Extreme precipitation (EP) is frequently observed in southwest Zhejiang Province of China in June. The present study reveals distinct atmospheric circulations for EP in early-middle and late June. The early-middle June EP is influenced by both mid-latitude and tropical systems. It tends to occur accompanying westward extended western Pacific subtropical high, eastward extended South Asian high, enhanced East Asian jet stream, East Asian meridional wave pattern, and mid-latitude zonal wave pattern. The EP region is located to north of climatological rain band. The late June EP is mainly induced by mid-latitude systems. It is inclined to occur accompanying southward shifted East Asian jet stream, deepened East Asian trough, and mid-latitude zonal wave pattern. The EP region is located to south of climatological rain band. Anomalous ascent leading to EP is contributed by both lower-level convergence and upper-level divergence in early-middle June, but is mainly due to upper-level divergence in late June. Geopotential height anomalies switch from negative at lower troposphere to positive at upper troposphere over eastern China corresponding to early-middle June EP. This is related to positive temperature anomalies attributed to anomalous southwesterly flow. The accompanying increase of northward pressure gradient with the altitude leads to enhancement and expansion of the East Asian jet stream. Negative geopotential height anomalies increase with the altitude over eastern China corresponding to late June EP. This is associated with negative temperature anomalies attributed to anomalous northerly flows. The resultant increase of northward pressure gradient with the altitude causes southward shift of the East Asian jet stream.

More than half of the winter extreme precipitation days in the southern Philippines occurred in La Ni & ntilde;a years during 1996-2022. The present study investigates atmospheric circulation patterns and synoptic systems leading to the occurrence of those extreme precipitations. It is found that La Ni & ntilde;a winter extreme precipitation in the southern Philippines tends to occur when the East Asian winter monsoon is stronger. Extreme precipitation in the southern Philippines is caused by three synoptic systems: westward-moving tropical cyclones (TCs) and tropical depressions (TDs) generated in the Philippine Sea, northeasterly cold surges (CSs) originating from midlatitude East Asia, and local vortices (LVs). Those synoptic systems act individually or in combination in causing extreme precipitation in the southern Philippines. They are associated with different atmospheric circulation patterns. TCs/TDs play the role when anomalous upper-level divergence over the tropical central Pacific is located northward and the westward steering flows are present over the Philippine Sea, favorable for the westward move of TCs/TDs generated in the Philippine Sea. CSs play the role when the East Asian trough is intensified and the East Asian westerly jet stream is enhanced, which is favorable for the occurrence and southward move of the CSs. LVs play the role when anomalous downward motion over the tropical central Pacific is located southward and anomalous lower-level convergence over the southern Philippines is shifted southward, favorable for the formation of LVs.

Extreme cold winters and hot summers over Eurasia are intensifying under global warming, posing substantial risks to agriculture, ecosystems, and human health. Here, we show that a colder winter tends to be followed by a hotter summer over Eurasia. This winter-summer extreme temperature reversal is linked to the phase switch of the Arctic oscillation (AO) from winter to summer, which is driven by the North Atlantic air–sea interaction and Arctic sea ice-atmosphere coupling. Specifically, a negative AO in winter weakens high-latitude westerlies, causing cold extremes over Eurasia. Negative AO also induces a tripolar sea surface temperature anomaly in the North Atlantic that persists into the following summer and triggers positive AO-like atmospheric anomalies, leading to a hotter summer across Eurasia. Moreover, winter atmospheric anomalies reduce the Barents–Kara sea ice through horizontal moisture transport. This sea ice loss persists into summer and contributes to the formation of positive AO-like atmospheric anomalies. These processes establish a cross-seasonal transition from extreme cold winters to extreme hot summers over Eurasia, offering new insight into the prediction of summer extreme events.

