"El Niño Set to Peak in December, WMO Warns"
ENSO
El Niño-Southern Oscillation, a recurring Pacific Ocean cycle with warm, neutral and cool phases
Niño 3.4 Index
measure of sea-surface temperature anomaly used to track and declare El Niño/La Niña
El Niño is the warm phase of the El Niño-Southern Oscillation (ENSO), a cycle in sea-surface temperature and air pressure across the tropical Pacific Ocean. This cycle repeats every two to seven years. Normally, trade winds (steady winds blowing east to west near the equator) push warm surface water toward Asia and Australia. During an El Niño, these winds weaken. Warm water then spreads toward the eastern Pacific, off the coast of South America. The World Meteorological Organization (WMO) tracks this shift using the Niño 3.4 Index. This index measures the temperature anomaly (deviation from normal) in a fixed part of the central-eastern Pacific. El Niño is declared when this anomaly crosses 0.5°C above normal. In August, the Niño 3.4 region was running 2.5°C above normal. This shows how fast the current event has strengthened.
El Niño's most important effect on India is a weakening of the southwest monsoon. However, this link is not automatic. The Indian Ocean Dipole is the temperature difference between the western and eastern Indian Ocean. It can soften or sharpen El Niño's pull on Indian rainfall in a given year. Forecasters also track Ocean Mean Temperature (OMT). This is the average sea temperature measured down to the depth of the 26°C isotherm (the depth where temperature falls to 26°C) in the south-western Indian Ocean during January-March. OMT readings help predict whether the coming monsoon will bring more or less rain than the long-term average. This year, the southwest monsoon closed with a 13% rainfall deficit. This makes 2026 the fourth driest monsoon since 2001. El Niño's influence was concentrated in the second half of the season.
Ocean Mean Temperature (OMT) is measured down to the 26°C isotherm depth in the south-western Indian Ocean during January-March. It is used to predict whether the monsoon will bring above or below long-term average rainfall. Wet-bulb temperature is the lowest temperature to which air can be cooled by evaporative cooling. When it exceeds 35°C, the human body cannot shed heat effectively through perspiration. This makes survival difficult.
ENSO cycles through three phases: El Niño (warm), a neutral phase, and La Niña (cool). Each phase changes global rainfall and temperature patterns. It does this by shifting where warm ocean water and rising air sit over the Pacific. During El Niño, rising air and rainfall shift eastward. They move away from Asia and Australia, toward the central Pacific. This weakens the monsoon winds that normally carry moisture into India. It suppresses rainfall and raises the risk of drought. The opposite pattern, La Niña, tends to bring stronger and wetter monsoons.
Extreme heat in an El Niño year becomes dangerous to human health through a specific limit: wet-bulb temperature. …
With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct?
1.OMT is measured up to a depth of 26°C isotherm which is 129 metres in the south-western Indian Ocean during January-March.
2.OMT collected during January-March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.
Which of the statements given above is/are correct?
The World Bank warned that India could become one of the first places where wet-bulb temperatures routinely exceed 35°C. Which of the following statements best reflect(s) the implication of the above-said report?
I.Peninsular India will most likely suffer from flooding, tropical cyclones and droughts.
II.The survival of animals including humans will be affected as shedding of their body heat through perspiration becomes difficult.
Select the correct answer using the code given below.
Consider the following statements regarding El Niño:
1.El Niño is declared when the sea-surface temperature anomaly in the Niño 3.4 region exceeds 0.5°C above normal.
2.El Niño typically strengthens the Indian southwest monsoon.
Which of the statements given above is/are correct?
Consider the following statements regarding wet-bulb temperature:
1.It combines the effects of heat and humidity on the human body's cooling ability.
2.Once wet-bulb temperature approaches 35°C, sweat evaporation becomes a more effective cooling mechanism for the human body.
Which of the statements given above is/are correct?
With reference to Ocean Mean Temperature (OMT), consider the following statements:
1.It is measured in the south-western Indian Ocean during the January-March period.
2.It is used to assess whether the coming monsoon's rainfall will be above or below the long-term average.
Which of the statements given above is/are correct?
Match List-I (ENSO Phase) with List-II (Typical Effect on Indian Monsoon) and select the correct answer using the code given below:
List-I
A.El Niño
B.La Niña
C.Neutral phase
List-II
1.No strong systematic ENSO-driven shift in rainfall
2.Tends to weaken monsoon rainfall
3.Tends to strengthen monsoon rainfall
Which of the following best explains the physical mechanism by which an El Niño event develops?
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