Understanding the factors that control typhoon rainfall distribution is critical for improving rainfall forecasting,especially for landfall typhoons. This study investigated the impact of typhoon size on rainfall char...Understanding the factors that control typhoon rainfall distribution is critical for improving rainfall forecasting,especially for landfall typhoons. This study investigated the impact of typhoon size on rainfall characteristics at landfall in eastern coast of China. Typhoons Ampil(2018) and Rumbia(2018), which had similar intensities, were investigated to explore the connection between storm size and rainfall. The larger cyclonic wind field in Typhoon Rumbia led to greater vorticity and broader convergence compared to Typhoon Ampil, along with an ascending region outside the eyewall, which promoted more vigorous rainbands. Rumbia′s larger size exhibited greater outer-core radial vorticity advection relative to Ampil. This maintained its extensive outer-core wind field and intensified outer rainband development. Consequently,Rumbia generated more extensive and prolonged rainfall post-landfall compared to Ampil. A composite analysis of typhoons making landfall in eastern China(2001-2021) further examines the statistical correlation between typhoon size and rainfall distribution. Results indicate that larger typhoons are more likely to generate heavier and more spatially extensive rainfall in regions beyond their eyewalls. These findings highlight that typhoon size significantly regulates rainfall evolution during landfall, underscoring the necessity of incorporating this parameter into operational rainfall forecasting models for landfalling typhoons.展开更多
Previous studies have revealed that typhoons can affect the ionosphere.This paper uses GNSS observations provided by GNSS tracking stations of Taiwan region,ERA5 gravity wave dissipation products,and Himawari-8 band 0...Previous studies have revealed that typhoons can affect the ionosphere.This paper uses GNSS observations provided by GNSS tracking stations of Taiwan region,ERA5 gravity wave dissipation products,and Himawari-8 band 07 brightness temperature observation data to analyze the impact of Typhoon Meranti on Taiwan region's ionosphere from September 13 to 15,2016.In addition to the daily effects of traveling ionospheric disturbances(TIDs),TIDs of various intensities caused by Meranti-induced gravity waves were observed during this period,which is inseparable from the state of the typhoon and the topographic features during its progress.The ionospheric disturbance caused by the edge of a typhoon is usually larger than that at the typhoon eye.When the typhoon approached Taiwan region with high intensity on September 14,it was observed that the gravity waves caused by the typhoon had a wavelength of about 174-293 km,a period of 13.5-23.5 min,and a propagation speed of 142-302 m/s.When the vortex structure of a typhoon interacts with complex surfaces such as mountains,it is easier to excite more medium-scale gravity waves.The origin that excites gravity waves and causes ionospheric anomalies is different from the location of the typhoon eye and changes over time.The gravity waves caused by the typhoon lasted for three days in the central mountains of Taiwan region.Still,background wind conditions restricted the propagation of gravity waves from the mesosphere to the thermosphere and led to TID predominantly concentrated between 06:00 and 13:00 UT each day.展开更多
Measurements from a hyperspectral infrared(HIR) sounder onboard a satellite in geostationary orbit not only provide atmospheric thermodynamic information,but also can be used to infer dynamic information with high tem...Measurements from a hyperspectral infrared(HIR) sounder onboard a satellite in geostationary orbit not only provide atmospheric thermodynamic information,but also can be used to infer dynamic information with high temporal resolution.Radiance measurements from the Geostationary Interferometric Infrared Sounder(GIIRS),obtained with 15-min temporal resolution during Typhoon Maria(2018) and 30-min temporal resolution during Typhoon Lekima(2019),were used to derive three-dimensional(3D) horizontal winds by tracking the motion of atmospheric moisture.This work focused on the impact of assimilation of 3D winds on typhoon analyses and forecasts using the operational NWP model of the China Meteorological Administration(CMA-MESO),and improved understanding of the potential benefits of assimilating dynamic information from geostationary sounder data with higher temporal resolution.The standard deviation of the observations minus simulations revealed that the accuracy of the derived 3D winds with 15-min resolution was higher than that of derived winds with 30-min resolution.Experiments showed that the assimilation system can effectively absorb the information of the derived 3D winds,and that dynamic information from clear-sky areas can be transferred to typhoon areas.In typhoon prediction,assimilation of the derived 3D winds had greatest influence on the typhoon track,and less influence on the maximum wind speed.Assimilation of the derived 3D winds reduced the average track error by 17.4% for Typhoon Maria(2018) and by 3.5% for Typhoon Lekima(2019) during their entire 36-h forecasts initiated at different times.Assimilation of GIIRS dynamic information can substantially improve forecasts of heavy precipitation by CMAMESO.Results indicate that the assimilation of dynamic information from high-temporal-resolution geostationary HIR sounder data adds value for improved numerical weather prediction.展开更多
