An Optimized Variational Processing Method Based on Satellite-Station Data on Snow Cover Days on the Qinghai–Tibet Plateau

Abstract

The Qinghai–Tibet Plateau is a sensitive area to climate change, and snow cover has an important impact. Due to the high altitude and complex terrain, station observations of snow cover on the plateau are sparse but objective, while satellite data have high resolution but limited accuracy. Therefore, an optimized variational processing method based on daily satellite data from 1989 to 2020 and monthly snow cover day data from stations is used to combine their advantages, and a high-resolution (0.1° × 0.1°) monthly dataset of snow cover days during 1989–2020 is obtained. This study analyzes the spatial and temporal characteristics of snow cover days on the Qinghai–Tibet Plateau over the past 30 years and compares the differences before and after applying the optimized variational processing method. The variational processing method is also used to reanalyze data on temperature and precipitation. This study confirms the objectivity of the processing method and reveals the regional characteristics of snow cover days and their correlation with temperature and precipitation. The data obtained after optimized variational processing provide a more accurate and detailed representation of the spatial and temporal characteristics of snow cover days. The distribution and variation trends of snow cover days on the Qinghai–Tibet Plateau exhibit significant spatial differences. The average number of snow cover days during the snow season is 45.51 d, with 22.74 d in winter. The Qaidam Basin and the southwestern part of the plateau are areas with low snow cover days, while high-altitude mountainous areas have higher values. Overall, there is no significant change in snow cover days during the snow season, but there is a significant decreasing trend of −1.50 d/10 yr in winter. The snow cover days in the plateau’s hinterland and low-altitude areas mainly show a decreasing trend, while high-altitude mountainous areas show an increasing trend. Snow cover days in the western part of the Qinghai–Tibet Plateau are both influenced by temperature and precipitation in winter, while precipitation dominates in the eastern part.