Dynamic changes of extreme temperature occurrence time in China

The dynamic changes in the occurrence time of temperature extremes is one of the important reasons for some natural disasters. In this study, a set of evaluation indices was defined to quantify the dynamic changes in occurrence time of temperature extremes, including 5 cold indices, 4 warm indices, 2 extreme indices, and 4 phenological indices. The dynamic changes of temperature extremes occurrence time in China were examined through the analysis of daily temperature data obtained from 596 meteorological stations spanning the period from 1960 to 2019. Additionally, an exploration of the correlation between the dynamic changes in temperature extremes occurrence time and atmospheric circulation was conducted. The findings indicate that in China: (1) All cold indices, such as the frost start date (SD0), cold day start date (SD3), very cold day start date (DTN90) and extreme low temperature start date (DTN95), showed a significantly delayed trend ( P