Under ongoing global warming, Eurasia has experienced more frequent extreme temperature events, which heighten the risks to food security, ecosystems, water resources, and socio-economic stability. Previous studies have indicated that colder Eurasian winters are often followed by hotter summers. Here, we show that the out-of-phase relationship between Eurasian winter and subsequent summer surface air temperature (SAT) anomalies has strengthened significantly since the early 1990s. After the early 1990s, colder Eurasian winters are due to a negative Arctic Oscillation (AO)-induced atmospheric anomalies. Negative AO also excites a tripolar North Atlantic sea surface temperature (SST) anomalies that persist into the subsequent summer via air-sea interaction. In addition, winter sea-ice decreases in the Barents-Kara Sea related to the negative AO persist to the following summer. These lagged SST and sea-ice anomalies jointly favor a transition toward a positive AO in the following summer, leading to a hotter summer and establishing a robust reversal of SAT anomalies from winter to summer over Eurasia. Before the early 1990s, the winter AO pattern was weaker and shifted northward, failing to trigger a tripolar North Atlantic SST anomaly pattern, and the North Atlantic SST anomalies cannot persist to the following summer. Consequently, no robust signal of reversal in winter-summer SAT anomalies emerged over Eurasia.

Droughts of different durations affect water resources and ecosystems in distinct ways. Human activities have been confirmed to contribute to the increased occurrence of droughts; however, the dependence of these impacts on the durations of drought, and whether they differ between drylands and humid regions, remains insufficiently understood. This study investigates the human influence on droughts of different durations using the Standardized Precipitation Evapotranspiration Index (SPEI), derived from multi-source observations and four sets of Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model simulations. The results show that human activities cause an intensification of long-term droughts, particularly in drylands. This is primarily attributed to rising greenhouse gas (GHG) emissions, with both GHGs and aerosols exerting stronger impacts on droughts in drylands than in humid regions, though aerosols partly offset the intensifying effect. GHGs contribute to more extreme multi-year droughts over drylands by amplifying temperature-induced water demand, whereas aerosols reduce drought occurrence in drylands by enhancing precipitation, in contrast to their precipitation-suppressing effects in humid areas in the past decades.

Extreme precipitation in New Guinea may induce anomalous heating, leading to change in the Walker circulation. Present study investigates the reason for the occurrence of extreme precipitation in New Guinea during boreal winters of 1996–2022 using multiple datasets. Composite analysis reveals distinct atmospheric circulation patterns corresponding to New Guinea extreme precipitation during El Niño and La Niña winters. During El Niño winters, anomalous upward motion extends westward from the equatorial central Pacific to New Guinea, indicating a broad eastward shift of the Walker circulation. During La Niña winters, anomalous upward motion dominates New Guinea and anomalous downward motion lies over the equatorial central Pacific, signifying an eastward extension of the ascending branch of the Walker circulation. Cluster analysis reveals two types of atmospheric circulation patterns and synoptic disturbances leading to extreme precipitation in New Guinea. During El Niño winter, one cluster features a northwest-southeast contrast of anomalous vertical motion between the South China Sea-Philippines and New Guinea and the other cluster a west-east contrast of anomalous vertical motion between southeast tropical Indian Ocean and New Guinea. The synoptic disturbance leading to extreme precipitation in New Guinea is a southeastward moving anomalous cyclone from the South China Sea and a westward moving anomalous cyclone from the tropical central Pacific, respectively. During La Niña winters, both clusters features a west-east contrast of anomalous vertical motion. The synoptic disturbance leading to extreme precipitation in New Guinea is a pair of westward moving anomalous cyclone from east and an anomalous cyclone from southeast, respectively.

The intensification rate (IR) of tropical cyclones (TCs) is influenced by environmental conditions. Atmospheric and oceanic conditions for TC intensification are non-uniform in the western North Pacific (WNP). This study compares environmental factors of slow intensification (SI) and rapid intensification (RI) TCs and their spatial dependence in the WNP during 1980–2021. SI and RI TCs are classified into two clusters using the K-means clustering method. The cluster 1 and cluster 2 TCs are located in the western and eastern WNP, respectively. It is found that the effects of mid-level humidity anomalies are larger in the eastern than western WNP and sea surface temperature anomalies have a negative effect on SI TCs in both the western and eastern WNP. A quantitative analysis based on the decomposition of the genesis potential index reveals that low-level vorticity is the dominant factor influencing TC IR, mid-level relative humidity and VWS have a secondary contribution, and the oceanic condition has a small effect in both the western and eastern WNP.

