Abstract. Cities are major sources of global carbon. Accurately quantifying urban-scale carbon dioxide (CO2) fluxes is essential for supporting targeted emission reduction policies and effective monitoring. To address the limitations in the accuracy of current urban carbon emission estimates, we developed FEISSO, an urban-scale CO2 flux inversion system that integrates a Lagrangian atmospheric transport model with a Bayesian assimilation framework. FEISSO was used to systematically explore the feasibility of retrieving high-resolution flux distributions from satellite-based XCO2 observations. Sensitivity experiments were conducted in Weifang, Chengdu, and Xining (China) to identify key influencing factors in CO2 flux inversion. Results show that the resolution of meteorological drivers substantially affects the accuracy of simulated transport trajectories, with higher resolution (0.25°) improving the spatial fidelity of flux retrieval. Sensitivity analysis indicates that the column-averaged CO2 observation error and the total error for the inversion domain are the dominant factors affecting the total flux estimates, and they induce a "seesaw" effect in the spatial distribution of emissions. In contrast, prior flux error and spatial correlation length for land have limited influence on the total emissions but primarily affect the spatial pattern of weak emission regions and the smoothness of flux fields, respectively. Differences in topography and meteorological conditions across cities govern the temporal response of flux estimates to observations. With optimized parameter settings, the system successfully retrieved 10-days of total CO2 emissions for Weifang, Chengdu, and Xining, showing overall consistency with EDGAR and local inventory data. The retrieved emissions correspond to 85.8 %, 190.42 %, and 86.4 % of the EDGAR estimates for the three cities, respectively, while the relative differences from local inventories are 2.3 % for Weifang and 10.9 % for Xining. The results from this study demonstrate the applicability and scalability of the FEISSO system for urban CO2 flux estimation. In this study, the frequency of urban-scale inversions was limited by the current orbital coverage of the OCO-2 satellite. With future improvements in satellite observation capabilities, particularly in spatial resolution and revisit frequency, FEISSO is expected to play a pivotal role in global urban carbon emission monitoring and in the evaluation of emission reduction policy.

In this work, simulation data of Super typhoon Lekima (2019) produced by the Weather Research and Forecasting model are analyzed to study its symmetric inner and outer dynamics during its size expansion. The analysis includes the calculation of the symmetric rotational kinetic energy budget in the cylindrical coordinates and the separation of dominant budget terms. In the outer area, the conversion from symmetric divergent kinetic energy through the advection of symmetric divergent flow by symmetric rotational flow was the primary process for enhancing symmetric rotational kinetic energy. The conversion from environmental kinetic energy due to the advection of environmental flow by symmetric typhoon flow was secondary. In the inner area, frictional dissipation was the primary factor responsible for reducing the symmetric rotational kinetic energy. The flux divergence of symmetric rotational kinetic energy by symmetric divergent circulation was secondary.摘要本文利用高分辨率WRF模式模拟数据, 分析了超强台风“利奇马” (2019) 在快速增强期间的对称性内外圈动力学差异. 通过在柱坐标中计算并分解对称旋转动能收支, 揭示了主要能量转换过程. 结果表明, 外圈对称旋转动能的增加主要来自对称旋转运动平流引起的对称辐散动能向外圈对称旋转动能的能量转换, 其次为同样是对称旋转运动平流引起的环境动能的转换贡献; 而内圈对称旋转动能的减少由摩擦耗散 (主要) 和对称辐散流引起的对称旋转动能水平通量散度变化 (次要) 造成.

