Spatiotemporal variation of snow cover days and influencing factors in north and south Qinling Mountains based on remote sensing monitoring

It is a hot issue in climate change research to study the response mechanism of mountain snow cover to climate warming based on elevation-dependent warming. Based on Terra Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover phenology datasets from 2000 to 2019, we analyzed the spatiotemporal variation of snow cover days in the north and south of the Qinling Mountains by the methods of trend and detrended correlation analysis. Meanwhile, we identified the influencing factors of snow cover days from the perspectives of sea surface temperature (SST) in autumn and winter of the equatorial Pacific, high pressure over the Qinghai-Tibet Plateau, respectively. The results are as follows: (1) after 2013, climate condition in the north and south of the Qinling Mountains shifted from "warming hiatus" to "warming up", followed by declining snow cover days. And the proportion of areas with snow cover more than 10 days decreased from 35.1% to 8.6%. (2) We identified 1950-2000 m in the Qinling Mountains and 1600-1650 m in the Daba Mountains as transition zones of snow cover days. Above the transition zone, the increasing rate of snow cover days with altitude is higher than that of the low altitude area. Particularly, the altitudinal belt between 2100 m and 3150 m is the sensitivity zone of snow cover days to climate change. On the basis of the reference period of 2000-2004, we find that the elevation with 40, 60 and 80 days of snow cover increased by 100 m, 100 m and 150 m for the period of 2015-2019. (3) The SST in autumn and winter over NINO C and NINO Z regions and the winter high pressure over Qinghai-Tibet Plateau are two effective indicators of snow cover days anomaly in the Qinling Mountains, Hanjiang Valley and Daba Mountains. The lower SST of the central equatorial Pacific in autumn and winter, or the lower the winter high pressure over the Qinghai-Tibet Plateau is, the more excessive snow cover days would occur. (4) In terms of circulation mechanism, during the years with more snow cover days, the 0 ℃ isotherm in January and February was southerly, providing the proper temperature for increasing snow and ice accumulation and delaying snow and ice melting. Moreover, there was a weak water vapor convergence zone in January, which provided water vapor conditions for increasing snow and ice accumulation. The findings can enrich our understanding of winter climate change and provide early warning information of snow anomaly in the subtropical and warm-temperate zones in China. © 2023, Science Press. All right reserved.