The Asynchronous Evolution of Cold Waves Over China Revealed by 3D Spatiotemporal Tracking

Abstract Cold waves pose substantial risks to ecosystems, infrastructure, and society. While most studies have examined their station‐level frequency or regional intensity, the joint behaviors in both time and space remain largely unexplored. Here, we apply a three‐dimensional connected‐component labeling algorithm to daily temperature observations across China from 1960 to 2020, reconstructing spatiotemporally contiguous cold events (SCCEs) as independent Event IDs. This framework diagnoses outbreak origins, propagation, spatial footprint, and life‐cycle phase evolution. We find that while station‐level cold wave frequency increased locally in North China, nationwide SCCEs show declining accumulated cooling. Tracked events predominantly originate from high latitudes with robust southward propagation. Crucially, life‐cycle composites reveal that cold waves are shifting toward a distinct “warmer yet extensive” regime. Cold surges decay continuously after maturity, whereas cold waves exhibit asynchronous decay: despite significantly shortened lifespans and weakened thermodynamic cooling, their synoptic‐scale severity remains sustained after the spatial footprint begins to contract.