This study investigates the trans-seasonal connection between boreal spring (MAM) Tibetan Plateau snow cover (TPSC) and subsequent summer-fall (JJASON) western North Pacific (WNP) tropical cyclone (TC) formation during 1979-2020. It is found that increased MAM TPSC suppresses TC formation in the southeastern WNP. The remote influence of MAM TPSC is transferred by anomalous atmospheric heating/cooling and tropical WNP sea surface temperature (SST) anomalies. Specifically, excessive TPSC enhances surface upward short-wave radiation reflection, inducing atmospheric cooling above the Plateau. This atmospheric cooling over the Tibetan Plateau could lead to enhancement and southward extension of an atmospheric Rossby wave train that propagates to the WNP, generating an anomalous lower-level anticyclone and an upper-level cyclone. Through a positive air-sea feedback mechanism, this atmospheric pattern persists into the JJASON season. Consequently, the combined effect of lower-tropospheric easterlies and upper-tropospheric westerlies on the southern flank of these anomalies enhances vertical wind shear over the southeastern WNP, thereby inhibiting TC genesis during JJASON.

Since the 1990s, inter-tropical Africa (ITA) has experienced consecutive calamitous droughts during the boreal spring. Although the observed precipitation regime changes have been attributed to tropical Indian Ocean-western Pacific warming and/or tropical Pacific La Niña-like cooling, the model-projected past-to-future widespread wetting response to anthropogenic warming overshadows qualitative attributions of decadal shifts in historical precipitation regimes and the reliability of near-term projections. The causes of ITA precipitation regime shifts and the likelihood of their future continuation remain unclear. Here, we reveal that the observed monopolar precipitation changes in ITA are primarily driven by the tropical easterly jet (TEJ)-dominated pattern, with a secondary contribution from the intertropical convergence zone (ITCZ)-mediated pattern. The Indo-Pacific warming-induced TEJ strengthening favors a monopolar drying trend from 1950 to 2022, while the northward-shifted ITCZ drives a west drying-east wetting dipolar pattern. Considering an observational TEJ constraint, an accelerated TEJ with an amplitude of -2 standard deviations could cause an almost threefold increase in extreme drying trends in the near term (2026–2045). Instead, ITA could face a higher likelihood of extreme wetting tendency due to a near-term TEJ weakening. Our findings underscore the importance of realistic TEJ simulations in enhancing confidence in future precipitation projections across hydroclimate-vulnerable Africa.

Abstract The Indian Ocean Dipole (IOD) can influence the El Niño‐Southern Oscillation (ENSO) development 1 year ahead, allowing for prediction of ENSO events up to 14 months in advance. Using observational data sets and numerical experiments, we demonstrate that this IOD‐ENSO connection varies considerably on multidecadal timescales, which are largely controlled by the Atlantic Multidecadal Oscillation (AMO). During the negative AMO phase, sea surface temperature cooling in the tropical Atlantic enhances mean precipitation and convective activity over the tropical western‐central Pacific. This intensifies the Indo‐Pacific Walker circulation and strengthens the IOD‐related surface zonal wind anomalies over the tropical western Pacific. These amplified wind anomalies, in turn, generate larger subsurface ocean temperature anomalies in the region, creating more favorable conditions for the development of ensuing ENSO events. In contrast, these modulations are absent during the positive AMO phase. Our findings enhance the understanding of inter‐basin interactions and are critical for improving ENSO prediction.