The dynamic processes responsible for the movement of tropical cyclone Khanun (2017) were studied by analyzing data from the mesoscale WRF model simulation. The simulated motion was induced by the ventilation flow of both the environmentaland asymmetric rotational wind averaged over an area within a radius of 200 km from Khanun’s center. The results revealed that during Khanun’s intensification period, environmental wind barely changed, whereas the speed and direction of asymmetric rotational wind exhibited significant changes as Khanun’s southwestward movement switched to a northwestward movement. The streamfunction analysis revealed that the change in the direction of movement was consistent with the ventilation flow of asymmetric rotational wind across Khanun’s center associated with the asymmetric circulation rotation. The cyclonic circulation center rotated counterclockwise, moving from the northeast to the north before and during the rapid intensification period, and exhibited wandering behavior during this period. The rotational rate of asymmetric circulation was quantitatively estimated using the formulation based on the budget of asymmetric rotational kinetic energy. This calculation revealed that the rapid counterclockwise rotation resulted from the conversion of environmental to asymmetric rotational kinetic energy and was related to the horizontal advection of environmental tangential flow. The rotation of the asymmetric circulation displayed a wandering behavior when the dissipation term became significant. The dissipation term plus the conversion from symmetric to asymmetric rotational kinetic energy associated with the advection of symmetric tangential wind by the environmental radial wind led to a slow clockwise rotation of the asymmetric cyclonic center to the north.

Tropical cyclone (TC) Khanun in 2017 was simulated in this study by the Weather Research and Forecasting (WRF) model. The observation-validated simulation data were used to examine dominant dynamic processes resulting in the contraction of the radius of maximum kinetic energy of symmetric rotational flow. The contraction rate was quantified by calculating the radial derivatives of symmetric rotational kinetic energy budget. The radius of maximum symmetric rotational energy was contracted rapidly before rapid intensification (RI) and moved inward slowly, then barely moved, and moved inward slowly again during RI. The conversion from kinetic energy of asymmetric rotational flow to symmetric rotational flow induced by advection of asymmetric rotational tangential wind by asymmetric divergent radial wind at dominant azimuthal wavenumber-1 asymmetry and convergence of inward flux of symmetric rotational flow led to the rapid contraction before RI. During RI, symmetric rotational energy grew in the lower troposphere significantly, and upward flux convergence was equally important as inward flux convergence of symmetric rotational flow, which caused the first slow contraction. The conversion from kinetic energy of symmetric divergent wind to symmetric rotational flow associated with co-locations of maximum symmetric rotational energy and maximum symmetric inward radial flow produced stationary maximum symmetric rotational energy. Finally, horizontal and vertical flux convergence of symmetric rotational flow, and the conversion from environmental kinetic energy to symmetric rotational kinetic energy through the interaction between symmetric rotational flow and symmetric radial environmental flow generated the second slow contraction.

Abstract North China experienced an extreme precipitation event from July 29 to August 1, 2023 (i.e., the “23.7” event) causing severe floods, significant infrastructure damage and multiple fatalities. To enhance comprehension of the mechanism behind the extreme precipitation of the “23.7” event, water vapor transport paths and sources were determined, and water vapor contribution of each source was quantitatively evaluated based on Lagrangian methods. Results showed that the extreme precipitation of the “23.7” event was closely related to large‐scale water vapor transport and convergence from low‐latitude oceans. There were five main water vapor sources which corresponded to five transport pathways. Path 1 was derived from tropical West Pacific, containing the most trajectories (195), carrying the most water vapor (69.3%) and contributing the most to the extreme precipitation of the “23.7” event (45.7%). Path 2 was guided by the cross‐equatorial flow through South China Sea, contributing to 10.1% of the precipitation. Path 3 originating from eastern tropical Indian Ocean and Path 4 from the west source near the Caspian Sea contributed less to the precipitation. Last but not the least, water vapor evaporation from eastern China contributed more than 30% to the extreme precipitation, making this region another important water vapor source.

