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This study explored the interannual characteristics of the out‐of‐phase pattern of summer precipitation over northern China during the past years, as well as the possible underlying mechanisms. The out‐of‐phase pattern is characterized by the positive precipitation anomaly in Northwest China (NWC) and the negative anomaly in North China (NC). Our analyses indicate that the variation of Asian westerly jet (AWJ) is found evidently associated with this out‐of‐phase pattern of summer precipitation. The meridional displacement of AWJ induces opposite trends in water vapour transport and circulation anomalies between NWC and NC, leading to the out‐of‐phase pattern. Further analyses suggest that the anomalies of Arctic sea ice concentration (SIC), North Atlantic and Northwest Pacific sea surface temperature (SST) can impact the variation of AWJ by triggering the Eurasian (EU), polar‐Eurasia (POL) and Pacific‐Japan (PJ) teleconnection patterns, respectively, which in turn modulate the formation of this pattern. The precipitation in NWC is primarily affected by the North Atlantic and Northwest Pacific SST anomalies, whereas the precipitation in NC is notably influenced by both SST anomalies and the Arctic SIC anomaly. However, the role of SST anomalies on precipitation in NWC and NC exhibits an evident contrast, leading to the out‐of‐phase pattern of summer precipitation. [ABSTRACT FROM AUTHOR]

This study assessed the capability of the historical simulations of phase 5 and 6 of the Coupled Model Intercomparison Project (CMIP5/6) in reproducing the temporal and spatial characteristics of the Interdecadal Pacific Oscillation (IPO) and its impact on global surface air temperature (SAT), surface equivalent potential temperature (Thetae_sfc) and precipitation. The IPO index time series simulated by CMIP5/6 models deviated from observations and struggled to capture the phase evolution characteristics of the IPO. Nevertheless, CMIP5/6 models successfully captured the horseshoe‐shaped sea surface temperature anomaly in the Pacific. Additionally, the CMIP5/6 models were able to simulate the IPO's 10–30‐year period. Notably, the simulated IPO index exhibited a statistically significant upward trend, which was absent in observations. Additionally, the IPO‐related global land SAT, Thetae_sfc and precipitation simulated by CMIP5/6 models performed differently in boreal winter and boreal summer. Furthermore, the IPO‐related global land SAT performed better in CMIP5/6 models during boreal winter than that in boreal summer. In CMIP6 models, it improved during both boreal winter and summer compared to CMIP5 models. In terms of the IPO‐related global land Thetae_sfc, CMIP5/6 models also performed better during boreal winter than in boreal summer. However, CMIP5 models outperformed CMIP6 models during the boreal summer. In terms of the IPO‐related global land precipitation, CMIP5/6 models performed better during boreal summer compared to boreal winter. Moreover, the IPO‐related global land precipitation in CMIP6 models improved significantly in boreal winter, but almost the same in boreal summer, compared to CMIP5 models. Further studies showed that the enhancements in simulating IPO's spatial pattern did not correspond to improvements in the model's ability to simulate IPO's global teleconnections. [ABSTRACT FROM AUTHOR]