Typhoons,as strong convective systems,can excite multi-scale atmospheric gravity waves that travel long distances,and play an important role in momentum and energy transmission between the middle and upper atmosphere....Typhoons,as strong convective systems,can excite multi-scale atmospheric gravity waves that travel long distances,and play an important role in momentum and energy transmission between the middle and upper atmosphere.In this paper,the research progress in the observation techniques,generation mechanism and propagation characteristics of typhoon-induced gravity waves were systematically reviewed.These studies show that based on the combined application of ground-based and space-based observation(sounding balloons,airglow imaging,and satellite remote sensing)and reanalysis data(such as ERA5),with the aid of ray tracing theory and numerical simulation technology,the mechanism of typhoon induced gravity waves and its dynamic characteristics in the middle and upper atmosphere have been better revealed.At present,there are still some insufficiencies in the fields of propagation path tracking of gravity waves,terrain multi-scale effect modeling and parameterization of inertial gravity waves,which need to be further studied in the future.展开更多
Amid growing typhoon risks driven by climate change with projected shifts in precipitation intensity and temperature patterns,Taiwan faces increasing challenges in flood risk.In response,this study proposes a geograph...Amid growing typhoon risks driven by climate change with projected shifts in precipitation intensity and temperature patterns,Taiwan faces increasing challenges in flood risk.In response,this study proposes a geographic information system(GIS)-based artificial intelligence(AI)model to assess flood susceptibility in Keelung City,integrating geospatial and hydrometeorological data collected during Typhoon Krathon(2024).The model employs the random forest(RF)algorithm,using seven environmental variables excluding average elevation,slope,topographic wetness index(TWI),frequency of cumulative rainfall threshold exceedance,normalized difference vegetation index(NDVI),flow accumulation,and drainage density,with the number of flood events per unit area as the output.The RF model demonstrates high accuracy,achieving the accuracy of 97.45%.Feature importance indicates that NDVI is the most critical predictor,followed by flow accumulation,TWI,and rainfall frequency.Furthermore,under the IPCC AR5 RCP8.5 scenarios,projected 50-year return period rainfall in Keelung City increases by 42.40%-64.95%under+2℃to+4℃warming.These projections were integrated into the RF model to simulate future flood susceptibility.Results indicate two districts in the study area face the greatest increase in flood risk,emphasizing the need for targeted climate adaptation in vulnerable urban areas.展开更多
The extraordinary Super Typhoon(STY)Muifa(2022)made landfall four times and had a significant impact on the coastal regions from south to north of China.Although previous studies have demonstrated the‘pumping effect&...The extraordinary Super Typhoon(STY)Muifa(2022)made landfall four times and had a significant impact on the coastal regions from south to north of China.Although previous studies have demonstrated the‘pumping effect'of typhoons on the enhancement of reactive nitrogen(Nr)wet deposition over the ocean,it is uncertain how Nr deposition is influenced by typhoons thatmake prolonged mechanism due tomultiple landfalls.In this study,theNr wet deposition induced by STYMuifawas investigated fromthe perspective of in-and below-cloud processes based on the Nested Air Quality Prediction Modeling System with an online tracer-tagging module.High volume of Nr wet deposition caused by Muifa migrated from south to north,passing over half of China's coastal cities.Compared to the typhoon generated vicinity,both mean values of the oxidized and reduced nitrogen wet deposition over the Typhoon affected regions were increased about 20.4 and 66.1 times after landfall even with the similar rainfall.Emissions from the four landfall areas of China contributed to the majority of Nr wet deposition with significantly enhanced proportion of in-cloud deposition.The strong pumping effect of typhoon to the Nr deposition along the coastal areas and the risk of ecosystem effects requires further researches and higher demands on the control of nitrogen emissions of National Industrial Park,which usually located in China's coastal cities.展开更多
