature of El Niño's impact on Indian climate.
• Agricultural Sector Impact:
  • El Niño directly influences India's agricultural sector, leading to reduced output of crucial summer crops such as rice, sugarcane, cotton, and oilseeds. The diminished agricultural productivity has economic ramifications.
• Economic Consequences:
  • The agricultural sector plays a significant role in the Indian economy, accounting for around 14% of GDP. El Niño-induced droughts contribute to reduced agricultural output, leading to high inflation and low GDP growth.
  • Understanding the complex interplay between El Niño events and the Indian monsoon is crucial for policymakers, farmers, and the broader economy. The variable outcomes highlight the need for adaptive strategies to mitigate the impact of El Niño on India's agriculture and overall economic stability.

El Niño-Southern Oscillation (ENSO)

The El Niño-Southern Oscillation (ENSO) is a climatic phenomenon characterized by the periodic fluctuation in pressure conditions between the tropical South Pacific Ocean and the tropical Indian Ocean.

• Normal Pressure Conditions:
  • Under normal circumstances, the tropical South Pacific Ocean experiences high pressure, while the tropical Indian Ocean encounters low pressure. This typical pressure distribution contributes to regular climatic patterns.
• Reversed Pressure Conditions - Southern Oscillation:
  • However, ENSO introduces the possibility of a reversal in pressure conditions. This reversal manifests as low pressure in the Pacific and high pressure in the Indian Ocean. This atmospheric shift is referred to as the Southern Oscillation.
• Periodic Fluctuation:
  • The Southern Oscillation is a periodic fluctuation in pressure conditions, occurring over intervals that can impact weather patterns and climate variability.
• Link to El Niño Phenomenon:
  • The variations in pressure conditions developing in the Pacific and Indian seas are intricately linked to the El Niño phenomenon. The Southern Oscillation and El Niño together form a coupled phenomenon known as El Niño-Southern Oscillations (ENSO).
• ENSO's Impact on Climate:
  • ENSO has a profound impact on global climate patterns, influencing temperature, precipitation, and atmospheric circulation. El Niño and La Niña events, components of ENSO, bring about distinct climatic anomalies.
• El Niño and La Niña Phases:
  • During El Niño, warmer-than-average sea surface temperatures in the central and eastern Pacific lead to altered weather patterns, while La Niña is characterized by cooler-than-average sea surface temperatures and its associated climate effects.
  • Understanding ENSO is crucial for meteorologists, climatologists, and policymakers as it significantly influences weather and climate conditions worldwide. The interconnected dynamics of the Southern Oscillation and El Niño underscore the complexity of this climatic phenomenon.

El Niño Modoki

El Niño Modoki is a tropical Pacific ocean-atmosphere phenomenon that differs from the conventional El Niño, presenting distinct characteristics in the distribution of sea surface temperatures.

• Linked Ocean-Atmosphere Event:
  • El Niño Modoki is a phenomenon where oceanic and atmospheric conditions in the tropical Pacific are interlinked, influencing global climate patterns.
• Distinguishing Feature from El Niño:
  • In contrast to the conventional El Niño, El Niño Modoki exhibits a different pattern of sea surface temperature anomalies in the tropical Pacific.
• Conventional El Niño:
  • Traditional El Niño is characterized by significant anomalous warmth in the eastern equatorial Pacific, particularly near the coast of South America.
• El Niño Modoki Characteristics:
  • El Niño Modoki is associated with significant anomalous warming in the central tropical Pacific, accompanied by cooling in both the eastern and western tropical Pacific.
• Distinct Temperature Gradients:
  • El Niño Modoki is defined by an anomalously warm central equatorial Pacific, creating zones of anomalously chilly temperatures to the west and east.
• Zonal Gradients and Walker Circulation:
  • The distinctive temperature gradients associated with El Niño Modoki result in an unusual two-cell Walker Circulation in the tropical Pacific. This circulation pattern creates a wet zone in the central Pacific.

El Niño - Significant Past Events

El Niño events have historically demonstrated substantial impacts on global weather patterns. Two noteworthy occurrences are highlighted below:

• 1982-1983 El Niño:
  • The El Niño event of 1982-1983 stands out as one of the most severe in the twentieth century.
  • Sea surface temperatures in the eastern tropical Pacific during this episode reached exceptionally high levels, ranging from 9 to 18 degrees Fahrenheit above the normal average.
• 1997-1998 El Niño:
  • The El Niño event spanning 1997-1998 was the first to be systematically tracked from its initiation to conclusion.
    • Impact on Southeast Asia: Indonesia, Malaysia, and the Philippines experienced drought conditions during this period.
    • Impact on South America and California: Peru and California, on the other hand, faced heavy rainfall and flooding.
    • Unique Weather Patterns: The Midwest in the United States witnessed an unusual phenomenon known as "the year without a winter," marked by record-breaking warm temperatures.
  • These significant El Niño events serve as key examples of the far-reaching consequences this phenomenon can have on climates across different regions of the world. The extremes in sea surface temperatures during these occurrences contributed to varied and impactful weather patterns.

FAQs - El Niño and Related Phenomena

1. What is El Niño, and how is it characterized?

Ans. El Niño is a meteorological phenomenon marked by the abnormal warming of surface waters in the eastern tropical Pacific Ocean. It occurs more frequently than La Niña, which is its counterpart. Fishermen off the coast of Peru recognize El Niño when they observe unusually warm water conditions.

2. How often does El Niño occur, and is it predictable?

Ans. El Niño occurs more frequently than La Niña. However, unlike ocean tides, El Niño does not follow a regular or predictable cycle. Its intervals range from two to seven years, and its occurrence is not part of a set pattern.

3. How was El Niño initially observed, and why is it called "the little boy"?

Ans. El Niño was first observed off the coast of Peru by Peruvian fishermen who noted unusually warm water. The term "El Niño," meaning "the little boy" in Spanish, was coined by Spanish immigrants.

4. What are the broader climatic changes associated with El Niño?

Ans. Over time, El Niño has expanded to signify erratic and extreme climatic changes beyond the warming of coastal surface waters. These events are not part of a regular cycle and occur unpredictably.

5. What is the El Niño-Southern Oscillation (ENSO), and how are they connected?

Ans. ENSO is a climatic phenomenon characterized by the periodic fluctuation in pressure conditions between the tropical South Pacific Ocean and the tropical Indian Ocean. El Niño and the Southern Oscillation together form the coupled phenomenon known as ENSO.

6. How does El Niño impact global climate and weather patterns?

Ans. El Niño influences ocean temperatures, ocean currents, coastal fisheries, and local weather patterns worldwide. It brings about increased precipitation, diseases, wildfires, and impacts on agriculture and water resources.

7. What is the relationship between El Niño and the Indian monsoon?

Ans. El Niño and the Indian monsoon exhibit an inverse relationship, with El Niño often leading to adverse effects on India's climate and agriculture. Historical droughts in India often coincide with El Niño events.

8. What is El Niño Modoki, and how does it differ from conventional El Niño?

Ans. El Niño Modoki is a tropical Pacific ocean-atmosphere phenomenon that differs from conventional El Niño. It is characterized by warming in the central tropical Pacific and cooling in the eastern and western tropical Pacific, creating unique temperature gradients.

9. Can you provide examples of significant El Niño events in the past?

Ans. Two notable events are the 1982-1983 El Niño and the 1997-1998 El Niño, both severe occurrences with widespread impacts, including extreme sea surface temperatures and unique weather patterns.