Jingliang Huangfu

Summer 2024 observed a record‐low tropical cyclone (TC) landfall activity over China, with only two landfalls representing a 59.8% reduction from the 1979–2023 climatological mean. This study investigates the characteristics and underlying mechanisms of this extreme suppression, revealing distinct monthly variations driven by divergent genesis‐related factors. In June, no TCs formed, attributable to an anomalously strong and westward‐extended western Pacific subtropical high (WPSH) that suppressed monsoon trough‐associated convection. July recorded near‐normal landfall frequency despite moderately suppressed genesis, as westward‐displaced TC formations and southeasterly steering flows favored TC tracks toward southeastern China. In August, extreme landfall suppression (zero landfalls) occurred despite normal genesis frequency, primarily due to a pronounced northward shift in genesis locations (mean latitude: 24.7°N) induced by northeastward‐propagating boreal summer intraseasonal oscillation (BSISO)‐associated westerly surges, coupled with anomalous steering flows that deflected all TCs away from China. From a seasonal perspective, this suppressed activity was fundamentally driven by the 2023/2024 “double‐peaked” El Niño event, characterized by dual warming centers in the eastern Pacific (EP) and central Pacific (CP). The persistent Indian Ocean warming after this event operated via the Indian Ocean capacitor pathway, triggering unprecedented intensification and meridional expansion of the WPSH and producing persistent suppressive large‐scale dynamical conditions throughout summer 2024. These findings highlight the critical role of the BSISO and “double‐peaked” El Niño events in modulating western North Pacific TC landfall activity.

Tropical cyclones (TCs) affecting China pose a major threat to coastal populations and economies, yet the large-scale climate controls on these TCs may vary over time. Here, we show that the influence of the Pacific–Japan (PJ) pattern on summertime (June–August) TCs affecting China has weakened markedly since the early-2000s. During 1979–2002, positive PJ phases were associated with significantly more TCs affecting China than negative phases, whereas this contrast largely disappeared during 2003–2025. This weakening primarily resulted from an eastward displacement of the PJ pattern and the associated circulation anomalies during summer. Before the early-2000s, the positive PJ phase enhanced TC genesis over the South China Sea and Philippine Sea, accompanied by easterly steering flow that favored westward propagation toward China. After the early-2000s, the PJ-related TC genesis enhancement became concentrated farther east over the western North Pacific, substantially weakening the PJ modulation of TCs in regions closer to China. Meanwhile, the PJ-related steering flow became less favorable for westward TC propagation toward China. These findings demonstrate that interdecadal shifts in the spatial structure of climate modes can fundamentally alter established climate–hazard relationships and reshape regional TC risk.

This study reveals the remarkable differences in the synoptic‐scale tropical waves before and after the South China Sea (SCS) summer monsoon (SCSSM) onset. Before the monsoon onset, the dominant synoptic‐scale systems around the SCS are the eastward‐propagating equatorial Kelvin waves. After the SCSSM onset, while the Kelvin waves remain largely unaltered, the transitions from mixed Rossby‐gravity waves to tropical depression (TD)‐type waves become more pronounced. Such distinctive features of the tropical waves before and after SCSSM onset are attributable to the adjustments in atmospheric mean flow. An anomalous low‐level cyclone develops around the SCS after the monsoon onset. The convergence and shear of this anomalous low‐level cyclone contribute to the barotropic energy conversion from the mean flow to the synoptic‐scale systems, which is conducive to the development of TD‐type waves and genesis of tropical cyclones.

This study focuses on the primary synoptic‐scale patterns and precursors of extreme and non‐extreme precipitation over the Tibetan Plateau (TP). Atmospheric circulation anomalies and their precursors associated with regional extreme precipitation events (REPE) demonstrate distinct precursor wave train and heightened intensity than regional non‐extreme precipitation events (non‐REPE). Specifically, REPE over the northwestern TP (NWTP) exhibits a geopotential height anomaly induced by a latitudinal propagating Rossby wave train along 40°N. In contrast, over the southeastern TP (SETP), REPE is characterized by a geopotential height anomaly caused by a northwest‐southeastward propagating Rossby wave train. The ascending motion anomalies of REPE over both NWTP and SETP are primarily attributed to the geostrophic zonal temperature advection, which is significantly stronger during REPE compared to non‐REPE. This finding provides valuable insights for forecasting summer extreme precipitation over TP.

This study developed an objective identification algorithm for the Southwest Vortex (SWV), the dominant rainstorm system prevalent in Southwest China. Based on the TempestExt package, the newly developed SWV identification algorithm employed a 12 h minimum duration threshold, utilizing the high-resolution ERA5 dataset with 1 h intervals. The results reveal that the algorithm precisely identifies the SWV records documented in the SWV Yearbooks, achieving an optimal balance of high probability of detection and low false alarm rate. In addition, the algorithm can detect the SWVs in advance, offering a significant enhancement to SWV monitoring. Notably, the algorithm-detected SWVs exhibit a strong correlation with rainstorms, with a correlation coefficient of 0.70. From an on-site precipitation perspective, the algorithm-detected SWVs account for 87.6% of the observed rainstorm days. Collectively, this study introduces an updated tool for the SWV identification and underscores the algorithm’s promising potential in improving rainstorm forecasts in Southwest China.

