This study presents a comprehensive evaluation of tropical cyclone(TC)forecast performance in the western North Pacific from 2013 to 2022,based on operational forecasts issued by the China Meteorological Administratio...This study presents a comprehensive evaluation of tropical cyclone(TC)forecast performance in the western North Pacific from 2013 to 2022,based on operational forecasts issued by the China Meteorological Administration.The analysis reveals systematic improvements in both track and intensity forecasts over the decade,with distinct error characteristics observed across various forecast parameters.Track forecast errors have steadily decreased,particularly for longer lead times,while error magnitudes have increased with longer forecast lead times.Intensity forecasts show similar progressive enhancements,with maximum sustained wind speed errors decreasing by 0.26 m/s per year for 120 h forecasts.The study also identifies several key patterns in forecast performance:typhoon-grade or stronger TCs exhibit smaller track errors than week or weaker systems;intensity forecasts systematically overestimate weaker TCs while underestimating stronger systems;and spatial error distributions show greater track inaccuracies near landmasses and regional intensity biases.These findings highlight both the significant advances in TC forecasting capability achieved through improved modeling and observational systems,and the remaining challenges in predicting TC changes and landfall behavior,providing valuable benchmarks for future forecast system development.展开更多
In this study,tropical cyclone(TC)translation speed was introduced as a new similarity factor within the generalized initial value(GIV)framework,enhancing the disaster preassessment capability of the dynamical statist...In this study,tropical cyclone(TC)translation speed was introduced as a new similarity factor within the generalized initial value(GIV)framework,enhancing the disaster preassessment capability of the dynamical statistical analog ensemble forecast model for landfalling TC disasters(DSAEF_LTD model).Three TC translation speed indicators most relevant to TC precipitation were incorporated:the maximum speed on Day 1(the first day of TC-induced precipitation and wind occurring on land)and the average and minimum speeds over All Days(all days of TC-induced precipitation and wind occurring on land),all classified using the Kmeans clustering algorithm.Simulation experiments showed that integrating TC translation speed enhanced the model's performance.The model provided a better optimal common scheme,with the TSS UM(sum of threat scores for severe and above and extremely severe and above disasters)increasing by 2.66%(from 0.5117 to 0.5253)compared with the original model.More importantly,its preassessment ability improved significantly,with the average TSS UM for independent samples increasing by 6.43%(from 0.6488 to0.6905).The modified model demonstrated greater accuracy in capturing disaster severity and distribution of TCs with significant speed characteristics or with regular tracks.This improvement stemmed from reduced false alarms due to the selection of analogs that are more similar to the target TC.The enhanced preassessment ability can be attributed to the key role of TC translation speed,which significantly influences TC precipitation patterns and improves TC precipitation forecasting.Since precipitation is one of the most crucial disaster-causing factors,better TC precipitation forecasting leads to improved disaster preassessment outcomes.These findings emphasize the promising potential of the DSAEF_LTD model for future TC disaster research and management,contributing to the achievement of the Sustainable Development Goals set by the United Nations 2030 Agenda by strengthening coastal resilience.展开更多
This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shea...This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shear(VWS),using idealized numerical experiments.Results reveal that the SE develops greater radial extent when surface winds align with VWS compared to counter-aligned conditions.In alignment configurations,shear-enhanced surface winds on the right flank amplify surface enthalpy fluxes,thereby elevating boundary-layer entropy within the downshear outer-core region.Subsequently,more vigorous outer rainbands develop,inducing marked acceleration of tangential winds in the outer core preceding SE formation.The resultant radial expansion of supergradient winds near the boundary-layer top triggers widespread convective activity immediately beyond the inner core.Progressive axisymmetrization of this convective forcing ultimately generates an expansive SE structure.展开更多
The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study pro...The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.展开更多
Accurate forecasting of tropical cyclone(TC)tracks and intensities is essential.Although the TianXing large weather model,a six-hourly forecasting model surpassing operational forecasts,exhibits superior performance,i...Accurate forecasting of tropical cyclone(TC)tracks and intensities is essential.Although the TianXing large weather model,a six-hourly forecasting model surpassing operational forecasts,exhibits superior performance,its TC forecasts still require enhancement.Prediction errors persist due to biases in the training data and smoothing effects in data-driven methods.To address this,we introduce CycloneBCNet,a deep-learning model designed to correct TianXing’s TC forecast biases by leveraging spatial and temporal data.CycloneBCNet utilizes the SimVP(simpler yet better video prediction)framework with spatial attention to highlight cyclone core regions in forecast fields.It also incorporates TC trend information(center position,maximum wind speed,and minimum sea level pressure)via an LSTM(long short-term memory)module.These TC vectors are derived from post-processed TianXing forecasts.By fusing features from forecast fields and TC vectors,CycloneBCNet corrects biases across multiple lead times.At a 96-h lead time,the track error reduces from 162.4 to 86.4 km,the wind speed error from 17.2 to 6.69 m s^(-1),and the pressure error from 22.2 to 9.36 hPa.Interpretability analysis shows that CycloneBCNet adjusts its attention across forecast lead times.Intensity corrections prioritize inner-core dynamics,particularly the eye and eyewall,while track corrections shift from lower-level variables and the cyclone’s core to broader environmental factors and mid-to upper-level features as the forecast duration increases.These findings demonstrate that CycloneBCNet effectively captures key TC dynamics consistent with meteorological principles,including the dominance of near-surface conditions for intensity and the increasing influence of steering currents on track prediction.展开更多
The operational Tropical Regional Atmospheric Model System(TRAMS)often underestimates initial typhoon intensity when using the global analysis field as the initial condition.The TRAMS tropical cyclone(TC)initializatio...The operational Tropical Regional Atmospheric Model System(TRAMS)often underestimates initial typhoon intensity when using the global analysis field as the initial condition.The TRAMS tropical cyclone(TC)initialization scheme,developed based on the incremental analysis updates(IAU)technique,effectively reduces initial bias.However,the original IAU-based TC initialization scheme only adjusts the wind field at the analysis moment,with other variables adjusted implicitly under the model's constraints according to a gradually inserted wind increment(named“univariate adjustment scheme”hereafter).The univariate adjustment scheme requires approximately 3 h to reach a dynamic equilibrium state,which constrains the assimilation of hourly TC observations and causes excessive dissipation of meaningful short-wave information in adjustment increments.To address this limitation,this study develops a multivariate adjustment IAU-based TC initialization scheme that incorporates gradient wind balance and hydrostatic balance as its largescale constraints.Numerical experiments with TC Hato(2017)demonstrate that the multivariate adjustment scheme reduces the IAU relaxation time to 1 h while marginally improving forecast skill.These findings are consistently replicated across 12 additional TC cases.The development of the IAU-based multivariate adjustment initialization scheme establishes a foundation for 4-D initialization using hourly TC observations.展开更多
