Dynamic monitoring of the freezing-thawing parameters in the Qinghai-Tibet plateau from 1950 to 2023 based on ERA5-LAND data

By downloading and processing ERA5-LAND data, the freezing-thawing parameters are acquired in the Qinghai-Tibet Plateau from 1950 to 2023. Then, the spatio-temporal change rules are achieved by using the Theil-Sen slope estimation and Mann-Kendall trend analysis methods. The research results show: the spatial distribution has evident east-west zonal differences; the freezing starting time in the northwest region is earlier, and the freezing end time is later; the freezing duration and the freezing days are longer; the air/ground freezing indexes are higher, and the air/ground thawing indexes are lower. The freezing-thawing parameters change significantly with altitude. With increasing altitude, the freezing start time is delayed, and the freezing end time is advanced; the freezing duration and freezing days are shortened; the air/ground freezing indexes are increased, and the air/ground thawing indexes are decreased. About the overall change trend, the freezing-thawing parameters change significantly. The proportion area of the significantly increased freezing start time is 20.64%; the proportion area of the significantly decreased freezing end time is 15.35%; the proportion area the significantly decreased freezing duration is 26.86%; the proportion area of the significantly decreased freezing days is 44.89%; the proportion areas of the significantly decreased air/ground freezing indexes are 83.98%/70.12%, respectively; as to the significantly increased air/ground thawing indexes, the proportion areas are 65.98 %/45.54%, respectively.