The East Asian summer monsoon (EASM) rainfall often causes casualties and property damage in the region. Although there is a long history of studying and predicting EASM rainfall, prediction skill remains low. In this work, we identify the leading coupled modes between tropical sea surface temperature (SST) and EASM rainfall variations in observations and compare them with the corresponding modes in model predictions. Lastly, we propose a hybrid approach from a coupled-mode perspective to enhance the prediction skill of EASM rainfall. Two leading modes are dominant in the observations. One is associated with warming trends in tropical oceans and rainfall increases over eastern China and Japan. The other represents the influence of the El Niño-Southern Oscillation (ENSO). A climate model (CFSv2) only partially captures the temporal evolution and spatial patterns of the observed two leading modes with noticeable deficiencies. These biases may be part of the reason for the low prediction skill. We combine the trends and ENSO impacts in the observations with model-predicted ENSO index and construct a hybrid approach that exhibits skill exceeding the CFSv2 predictions initialized in May. This encouraging result implies potential value in the operational application of this hybrid approach.

Marine isoprene emissions contribute to atmospheric organic aerosols and climate feedbacks, but their drivers in remote ocean regions remain poorly understood due to limited high-resolution data. Analyzing over 300 large emission events from a 20-year dataset of daily emissions combined with four cruise observations, here we find that large-scale atmospheric circulation patterns orchestrate these events by jointly modulating surface meteorology — solar radiation, wind speed, sea-surface temperature and mixed-layer depth — enhancing isoprene production and transfer from the sea-surface microlayer to the atmosphere. Emission peaks lag peak solar radiation by 3–4 days, reflecting the synergistic response of the ocean surface. This mechanism links synoptic-scale variability to marine volatile organic compound emissions, with implications for secondary organic aerosol formation and climate feedbacks over remote oceans. These findings highlight the critical role of atmosphere–ocean interactions in regulating marine emissions. Large-scale atmospheric circulation patterns modulate surface meteorology, enhancing isoprene production and transfer from the sea-surface microlayer to the atmosphere, according to combined emissions and cruise observations.

Marine Cloud Brightening (MCB) is a geoengineering scheme to increase Earth’s albedo and reduce global warming. Previous studies mainly focused on mean climate response to MCB, leaving the response of global tropical cyclones (TCs), among the most devastating climate extremes, uninvestigated. Here, large-ensemble simulations are conducted using a newly developed observationally validated physics-based TC downscaling model under scenarios with and without regional MCB. It is found that regional MCB implemented mostly over the eastern Pacific can limit global warming to 2°C above pre-industrial levels through the 21st century. However, it also alters TC genesis locations and steering flow, unintentionally increasing the proportion of TC near-land (≤ 300 km) hours by ∼ 26% by 2081–2100. This shift in TC tracks drives ∼ 45% and ∼ 68% increases in annual land exposure area-hour and cumulative person-hour exposure, respectively. These findings underscore the need to integrate a better understanding of climate extremes in response to geoengineering.

This study compares atmospheric conditions and sea surface temperature (SST) anomalies for rapid intensification (RI) of tropical cyclones (TCs) in the western North Pacific (WNP) during boreal summer and autumn of 1980-2021. TC RI is classified into two clusters using the K-means clustering method with cluster 1 and cluster 2 located in the western and eastern WNP, respectively. Cluster 1 RI in summer is mainly due to lower-level vorticity anomalies induced by negative SST anomalies in the southeastern tropical Indian Ocean (SEIO)southwestern tropical Pacific Ocean (SWPO) and positive SST anomalies in the equatorial central-eastern Pacific (ECEP). Cluster 1 RI in autumn is mainly due to middle-level humidity anomalies induced by negative SST anomalies in ECEP and positive SST anomalies in tropical WNP. Cluster 2 RI in both summer and autumn is contributed by lower-level vorticity and middle-level humidity anomalies attributed to positive SST anomalies in ECEP and the eastern North Pacific with additional contribution of negative SST anomalies in SEIO-SWPO in autumn. The influence of negative SEIO-SWPO SST anomalies is through a cross-equatorial overturning circulation. The influence of positive ECEP, eastern North Pacific and tropical WNP SST anomalies is through a Rossby wave response. The influence of negative ECEP SST anomalies is through an anomalous Walker circulation.