Based on datasets from the International Best-Track Archive for Climate Stewardship(IBTrACS)and the fifth major global reanalysis produced by ECMWF(ERA5),the authors found that 29%of tropical cyclones(TCs)in the weste...Based on datasets from the International Best-Track Archive for Climate Stewardship(IBTrACS)and the fifth major global reanalysis produced by ECMWF(ERA5),the authors found that 29%of tropical cyclones(TCs)in the western North Pacific underwent extratropical transition(ET)from 1979 to 2022,with the frequency of ET events showing a slow decreasing trend.The extratropical transition tropical cyclones(ETCs)are classified into four clusters using the k-means clustering method based on their track patterns:recurving ETCs,westward ETCs,northwestward ETCs,and abnormal track ETCs.The transition process of recurving ETCs mostly occurs after the recurvature is completed,while 63.7%of the westward ETCs complete their transition after landfall.Abnormal track ETCs undergo transition over high-latitude oceans.Northwestward ETCs have the longest duration and slowest transition speed during the ET period,resulting in a prolonged impact.The ET process occurs at the edges of the western Pacific subtropical high(WPSH),with higher frequency during westward extension and lower during eastward retreat.While westward ETCs transition through surface friction effects,others complete ET in the northwest baroclinic zone of the WPSH.展开更多
Explosive cyclones(ECs) are rapidly intensifying subtropical cyclones that can develop within a short time and pose considerable threats to coastal areas in middle and high latitudes.Gaining a comprehensive understand...Explosive cyclones(ECs) are rapidly intensifying subtropical cyclones that can develop within a short time and pose considerable threats to coastal areas in middle and high latitudes.Gaining a comprehensive understanding of their formation,evolution,and mechanisms of explosive development is essential for improving forecasts of extreme weather events and mitigating associated impacts.Potential vorticity(PV),which is closely related to cyclone dynamics,serves as a valuable diagnostic tool in the study of ECs.In this study,two wintertime ECs of differing intensity over the Northwestern Pacific Ocean are analyzed to examine how different atmospheric processes influence PV generation and the rapid development of ECs.The maximum deepening rates of the two ECs are 2.81 Bergeron(called EC1) and 1.52 Bergeron(referred to as EC2).Results indicate that different stages of EC evolution are closely associated with PV tendency changes at different atmospheric levels.Using the PV tendency equation,during the explosive development of EC1,latent heat release may trigger the downward propagation of upper-level PV.For EC2,latent heat release notably enhances low-level PV,directly contributing to its rapid intensification.To validate these findings,sensitivity tests are conducted using the Weather Research and Forecasting model,with latent heat release turned off in the microphysical scheme for both cases.The results confirm the crucial role of latent heat release in generating low-level PV,further revealing that latent heat release contributes more to the explosive development of EC2 than that of EC1.展开更多
A modified three-dimensional turbulence parameterization scheme,implemented by replacing the conventional eddydiffusivity formulation with the H-gradient model,has shown good performance in representing the subgrid-sc...A modified three-dimensional turbulence parameterization scheme,implemented by replacing the conventional eddydiffusivity formulation with the H-gradient model,has shown good performance in representing the subgrid-scale(SGS)turbulent fluxes associated with convective clouds in idealized tropical cyclone(TC)simulations.To evaluate the capability of the modified scheme in simulating real TCs,two sets of simulations of TC Soudelor(2015),one with the modified scheme and the other with the original scheme,are conducted.Comparisons with observations and coarse-grained results from large eddy simulation benchmarks demonstrate that the modified scheme improves the forecasting of the intensity and structure,as well as the SGS turbulent fluxes of Soudelor.Using the modified turbulence scheme,a TC with stronger intensity,smaller size,a shallower but stronger inflow layer,and a more intense but less inclined convective updraft is simulated.The rapid intensification process and secondary eyewall features can also be captured better by the modified scheme.By analyzing the mechanism by which turbulent transport impacts the intensity and structure of TCs,it is shown that accurately representing the turbulent transport associated with convective clouds above the planetary boundary layer helps to initiate the TC spin-up process.展开更多
In this study,numerical experiments with different initial radius of maximum wind(RMW)are performed to study the effects of tropical cyclone(TC)size combined with land-sea contrast on TC motion and low-level wind stru...In this study,numerical experiments with different initial radius of maximum wind(RMW)are performed to study the effects of tropical cyclone(TC)size combined with land-sea contrast on TC motion and low-level wind structure before landfall.By idealized numerical simulations,we found that larger TC arrived coastline earlier than smaller TC,when they started moving from the same position.This is because that the larger TCs not only accelerate earlier but also have greater movement speed than smaller TCs when they approach the coastline.The mechanism responsible for this is that the edge of large TCs reach coastline earlier,thus their movement speed accelerated earlier than small TCs,due to the asymmetries in diabatic heating and radial flow generated by the land-sea contrast.Moreover,when TCs in three experiments all affected by the land-sea contrast,the stronger asymmetries generated in larger TC,thus resulting in faster movement in larger TC.The stronger inflow in western quadrant and weaker inflow(even outflow)in eastern quadrant of larger TC deduced apparently difference in vertical motion and diabatic heating between western and eastern quadrant of TC before landfall.An analysis of potential vorticity tendency proved that the diabatic heating terms were important and considered in determining the TC landward drift because asymmetries in vertical motion and relative vorticity developed due to asymmetric flow.展开更多