Nights with high temperatures and humidity often bring more fatal consequences during the human sleeping process. A significantly increasing trend in the intensity and frequency of humid‐heat nights has been observed in eastern China from 1961 to 2014. Detection analyses show that the fingerprinting of anthropogenic forcing, in which the greenhouse gas forcing is critical, can be identified for changes in the humid‐heat nights in eastern China. However, the roles of anthropogenic aerosols and external natural forcings cannot be detected, and their effects on the observed changes in humid‐heat nights over eastern China are generally negligible. Under different warming scenarios, there is a projected continuation of increasing intensity and frequency of humid‐heat nights, although the magnitudes are reduced after constraining. In eastern China, the areal mean intensity of humid‐heat nights is projected to increase by approximately 0.9, 1.5, 2.5, and 3.5°C (relative to 1995–2014) for 1.5, 2.0, 3.0, and 4.0°C global warming, while the occurrence of extreme humid‐heat night is 1.1, 1.2, 1.2, and 1.3 times more than the current period. Moreover, the population exposed to humid‐heat nights in eastern China, particularly in the northern regions, is expected to increase in the future. Our results enhance the understanding of the potential risks of humid‐heat nights, which is critical for climate‐change policy in China. Plain Language Summary: Eastern China experienced a significant rise in the intensity and frequency of heat stress events during nighttime from 1961 to 2014. Based on a detection technique, the anthropogenic influence, specifically greenhouse gas forcing, has been identified as the primary driver of these changes. Despite some mitigation, the intensity and frequency of humid‐heat nights are projected to keep increasing under different warming scenarios. Consequently, the population exposed to these events, particularly in northern regions, will continue to grow. Urgent implementation of adaptation measures is crucial to mitigate the escalating risks posed by nighttime heat stress in eastern China. Key Points: A significantly increasing trend in the intensity and frequency of humid‐heat nights has been observed in eastern ChinaAnthropogenic influence, driven by greenhouse gas emissions, is detectable in intensified humid‐heat nightsHumid‐heat nights are expected to intensify, leading to a higher population exposed to these events in the future [ABSTRACT FROM AUTHOR]

This study investigates the spatiotemporal variations of the summer frequency of daytime–nighttime compound extreme high-temperature events (FCEHEs) in the mid–high latitudes of Asia (MHA) from 1979 to 2014. Results show that FCEHE has shown an upward trend with fluctuations, especially in Mongolia–Baikal. The descending anomaly caused by the anomalous high pressure over Mongolia–Baikal results in reduced cloud cover, which increases solar radiation reaching the ground, favoring the higher FCEHE. This process is consistent during the daytime and nighttime periods, with relatively limited nighttime solar radiation, potentially compensated by the increased downward longwave radiation to sustain the extreme high temperatures. This benefit process is closely connected with two main factors: the increased sea ice in the Barents Sea during spring and the anomalously warm sea surface temperature (SST) in the Northwest Pacific during summer. The increased sea ice can affect the Eurasia (EU) teleconnection, while the warm SST affects the Pacific-Japan/East Asia–Pacific pattern (PJ/EAP). Subsequently, these factors further modulate the circulation anomalies and then FCEHE. Significance Statement: This study provides valuable insights into the spatiotemporal variations and the possible underlying mechanisms for change in the frequency of daytime–nighttime compound extreme high-temperature events (FCEHEs) in the mid–high latitudes of Asia. The spring sea ice anomalies over the Barents Sea and summer sea surface temperature anomalies in the Northwest Pacific affect the local anticyclonic circulation in Mongolia–Baikal through Eurasia (EU) and Pacific-Japan/East Asia–Pacific (PJ/EAP) patterns, respectively. The resulting descending anomaly and reduced cloud cover contribute to interannual variations of FCEHE, which is highly similar during the daytime and nighttime periods. During the nighttime, when the solar radiation is relatively limited, the increased downward longwave radiation may compensate to sustain extreme high temperatures. [ABSTRACT FROM AUTHOR]

More than 1000 years, the Meiyu–Baiu have shaped the uniqueness of natural resources, civilization and culture in the Yangtze River Basin of China and the main islands of Japan. In recent decades, frequent rainstorms and droughts have seemingly diminished the misty features of traditional Meiyu–Baiu rainfall. However, there is still no consensus on whether their traditional nature is suspended. In this study, we quantitatively demonstrate that the Meiyu–Baiu almost completely lost their traditional features during 1961–2023, ∼80% of which can be attributed to anthropogenic warming. Furthermore, in a warmer future, the traditional Meiyu–Baiu will be more unlikely to appear. This study underscores the urgency in adapting to climate shift because destructive extremes are measurably taking the place of mild and maternal rains. [ABSTRACT FROM AUTHOR]