The Pacific meridional mode (PMM) is a dominant air-sea interaction pattern in the subtropical northeastern Pacific. It exerts a significant influence on the tropical cyclone (TC) activity in the North Pacific. This study reveals that the spring PMM can be classified into two types: the subtropical North PMM (SNPMM) and the central tropical PMM (CTPMM). The key difference between SNPMM and CTPMM lies in the sea surface temperature (SST) anomaly pattern. SST anomalies associated with the SNPMM are confined to the subtropics, whereas those associated with the CTPMM can spread to the tropical Pacific. Further analysis shows that the SNPMM exerts little influence on TC genesis frequency (TCGF) in the tropical North Pacific. In contrast, the CTPMM suppresses TCGF in summer and autumn over the northwestern west Pacific but promotes it over the southeastern (SE) west Pacific and eastern northwest Pacific (ENW). The impact of the spring CTPMM on the tropical North Pacific TCGF during the following summer and autumn is mainly through inducing SST anomalies in the tropical Pacific. Eastward shift of the tropical Pacific Walker circulation and cold SST anomalies in the tropical western Pacific related to the CTPMM result in negative potential intensity anomalies over the northwestern west Pacific and thus suppress TCGF therein. However, the CTPMM-related tropical SST anomalies favor TCGF in the SE and ENW regions by weakening vertical wind shear and enhancing low-level vorticity. The physical mechanism by which the CTPMM influences TCGF was further confirmed by numerical experiments. This study highlights that not all PMM events can influence TCGF in the North Pacific. SIGNIFICANCE STATEMENT: Tropical cyclone (TC) is one of the most devastating weather systems, often resulting in substantial casualties and economic losses. TC occurs frequently across the Pacific region. Therefore, investigating the factors that influence TC genesis frequency (TCGF) is of great importance, which can help to improve the prediction skill of TCGF and reduce risks to human society. Previous studies have suggested that interannual variability of TCGF in the North Pacific is closely linked to the Pacific meridional mode (PMM). However, the influence of the PMM on TCGF remains controversial, with several studies arguing that the PMM cannot reliably predict TCGF in the North Pacific. Our analysis reveals that there exist two distinct types of PMM event characterized by different spring SST anomaly patterns, called subtropical North PMM (SNPMM) and central tropical PMM (CTPMM), respectively. The main difference between SNPMM and CTPMM is that SST anomalies associated with SNPMM (CTPMM) cannot (can) extend from the subtropics to the tropical Pacific. The SNPMM events have no clear influence on TCGF in the North Pacific. In contrast, CTPMM events have a pronounced impact on the North Pacific TCGF during the following summer and autumn. The warm SST anomalies in the northeastern Pacific associated with the CTPMM can propagate into the tropical central Pacific and further extend eastward during the following summer and autumn. These tropical SST anomalies subsequently affect the TCGF in the tropical North Pacific. Our study shows that PMM events are not uniform but include distinct subtypes that can cause different climate impacts. We identify CTPMM as a key subtype that has a strong influence on TCGF in the North Pacific and offers predictive value for seasonal forecasts. By highlighting these differences, our work improves understanding of PMM mechanisms and enhances the practical predictability of the North Pacific.

The hurricane, with maximum wind speed over 64 kts, is among the most terrible calamities over the northern Atlantic (NATL). Previous studies identified a poleward migration of tropical cyclone (TC) genesis over the Pacific Ocean, but the shift over the NATL is statistically insignificant. The present study detects a robust southward migration in the genesis latitude of NATL TCs that later reach hurricane strength after 1979, which is consistent with a growth in hurricane frequency in the southern part (10°-20°N) of NATL. This increasing trend of hurricane frequency is intimately attributable to the decreasing vertical shear of zonal wind, resulting from a decreasing north-south temperature gradient. The reduced north-south temperature gradient is primarily caused by greater warming trend in tropospheric temperature in the subtropics, driven by intensified static stability. The present research suggests a potential increase in the hazards confronted by low-latitude islands and coastal nations in Northern America.

