What Controls the Interannual Variability of Extreme Precipitation?

The controlling factors of the interannual variability of extreme precipitation (EP) are examined on a global scale. We quantify the moisture (thermodynamic) and vertical motion (dynamic) contributions to the interannual variability of EP by applying a physical scaling diagnosis. The thermodynamic contribution is small and the dynamic contribution dominates the interannual variability of EP. We further apply a quasi-geostrophic diagnosis on EP to decompose the vertical motion and its variability into components due to the large-scale adiabatic perturbations (dry dynamics) and the diabatic heating feedback (moist dynamics). The variability of vertical motion associated with large-scale adiabatic perturbations is approximately twice that of the diabatic heating feedback. These results highlight the dominant role of the large-scale adiabatic perturbations on the year-to-year variability of EP, in contrast to the responses of EP to global warming, in which both the large-scale adiabatic perturbations and diabatic heating feedback are important.