During the recent decades of satellite era, more tropical cyclogenesis locations (TCLs) were observed over the northwestern part of the western North Pacific (WNP), relative to the southeastern part, during the boreal autumn. This increase in TCLs over the northwestern WNP is largely attributed to the synergy of shifting El Niño-Southern Oscillation (ENSO) and the 1998 Pacific climate regime shift. Both central Pacific (CP) La Niña and CP El Niño have occurred more frequently since 1998, with only one eastern Pacific El Niño observed in autumn 2015. The change in the mean longitude of TCLs is closely linked to the ENSO diversity, whereas the change in the mean latitude is dominated by the warming of the WNP induced by an interdecadal tendency of CP La Niña-like events. The physical mechanisms responsible for this shifting ENSO-TCL linkage can be potentially explained by the tacit-and-mutual configurations between tropical upper-tropospheric trough and monsoon trough, on both interannual and interdecadal timescales, which is mainly due to the ENSO-related large-scale environment changes in ocean and atmosphere that modulate the WNP TCL.

Arctic climate changes include not only changes in trends and mean states but also strong interannual variations in various fields. Although it is known that tropical-extratropical teleconnection is sensitive to changes in flavours of El Niño, whether Arctic climate variability is linked to El Niño, in particular on interannual timescale, remains unclear. Here we demonstrate for the first time a long-range linkage between central Pacific (CP) El Niño and summer Arctic climate. Observations show that the CP warming related to CP El Niño events deepens the tropospheric Arctic polar vortex and strengthens the circumpolar westerly wind, thereby contributing to inhibiting summer Arctic warming and sea-ice melting. Atmospheric model experiments can generally capture the observed responses of Arctic circulation and robust surface cooling to CP El Niño forcing. We suggest that identification of the equator-Arctic teleconnection, via the ‘atmospheric bridge', can potentially contribute to improving the skill of predicting Arctic climate.

No abstract

No abstract

Springtime rainfall, accounting for 25–40% of the annual rainfall in southern China, exerts great agricultural and socioeconomic impacts on the region. In the recent decades, southern China has experienced a significant declining trend of precipitation in boreal spring. Meanwhile, precipitation has increased over the South China Sea and the Philippine Sea (SCS-PhS). This paper presents observational and modeling evidences suggesting that the intensified latent heating released by the convection over SCS-PhS leads to suppressed springtime rainfall over southern China. Moisture budget analysis indicates that the drying trend over southern China is due mainly to weakened convergence of moisture flux, which is controlled by a heat-induced anomalous overturning circulation reinforced by the convection over SCS-PhS. Further idealized simulations support the feature that the heat-induced overturning circulation and its corresponding anomalous cyclone can be well established in several days under the spring mean flow condition. Thus, this rapid dynamic process is associated with both the intraseasonal-to-interannual variations and the long-term change of the springtime rainfall over southern China.

Southwestern China (SWC) has suffered from increasing frequency of heat wave (HW) in recent summers. While the local drought-HW connection is one obvious mechanism for this change, remote controls remain to be explored. Based on ERA-5 reanalysis, it is found that the SWC summer HWs are significantly correlated with sea-ice losses in the Barents Sea, Kara Sea and the Arctic pole. The reduction of Arctic sea ice can cause low pressure anomalies over the polar region due to increased heat-flux exchanges at the sea-air interface, which subsequently triggers southeastward Rossby wave trains propagating from northern Europe to East Asia that induce anomalous anticyclone over SWC. As a result, the North Pacific subtropical high extends westward, accompanied by divergent winds, decreased cloud cover and increased insolation in SWC, which leads to above-normal air temperatures there. In addition, the East Asian westerly jet stream is shifted northward, which enhances (reduces) the moisture convergence in North China (SWC), resulting in prominently drier soil in SWC. Therefore, the sea ice—forced changes in atmospheric circulation and surface conditions favor the occurrences of SWC summer HWs.

Increasing intense landfalling typhoons (LFTYs) are of great coastal threatens to southern China. However, changes in genesis location and landfalling frequency of western North Pacific (WNP) LFTY dedicated to southern China remain unclear. Here we identified such LFTYs during peak summer and found that most LFTYs formed south of 20°N and the LFTY genesis locations over southern WNP have also experienced a sharp interdecadal shift since 1998, which are mainly attributed to the large‐scale environment changes induced by the Mega‐La Niña‐like climate shift. However, LFTY frequency (= “landfalling frequency of southern China typhoon”) shows a slight increasing trend but without significant interdecadal variation. Variations of LFTY frequency are mainly affected by the easterly steering flows near 20°N over the South China Sea and the Philippine Sea, which are closely linked to the WNP subtropical high activity. Our results provide a new perspective on the LFTY activities dedicated to southern China.

Using observational analysis and numerical experiments, we identify that the dipole mode of spring surface wind speed (SWS) over the Tibetan Plateau (TP) could act as a trigger for subsequent winter El Niño–Southern Oscillation events. During the positive phase of spring SWS dipole mode (south‐positive and north‐negative), a self‐sustaining “negative sensible heating–baroclinic structure” prevails over the western TP, which is characterized by negative surface sensible heating anomalies, anomalous low‐level anticyclones, and mid–high‐level cyclones. The “negative sensible heating–baroclinic structure” stimulates the surface westerly wind anomalies over the tropical western Pacific in May through two pathways, favoring the occurrence of subsequent El Niño events. One is through weakening the zonal monsoon circulation over the tropical Indian Ocean and the Walker circulation over the tropical western Pacific. The other is modulating the air–sea interaction over the North Pacific through triggering Rossby waves. The negative SWS dipole mode tends to induce La Niña events.