A Novel Snow Cover Occurrence Index (SCOI) for the Dynamics of Snow Duration and Glacier Extent in Mountainous Regions

The snow cover occurrence index (SCOI), deffned as the ratio of the number of times that a pixel is classiffed as snow to the number of times that the pixel is observed in optical remote sensing data over a given year, can effectively mitigate the inffuence of clouds and holds great potential for extracting the annual snow duration and glacier extent in mountainous regions. The SCOI of the Qinghai–Tibet plateau (QTP) is calculated and analyzed on the basis of Landsat images from 1985 to 2021. The results indicate the following: 1) the evaluation based on station snow depth reveals that the SCOI is stable when the number of combined years reaches 5; 2) the SCOI has a strong correlation with snow cover days (SCD) determined from Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover products; and 3) the SCOI has good potential for glacier extraction and exhibits a high level of consistency with glacier boundary survey data. Overall, owing to the higher spatial resolution and longer duration of the Landsat-based SCOI, it can accurately describe the distribution characteristics and changes in snow cover and glaciers in complex mountainous areas.