An extreme rainfall event occurred over Hangzhou, China, during the afternoon hours on 24 June 2013. This event occurred under suitable synoptic conditions and the maximum 4-h cumulative rainfall amount was over 150 mm. This rainfall event had two major rainbands. One was caused by a quasi-stationary convective line, and the other by a back-building convective line related to the interaction of the outflow boundary from the first rainband and an existing low-level mesoscale convergence line associated with a mei-yu frontal system. The rainfall event lasted 4 h, while the back-building process occurred in 2 h when the extreme rainfall center formed. So far, few studies have examined the back-building processes in the mei-yu season that are caused by the interaction of a mesoscale convergence line and a convective cold pool. The two rainbands are successfully reproduced by the Weather Research and Forecasting (WRF) model with four-level, two-way interactive nesting. In the model, new cells repeatedly occur at the west side of older cells, and the back-building process occurs in an environment with large CAPE, a low LFC, and plenty of water vapor. Outflows from older cells enhance the low-level convergence that forces new cells. High precipitation efficiency of the back-building training cells leads to accumulated precipitation of over 150 mm. Sensitivity experiments without evaporation of rainwater show that the convective cold pool plays an important role in the organization of the back-building process in the current extreme precipitation case.

Abstract Coastal El Niño is an extreme situation of El Niño‐Southern Oscillation (ENSO) with sea surface temperature warming confined in the far‐eastern equatorial Pacific. Some coastal El Niños evolve into a basin scale El Niño, and some don't, implying a diversity in ENSO evolutions after a coastal El Niño event. In this study, the coastal El Niños in 2017 and 2023 are selected to examine their subsequent evolution. Both coastal El Niños developed after a La Niña, with the former followed by a La Niña and the latter by a basin‐scale El Niño. The cold (warm) subsurface temperatures in 2017 (2023) were key factors leading to the divergent ENSO evolution. Convection over the western tropical Pacific and the atmospheric circulation anomalies across the equatorial Pacific also contributed to the differences. Model predictions suggest that differences in ENSO evolution after a coastal El Niño are associated with differences in ENSO predictability.

This study investigated radiative effects on kinetic and potential energy budgets associated with the rapid intensification of typhoon Mujigae in 2015 by conducting sensitivity experiments using Weather Research and Forecasting(WRF)model simulations.The authors found that the radiations have a significant effect on the symmetric rotational kinetic energy and symmetric potential energy of typhoon.The infrared longwave radiation mainly enhances the symmetric rotational kinetic energy,the shortwave radiation being the main contributor to the symmetric potential energy.The comparison between sensitivity experiments excluding radiative effects and retaining solar shortwave radiative effects reveals that the inclusion of infrared longwave radiative effects destabilizes the moist atmosphere and augments the conversion from symmetric potential energy to symmetric divergent kinetic energy.This further enhances symmetric rotational kinetic energy through the strengthened conversion from symmetric divergent kinetic energy to symmetric rotational kinetic energy.

The El Niño−Southern Oscillation (ENSO) is the strongest interannual variability in tropical oceans and the premier source of global climate predictability. Since 2000, ENSO has shifted to a regime with smaller variability and higher frequency, as a result, ENSO prediction skills degraded due to the weakened connection between ENSO sea surface temperature and warm water volume (WWV) along the equatorial Pacific. That is connected with the enlarged zonal contrast in the mean sea surface temperature across the tropical Pacific and the westward shift of the dominant region of the atmosphere-ocean coupling associated with ENSO. We noted that the recharge/discharge processes associated with ENSO vary with decade, time scale, and longitude. The weakening of the recharge/discharge processes since 2000 is mainly at the interannual time scale without significant changes at the intraseasonal and interseasonal time scales. The weakened connection between the WWV and the Niño3.4 indices since 2000 is mainly due to the weakened connection with the western tropical Pacific WWV (WWVw). It is hypothesized that the enlarged mean state contrast across the equatorial Pacific with enhanced thermocline slope and strengthened easterly trade wind made the WWV less efficient in El Niño growth.

