Is earlier always better? A comparative assessment of an early-stage response window for rainfall timing in multiyear drought alleviation in China

Multiyear droughts (MYDs) are severe drought events with profound impacts on human activities and ecosystems. However, the timing that maximizes drought attenuation efficiency under additional precipitation ( t optimal ) remains insufficiently quantified. With that in mind, we conducted a retrospective grid-based analysis of historical MYDs in China using the Palmer Drought Severity Index (PDSI) over 1961–2020, with a calibration period of 1961–1990, and performed numerical experiments with hypothetical precipitation gradient increases during 1991–2020. We defined k to quantify the sensitivity of drought alleviation to precipitation input. Actual k values derived from the numerical experiments showed strong consistency with theoretical k derived from a drought attenuation quantitative model (DAQM). Theoretical k was further used to quantify MYD attenuation efficiency, with t optimal identified as the timing of maximum theoretical k ( k max⁡ ). Overall, drought severity (DS) exhibits a nonlinear response to hypothetical precipitation increases. Both numerical experiment-based and DAQM-derived results identify an early-stage response window within the first three months ( t 1 ∼ t 3 ), and multiple robustness analyses confirm its stability. k max⁡ occurs most frequently at t 1 , in 58.79 % of all grids, while t 2 and t 3 were also non-negligible (22.11 % and 11.06 %). This suggests that missing t 1 within this window does not necessarily imply a substantial reduction in k . Compared with humid river basins in southern China, arid and semi-arid northern basins show a higher probability that k at t 2 or t 3 exceed k at t 1 . Drought duration (DD) is a key factor, as longer DD is associated with a greater likelihood of t 2 or t 3 being the t optimal ( R 2 =0.526 and 0.578). We noticed that k is jointly influenced by the cumulative temporal advantage of earlier precipitation input and the higher sensitivity of standardized drought indices under severe drought conditions. This study identifies an early-stage response window during MYD evolution and provides conceptual guidance for understanding how precipitation input timing influences drought alleviation across regions.