Spaceborne microwave instruments possess the capability of day-and-night and all-weather measurements that can penetrate clouds and fog,and directly measure tropical cyclone(TC)ocean surface winds.In this study,we est...Spaceborne microwave instruments possess the capability of day-and-night and all-weather measurements that can penetrate clouds and fog,and directly measure tropical cyclone(TC)ocean surface winds.In this study,we establish an effective methodology to estimate TC dynamic characteristic parameters(DCP),including the storm center location,intensity,radius of maximum wind(RMW)and wind structure,purely from TC ocean winds measured by multi-platform spaceborne microwave instruments.Combining measurements from active and passive sensors can provide long time series data for monitoring changes in storm DCP.Here,the evolution of the DCP for TC Freddy(2023),from its genesis to its landfall,is evaluated using data from synthetic aperture radars(SARs),as well as radiometer(RAD)and scatterometer(SCA)observations.Comparing the results to the best-track datasets for the longitudes and latitudes of the storm centers,we show that the root-mean-square errors(RMSEs)are 0.22°and 0.31°,respectively,both with a correlation of 0.99.For the detected intensity,the RMSEs are 6.8 m s^(−1) for SARs and 7.3 m s^(−1) for RADs.However,TC intensities measured by C-band SCAs are significantly underestimated,especially for wind speeds less than 50 m s^(−1).In terms of RMW and wind radii,the SARs,RADs and SCAs demonstrate good accuracy and applicability.Our investigation emphasizes the crucial role played by spaceborne microwave instruments in the study of TCs.This is helpful in monitoring,and in the future,will help improve the forecasting of TC intensities and their characteristic structures.展开更多
At present,the identification of tropical cyclone remote precipitation(TRP)requires subjective participation,leading to inconsistent results among different researchers despite adopting the same identification standar...At present,the identification of tropical cyclone remote precipitation(TRP)requires subjective participation,leading to inconsistent results among different researchers despite adopting the same identification standard.Thus,establishing an objective identification method is greatly important.In this study,an objective synoptic analysis technique for TRP(OSAT_TRP)is proposed to identify TRP using daily precipitation datasets,historical tropical cyclone(TC)track data,and the ERA5 reanalysis data.This method includes three steps:first,independent rain belts are separated,and those that might relate to TCs'remote effects are distinguished according to their distance from the TCs.Second,the strong water vapor transport belt from the TC is identified using integrated horizontal water vapor transport(IVT).Third,TRP is distinguished by connecting the first two steps.The TRP obtained through this method can satisfy three criteria,as follows:1)the precipitation occurs outside the circulation of TCs,2)the precipitation is affected by TCs,and 3)a gap exists between the TRP and TC rain belt.Case diagnosis analysis,compared with subjective TRP results and backward trajectory analyses using HYSPLIT,indicates that OSAT_TRP can distinguish TRP even when multiple TCs in the Northwest Pacific are involved.Then,we applied the OSAT_TRP to select typical TRPs and obtained the synoptic-scale environments of the TRP through composite analysis.展开更多
Tropical cyclones(TCs)are one of the most serious types of natural disasters,and accurate TC activity predictions are key to disaster prevention and mitigation.Recently,TC track predictions have made significant progr...Tropical cyclones(TCs)are one of the most serious types of natural disasters,and accurate TC activity predictions are key to disaster prevention and mitigation.Recently,TC track predictions have made significant progress,but the ability to predict their intensity is obviously lagging behind.At present,research on TC intensity prediction takes atmospheric reanalysis data as the research object and mines the relationship between TC-related environmental factors and intensity through deep learning.However,reanalysis data are non-real-time in nature,which does not meet the requirements for operational forecasting applications.Therefore,a TC intensity prediction model named TC-Rolling is proposed,which can simultaneously extract the degree of symmetry for strong TC convective cloud and convection intensity,and fuse the deviation-angle variance with satellite images to construct the correlation between TC convection structure and intensity.For TCs'complex dynamic processes,a convolutional neural network(CNN)is used to learn their temporal and spatial features.For real-time intensity estimation,multi-task learning acts as an implicit time-series enhancement.The model is designed with a rolling strategy that aims to moderate the long-term dependent decay problem and improve accuracy for short-term intensity predictions.Since multiple tasks are correlated,the loss function of 12 h and 24 h are corrected.After testing on a sample of TCs in the Northwest Pacific,with a 4.48 kt root-mean-square error(RMSE)of 6 h intensity prediction,5.78 kt for 12 h,and 13.94 kt for 24 h,TC records from official agencies are used to assess the validity of TC-Rolling.展开更多
Traditional pyrometallurgical and hydrometallurgical methods to extract bismuth from sulfide ores face problems such as high cost,low-concentration SO_(2)generation,and long process time.In this study,the cyclone tech...Traditional pyrometallurgical and hydrometallurgical methods to extract bismuth from sulfide ores face problems such as high cost,low-concentration SO_(2)generation,and long process time.In this study,the cyclone technology and slurry electrolysis method were combined.The bismuth sulfide ore was dissolved directly at the anode,while the high purity bismuth was deposited efficiently at the cathode under the advantages of the two methods.The short process and high-efficiency extraction of bismuth sulfide ore were realized,and the pollution of low-concentration SO_(2)was avoided.Then,the effects of several crucial experimental conditions(current density,reaction time,temperature,pH,liquid-solid ratio,and circulation flow rate)on the leaching efficiency and recovery efficiency of bismuth were investigated.The leaching and electrowinning mechanisms during the recovery process were also analyzed according to the research results of this paper to better understand the cyclone slurry electrolysis process.The experimental results showed that 95.19%bismuth was leached into the acid solution in the anode area under optimal conditions,and the recovery efficiency and purity of bismuth on the cathode reached 91.13%and 99.26%,respectively,which were better than those by the traditional hydrometallurgy recovery process.展开更多
This study proposes a novel cyclone separator with a conical inner core to enhance particle classification efficiency in oil and gas wellhead-recovered liquids.Particle motion and force dynamics are analyzed to optimi...This study proposes a novel cyclone separator with a conical inner core to enhance particle classification efficiency in oil and gas wellhead-recovered liquids.Particle motion and force dynamics are analyzed to optimize key structural parameters,including inlet diameter(D_i),overflow pipe diameter(D_(e)),insertion depth(L_(e)),and bottom flow pipe diameter(D_(z)).Numerical simulations employ the Reynolds stress turbulence model,SIMPLEC algorithm,and discrete phase model to evaluate separation performance in a gas-liquid two-phase system.Results indicate that a smaller D_i improves fine particle separation but increases turbulence;an optimal range of D_i/D_(c)=0.35-0.4 is recommended.Larger D_(e) enhances the diversion ratio,aiding fine particle discharge(D_(e)/D_(c)=0.25-0.35).Increased Le facilitates fine particle overflow but induces vortices,whereas a smaller L_(e) stabilizes the bottom flow for larger particle separation(L_(e)/D_(c)=0.5-0.75).A reduced D_(z) enhances centrifugal force and separation efficiency but may cause turbulence;an optimal D_(z)/D_(c) of 0.6-0.65 is suggested for stability.These findings provide valuable design guidelines for improving cyclone separator performance in multiphase flow applications.展开更多
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 bot...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.展开更多
