Evolution of the specific surface area of snow during high‐temperature gradient metamorphism

Abstract

AbstractThe structural evolution of low‐density snow under a high‐temperature gradient over a short period usually takes place in the surface layers on clear, cold nights. In this paper, X‐ray computed microtomography (microCT) was combined with numerical simulations to investigate the temperature gradient metamorphism (TGM) on different types of snow. Precipitation particles (PP), small rounded particles (RGsr), and large rounded particles (RGlr) were each observed in high‐temperature gradients (100–500 K m−1) at a mean temperature of −4°C. The specific surface area (SSA) was used to characterize the TGM, which were influenced by both the magnitude of the temperature gradient and the initial snow structures. PP samples experienced a logarithmic decrease of SSA with time, and the depth hoar structures created under high TGM (500 K m−1) have higher SSA compared to those under lower TGM. Unlike previous observations, for initial rounded and connected structures, like RGlr samples, the SSA increased during TGM. Simulated normal vapor flux distributions for different snow types were used to help understand the structural evolution under TGM. Understanding the SSA increase is important in order to predict the enhanced uptake of chemical species by snow or increase in snow albedo.