A Systemic Shift towards Hydroclimatic Whiplash in India: Event-Based Evidence of Escalating Dry-Wet Transitions since 1951

Abstract. This study presents a comprehensive assessment of the evolution of hydroclimatic extremes, dry spells (DS), wet spells (WS), and their rapid transitions (whiplash) across India from 1951 till 2019. A marked reorganization of extremes emerged around the 1980s regime shift, characterized by widespread intensification of WS and a 40 % rise in DS-affected grids experiencing fewer but longer events. Using Event Coincidence Analysis, trigger relationships between extreme DS and WS are quantified, revealing that trigger coincidence rates exceeded 0.8 after the mid-1980s and increased spatially by nearly 49 % over the west coast, Central India, and the Northeast. Disaggregating transitions demonstrated an emerging dominance of dry-to-wet (DTW) behavior, with an increase of ~14 %, reflecting reorganized monsoon feedbacks. Quantification of whiplash severity revealed a 13 % and 8.7 % rise in extreme and severe whiplash frequencies and a 26.6 % increase in grids exhibiting simultaneous high frequency, duration, and intensity. Spatially, the southwest coast and northern India exhibit ‘persistently high’ risk with no recovery since 1951, while the east coast and central India show ‘emerging’ volatility. Crucially, this intensification translates into a quantifiable ‘climate penalty’ on agriculture: post-2000 wheat yields show persistent negative anomalies with an increase in exposure to extreme whiplash risk, which in turn demands an immediate pivot in adaptation and resource planning.