Thermodynamic Moistening and Decadal Circulation Modulation of the Recent Increase in Precipitation Extremes Over the Beijing‐Tianjin‐Hebei Region

Abstract

Extreme precipitation has intensified over North China during the early twenty‐first century, yet the interplay among thermodynamic moistening, atmospheric circulation, and decadal ocean variability remains insufficiently understood. Here we investigate summer precipitation extremes over the Beijing‐Tianjin‐Hebei (BTH) region using daily observations. Six precipitation‐extreme indices characterize changes in intensity, persistence, frequency, and accumulated extremes. Multiple extreme indices exhibit a coherent upward shift around 2015/2016, and extreme precipitation amount (R95p) increased by nearly 50% from 2001–2011(P1) to 2016–2025(P2). With regional and lower‐tropospheric warming, moisture content, saturation vapor pressure, and convective instability increased, establishing more favorable thermodynamic conditions. These conditions coincided with strengthened monsoon moisture transport, low‐level convergence, upper‐level divergence, and deep ascent, all associated with the western North Pacific subtropical high, South Asian high, and East Asian westerly jet. A grouped Shapley/LMG model explains 58.8% of interannual R95p variance during 2001–2025. Atmospheric circulation and decadal ocean variability contribute 30.7% and 31.5%, respectively, of the model‐explained variance. For the P1‐to‐P2 increase, atmospheric circulation has the largest central contribution (53.5%), compared with thermodynamic moistening (14.8%), moisture transport (17.0%), and Pacific Decadal Oscillation/AMO‐related decadal ocean variability (14.7%). These diagnostic results support that thermodynamic moistening and decadal circulation modulation jointly explain R95p increase.