Tropical cyclone activity has undergone significant changes under the impact of global warming since the 20th century.However,the characteristic and trend changes of landfalling tropical cyclones over China still need...Tropical cyclone activity has undergone significant changes under the impact of global warming since the 20th century.However,the characteristic and trend changes of landfalling tropical cyclones over China still need to be further clarified.The study conducted an analysis of the spatiotemporal characteristics and trends of landfalling tropical cyclones over China from 1949 to 2022 using the dataset of the best tracks of tropical cyclones from the China Meteorological Administration.Additionally,we explored the influences of ENSO and the Pacific Decadal Oscillation(PDO)on landfalling tropical cyclone activities.The results indicate that:(1)The annual average number of landfalling tropical cyclones over China is approximately 8.85,showing a significant decreasing trend,and the decreasing range becomes larger with lower latitude overall.However,both the proportion of landfalling tropical cyclones to the total number and the percentage of higher intensity tropical cyclones increase.(2)The landfall locations of tropical cyclones in China are mainly concentrated between 18°N and 26°N,accounting for approximately 88.2%of the total,and the landfall frequency shows a sharp decline in the regions north of 30°N.The central landfall location of tropical cyclones has shifted significantly northwestward,moving closer to China.Compared to 1949–1969,the central genesis location from 2010 to 2022 shifted 4.5°westward and 2.0°northward.(3)There is a correlation between ENSO and the genesis frequency variation of tropical cyclones in the Northwest Pacific and landfalling over China.El Ni?o promotes the genesis of strong tropical cyclones and leads to a more southeastern bias in the genesis location of landfalling tropical cyclones,while La Ni?a has an opposite effect.The PDO also affects the tropical cyclones to a certain extent.During the PDO warm phase,the genesis position of tropical cyclones is westward and the number is smaller than that in the cold phase.This study further clarifies the changing trends and characteristics of landfalling tropical cyclones over China since 1949.It also highlights the impacts of ENSO and the PDO on tropical cyclone activities.The findings can serve as a scientific basis for conducting simulations and assessments of tropical cyclones and for disaster prevention and mitigation efforts.展开更多
In recent years,torrential rain events caused by extratropical cyclones(ETCs)during the boreal midsummer(July-August)in Central and Eastern China have shown an increasing trend.For instence,in August 2024,two ETCs bro...In recent years,torrential rain events caused by extratropical cyclones(ETCs)during the boreal midsummer(July-August)in Central and Eastern China have shown an increasing trend.For instence,in August 2024,two ETCs brought large-scale heavy rainfall to North China,with daily precipitation exceeding 100 mm.Using reanalysis datasets and gridded precipitation data,the ETCs that affected Central and Eastern China during the boreal midsummer from 1981 to 2020 were objectively identified and tracked.ETCs causing precipitation were classified based on maximum daily precipitation,resulting in datasets for ETCs with torrential rain(daily precipitation exceeding 100 mm,referred to as ETC_R100)and heavy rain(daily precipitation exceeding 25 mm,referred to as ETC_R25).Comparative analysis can help highlight the characteristics of ETC_R100.This study compares the spatial distribution,movement paths,weather impacts,large-scale atmospheric circulation,and environmental conditions of these two types of precipitation-related ETCs.The following findings emerged:(1)ETC_R100 is driven by the combined forcing of upper-level troughs and warm-moist airflows at lower levels,exhibiting stronger thermal forcing than ETC_R25.(2)The moisture source for ETC_R100 are the Bay of Bengal and the Northwest Pacific,with moisture transported via the South China Sea.Compared to ETCs with nonextreme rainfall,ETC_R100 is characterized by greater atmospheric instability and better moisture conditions,resulting in higher precipitation intensity.(3)Regardless of the precipitation level,ETCs affected different regions but contributed significantly to precipitation in northern China,accounting for approximately 50%of the total precipitation.The results indicate that ETC_R100 differs significantly from ETCs with varying levels of precipitation in terms of statistical characteristics,weather impact,environmental conditions,and cyclogenesis conditions.展开更多
Forecasting tropical cyclone(TC)activities has been a topic of great interest and research.Taiwan Island(TW)is one of the key regions that is highly exposed to TCs originated from the western North Pacific.Here,the au...Forecasting tropical cyclone(TC)activities has been a topic of great interest and research.Taiwan Island(TW)is one of the key regions that is highly exposed to TCs originated from the western North Pacific.Here,the authors utilize two mainstream reanalysis datasets for the period 1979-2013 and propose an effective statistical seasonal forecasting model-namely,the Sun Yat-sen University(SYSU)Model-for predicting the number of TC landfalls on TW based on the environmental factors in the preseason.The comprehensive predictor sampling and multiple linear regression show that the 850-hPa meridional wind over the west of the Antarctic Peninsula in January,the 300-hPa specific humidity over the open ocean southwest of Australia in January,the 300-hPa relative vorticity over the west of the Sea of Okhotsk in March,and the sea surface temperature in the South Indian Ocean in April,are the most significant predictors.The correlation coefficient between the modeled results and observations reaches 0.87.The model is validated by the leave-one-out and nine-fold cross-validation methods,and recent 9-yr observations(2014-2022).The Antarctic Oscillation,variabilities of the western Pacific subtropical high,Asian summer monsoon,and oceanic tunnel are the possible physical linkages or mechanisms behind the model result.The SYSU Model exhibits a 98%hit rate in 1979-2022(43 out of 44),suggesting an operational potential in the seasonal forecasting of TC landfalls on TW.展开更多
基金supported by the National Key R&D Program of China [grant number 2023YFC3008004]。
文摘This study presents a comprehensive evaluation of tropical cyclone(TC)forecast performance in the western North Pacific from 2013 to 2022,based on operational forecasts issued by the China Meteorological Administration.The analysis reveals systematic improvements in both track and intensity forecasts over the decade,with distinct error characteristics observed across various forecast parameters.Track forecast errors have steadily decreased,particularly for longer lead times,while error magnitudes have increased with longer forecast lead times.Intensity forecasts show similar progressive enhancements,with maximum sustained wind speed errors decreasing by 0.26 m/s per year for 120 h forecasts.The study also identifies several key patterns in forecast performance:typhoon-grade or stronger TCs exhibit smaller track errors than week or weaker systems;intensity forecasts systematically overestimate weaker TCs while underestimating stronger systems;and spatial error distributions show greater track inaccuracies near landmasses and regional intensity biases.These findings highlight both the significant advances in TC forecasting capability achieved through improved modeling and observational systems,and the remaining challenges in predicting TC changes and landfall behavior,providing valuable benchmarks for future forecast system development.