The precipitation structures and microphysical characteristics of predecessor rain events (PREs) over the Yangtze River Delta area and related tropical cyclones (TCs) from 2014 to 2019 were investigated using Dual-frequency Precipitation radar data from Global Precipitation Measurement (GPM) for drop size distributions (DSDs). Results showed that the total mean rain rate of PREs was larger than that of TCs, primarily due to higher convective and stratiform rain rates, with enhanced fractional coverage of convective rain in PREs. Examination of microphysical characteristics revealed that a greater quantity of small-sized droplets and a smaller quantity of medium- as well as large-sized droplets contributed towards PREs in comparison with TCs. The conclusion still holds when partitioning DSDs based on different precipitation rate categories. Further investigation of DSDs using gamma functions illustrated that precipitation in PREs had lower average mass-weighted diameters (Dm) and enhanced normalized number concentration (Nw) compared with TCs; partitioning precipitation into convective and stratiform components illustrated a larger Dm and lower Nw in TCs than PREs. The analysis of microphysical and thermodynamical processes using the reanalysis data indicates that relatively intense convective activity with drier conditions may be favorable to enhancing raindrop growth through collisioncoalescence processes, as a result of larger Dm in TCs than PREs. The empirical relations (Z-R algorithms) applied in different rain regimes (stratiform, convective, and total PREs) revealed significant diversities, relying on weather conditions and geographical locations. Plain language summary: The Yangtze River Delta area is an important economic belt in China. Under climate change, observed frequent occurrences of weather extremes of heavy rainfall and tropical cyclones (TCs) exert adverse effects on economic development in this region. Thus, a deep understanding of the mechanism of TCs torrential rainfall in the Yangtze River Delta area is urgently necessary. In this study, we investigated the precipitation patterns and microphysical characteristics of predecessor rain events (PREs) in the Yangtze River Delta region, and their association with TCs in the South China Sea-Western North Pacific Ocean (SCS-WNPO) area from 2014 to 2019. We found that PREs had a higher total mean precipitation rate than TCs. Further examination using gamma functions demonstrated that PREs exhibited lower average mass-weighted diameters (Dm) and higher normalized intercept parameters (Nw) than TCs. This pattern persisted when distinguishing between convective and stratiform precipitation components. We believe that our study makes a significant contribution to the literature because these results provide valuable insights into the distinct precipitation characteristics of PREs and TCs in the study region and contribute to a better understanding of tropical cyclone-related rainfall patterns, and act as a scientific basis for disaster mitigation.

This study aimed to investigate the radiative impacts of cloud hydrometeors on the radial movement of the maximum wind of Typhoon Rammasun (2014), as indicated by the radial shift in the maximum symmetric rotational kinetic energy (Kψsmax). The sensitivity experiments conducted using the Weather Research and Forecasting (WRF) model indicated that the radial movement of Kψsmax remains unaffected by the radiative impacts of cloud water, raindrops, snow, and graupel. However, eliminating the radiative impacts of cloud ice produced a 10-h pause in Kψsmax and contraction of its radius, which eventually led to a delay in rapid intensification, resulting in a 13% reduction in intensity peak. The analysis reveals that removal of the radiative impacts of cloud ice induced the instability in the lower troposphere and enhanced the dissipation as well as the conversion from Kψs to asymmetric rotational kinetic energy (Kψa). This significantly reduced the Kψs tendency by offsetting the conversion from symmetric divergent kinetic energy (Kχs) to Kψs and Kψs flux convergence.

