Correct Option
El Niño and Southern Oscillation (ENSO) is a coupled ocean-atmosphere phenomenon in the tropical Pacific that significantly influences global weather patterns, including the Indian monsoon. During an El Niño event, there is an anomalous warming of the sea surface temperatures in the central and eastern tropical Pacific Ocean. This warming disrupts the normal atmospheric circulation, leading to a weakening of the Walker Circulation and a shift in convection patterns. For the Indian subcontinent, El Niño conditions are strongly associated with a reduction in monsoon rainfall, often resulting in droughts or delayed monsoons. The Southern Oscillation refers to the corresponding seesaw in atmospheric pressure between the eastern and western tropical Pacific. The combined El Niño-Southern Oscillation phenomenon is a primary factor considered for short-term climatic predictions concerning the variability of the Indian monsoon.
Incorrect Options
-
La Niña (A): This is the opposite phase of El Niño, characterized by cooler-than-average sea surface temperatures in the central and eastern tropical Pacific. La Niña events are generally associated with stronger-than-average monsoon rains over the Indian subcontinent, rather than weak monsoons.
-
Movement of Jet Stream (B): Jet streams influence atmospheric circulation and can affect monsoon patterns. However, their movement is not the primary event directly linked to occasional weak monsoon rains for short-term predictions in the same way as El Niño and Southern Oscillation.
-
Greenhouse effect at global level (D): The greenhouse effect refers to the warming of Earth's surface and atmosphere due to the trapping of heat by greenhouse gases. While it is a critical factor in long-term climate change and global warming, it is not an event used for short-term (inter-annual) climatic predictions of monsoon variability. Its impacts are observed over decades and centuries, not for occasional weak monsoon rains in a specific year or season.