基金supported by the Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(No.SCSF202307)the Basic Research Fund of CAMS(No.2023Z016)+1 种基金the National Natural Scientific Foundation of China(No.42275037)the Jiangsu Collaborative Innovation Center for Climate Change。
文摘In this study,tropical cyclone(TC)translation speed was introduced as a new similarity factor within the generalized initial value(GIV)framework,enhancing the disaster preassessment capability of the dynamical statistical analog ensemble forecast model for landfalling TC disasters(DSAEF_LTD model).Three TC translation speed indicators most relevant to TC precipitation were incorporated:the maximum speed on Day 1(the first day of TC-induced precipitation and wind occurring on land)and the average and minimum speeds over All Days(all days of TC-induced precipitation and wind occurring on land),all classified using the Kmeans clustering algorithm.Simulation experiments showed that integrating TC translation speed enhanced the model's performance.The model provided a better optimal common scheme,with the TSS UM(sum of threat scores for severe and above and extremely severe and above disasters)increasing by 2.66%(from 0.5117 to 0.5253)compared with the original model.More importantly,its preassessment ability improved significantly,with the average TSS UM for independent samples increasing by 6.43%(from 0.6488 to0.6905).The modified model demonstrated greater accuracy in capturing disaster severity and distribution of TCs with significant speed characteristics or with regular tracks.This improvement stemmed from reduced false alarms due to the selection of analogs that are more similar to the target TC.The enhanced preassessment ability can be attributed to the key role of TC translation speed,which significantly influences TC precipitation patterns and improves TC precipitation forecasting.Since precipitation is one of the most crucial disaster-causing factors,better TC precipitation forecasting leads to improved disaster preassessment outcomes.These findings emphasize the promising potential of the DSAEF_LTD model for future TC disaster research and management,contributing to the achievement of the Sustainable Development Goals set by the United Nations 2030 Agenda by strengthening coastal resilience.
基金jointly supported by the National Natural Science Foundation of China[grant numbers U2342202,42175005,and 42175016]the Qing Lan Project[grant number R2023Q06]。
文摘This study investigates the width of the secondary eyewall(SE)immediately following its formation in tropical cyclones with surface environmental winds aligned and counter-aligned with environmental vertical wind shear(VWS),using idealized numerical experiments.Results reveal that the SE develops greater radial extent when surface winds align with VWS compared to counter-aligned conditions.In alignment configurations,shear-enhanced surface winds on the right flank amplify surface enthalpy fluxes,thereby elevating boundary-layer entropy within the downshear outer-core region.Subsequently,more vigorous outer rainbands develop,inducing marked acceleration of tangential winds in the outer core preceding SE formation.The resultant radial expansion of supergradient winds near the boundary-layer top triggers widespread convective activity immediately beyond the inner core.Progressive axisymmetrization of this convective forcing ultimately generates an expansive SE structure.
基金supported by the National Natural Science Foundation of China(Grant Nos.42192551,42150710531).
文摘The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.
基金supported by the Meteorological Joint Funds of the National Natural Science Foundation of China(Grant No.U2142211)the National Natural Science Foundation of China(Grant Nos.42075141,42341202 and 62088101)+1 种基金the National Key Research and Development Program of China(Grant No.2020YFA0608000)the Shanghai Municipal Science and Technology Major Project(Grant No.2021SHZDZX0100).
文摘Accurate forecasting of tropical cyclone(TC)tracks and intensities is essential.Although the TianXing large weather model,a six-hourly forecasting model surpassing operational forecasts,exhibits superior performance,its TC forecasts still require enhancement.Prediction errors persist due to biases in the training data and smoothing effects in data-driven methods.To address this,we introduce CycloneBCNet,a deep-learning model designed to correct TianXing’s TC forecast biases by leveraging spatial and temporal data.CycloneBCNet utilizes the SimVP(simpler yet better video prediction)framework with spatial attention to highlight cyclone core regions in forecast fields.It also incorporates TC trend information(center position,maximum wind speed,and minimum sea level pressure)via an LSTM(long short-term memory)module.These TC vectors are derived from post-processed TianXing forecasts.By fusing features from forecast fields and TC vectors,CycloneBCNet corrects biases across multiple lead times.At a 96-h lead time,the track error reduces from 162.4 to 86.4 km,the wind speed error from 17.2 to 6.69 m s^(-1),and the pressure error from 22.2 to 9.36 hPa.Interpretability analysis shows that CycloneBCNet adjusts its attention across forecast lead times.Intensity corrections prioritize inner-core dynamics,particularly the eye and eyewall,while track corrections shift from lower-level variables and the cyclone’s core to broader environmental factors and mid-to upper-level features as the forecast duration increases.These findings demonstrate that CycloneBCNet effectively captures key TC dynamics consistent with meteorological principles,including the dominance of near-surface conditions for intensity and the increasing influence of steering currents on track prediction.
基金supported by the National University of Defense Technology(NUDT)Research Initiation Funding for High-Level Scientific and Technological Innovative Talents(202402-YJRC-LJ-001)the National Natural Science Foundation of China(Grant No.U2142213)+1 种基金the Basic and Applied Basic Research Foundation of Guangdong Province(Grants 2025A1515011835,2022A1515011870)the National Natural Science Foundation of China(Grant No.42305167)。
文摘The operational Tropical Regional Atmospheric Model System(TRAMS)often underestimates initial typhoon intensity when using the global analysis field as the initial condition.The TRAMS tropical cyclone(TC)initialization scheme,developed based on the incremental analysis updates(IAU)technique,effectively reduces initial bias.However,the original IAU-based TC initialization scheme only adjusts the wind field at the analysis moment,with other variables adjusted implicitly under the model's constraints according to a gradually inserted wind increment(named“univariate adjustment scheme”hereafter).The univariate adjustment scheme requires approximately 3 h to reach a dynamic equilibrium state,which constrains the assimilation of hourly TC observations and causes excessive dissipation of meaningful short-wave information in adjustment increments.To address this limitation,this study develops a multivariate adjustment IAU-based TC initialization scheme that incorporates gradient wind balance and hydrostatic balance as its largescale constraints.Numerical experiments with TC Hato(2017)demonstrate that the multivariate adjustment scheme reduces the IAU relaxation time to 1 h while marginally improving forecast skill.These findings are consistently replicated across 12 additional TC cases.The development of the IAU-based multivariate adjustment initialization scheme establishes a foundation for 4-D initialization using hourly TC observations.