Historically, La Niña events typically follow El Niño events, particularly in case of prolonged La Niña events that succeed strong El Niño events. However, the current triple-dip La Niña (CTD-La Niña) event during 2020–2023 occurred after a neutral event rather than a (strong) El Niño, which differs from the two historical triple-dip La Niña (HTD-La Niña; 1973–1976 and 1998–2001) events since 1950. Therefore, this paper aims to investigate the unique evolution and potential formation mechanisms of the CTD-La Niña event. Our results show that, in contrast to the HTD-La Niña, the CTD-La Niña event is not primarily influenced by tropical processes themselves. Instead, the consecutively in-phase (negative) North Pacific Meridional Mode and South Pacific Meridional Mode play a crucial role in initiating and sustaining the La Niña event of 2020–2023 through tropical-extratropical interactions. On one hand, their associated negative sea surface temperature (SST) anomalies extend toward the equatorial central Pacific each year from spring to summer, leading to negative SST and strengthening easterly surface wind anomalies in the equatorial Pacific. On the other hand, their related northeastern and southeastern wind stress can modify the wind stress curl over the equatorial Pacific, further intensifying the equatorward Ekman transport from the off-equator. These factors together provide favorable conditions for the re-occurrence of the La Niña event from 2020 to 2023. These findings may offer valuable insights into understanding the formation of long-lasting ENSO events.

Predecessor rain events (PREs) in the Yangtze River Delta (YRD) region associated with the South China Sea and Northwest Pacific Ocean (SCS-WNPO) tropical cyclones (TCs) are investigated during the period from 2010 to 2019. Results indicate that approximately 10% of TCs making landfall in China produce PREs over the YRD region; however, they are seldom forecasted. PREs often occur over the YRD region when TCs begin to be active in the SCS-WNPO with westward paths, whilst the cold air is still existing or beginning to be present. PREs are more likely to peak in June and September. The distances between the PRE centers and the parent TC range from 900 to 1700 km. The median value of rain amounts and the median lifetime of PREs is approximately 200 mm and 24 h, respectively. Composite results suggest that PREs form in the equatorward jet-entrance region of the upper-level westerly jet (WJ), where a 925-hPa equivalent potential temperature ridge is located east of a 500-hPa trough. Deep moisture is transported from the TC vicinity to the remote PREs region. The ascent of this deep moist air in front of the 500-hPa trough and frontogenesis beneath the equatorward entrance region of the WJ is advantageous for the occurrence of PREs in the YRD region. The upper-level WJ may be affected by the subtropical high and westerly trough in the Northwest Pacific Ocean, and the occurrence of PREs may favor the maintenance of the upper-level WJ. The upper-level outflow of TCs in the SCS plays a secondary role.

The Weather Research and Forecasting (WRF) model was used to examine the sensitivities of Typhoon Fitow (2013) to the variations in horizontal mesh spacing ranging from 9 km to 1 km and to different microphysics schemes. The minimum sea level pressure decreased by 5 hPa and the maximum wind speeds increased by 20 m s(-1) near the typhoon center as the horizontal grid spacing decreased from 9 km, 3 km, and 1 km in both PurdueLin and National Severe Storms Laboratory (NSSL) microphysics. The strengthening of the tropical cyclone may have been due to similar physical processes in the Purdue-Lin and NSSL simulations. Fine-resolution simulations produced localized and intense rainfall, in correspondence to localized and intense upward motions. Moreover, as the horizontal mesh spacing reduced from 9 km to 1 km, the distributions of the upward and downward motions broadened and the radar reflectivity bins with contour frequencies >10% increased. The simulated rainfall in the NSSL with a horizontal grid spacing below 3 km and in Purdue-Lin with a 1 km grid spacing reproduced spatial and temporal distributions similar to the actual observations. This suggested that the elaborate microphysics may compensate for the lack of horizontal resolution, to some extent. The precipitation budget analysis further suggested that the diminishment of rainfall was attributed to the reduced net condensation and hydrometeor convergence respectively in the Purdue-Lin and NSSL scheme as the mesh spacing reduced, which was further attributable to the decreased condensation or deposition.

