资源环境科技发展态势分析平台

Weakening of annual temperature cycle (ATC) on the Tibetan Plateau (TP) in the last decades has been identified, and there is a subsequent change in the frequency of the ATC magnitude extremes. These changes in the climate have a potential influence on biological and ecological systems. However, the frequency of occurrences of the ATC magnitude extremes in the recent decades compared to the preindustrial period, as well as the potential driving forces remains unclear. This can limit the robust predictions and risk assessments for extreme events of the ATC in the future. In this study, we analyzed the frequency of occurrence of the ATC magnitude extremes using both recent observations (1955-2011) and a tree-ring-based reconstruction covering the past three centuries over the TP. The results indicate that the ATC magnitude extremes in maximum obviously decrease and in minimum distinctly increase under climate warming, both for the instrumental period and the past three centuries. Moreover, the occurrence of the ATC magnitude extremes on the TP had a distinct regional characteristic and was mainly related to the winter temperature extremes triggered by the anomalous meridional gradient of geopotential height impelling cold air intrudes the TP. Although volcanic eruptions were expected to result in summer cooling and winter warming, and thus trigger the minimum ATC magnitude extremes, this effect only can be identified in event-specific eruptions (e.g., the 1835 Cosiguina eruption). Our study results provide an essential background for developing robust predictions and risk assessments for the ATC magnitude extremes on the TP.