Multiscale Changes in Snow Over the Tibetan Plateau During 1980-2018 Represented by Reanalysis Data Sets and Satellite Observations

The Tibetan Plateau has experienced substantial warming during the last few decades. As a result, the cryosphere of the Tibetan Plateau, including the snow cover, has shown significant changes. We characterized the changes in snow over the Tibetan Plateau using several snow-related indices, including snow depth and snow-covered days based on the MERRA-2 and JRA-55 reanalysis data set and passive microwave (MW) satellite observations. The analyses were performed over different time periods-including the last 38, 30, 20, and 10 snow seasons-from 1980 to 2018. The results show that the significant trends in snow depth and snow-covered days are dependent on both the season and region and vary with the data set and snow-related index used. There was a clear decrease in the annual maximum consecutive snow-covered days (CSCDMax), and this was characterized by a later begin time and an earlier end time for both MERRA-2 and JRA-55, but only a later begin time for MW during the time period 1980-2018. The changes in CSCDMax were generally dominated by changes in the begin time, which were mainly caused by the increase in the average 2-m air temperature for November-December. The relatively weak trends in the end time were a result of the combined impact of warmer temperatures and more precipitation in March-April. The CSCDMax averaged over the Tibetan Plateau showed decreasing trends in all studied time periods for JRA-55 and MW and in the last 38 and 10 snow seasons for MERRA-2 during the time period 1980-2018.