Regional covariation between climate-normalized storm rarity and landslide magnitude in Taiwan is sensitive to rainfall timing

Abstract Climate-normalized rainfall rarity may facilitate comparisons across climates, but pooled rainfall–landslide associations can obscure regional structure and rainfall timing. We examined 994 reported rainfall-induced landslides in Taiwan (1987–2018) using 2-km hourly precipitation and generalized extreme-value climatologies for 1980–2019. Rainfall rarity ( T max ) was defined as the maximum of 1–72-h duration-specific return periods, not the recurrence interval of an entire storm. Retrospective whole-storm T max was available for 912 records, including 708 with estimated volume. Within 18 selected spatial cells, 16 contained 393 volume-bearing records. Contextual decomposition yielded a positive between-cell rarity–volume coefficient ( β between = 0.945, 95% confidence interval (CI) = 0.642–1.248), but no detectable positive within-cell association ( β within = − 0.105, 95% CI = − 0.288–0.078). Cell-clustered inference was less decisive. The between-cell coefficient decreased to 0.279 after adjusting for absolute 24-h rainfall and to 0.317 after excluding Typhoon Morakot. When rarity was calculated using only rainfall preceding recorded failure, the positive between-cell association was not recovered ( β between = − 0.276, 95% CI = − 1.115–0.563; 361 volume-bearing records), although analytical populations differed. These findings identify a Morakot-anchored, inventory-specific association that is sensitive to absolute rainfall and exposure timing.