Context:
The India Meteorological Department (IMD) has predicted a plentiful monsoon season. The forecast indicates that rainfall from June to September is anticipated to exceed the average of 87 cm, with an expected increase of 6%. This is a notably assertive prediction from the agency, which typically refrains from indicating either surplus or deficit rainfall in its April forecasts. While this news may be welcomed, particularly in light of soaring temperatures and heatwaves in many southern states, there is a caveat to this optimistic outlook.
Relevance:
GS1- Geography- Important Geophysical Phenomena
Mains Question:
According to the IMD’s climate models, there is a 30% probability of “excessive” rainfall in India. In this context, explain the variation in the rainfall pattern in India with the El Niño-Southern Oscillation (ENSO) cycle and Indian Ocean Dipole. (10 Marks, 150 Words).
More on the Prediction:
- According to the IMD’s climate models, there is a 30% probability of “excessive” rainfall, defined as surpassing 10% of the normal rainfall amount.
- In comparison, the expectation of “above-normal” rainfall stands at 31%, defined as falling between 5% to 10% above normal levels.
- This slight difference suggests that the likelihood of excessive rainfall is nearly as high as that of merely above-normal showers.
- The majority of these heavy rains are anticipated in the latter half of the monsoon season, specifically in August and September.
Basis of this Prediction by IMD:
- The IMD’s models predict these conditions based on the emergence of a La Niña phenomenon, which is the opposite of El Niño and often leads to a reduction in monsoon rainfall.
- Additionally, La Niña is expected to be influenced by a positive Indian Ocean Dipole, characterized by cooler-than-normal temperatures in the eastern Indian Ocean compared to the western region, which typically brings rainfall to several states in southern India.
El-Nino and La-Nina:
- El Niño and La Niña are intricate weather phenomena arising from fluctuations in ocean temperatures in the Equatorial Pacific Region.
- They represent opposing phases within the El Niño-Southern Oscillation (ENSO) cycle, which characterizes temperature changes between the ocean and atmosphere in the east-central Equatorial Pacific.
- El Niño and La Niña events typically persist for nine to 12 months, though some prolonged occurrences may extend over several years.
- El Niño refers to a climate pattern marked by abnormal warming of surface waters in the eastern tropical Pacific Ocean, representing the “warm phase” of the ENSO cycle. It occurs more frequently compared to La Niña.
- On the other hand, La Niña, the “cool phase” of ENSO, entails unusual cooling of the tropical eastern Pacific. La Niña events can endure from one to three years, unlike El Niño, which typically lasts for no more than a year. Both phenomena often reach their peak during the Northern Hemisphere winter.
Indian Ocean Dipole (IOD):
- The Indian Ocean Dipole, also known as the Indian Nino, resembles the El Nino phenomenon but occurs within the Indian Ocean, spanning the area between the Indonesian and Malaysian coastlines in the east and the African coastline near Somalia in the west.
- El Nino, a component of the El Nino Southern Oscillation (ENSO), denotes a phase of warmer-than-normal temperatures and reduced rainfall in various regions worldwide, including India.
- During El Nino, one side of the ocean along the equator experiences higher temperatures than the other.
Positive and Negative Phases:
IOD is categorized as positive when the western side of the Indian Ocean near the Somalia coast becomes warmer than the eastern Indian Ocean, and negative when the western Indian Ocean is cooler.
Negative IOD:
- Under negative IOD conditions, air circulation within the Indian Ocean basin shifts from west to east near the surface, and conversely at higher levels.
- Typically, warmer waters from the western Pacific near Indonesia flow into the Indian Ocean, slightly warming that region. This warming leads to upward air movement, reinforcing prevailing circulation patterns.
- During negative IOD years, intensified air circulation pushes more warm surface waters from the African coast towards the Indonesian islands, resulting in an even warmer Indonesian region.
Positive IOD:
- During positive IOD events, air circulation weakens, and in rare instances, even reverses. Consequently, the African coast experiences higher temperatures while the Indonesian coastline cools.
- Positive IOD events often coincide with El Nino occurrences, while negative IOD events are sometimes linked with La Nina.
- El Nino’s influence causes cooling on the Pacific side of Indonesia, which in turn contributes to the development of a positive IOD in the Indian Ocean.
- While the IMD does not specify the quantity of rainfall expected in June and July, it anticipates “neutral conditions” during that period, with neither El Niño nor La Niña prevailing.
- Although two dry months followed by heavy rains in the last two months may benefit agriculture, it could also result in severe floods and, as seen in the past, substantial damage to lives, livelihoods, and infrastructure.
Susceptibility to Natural Disasters:
- States should promptly develop emergency plans based on their disaster management frameworks to enhance infrastructure, establish evacuation protocols, conduct assessments of dam structural integrity and distress signaling systems, and ensure the availability of comprehensive early warning networks.
- Additionally, it is imperative to inform India’s predominantly rain-fed agriculture-dependent farmers about the potential for a more intense second half of the monsoon and encourage them to incorporate this information into their planting strategies.
Conclusion:
The devastating floods experienced in Kerala in 2018 serve as a stark reminder of India’s susceptibility to natural disasters. While an updated forecast is anticipated towards the end of May, it is crucial to heed the current signal provided by the IMD without delay.
