A novel perspective on near-surface soil freeze states: Discontinuity of the freeze process

Abstract

The freeze state of near-surface soil is crucial for regional hydrology, ecosystems, and infrastructure, yet its discontinuous nature remains largely unknown. This research addresses this gap by employing soil temperatures at a depth of 5 cm from 335 meteorological stations across China, introducing three novel indicators—continuous freeze frequency, freeze fragmentation index, and freeze continuity index––to quantify freeze process discontinuity. The findings reveal significant regional variations in freeze discontinuity across China, primarily shaped by latitude. Further analysis reveals that snow depth can explain 27.3 % and 20.0 % of the variation in freeze continuity and continuous freeze frequency, respectively, while air temperature can account for 30.6 % of the variation in freeze fragmentation. The structural equation model suggests that precipitation, sunshine duration, and air temperature exert both direct and indirect effects on freeze discontinuity, and snow cover plays a key role in mediating the influence of other environmental variables on freeze discontinuity. This study offers a novel analytical perspective on the soil freeze state, enhancing our understanding of freeze dynamics under climate warming.