This study investigates the anthropogenic contribution to the summer precipitation changes over southern China and the underlying physical mechanisms. Observations show a wetting trend over southeastern China (SEC) but a drying trend over southwestern China (SWC) in summer of 1961–2014. The dipole pattern can be reasonably reproduced by the anthropogenic forcing simulations of CMIP6 models but with weak trends under the external natural forcing simulations, suggesting the vital human contribution to the observed changes. Particularly, anthropogenic greenhouse gases (GHG) dominate the wetting trend over SEC, while the drying trend over SWC is primarily attributed to anthropogenic aerosol (AA) emissions. Further analysis shows that the GHG concentrations enhance the subtropical high over the western North Pacific (WNP) via the heterogeneous warming of the sea surface temperature, decrease the sea level pressure over eastern China, and increase the atmospheric moisture, facilitating the moisture flux convergence (MFC) and the precipitation over SEC. The GHG‐induced wetting trend is somewhat offset by the inhibited evaporation due to the AA forcing. For SWC, the decreased precipitation is influenced by the anomalous high pressure from India to WNP, which is closely associated with the enhanced Asian AA emission and the interhemispheric asymmetrical distribution of AA emissions. In the upper troposphere, the uneven AA emissions between South and East Asia and Europe weaken the East Asian summer subtropical jet, resisting the western moisture to SWC. Both factors in the low‐and‐high levels suppress the MFC and precipitation over SWC, counteracted by the thermodynamical effects of GHG forcing. Plain Language Summary: Previous studies have documented the emergence of human signal in changes in precipitation over China, but how the anthropogenic forcing affects the precipitation changes across China is still unclear. This study examines the influence of human activities, such as greenhouse gases (GHG) and anthropogenic aerosol (AA) emissions, on summer precipitation changes in southern China. Observations show a wetting trend in southeastern China (SEC) and a drying trend in southwestern China (SWC) from 1961 to 2014. The simulations indicate that GHG contribute to the wetting trend in SEC, while AA emissions are responsible for the drying trend in SWC. GHG enhance the subtropical high over the WNP, increase atmospheric moisture, and promote precipitation in SEC. In SWC, the high pressures influenced by increased Asian AA emissions weaken moisture flow, leading to decreased precipitation. Uneven AA emissions between regions also impact the transport of moisture. Overall, human activities have a significant impact on the observed changes in summer precipitation in southern China. Key Points: The wetting trend in southeastern China is primarily attributed to the greenhouse gases emission through both dynamic and thermodynamic effectsAerosol emissions are responsible for the drying trend in southwestern China and the dynamic processes dominate the decreased precipitationAerosol induced evaporation decreases precipitation in southeastern China and the drying trend in southwestern China is offset by GHG effect [ABSTRACT FROM AUTHOR]

