The East Asian summer monsoon (EASM) has complex drivers and is characterized by an abrupt onset and northward jumps of the main rain band. By analyzing multisource observational data and reanalysis data sets during 1961–2016, we addressed the connection between the preceding diabatic heating of the Tibetan Plateau (TP) and the seasonal march of the EASM. We show that the positive surface sensible heating and condensation heating anomalies over the TP lead the onset, duration, and total precipitation of the rainy season in South China (the first stage of the EASM) by about 2 and 1 month, respectively. A significant positive condensation heating anomaly over the TP can be detected about 1 month before the onset of the rainy season in Southwest China (the second stage of the EASM). By contrast, the relationship between heating of the TP and the onset of the rainy season is relatively weak during the remaining stages of the EASM, including the Meiyu and North China rainy seasons. We suggest that the strong heating of the TP intensifies the low‐level southwesterly circulation to the southeast and facilitates the convergence of moisture and ascending motion, leading to an earlier onset of the rainy season. Sensitive experiments with a linear baroclinic model further confirmed the role of heating of the TP in generating circulation conditions favorable for the onset of the rainy season in both South and Southwest China. The TP heating anomaly therefore acts as a precursor of the early stage onset of the EASM.

Precipitation extremes over the Indochina and South China (INCSC) region simulated by 40 global climate models from phase 6 of the Coupled Model Intercomparison Project (CMIP6) were quantitatively assessed based on the skill score metrics of four extreme precipitation indices when compared with observational results from a high-resolution daily precipitation dataset for 1958–2014. The results show that it is difficult for most of the CMIP6 models to reproduce the observed spatial pattern of extreme precipitation indices in the INCSC region. The interannual variability of the extreme precipitation indices is relatively better simulated for South China than for Indochina. In general, most of the CMIP6 models perform better in South China compared with Indochina when taking both the simulations of spatial pattern and interannual variability into consideration. Only three models (EC-EARTH3, EC-EARTH3-Veg, and NorESM2-MM) can successfully reproduce both the spatial pattern and the interannual variability for the INCSC region. Through model ranking, the multimodel ensemble generated by a selection of the most skillful models leads to a more realistic simulation of the extreme precipitation indices both in South China and Indochina. Better simulation of the meridional wind component over South China and the water vapor convergence over Indochina can partly reduce the wet biases, resulting in a more realistic simulation of extreme precipitation indices over the INCSC region.

A future projection of four extreme precipitation indices over the Indochina Peninsula and South China (INCSC) region with reference to the period 1958–2014 is conducted through the application of a multimodel ensemble approach and a rank-based weighting method. The weight of each model from phase 6 of the Coupled Model Intercomparison Project (CMIP6) is calculated depending on its historical simulation skill. Then, the weighted and unweighted ensembles are used for future projections. The results show that all four extreme precipitation indices are expected to increase over the INCSC region, both in the middle (2041–60) and at the end (2081–2100) of the twenty-first century, under three Shared Socioeconomic Pathway (SSP) scenarios. The increases in total extreme precipitation (R95p), extreme precipitation days (R95d), and the fraction of total rainfall from events exceeding the extreme precipitation threshold (R95pT) in the Indochina Peninsula are more significant than those in South China. The occurrence of extreme rainfall events may become more frequent in the future over the INCSC region, since the probability that R95pT increases is larger than 0.7 in the whole INCSC region. A comparison between the weighted and unweighted ensemble means shows that the uncertainty over South China is almost always reduced after applying the weighted scheme to future probabilistic projection, while the reductions in uncertainty over the Indochina Peninsula may depend on SSPs. The more extreme precipitation over the INCSC region in the future may be related to the larger water vapor supply and the more unstable local atmospheric stratification.

This study examines the characteristics and mechanisms associated with the dominant intraseasonal oscillation (ISO) that controlled eastern Tibetan Plateau summer rainfall (ETPSR) over the period 1979–2011. The results of both power and wavelet spectrum analysis reveal that ETPSR follows a significant 7–20-day oscillation during most summers. The vertical structure of the ETPSR ISO in the dry phase is characterized by a vertical dipole pattern of geopotential height with a positive center on the eastern Tibetan Plateau (TP) and a negative center on the western TP. The wet phase shows the opposite characteristics to the dry phase. The transitions between the dry and wet phases during an ETPSR ISO cycle are related to a Rossby wave train that presents as large anomalous anticyclonic and cyclonic centers that alternate along the pathway from the eastern Atlantic to southern China via the TP. It corresponds to the evolution of the phase-independent wave-activity W, which implies an eastward/southeastward energy propagation of the ISO. The dominant modes of the daily 200-hPa geopotential height as identified by the rotated empirical orthogonal function (REOF) demonstrate that the different phases of the Rossby wave train influence the upper-level circulation over the eastern TP, which then impacts precipitation in the region. Furthermore, fluctuations in the eastern Atlantic may be the key factor for the propagation of the Rossby wave train that influences the upper-level circulation and rainfall variability over the eastern TP. Results from numerical experiments using an atmospheric general circulation model support the conclusion that the fluctuations over the eastern Atlantic contribute to the ISO of ETPSR.

The East Asian summer monsoon precipitation has exhibited a well-known “southern China flood and northern China drought” pattern in recent decades. The increase in aerosols and warming oceans are recognized as two important forcings that control of the precipitation trends over East Asian land. However, in this study, by using large ensemble simulations from the CMIP6 Polar Amplification Model Intercomparison Project (PAMIP), the influence of Arctic amplification, serving as the prominent feature of global warming, is very important in modulating the East Asian summer precipitation pattern, which is comparable to the influence of sea surface temperature (SST). Additionally, the observed “southern China flood and northern China drought” pattern only exists in July and August, whereas a triple pattern with the precipitation positive anomaly center over Middle China occurs in June. These patterns are closely connected with the regional differences in Arctic sea ice loss from June to July, affected through both the Rossby waves propagating in a weaker westerly jet and the decrease in the large-scale meridional thermal contrast in a warming climate.