Heatwave magnitude quantization and impact factors analysis over the Tibetan Plateau

More frequent and intense heatwave events (HWEs) on the Tibetan Plateau (TP) present substantial threats to the ecological and hydrological systems. However, understanding the changes in HWEs on the TP is limited, primarily from analyses at individual stations or single elements (glaciers, lakes). Here, using refined data, we quantify the heatwave magnitude by aggregating multiple indicators into a comprehensive index and explore the influence of environmental factors on the heatwave magnitude over the TP. Our findings indicate that the heatwave magnitude has significantly increased since the 21st century, especially in autumn. From 1979–2000 to 2001–2022, the heatwave magnitude hotspots migrated toward the northwestern TP, whereas the regions with the most rapid increase shifted in the opposite direction. During the inter-seasonal, from spring to winter, the migration direction of the heatwave magnitude hotspots changed from the northwest in the first 22 years (1979–2000) to the southeast in the recent 22 years (2001–2022). We also find that downward shortwave radiation plays a significant role in the spatial stratified heterogeneity (SSH) of the heatwave magnitude, while the trend of temperature plays a dominant role in the SSH of the trend of heatwave magnitude. Moreover, elevation is correlated with the heatwave magnitude variability. The elevation-dependence of the heatwave magnitude has become more pronounced in the recent 22 years, with a high-heatwave magnitude migrating to higher elevations. Furthermore, the difference in land cover type can also affect the intensity of the heatwave magnitude to some extent. Our findings underscore the migration patterns of the heatwave magnitude evolution around the 21st century and provide a scientific basis for understanding the interaction between environmental factors and the heatwave magnitude in different periods.