基金supported by the National Key Research and Development Program of China [grant number 2023YFF0807000]。
文摘Based on datasets from the International Best-Track Archive for Climate Stewardship(IBTrACS)and the fifth major global reanalysis produced by ECMWF(ERA5),the authors found that 29%of tropical cyclones(TCs)in the western North Pacific underwent extratropical transition(ET)from 1979 to 2022,with the frequency of ET events showing a slow decreasing trend.The extratropical transition tropical cyclones(ETCs)are classified into four clusters using the k-means clustering method based on their track patterns:recurving ETCs,westward ETCs,northwestward ETCs,and abnormal track ETCs.The transition process of recurving ETCs mostly occurs after the recurvature is completed,while 63.7%of the westward ETCs complete their transition after landfall.Abnormal track ETCs undergo transition over high-latitude oceans.Northwestward ETCs have the longest duration and slowest transition speed during the ET period,resulting in a prolonged impact.The ET process occurs at the edges of the western Pacific subtropical high(WPSH),with higher frequency during westward extension and lower during eastward retreat.While westward ETCs transition through surface friction effects,others complete ET in the northwest baroclinic zone of the WPSH.
基金financially supported by the National Key R&D Program of China (No. 2022YFC3004204)the National Natural Science Foundation of China (No. 42275001)the Natural Science Foundation of Shandong Province (No. ZR2022MD038)。
文摘Explosive cyclones(ECs) are rapidly intensifying subtropical cyclones that can develop within a short time and pose considerable threats to coastal areas in middle and high latitudes.Gaining a comprehensive understanding of their formation,evolution,and mechanisms of explosive development is essential for improving forecasts of extreme weather events and mitigating associated impacts.Potential vorticity(PV),which is closely related to cyclone dynamics,serves as a valuable diagnostic tool in the study of ECs.In this study,two wintertime ECs of differing intensity over the Northwestern Pacific Ocean are analyzed to examine how different atmospheric processes influence PV generation and the rapid development of ECs.The maximum deepening rates of the two ECs are 2.81 Bergeron(called EC1) and 1.52 Bergeron(referred to as EC2).Results indicate that different stages of EC evolution are closely associated with PV tendency changes at different atmospheric levels.Using the PV tendency equation,during the explosive development of EC1,latent heat release may trigger the downward propagation of upper-level PV.For EC2,latent heat release notably enhances low-level PV,directly contributing to its rapid intensification.To validate these findings,sensitivity tests are conducted using the Weather Research and Forecasting model,with latent heat release turned off in the microphysical scheme for both cases.The results confirm the crucial role of latent heat release in generating low-level PV,further revealing that latent heat release contributes more to the explosive development of EC2 than that of EC1.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC3000803)the National Natural Science Foundation of China(Grant Nos.42375149,41975133 and 42205070)the Shanghai Pujiang Program(Grant No.22PJ1415900)。
文摘A modified three-dimensional turbulence parameterization scheme,implemented by replacing the conventional eddydiffusivity formulation with the H-gradient model,has shown good performance in representing the subgrid-scale(SGS)turbulent fluxes associated with convective clouds in idealized tropical cyclone(TC)simulations.To evaluate the capability of the modified scheme in simulating real TCs,two sets of simulations of TC Soudelor(2015),one with the modified scheme and the other with the original scheme,are conducted.Comparisons with observations and coarse-grained results from large eddy simulation benchmarks demonstrate that the modified scheme improves the forecasting of the intensity and structure,as well as the SGS turbulent fluxes of Soudelor.Using the modified turbulence scheme,a TC with stronger intensity,smaller size,a shallower but stronger inflow layer,and a more intense but less inclined convective updraft is simulated.The rapid intensification process and secondary eyewall features can also be captured better by the modified scheme.By analyzing the mechanism by which turbulent transport impacts the intensity and structure of TCs,it is shown that accurately representing the turbulent transport associated with convective clouds above the planetary boundary layer helps to initiate the TC spin-up process.
基金The National Natural Science Foundation of China under contract Nos 42175011,42192554,and 42305007.
文摘In this study,numerical experiments with different initial radius of maximum wind(RMW)are performed to study the effects of tropical cyclone(TC)size combined with land-sea contrast on TC motion and low-level wind structure before landfall.By idealized numerical simulations,we found that larger TC arrived coastline earlier than smaller TC,when they started moving from the same position.This is because that the larger TCs not only accelerate earlier but also have greater movement speed than smaller TCs when they approach the coastline.The mechanism responsible for this is that the edge of large TCs reach coastline earlier,thus their movement speed accelerated earlier than small TCs,due to the asymmetries in diabatic heating and radial flow generated by the land-sea contrast.Moreover,when TCs in three experiments all affected by the land-sea contrast,the stronger asymmetries generated in larger TC,thus resulting in faster movement in larger TC.The stronger inflow in western quadrant and weaker inflow(even outflow)in eastern quadrant of larger TC deduced apparently difference in vertical motion and diabatic heating between western and eastern quadrant of TC before landfall.An analysis of potential vorticity tendency proved that the diabatic heating terms were important and considered in determining the TC landward drift because asymmetries in vertical motion and relative vorticity developed due to asymmetric flow.