The occurrence of extreme precipitation (EP) is closely associated with atmospheric circulation patterns. Present study documents the configuration of the East Asian jet stream corresponding to EP in central eastern China during June. The analysis is conducted for two sub-regions (26.5º–28.5ºN and 28.5º–30.5ºN within 116º–119.5ºE, denoted as the south and north region, respectively) separately. The two sub-regions have high frequency but distinct year-to-year variations of EP days. The preferred configuration of the East Asian jet stream differs for EP in the two sub-regions. The latitudinal shift of the East Asian jet stream accounts for most EP in the south region, while the intensification of the East Asian jet stream is the dominant configuration for EP in the north region. The changes in the location and intensity of the East Asian jet stream are associated with meridional wave patterns along East Asia and zonal wave patterns over mid-latitude Eurasia. The role of the western North Pacific subtropical high is robust but relatively larger for EP in the south region. The South Asian high plays an important role for EP in the south region, but its role is weak for EP in the north region. Wind-induced temperature anomalies modulate the vertical change of the meridional height gradient over eastern China and thus contributes to the latitudinal shift and intensity change of the East Asian jet stream. The present study suggests a strong dependence upon the EP region of atmospheric circulation systems that cause EP in central eastern China during June.

The impact of Arctic sea ice concentration (SIC) anomalies on the global climate system has received considerable attention in recent decades. Observations and model simulations indicate that winter Arctic SIC anomalies in the Greenland-Barents Seas significantly influence on the El Niño-Southern Oscillation (ENSO). However, whether this influence is symmetric remains unclear. Here, we demonstrate that the influence of SIC anomalies on the subsequent ENSO is asymmetric. An increase in SIC significantly affects the development of El Niño, whereas a decrease in SIC has only a weak influence on La Niña. Specifically, a winter SIC increase in the Greenland-Barents Seas induces deep Arctic cooling, which triggers an atmospheric wave train propagating to the subtropical North Pacific. The associated subtropical cyclonic anomaly leads to North Pacific Meridional Mode-like sea surface temperature (SST) warming in spring, which extends to the tropical Pacific via the wind-evaporation-SST feedback in the following summer and subsequently enhances El Niño development by tropical air-sea interaction processes. In contrast, a winter SIC decrease is accompanied by shallow Arctic warming, which is insufficient to generate an atmospheric wave train to modify the subtropical North Pacific oceanic and atmospheric states, and thus has a weak influence on the La Niña development. Further analysis suggests that the asymmetric impacts of Arctic sea ice anomalies on subtropical North Pacific air-sea conditions and ENSO events may also be partly due to differences in the atmospheric mean state between high and low SIC years. This study highlights the asymmetric impact of Arctic SIC anomalies on ENSO and tropical climate, emphasizing the need to consider these asymmetries when assessing global climate responses to Arctic sea ice variability.

During 29th July–1st August in 2023, a persistent heavy rainfall event (“23·7” event) hit North China causing severe floods, enormous infrastructure damage, and large economy loss. Observational analysis shows that the extremely large accumulation of precipitation and long duration of this event are closely related to a slowly moving landfall typhoon “Dusuari” over North China due to the blocking effect of an anomalous high over the mid‐high latitude Asia. The anomalous southeasterly flow induced by the typhoon “Dusuari” and another typhoon “Khanun” over the East China Sea jointly built a highly efficient channel of water vapor supply from southern oceans toward North China. A water vapor budget analysis indicates that precipitation of this event is mainly caused by the dynamic process involving strong ascending motion. Accompanying strong water vapor transportation and convergence over North China, large amount of latent heat is released in the middle and the lower troposphere. The physical mechanisms of heavy rainfall‐induced diabatic heating in maintaining the precipitation over North China is further investigated using statistical analysis and numerical experiments. On one hand, the latent heating released by heavy rainfall induces significant uplifting flows which causes more precipitation. On the other hand, the heavy rainfall‐induced diabatic heating contributes to the enhancement of the westward extension of high‐pressure dam over mid‐high latitude through a regional meridional circulation. This strengthened high‐pressure dam sustained the cyclonic circulation of “Dusuari” over North China, leading to continuous heavy rainfall there.