While steady improvements have been achieved for the track forecasts of typhoons,there has been a lack of improvement for intensity forecasts.One challenge for intensity forecasts is to capture the rapid intensificati...While steady improvements have been achieved for the track forecasts of typhoons,there has been a lack of improvement for intensity forecasts.One challenge for intensity forecasts is to capture the rapid intensification(RI),whose nonlinear characteristics impose great difficulties for numerical models.The ensemble sensitivity analysis(ESA)method is used here to analyze the initial conditions that contribute to typhoon intensity forecasts,especially with RI.Six RI processes from five typhoons(Chaba,Haima,Meranti,Sarika,and Songda)in 2016,are applied with ESA,which also gives a composite initial condition that favors subsequent RI.Results from individual cases have generally similar patterns of ESA,but with different magnitudes,when various cumulus parameterization schemes are applied.To draw the initial conditions with statistical significance,sample-mean azimuthal components of ESA are obtained.Results of the composite sensitivity show that typhoons that experience RI in 24 h favor enhanced primary circulation from low to high levels,intensified secondary circulation with increased radial inflow at lower levels and increased radial outflow at upper levels,a prominent warm core at around 300 hPa,and increased humidity at low levels.As the forecast lead time increases,the patterns of ESA are retained,while the sensitivity magnitudes decay.Given the general and quantitative composite sensitivity along with associated uncertainties for different cumulus parameterization schemes,appropriate sampling of the composite sensitivity in numerical models could be beneficial to capturing the RI and improving the forecasting of typhoon intensity.展开更多
The 2019 Typhoon Lekima triggered extensive landslides in Zhejiang Province.To explore the impact of typhoon paths on the distribution of landslide susceptibility,this study proposes a spatiotemporal zoning assessment...The 2019 Typhoon Lekima triggered extensive landslides in Zhejiang Province.To explore the impact of typhoon paths on the distribution of landslide susceptibility,this study proposes a spatiotemporal zoning assessment framework based on typhoon paths and inner rainbands.According to the typhoon landing path and its rainfall impact range,the study area is divided into the typhoon event period(TEP)and the annual non-typhoon period(ANP).The model uses 14 environmental factors,with the only difference between TEP and ANP being the rainfall index:TEP uses 48-hour rainfall during the typhoon,while ANP uses multi-year average annual rainfall.Modeling and comparative analysis were conducted using six machine learning models including random forest(RF)and support vector machine(SVM).The results show that the distribution pattern of high-risk landslide areas during TEP is significantly correlated with typhoon intensity:when the intensity is level 12,high-risk areas are radially distributed;at levels 10-11,they tend to concentrate asymmetrically along the coast;and when the intensity drops to below level 9,the overall susceptibility decreases significantly.During ANP,the distribution of landslides is relatively uniform with no obvious spatial concentration.Analysis on the factor contribution rate indicates that the rainfall weight in TEP is as high as 32.1%,making it the dominant factor;in ANP,the rainfall weight drops to 13.6%while the influence of factors such as slope and topographic wetness index increases,revealing differences in landslide formation mechanisms between the two periods.This study demonstrates that the spatiotemporal zoning method based on typhoon paths can effectively characterize the spatial susceptibility patterns of landslides and improve disaster identification capabilities under extreme weather conditions.The finally generated annual susceptibility zoning map divides the study area into four types of risk regions,providing a reference for dynamic monitoring and differentiated risk management of landslides in typhoon-prone areas.展开更多
To investigate the effect of typhoon path translation on storm surge augmentation,the storm surge during Typhoon 1909 Lekima in the East China Sea is simulated using Delft 3D.The model sets up three scenarios to analy...To investigate the effect of typhoon path translation on storm surge augmentation,the storm surge during Typhoon 1909 Lekima in the East China Sea is simulated using Delft 3D.The model sets up three scenarios to analyze the path’s effect on storm surge in the Shandong Peninsula Sea by shifting the typhoon path to the east and west.Results show that the areas of maximum storm surge in each scenario are located on both sides of the typhoon path and shift along with its movement.When the typhoon path shifts eastward,the maximum storm surge intensifies at Zhifu Island station 8 hours earlier.Conversely,a westward shift in the typhoon track leads to a maximum storm surge increase at Shidao Island station 12 hours earlier.Other scenarios exhibit minimal deviation from the original route.Typhoons penetrating deep inland can induce substantial storm surges,with the most extensive surge area situated in the western part of the Shandong Peninsula.展开更多
An analysis is conducted on the hydrodynamic response law of a single module maritime airport,considering the atmospheric variables of the wind and wave field.The analysis is based on hydroelastic theory and focuses o...An analysis is conducted on the hydrodynamic response law of a single module maritime airport,considering the atmospheric variables of the wind and wave field.The analysis is based on hydroelastic theory and focuses on the typhoon-driven very large floating structures(VLFS)configuration of the maritime airport.The findings indicate that the proposed method enables efficient information exchange between the fluid and structure domains through the coupling interface.The displacement of the maritime airport affected by the typhoon’s wave field is mostly determined by the direction of the flow.The wave loads acting on the floating body also influence the wave profile of the irregular wave and the deformation of the floating body.The von Mises stress distribution is not significant in all parts of the floating body.展开更多