基金supported by the Zhejiang Provincial Natural Science Foundation of China (Grant Nos. LZJMZ25D050008 and LQ21D060001)the National Natural Science Foundation of China (Grant No. 42305153)+4 种基金the East China Meteorological Science and Technology Collaborative Innovation Foundation Cooperation Project (Grant No. QYHZ202307)the Zhejiang Meteorological Science and Technology Plan Project (Grant Nos. 2021YB07, 2022ZD06 and 2023YB06)the Youth Innovation Team Fund of the China Meteorological Administration (Grant No.CMA2023QN12)support of the Canadian program “Transforming Climate Action” led by Dalhousie University in Canadathe Canadian Space Agency (CSA) projects “Ocean surface features related to aggregation of North Atlantic Right Whales (NARWs)” and “Fine resolution classification of sea ice from the RADARSAT Constellation Mission (RCM)”
文摘Spaceborne microwave instruments possess the capability of day-and-night and all-weather measurements that can penetrate clouds and fog,and directly measure tropical cyclone(TC)ocean surface winds.In this study,we establish an effective methodology to estimate TC dynamic characteristic parameters(DCP),including the storm center location,intensity,radius of maximum wind(RMW)and wind structure,purely from TC ocean winds measured by multi-platform spaceborne microwave instruments.Combining measurements from active and passive sensors can provide long time series data for monitoring changes in storm DCP.Here,the evolution of the DCP for TC Freddy(2023),from its genesis to its landfall,is evaluated using data from synthetic aperture radars(SARs),as well as radiometer(RAD)and scatterometer(SCA)observations.Comparing the results to the best-track datasets for the longitudes and latitudes of the storm centers,we show that the root-mean-square errors(RMSEs)are 0.22°and 0.31°,respectively,both with a correlation of 0.99.For the detected intensity,the RMSEs are 6.8 m s^(−1) for SARs and 7.3 m s^(−1) for RADs.However,TC intensities measured by C-band SCAs are significantly underestimated,especially for wind speeds less than 50 m s^(−1).In terms of RMW and wind radii,the SARs,RADs and SCAs demonstrate good accuracy and applicability.Our investigation emphasizes the crucial role played by spaceborne microwave instruments in the study of TCs.This is helpful in monitoring,and in the future,will help improve the forecasting of TC intensities and their characteristic structures.
基金supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_1136)the National Natural Scientific Foundation of China(No.42275037)+2 种基金the Basic Research Fund of CAMS(No.2023Z016)the Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(No.SCSF202202)supported by the Jiangsu Collaborative Innovation Center for Climate Change。
文摘At present,the identification of tropical cyclone remote precipitation(TRP)requires subjective participation,leading to inconsistent results among different researchers despite adopting the same identification standard.Thus,establishing an objective identification method is greatly important.In this study,an objective synoptic analysis technique for TRP(OSAT_TRP)is proposed to identify TRP using daily precipitation datasets,historical tropical cyclone(TC)track data,and the ERA5 reanalysis data.This method includes three steps:first,independent rain belts are separated,and those that might relate to TCs'remote effects are distinguished according to their distance from the TCs.Second,the strong water vapor transport belt from the TC is identified using integrated horizontal water vapor transport(IVT).Third,TRP is distinguished by connecting the first two steps.The TRP obtained through this method can satisfy three criteria,as follows:1)the precipitation occurs outside the circulation of TCs,2)the precipitation is affected by TCs,and 3)a gap exists between the TRP and TC rain belt.Case diagnosis analysis,compared with subjective TRP results and backward trajectory analyses using HYSPLIT,indicates that OSAT_TRP can distinguish TRP even when multiple TCs in the Northwest Pacific are involved.Then,we applied the OSAT_TRP to select typical TRPs and obtained the synoptic-scale environments of the TRP through composite analysis.
基金jointly supported by the National Natural Science Foundation of China(Grant Nos.42075138 and 42375147)the Program on Key Basic Research Project of Jiangsu(Grant No.BE2023829)。
文摘Tropical cyclones(TCs)are one of the most serious types of natural disasters,and accurate TC activity predictions are key to disaster prevention and mitigation.Recently,TC track predictions have made significant progress,but the ability to predict their intensity is obviously lagging behind.At present,research on TC intensity prediction takes atmospheric reanalysis data as the research object and mines the relationship between TC-related environmental factors and intensity through deep learning.However,reanalysis data are non-real-time in nature,which does not meet the requirements for operational forecasting applications.Therefore,a TC intensity prediction model named TC-Rolling is proposed,which can simultaneously extract the degree of symmetry for strong TC convective cloud and convection intensity,and fuse the deviation-angle variance with satellite images to construct the correlation between TC convection structure and intensity.For TCs'complex dynamic processes,a convolutional neural network(CNN)is used to learn their temporal and spatial features.For real-time intensity estimation,multi-task learning acts as an implicit time-series enhancement.The model is designed with a rolling strategy that aims to moderate the long-term dependent decay problem and improve accuracy for short-term intensity predictions.Since multiple tasks are correlated,the loss function of 12 h and 24 h are corrected.After testing on a sample of TCs in the Northwest Pacific,with a 4.48 kt root-mean-square error(RMSE)of 6 h intensity prediction,5.78 kt for 12 h,and 13.94 kt for 24 h,TC records from official agencies are used to assess the validity of TC-Rolling.
基金Projects(52104355,52074363,52374364)supported by the National Natural Science Foundation of ChinaProject(2023YFC2907904)supported by the National Key R&D Program of China。
文摘Traditional pyrometallurgical and hydrometallurgical methods to extract bismuth from sulfide ores face problems such as high cost,low-concentration SO_(2)generation,and long process time.In this study,the cyclone technology and slurry electrolysis method were combined.The bismuth sulfide ore was dissolved directly at the anode,while the high purity bismuth was deposited efficiently at the cathode under the advantages of the two methods.The short process and high-efficiency extraction of bismuth sulfide ore were realized,and the pollution of low-concentration SO_(2)was avoided.Then,the effects of several crucial experimental conditions(current density,reaction time,temperature,pH,liquid-solid ratio,and circulation flow rate)on the leaching efficiency and recovery efficiency of bismuth were investigated.The leaching and electrowinning mechanisms during the recovery process were also analyzed according to the research results of this paper to better understand the cyclone slurry electrolysis process.The experimental results showed that 95.19%bismuth was leached into the acid solution in the anode area under optimal conditions,and the recovery efficiency and purity of bismuth on the cathode reached 91.13%and 99.26%,respectively,which were better than those by the traditional hydrometallurgy recovery process.
