Energy balance effects of extreme snow events on shallow frozen and thawed surfaces in highland pastoral areas

Abstract

Energy balance serves as a critical benchmark for validating land-atmosphere interaction models. Extreme snowfall events profoundly alter snowpack dynamics and disrupt shallow soil energy partitioning during freeze-thaw cycles, yet remain inadequately characterized. We established meteorological stations near Namtso Lake in the alpine grasslands, monitoring air and soil parameters (temperature, moisture), radiation fluxes, and snow depth to quantify energy budget perturbations under extreme conditions. The study phase successfully captured rare extreme snowfall events and concurrent surface freeze-thaw processes, providing pivotal observational data. Novel computational approaches were subsequently developed to quantify individual energy fluxes, enabling rigorous assessment of energy balance within this complex environment. Extreme snowfall exerts dominant control over energy partitioning during soil freeze-thaw cycles, significantly modifying surface energy fluxes despite diminishing effects on closure rate with increasing snow depth. Our findings reveal that: (1) Individual energy fluxes maintain diurnal cyclicity independent of snow cover; (2) Energy closure is enhanced during snowfall phases relative to snowmelt phases; (3) The Energy Closure Ratio (CR) during snowfall exhibits a concave relationship with snow depth (initial decrease followed by increase), while CR during snowmelt demonstrates monotonic decline. This study advances our understanding of snow-permafrost interactions in mid-latitude, high-elevation regions, providing a mechanistic framework for analyzing extreme snow events.