Along the East Asian coast, the interdecadal variation in tropical cyclone (TC) landfall activities in the early 2010s shows a tripole change pattern characterized by significantly increased (decreased) TC landfalls to the north of 30°N and to the south of 20°N (between 20° and 30°N). The increased TC landfalls in the East Asian subregion north to 30°N mean greater TC damage in the most populous regions, including southeastern China, the Korean Peninsula, and Japan, since the early 2010s. The present work uses an objective clustering technique to analyze the internal dynamical causes of this interdecadal variation. The increased TC landfall activities in the East Asian subregion north of 30°N are attributed to the increase in TCs with a northwestward-moving track (cluster defined as C1), whereas the increased TC landfall activities to the south of 20°N and the decrease between 20° and 30°N are mainly due to the southward shift of TCs with a westward-moving track (cluster defined as C2). This work focuses on different TC track groups (C1 and C2) based on daily data, showing that the interdecadal changes in the synoptic-scale monsoon trough and subtropical high provide important environment for different groups of TCs. The ascending phase of the PDO with significant warming over the central Pacific favors the interdecadal tripole changes in TC landfalls.

Along the East Asian coast, the interdecadal variation in tropical cyclone (TC) landfall activities in the early 2010s shows a tripole change pattern characterized by significantly increased (decreased) TC landfalls to the north of 30°N and to the south of 20°N (between 20° and 30°N). The increased TC landfalls in the East Asian subregion north to 30°N mean greater TC damage in the most populous regions, including southeastern China, the Korean Peninsula, and Japan, since the early 2010s. The present work uses an objective clustering technique to analyze the internal dynamical causes of this interdecadal variation. The increased TC landfall activities in the East Asian subregion north of 30°N are attributed to the increase in TCs with a northwestward-moving track (cluster defined as C1), whereas the increased TC landfall activities to the south of 20°N and the decrease between 20° and 30°N are mainly due to the southward shift of TCs with a westward-moving track (cluster defined as C2). This work focuses on different TC track groups (C1 and C2) based on daily data, showing that the interdecadal changes in the synoptic-scale monsoon trough and subtropical high provide important environment for different groups of TCs. The ascending phase of the PDO with significant warming over the central Pacific favors the interdecadal tripole changes in TC landfalls.

Convectively coupled equatorial waves (Kelvin waves, equatorial Rossby waves, the Madden–Julian Oscillation, tropical depression–type waves, and mixed Rossby–gravity (MRG) waves) are important components of the tropical atmosphere. It is already known that the first four kinds of equatorial waves can trigger the onset of the South China Sea summer monsoon (SCSSM). This study provides observational evidence that an MRG wave contributes to triggering the onset process of the SCSSM in 2023, which took place very early (advanced by two weeks). Specifically, anomalous upper-tropospheric southerly winds first appeared in the equatorial central Pacific at the end of April. These southerly winds propagated westwards and downwards to the equatorial western Pacific and became an MRG wave. As this MRG wave continued to propagate westwards, the associated southwesterly winds contributed to the SCSSM onset. In addition to the MRG wave, the westerly phase of the Madden–Julian Oscillation is located around the Maritime Continent, which also creates a favorable environment for the SCSSM onset in 2023. After addressing the important role of the MRG wave, this study completes the last piece of the puzzle of the impacts of equatorial waves on the monsoon onset.

This paper is written to commemorate the 10th anniversary of academician Ye Duzheng (Yeh T.C.) pass away and his great contributions to the development of atmospheric dynamics. Under the inspiration and guidance of the theory of Rossby wave energy dispersion, remarkable progresses have been made in research on planetary wave dynamics and teleconnections of atmospheric circulation anomalies. This paper aims to make a brief review of the studies on the propagating characteristics of quasi-stationary planetary waves in a three-dimensional spherical atmosphere and the dynamic processes of the interannual and interdecadal variabilities of the East Asian summer and winter monsoon systems. Especially, this paper systematically reviews the progresses of the studies on the impacts of the interannual and interdecadal variabilities of the East Asia/Pacific (EAP) pattern teleconnection wave train propagating along the meridional direction over East Asia and the “Silk Road” pattern teleconnection wave train propagating along the zonal direction within the subtropical jet from West Asia to East Asia on the East Asian summer monsoon system and the summer precipitation variability in China, under the guidance of the theory of Rossby wave energy dispersion. Moreover, this paper reviews the dynamic processes of the impact of the interannual and interdecadal oscillations of the propagating waveguides of boreal quasi-stationary planetary waves on the variability of the East Asian winter monsoon system.