This study focuses on regional extreme precipitation (REP) in North China. We found a trend turning in summer (July and August) REP frequencies and intensities from a decrease trend in 1961-2002 to an increase trend in 2003-2020, accompanying which, the extreme rain belt shows a southward shift, and the connections of the REP with Ural blocking and with the western Pacific subtropical high (WPSH) are enhanced in 2003-2020. The low and high pressures at west and east of North China (the low-high dipole, LHD) leads to northward moisture transport, air rising and rain there. During the REP the high pressure of the LHD at Northeast China (the NEH) is strongly amplified through the forcing of Rossby wave energy propagating along the zonal subpolar/subtropical wave guide over Eurasian on the preexisting northeast Asia stationary ridge. In 2003-2020, the enhancement of Ural stationary ridge favors the development of Ural blockings (UB), and leads to a change of the eastward Rossby wave propagating path from along the subtropical wave guide in 1961-2002 to along the polar wave guide in 2003-2020, which connects the UB and the LHD, leads to a strengthened-and- northeastward-shift/southwestward-shift of the low/high of the LHD. The JA mean WPSH expands more westward-northward in 2003-2020 than in 1961-2002. It provides a condition for a further westward-northward expanding of the daily WPSH under the influence of the NEH before the REP, which brings strong moisture from north Pacific and results in a strengthening of extreme rain over southern North China.

This study focuses on regional extreme precipitation (REP) in North China. We found a trend turning in summer (July and August) REP frequencies and intensities from a decrease trend in 1961–2002 to an increase trend in 2003–2020, accompanied by a southward shift of the extreme rain belt, and an enhanced connection with the Ural blocking and the Western Pacific Subtropical High Pressure (WPSH) in 2003–2020. Rains in North China are accompanied by a west-east low-high dipole (LHD) at upper troposphere. During the REP, the high of the LHD at Northeast China (the NEH) is strongly amplified from a pre-existing stationary ridge at northeast Asia under the influence of eastward propagating Rossby wave energies along the subpolar/subtropical wave guide over Eurasia. For the REP years, an enhanced stationary ridge over the Ural Mountains in the period 2003–2020 replaces the stationary Ural trough in the period 1961–2002, favouring the development of Ural Blockings (UB) and leading to a change of the Rossby wave propagation path from along the subtropical wave guide in 1961–2002 to along the polar wave guide in 2003–2020. Therefore, a connection between the NEH and the UB forms, which may lead to a higher probability of extreme precipitation in North China since blocking is a major source of strong circulation anomalies. The mean summer WPSH expands more westward-northward in 2003–2020 than in 1961–2002, providing the background conditions for further westward-northward expanding of the daily WPSH under the influence of the NEH before the REP day leading to strong moisture transport from north Pacific and increased intensity and probability of extreme precipitation over southern North China.