Fig. 1: Interannual variability in extreme long-duration events since 1980s.

Interannual changes in the frequency (a), duration (b), and intensity (c) of extreme long-duration events since 1980. The lines and points represent the annual average values of long-duration events and its deviation. The coefficients at the top of the panels indicate robust Theil-Sen’s slopes and their deviations, and their corresponding P values, examined by Mann–Kendall (MK) test (n = 43). The right boxplots denote the difference before 2000 (blue) and after 2000 (red) examined by one-way analysis of variance (ANOVA). *** represents the significance under the level of P < 0.001 (n = 21 for years during 1980–2000 and n = 22 for years during 2001–2022). The boxes and lines indicate the interquartile range and the median, respectively, and whiskers represent the minimum and maximum. Black dashed lines denote linear fitting of annual average values. Rank ordering of the annual average frequency (d), duration (e), and intensity (f) of extreme long-duration events across the surveyed 43 years, in which years between 1980 and 2000 are labeled with black and those between 2001 and 2022 are labeled with red. Source data are provided as a Source Data file.