Reply on RC2

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> An extreme dry-slab snow-avalanche occurred on 10 Jan. 2021 at Mt. Nodanishoji, Gifu, Japan, during a heavy snowfall. The avalanche ran down approximately 2,800 m and caused damage to trees and infrastructures. Although this avalanche was estimated to be the second largest in Japan, physical snowpack properties and their vertical structure and spatial distribution, that caused the avalanche, were not addressed in the release area just after the avalanche fall, mainly due to unsafe and lousy weather. Based on a snow depth distribution observed by an unmanned aerial vehicle and a numerical snowpack simulation in the avalanche release area, the spatial distributions of the mechanical snowpack stability and slab mass and their temporal evolutions were estimated in this study. The procedure was validated by comparing the calculation results with the observed snowpit and spatial snow depth data. The results indicated that two heavy snowfall events, ~3 and 10 days before the avalanche onset, generated two different weak layers made of precipitation particles and associated slabs above other weak layers. The older weak layer was only generated on the northward slope due to its low temperature, whereas the newer layer was predominant over the avalanche release area. The fraction of contributions of the slabs associated with the two weak layers to the total slab mass over the calculation domain was found to be 1 : 2.