06 · GS-I & GS-III: Climatology, Monsoon Dynamics & Ocean-Atmosphere Interaction
Southwest Monsoon Dynamics: ENSO-Neutral to La Niña Transition, Indian Ocean Dipole (IOD) and Spatial Rainfall Disparities
NEWS PEG
- The India Meteorological Department (IMD) reported that the southwest monsoon covered the entire country six days ahead of schedule, with seasonal cumulative rainfall recording 104% of the Long Period Average (LPA).
- Climatologists analyzed the oceanic transition from fading El Niño to developing La Niña conditions in the equatorial Pacific Ocean, combined with a neutral to positive Indian Ocean Dipole (IOD), which significantly bolstered moisture influx across central and northwest India.
- Despite normal aggregate national rainfall, severe intra-seasonal and spatial anomalies were recorded—with western Rajasthan and Gujarat experiencing excess rainfall while eastern agricultural belts (Bihar, Gangetic West Bengal) faced a 20–30% precipitation deficit during key Kharif paddy transplantation weeks.
STATIC FOUNDATION
- Long Period Average (LPA): The average rainfall calculated over a 50-year period; IMD currently uses the 1971–2020 baseline (LPA for southwest monsoon across the country as a whole is 868.6 mm / 86.8 cm).
- Monsoon Rainfall Categorization: Normal (96–104% of LPA), Below Normal (90–95%), Above Normal (105–110%), Deficient (<90%), Excess (>110% of LPA).
- El Niño vs La Niña: El Niño (unusual warming of central/eastern equatorial Pacific sea surface temperatures) generally suppresses Indian monsoon rainfall; La Niña (unusual cooling of equatorial Pacific) generally enhances Indian monsoon precipitation.
- Indian Ocean Dipole (IOD): Difference in sea surface temperature between the western tropical Indian Ocean and the eastern tropical Indian Ocean (Positive IOD enhances Indian monsoon rainfall; Negative IOD suppresses it).
PRELIMS TRAP & PYQ BRIDGE
MAINS ENHANCEMENT
- Agrarian Climate Resilience: Adapting to Erratic Monsoon Spatial Distribution — Expanding micro-irrigation and drought-tolerant seed varieties in chronically deficit eastern plains.
- Urban Drainage Preparedness: Managing Extreme Short-Duration Rainfall Events — Upgrading urban stormwater channels to handle intense 100 mm/hour convective rain bursts.
- High-Resolution Forecasting: Mission Mausam & AI Weather Modeling — Enhancing block-level agro-meteorological advisories to guide sowing dates for smallholder farmers.