Abstract As El Niño's little brother in the equatorial Atlantic Ocean, Atlantic Niño affects the climate variability in the tropical Atlantic Ocean and the vicinity. In 2019–2021, two extremely strong Atlantic Niños occurred with peaks in January 2020 and July 2021, respectively. The coupling between the ocean and atmosphere associated with the Atlantic Niños is similar to that associated with El Niño‐Southern Oscillation. Both the Atlantic Niños were triggered and modulated by a Benguela Niño‐like warming, through inducing wind stress anomalies in the South and equatorial Atlantic Ocean. In addition to the atmosphere‐ocean coupling at intraseasonal‐interseasonal time scales, interdecadal and longer time scale variation amplified the Atlantic Niños. Model predictions only capture the evolution of the Atlantic Niños at a 1‐month lead, consistent with the low prediction skill for sea surface temperature anomalies in the tropical Atlantic Ocean.

During the spring and summer seasons, in the South China region where abundant water vapor is present, squall lines can rapidly develop into larger scales within a short period of time. In order to explore the influence of water vapor content on the process of squall line scale growth in South China, using the WRF model, a numerical simulation was conducted for a squall line system in South China on 11 May 2020. We investigated the effect of the variation of water vapor at different levels on its intensity and structure, and discussed the growth mechanism of the squall line system. This squall line occurred with the presence of high-level jet and low-level wind shear complementing each other, within an unstable layer of "dry at the high level and wet at the low level". The simulation showed that, in the early stage of the squall line development, a large maximum convective available potential energy (MCAPE) was observed in the southern part of the convection and coastal warm areas, which is beneficial for the accumulation of unstable energy here. Meanwhile, with the high low-level wind shear, the linear structure of the convection was well maintained. Subsequently, the squall line propagated southward and merged with warm region convection, resulting a further scale growth. Water vapor experiments showed that the MCAPE values are primarily influenced by the moisture content in the low-level atmosphere. More low-level moisture content causes stronger thunderstorm high pressure. Additionally, the presence of higher MCAPE values and larger low-level vertical wind shear contribute to the growth of convective cells in the post-convective stage, prolonging their existence. Reducing the mid-level water vapor content results in a decrease in intense surface precipitation, a weakening of convective intensity, and a quick dissipation into individual convective cells. But when the squall line moves into the area with high MCAPE values, it once again develops into a linear structure. Therefore, an increase in low-level moisture or a decrease in mid-level moisture favors the genesis of convection. However, reducing mid-level moisture results in relatively drier air at mid-levels, making it difficult for the linear structure to be sustained. Further investigation into the internal structure of the squall line reveals that vertical motion and rear inflow also influence the scale growth of the squall line. In the convective system analyzed in this study, the strong rearward inflow enhances the upward motion and generates forward outflow, leading to severe surface wind. Strengthening low-level moisture not only increases the size of the stratiform cloud region at the rear of the convection, but also leads to a stronger upward motion sustaining vertically, which promotes prolonged convective activity. On the other hand, reducing mid-level moisture weakens convective intensity and lowers the height of the echo tops. During the development stage, the rearward inflow intensifies, and dry cold air descends rapidly, leading to the strengthening of the surface cold pool, and causing strong winds due to the forward outflow.

Compared with well documented and frequent occurrence of multi-year La Niña, double-year El Niño is less frequent and has not been well investigated. Both of them are a discrepancy from the cyclic behavior of the El Niño-Southern Oscillation and deserve investigation. Here, we demonstrate the diversity of single- and double-year El Niño events in their strengths, flavors, as well as associations with the recharge/discharge processes. The possible different climate impacts are also discussed. During 1950–2021, 75% of El Niño events persist for one year, and 25% of them last for two years. Both central and eastern Pacific type El Niños occur in the single-year and double-year El Niños with various strengths. On average, there is no relationship between the initial time and duration of an El Niño event. Compared with the single-year El Niños, the averaged warm water volume (WWV) is larger in the peak and declines slower for the double-year El Niños, suggesting that a persistently recharged heat condition of the equatorial Pacific is a precondition for the emergence of a second-year El Niño. The faster decline of WWV in the single-year El Niños is associated with the in-phase decrease of its intraseasonal-interseasonal and interannual components, while the slower decline of WWV in the double-year El Niños is determined by the interannual component. In addition, the single-year and double-year El Niño may have different impacts on regional climate.