One prominent mode of the variability in the summer wet‐bulb temperature (WBT) over eastern China exhibits a distinct north‒south dipole pattern. This pattern demonstrates a positive center in northern China (NC), while a negative center is observed in southern China (SC). Our results indicate that the dipole mode of WBT could be partially ascribed to the impact of spring snow anomalies in eastern Europe–western Siberia (EEWS). The reduction in the snow depth, coupled with dry soil conditions, enhances the surface heat flux and consequently leads to an increase in the near‐surface air temperature. The signal of soil moisture could persist from spring to summer, stimulating the generation of zonal Rossby waves. Consequently, the significant wave flux anomalies propagate from EEWS downstream and influence the atmospheric circulation over eastern China. These patterns play a role in the increase in the surface air temperature and moisture accumulation over NC, ultimately leading to the establishment of the dipole mode of WBT over eastern China in summer. Further analysis indicates that the atypical low sea surface temperature in the tropical Ocean, induced by the El Niño‐Southern Oscillation, establishes a climatic context favorable for the persistence of an anomalous cyclone in the Northwest Pacific (NWP) throughout the summer season. The strengthened convection over the NWP and SC induces a dipole pattern of atmospheric circulation by stimulating a meridional wave train. This pattern creates favorable temperature and moisture conditions, contributing to the development of the dipole mode of the summer WBT across eastern China. Plain Language Summary: In recent decades, the social loss associated with high‐temperature and high‐humidity conditions has sharply increased. The wet‐bulb temperature (WBT) is widely regarded as a highly effective metric for characterizing the combined stress of humidity and heat. In this study, we emphasized one of the important modes (a north‒south dipole pattern) of the variability in the summer WBT over eastern China and revealed the corresponding underlying mechanisms. We found that mid‐high and low latitudinal dynamic processes may exert a synergistic effect on WBT over eastern China. On one side, spring snow depth anomalies could be coupled with spring soil moisture anomalies over eastern Europe–western Siberia and subsequently influence the dipole mode of the summer WBT over eastern China by triggering the stimulation of zonal Rossby waves. On the flip side, the anomalous low sea surface temperature in the tropical Ocean, driven by the ENSO, could yield a climatic state that supports the prolonged existence of an anomalous cyclone over the Northwest Pacific throughout the summer season. This cyclone exerts a significant impact on the dipole mode of the summer WBT over eastern China. Our study compensates for the lack of humid heat effect‐related research across eastern China and contributes to establishing a solid theoretical foundation for comprehending and forecasting the summer WBT in the region. Key Points: One significant pattern of the variability in the summer wet‐bulb temperature (WBT) over eastern China is manifested as a north‒south dipole modeAnomalous spring snowfall over Eurasia can impact the dipole mode of summer WBT over eastern China via the stimulation of zonal Rossby wavesThe anomalous sea surface temperature over tropical ocean, triggered by El Niño‐Southern Oscillation, establishes a climatic context conducive to the dipole mode over eastern China [ABSTRACT FROM AUTHOR]

This study reveals a significant subseasonal reversal of precipitation on the western Tibetan Plateau (WTP) from a deficit in December to an increase in January and February (JF). Changes in vertical moisture advection induced by the dynamic effects contribute mostly to the subseasonal precipitation trend reversal. This process involves the reversal of the subseasonal westerly driven uplift, accompanied by the weakened (enhanced) subtropical westerly jet and anticyclonic (cyclonic) anomalies over the WTP in December (JF). Further analysis shows that the North Atlantic Tripolar‐like (NAT) sea surface temperature (SST) modes could regulate the sunseasonal winter precipitation reversal over the WTP. The spatially inconsistent changes in SST can result in subseasonal reversed turbulent heat flux anomalies over Iceland‐Scandinavia in December and JF. In particular, the suppressed turbulent heat flux over the extratropical Northeast Atlantic in December leads to significant descending motion and upper tropospheric convergence. The advection of absolute vorticity induced by convergent winds associated with the NAT favors the generation of Rossby wave sources over Iceland‐Scandinavia, which then enhances the wave activity fluxes propagation. However, there are no significant changes in wave sources over Iceland‐Scandinavia in JF. The discrepancies in wave propagation intensity over Iceland‐Scandinavia determine the changes in the atmospheric pattern over the WTP, with anomalous anticyclone in December and cyclone in JF, and ultimately lead to the precipitation reversal. Furthermore, our results show that the suppressed transient eddies over the Atlantic storm track in JF may also contribute to the weakened wave propagation over Iceland‐Scandinavia. Key Points: A subseasonal reversal of precipitation in winter is evident in precipitation anomalies over the western Tibetan PlateauThe main contributor to the precipitation reversal is the subseasonal reversal of vertical moisture advection due to dynamic effectsThe Atlantic tripolar sea surface temperature anomalies could regulate precipitation reversal through stimulating asymmetric circulation mode over Eurasia [ABSTRACT FROM AUTHOR]