基金supported by the National Natural Science Foundation of China(52074341)。
文摘This study proposes a novel cyclone separator with a conical inner core to enhance particle classification efficiency in oil and gas wellhead-recovered liquids.Particle motion and force dynamics are analyzed to optimize key structural parameters,including inlet diameter(D_i),overflow pipe diameter(D_(e)),insertion depth(L_(e)),and bottom flow pipe diameter(D_(z)).Numerical simulations employ the Reynolds stress turbulence model,SIMPLEC algorithm,and discrete phase model to evaluate separation performance in a gas-liquid two-phase system.Results indicate that a smaller D_i improves fine particle separation but increases turbulence;an optimal range of D_i/D_(c)=0.35-0.4 is recommended.Larger D_(e) enhances the diversion ratio,aiding fine particle discharge(D_(e)/D_(c)=0.25-0.35).Increased Le facilitates fine particle overflow but induces vortices,whereas a smaller L_(e) stabilizes the bottom flow for larger particle separation(L_(e)/D_(c)=0.5-0.75).A reduced D_(z) enhances centrifugal force and separation efficiency but may cause turbulence;an optimal D_(z)/D_(c) of 0.6-0.65 is suggested for stability.These findings provide valuable design guidelines for improving cyclone separator performance in multiphase flow applications.
基金supported by the National Natural Science Foundation of China(Grant No.41930967)。
文摘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.
基金Young Taishan Scholars Program of Shandong Province,No.tsqn202103065National Natural Science Foundation of China,No.42371084。
文摘Tropical cyclone activity has undergone significant changes under the impact of global warming since the 20th century.However,the characteristic and trend changes of landfalling tropical cyclones over China still need to be further clarified.The study conducted an analysis of the spatiotemporal characteristics and trends of landfalling tropical cyclones over China from 1949 to 2022 using the dataset of the best tracks of tropical cyclones from the China Meteorological Administration.Additionally,we explored the influences of ENSO and the Pacific Decadal Oscillation(PDO)on landfalling tropical cyclone activities.The results indicate that:(1)The annual average number of landfalling tropical cyclones over China is approximately 8.85,showing a significant decreasing trend,and the decreasing range becomes larger with lower latitude overall.However,both the proportion of landfalling tropical cyclones to the total number and the percentage of higher intensity tropical cyclones increase.(2)The landfall locations of tropical cyclones in China are mainly concentrated between 18°N and 26°N,accounting for approximately 88.2%of the total,and the landfall frequency shows a sharp decline in the regions north of 30°N.The central landfall location of tropical cyclones has shifted significantly northwestward,moving closer to China.Compared to 1949–1969,the central genesis location from 2010 to 2022 shifted 4.5°westward and 2.0°northward.(3)There is a correlation between ENSO and the genesis frequency variation of tropical cyclones in the Northwest Pacific and landfalling over China.El Ni?o promotes the genesis of strong tropical cyclones and leads to a more southeastern bias in the genesis location of landfalling tropical cyclones,while La Ni?a has an opposite effect.The PDO also affects the tropical cyclones to a certain extent.During the PDO warm phase,the genesis position of tropical cyclones is westward and the number is smaller than that in the cold phase.This study further clarifies the changing trends and characteristics of landfalling tropical cyclones over China since 1949.It also highlights the impacts of ENSO and the PDO on tropical cyclone activities.The findings can serve as a scientific basis for conducting simulations and assessments of tropical cyclones and for disaster prevention and mitigation efforts.
基金National Natural Science Foundation of China(42375014,42088101,42030605)Joint Research Project for Meteorological Capacity Improvement(24NLTSZ010)Young Elite Scientists Sponsorship Program by BAST(BYESS2023205)。
文摘In recent years,torrential rain events caused by extratropical cyclones(ETCs)during the boreal midsummer(July-August)in Central and Eastern China have shown an increasing trend.For instence,in August 2024,two ETCs brought large-scale heavy rainfall to North China,with daily precipitation exceeding 100 mm.Using reanalysis datasets and gridded precipitation data,the ETCs that affected Central and Eastern China during the boreal midsummer from 1981 to 2020 were objectively identified and tracked.ETCs causing precipitation were classified based on maximum daily precipitation,resulting in datasets for ETCs with torrential rain(daily precipitation exceeding 100 mm,referred to as ETC_R100)and heavy rain(daily precipitation exceeding 25 mm,referred to as ETC_R25).Comparative analysis can help highlight the characteristics of ETC_R100.This study compares the spatial distribution,movement paths,weather impacts,large-scale atmospheric circulation,and environmental conditions of these two types of precipitation-related ETCs.The following findings emerged:(1)ETC_R100 is driven by the combined forcing of upper-level troughs and warm-moist airflows at lower levels,exhibiting stronger thermal forcing than ETC_R25.(2)The moisture source for ETC_R100 are the Bay of Bengal and the Northwest Pacific,with moisture transported via the South China Sea.Compared to ETCs with nonextreme rainfall,ETC_R100 is characterized by greater atmospheric instability and better moisture conditions,resulting in higher precipitation intensity.(3)Regardless of the precipitation level,ETCs affected different regions but contributed significantly to precipitation in northern China,accounting for approximately 50%of the total precipitation.The results indicate that ETC_R100 differs significantly from ETCs with varying levels of precipitation in terms of statistical characteristics,weather impact,environmental conditions,and cyclogenesis conditions.
基金jointly supported by the Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)[grant number 316323005]the Guangdong Basic and Applied Basic Research Foundation[grant numbers 2023A1515010741 and 2024B1515020035]the Science and Technology Planning Project of Guangdong Province[grant number 2023B1212060019]。
文摘Forecasting tropical cyclone(TC)activities has been a topic of great interest and research.Taiwan Island(TW)is one of the key regions that is highly exposed to TCs originated from the western North Pacific.Here,the authors utilize two mainstream reanalysis datasets for the period 1979-2013 and propose an effective statistical seasonal forecasting model-namely,the Sun Yat-sen University(SYSU)Model-for predicting the number of TC landfalls on TW based on the environmental factors in the preseason.The comprehensive predictor sampling and multiple linear regression show that the 850-hPa meridional wind over the west of the Antarctic Peninsula in January,the 300-hPa specific humidity over the open ocean southwest of Australia in January,the 300-hPa relative vorticity over the west of the Sea of Okhotsk in March,and the sea surface temperature in the South Indian Ocean in April,are the most significant predictors.The correlation coefficient between the modeled results and observations reaches 0.87.The model is validated by the leave-one-out and nine-fold cross-validation methods,and recent 9-yr observations(2014-2022).The Antarctic Oscillation,variabilities of the western Pacific subtropical high,Asian summer monsoon,and oceanic tunnel are the possible physical linkages or mechanisms behind the model result.The SYSU Model exhibits a 98%hit rate in 1979-2022(43 out of 44),suggesting an operational potential in the seasonal forecasting of TC landfalls on TW.