This study compares the evolution of atmospheric and oceanic anomalies as well as predictions for the two most recent triple‐dip La Niña events in 1998–2001 and 2020–2023. Subsurface cooling in the equatorial Pacific was stronger and more persistent during 1998–2001. In contrast, surface easterly winds were stronger during 2020–2023 as was the east‐west sea surface temperature (SST) contrast along the equator. We argue that in the absence of appreciable equatorial Pacific heat discharge, persistent and strong surface trade winds and a strengthened mean zonal SST contrast across the tropical Pacific contributed to the development of the 2020–2023 triple‐dip La Niña. In terms of the subsurface layer heat budget, the growth and maintenance of unusually cold SSTs during the triple‐dip La Niña in 1998–2001 were mainly the result of ocean vertical entrainment and diffusion, as well as meridional advection, associated with enhanced equatorial upwelling; while for the triple‐dip La Niña in 2020–2023, zonal advection was the largest contributor. The two events were mostly well predicted by multi‐model averages at 1–8 months lead times. We hypothesize that mean state change with enhanced zonal SST contrast and trade winds over the last several decades altered the physical processes associated with the growth and maintenance of the most recent La Niña, affecting its predictability. Successful prediction in real‐time of the 2020–2023 event more than half a year in advance was surprising because there was little memory in oceanic heat content which is often considered a key predictor.

Knowledge about the El Niño-Southern Oscillation (ENSO) is the scientific foundation for short-term climate prediction, due to its global influence. In operation and research communities, the ENSO state is often represented by various ENSO indices. However, it is unclear which index is the strongest for capturing ENSO’s global climate influence. By examining the correlations of eleven ENSO indices with monthly mean global precipitation and surface temperature (TS), we illustrate the similarities and differences in the connections, identify the strongest index, and discuss the physics behind the differences. For the global average, the Niño3.4 and relative Niño3.4 indices are the two strongest indices and the warm pool index is the weakest one for capturing the impact of ENSO on global precipitation, while the Niño4 and Niño3.4 indices are the two strongest indices and the Modoki index is the weakest one for capturing the ENSO’s influence on TS variations. In addition to the dependence on the variables and ENSO indices, the representations of climate variability associated with ENSO depend on the region. For example, in Australia, the southern oscillation index has the most significant correlations with precipitation and its correlations with TS are relatively weaker than those of some of the other indices. These differences associated with the various ENSO indices may be due to their representation of the deep convection in the tropical Pacific. These results can serve as a benchmark to understand the global picture of monthly mean precipitation and TS influenced by ENSO and to verify model’s ability in capturing these connections.

In the background of long‐term global warming, the northern hemisphere experienced an extremely hot summer in 2022 with the hottest on record for Europe and China, and the second‐hottest for North America and Asia. The hot summer concurred with a triple‐dip La Niña in the tropical Pacific. Given the extremity of the hot summer in East Asia in 2022, in this work, we examine the associated atmospheric circulation and assess the real‐time predictions from the North American Multimodel Ensemble (NMME). Also, we identify the contributions of long‐term warming trends, sea surface temperature (SST) forcing, and an atmospheric feedback to the hot summer. The hot summer in East Asia in 2022 is due to the extremely strong and westward expanded western Pacific subtropical high. That leads to cloud cover reduction and increases in net downward shortwave radiation at the surface, and further strengthens the positive surface air temperature (SAT) anomalies. In contrast, the seasonal‐interannual variation of SST has a minor impact. Thus, the hot summer is mainly associated with the long‐term trend and amplified by the positive feedback among the SAT, cloud cover, and net downward shortwave radiation. NMME with the initial conditions in May 2022 predicts positive SAT anomalies in most regions of East Asia, but does not capture the observed spatial distribution pattern and amplitudes. The failure implies the challenge of state‐of‐the‐art climate models in predicting such extreme events.