三江源地区是我国重要的水源涵养地与生态保护区，揭示其冻融指数特征变化可为当地 多年冻土环境评估以及应对气候变化提供科学依据。利用第三极地区地面气象要素驱动数据集 （TPMFD）的逐日气温数据，通过大气冻融指数等方法分析了该地区1979—2022 年大气冻融指数 的时空变化特征。结果表明，近44 年三江源地区大气冻结指数平均为1 930.23 ℃·d，在空间上呈 现自西向东逐渐降低的特征；融化指数表现出相反的空间格局，平均值为879.25 ℃·d。总体来看， 近44 年三江源区大气冻结指数以-10.01 ℃·d/a 的速率呈波动减少趋势，且在2001 年发生突变；融 化指数以6.29 ℃·d/a的速度呈波动上升趋势，没有发生显著的突变。海拔作为关键影响因子，对三江 源地区冻融指数表现出显著的相关性，海拔每升高100 m，研究区融化指数约减少87 ℃·d，冻结指数 约增加107 ℃·d。

The Three Rivers Source Region (TRSR) is an important water source and ecological reserve in China, and revealing the changes in the characteristics of its freeze-thaw index can provide a scientific basis for the assessment of the local permafrost environment as well as the response to climate change. In this study, the temporal and spatial characteristics of the Air Freezing and Thawing Indices (AFTI) in the TRSR for the period 1979-2022 were analyzed using the day-by-day air temperature data from a high-resolution near-surface meteorological forcing dataset for the Third Pole region (TPMFD) by means of air freezing and thawing index and other methods. The results show that the mean value of the freezing index in the TRSR over the past 44 years is 1 930.23 °C·d, exhibiting a spatial pattern of gradually decreasing from west to east. In contrast, the thawing index displays an opposite spatial pattern with an average value of 879.25 °C·d. Overall, the freezing index in the TRSR has shown a fluctuating decreasing trend at a rate of -10.01 °C·d/a for the last 44 years with an abrupt change in 2001, while the thawing index has shown a fluctuating increasing trend at a rate of 6.29 °C·d/a with no significant abrupt change. Altitude, as a key factor of freezing and thawing indices in the TRSR, showed a significant correlation, and for every 100 m increase in altitude, the thawing index in the TRSR decreased by about 87 °C·d, and the freezing index increased by about 107 °C·d.