Large-scale low-frequency rainfall regimes and their transition modes in summertime over China

Seven large-scale low-frequency rainfall regimes (LFRRs) in summertime are identified for China in a 10-dimensional phase space by using a 40-year daily precipitation dataset. Corresponding to the local extrema of observed probability density in phase space, the LFRRs are characterized by the persistence and transitions that reflect the spread and jump features of low-frequency rainfall centers. The LFRRs are generally consistent with summer monsoon rainbelts on the intraseasonal timescale, and there exist the preferred transition relationships between the LFRRs. Four LFRRs’ transition modes (LFRRTMs), which are the dominant components of the interannual and intraseasonal variability of summer rainfall in China, are further induced. Analyses of atmospheric circulation system show that the anomalies of the subtropical high over the western Pacific (SHWP) and blockings in mid-high latitudes, the low-latitude circulation anomalies, and the wavetrains over the East Asia-Pacific region (EAPWs), play crucial roles in the occurrence and transitions of the LFRRs. Moreover, the evolution of the SHWP and blockings, the distribution and movement of the EAPWs, and the intraseasonal variability of the East Asian-Pacific jet stream may be principal factors of the formations of the LFRRTMs.