In 2021,Cempaka,a tiny tropical cyclone,made landfall in China.As the TC intensified prior to landfall,the tropical cyclone size measured with precipitation decreased significantly.A numerical simulation was conducted...In 2021,Cempaka,a tiny tropical cyclone,made landfall in China.As the TC intensified prior to landfall,the tropical cyclone size measured with precipitation decreased significantly.A numerical simulation was conducted to examine the possible processes modulating the storm size.Azimuthally mean potential vorticity(PV)was found to decrease mainly in the middle to upper troposphere between 50-and 80-km radii.The PV budget results indicate that the advection and generation of mean PV associated with asymmetric processes,rather than the symmetric processes,primarily contributed to the decrease in mean PV.These asymmetric processes leading to a negative PV tendency were likely associated with inactive outer rainbands.In contrast,the tangential winds simultaneously expanded radially outward,possibly related to inner-core diabatic heating.The findings here emphasize the importance of outer rainband activity in tropical cyclone size change.展开更多
Frequent typhoons can significantly change the temperature,nutrient availability,and phytoplankton biomass in marginal seas.The oceanic response to typhoons is usually influenced by the features of the typhoon,among w...Frequent typhoons can significantly change the temperature,nutrient availability,and phytoplankton biomass in marginal seas.The oceanic response to typhoons is usually influenced by the features of the typhoon,among which the translational speed is critically important.By using a high resolution coupled physical-biological model,we investigated the response of the Yellow and East China seas(YECS)to two typhoons at different translational speeds,Muifa in August 2011 and Bolaven in August 2012.The model well reproduced the spatial and temporal variations of temperature,chlorophyll-a concentration over the YECS.Results show that typhoons with slower translational speeds uplift more deep water,leading to a more significant oceanic response.Divergence and convergence caused nutrient fluxes in opposite directions in the surface and bottom layers.Moreover,the nutrient flux in the bottom layer was greater than that in the surface layer.These phenomena are closely related to the spatial distribution of nutrients.Further studies show that the degree of ocean response to typhoons is highly correlated with the initial conditions of physical and biological elements of the upper ocean before the typhoon,as well as with ocean structure.Pretyphoon initial conditions of oceanic physical and ecological elements,mixed layer depth,and potential energy anomalies can all alter the degree of typhoon-induced oceanic response.This study emphasizes the important roles of the translational speed of typhoons and the initial oceanic conditions in the oceanic response to typhoons.展开更多
Ocean waves and Stokes drift are generated by typhoons.This study investigated the characteristics of ocean waves and wave-induced Stokes drift and their effects during Typhoon Mangkhut using European Centre for Mediu...Ocean waves and Stokes drift are generated by typhoons.This study investigated the characteristics of ocean waves and wave-induced Stokes drift and their effects during Typhoon Mangkhut using European Centre for MediumRange Weather Forecasts(ECMWF)ERA5 datasets and observational data.The results revealed that the typhoon generated intense cyclones and huge typhoon waves with a maximum wind speed of 45 m/s,a minimum pressure of955 h Pa,and a maximum significant wave height of 12 m.The Stokes drift caused by typhoon waves exceeded 0.6m/s,the Stokes depth scale exceeded 18 m,and the maximum Stokes transport reached 6 m^(2)/s.The spatial distribution of 10-m wind speed,typhoon wave height,Stokes drift,Stokes depth,and Stokes transport during the typhoon was highly correlated with the typhoon track.The distribution along the typhoon track showed significant zonal asymmetry,with greater intensity on the right side of the typhoon track than on the left side.These findings provide important insights into the impact of typhoons on ocean waves and Stokes drift,thus improving our understanding of the interactions between typhoons and the ocean environment.This study also investigated the contribution of Stokes transport to the total net transport during typhoons using Ekman-Stokes Numbers as a comparative measure.The results indicated that the ratio of Stokes transport to the total net transport reached up to 50%within the typhoon radius,while it was approximately 30%outside the radius.Strong Stokes transport induced by typhoon waves led to divergence in the transport direction,which resulted in upwelling of the lower ocean as a compensation current.Thus,Stokes transport played a crucial role in the vertical mixing of the ocean during typhoons.The findings suggested that Stokes transport should be paid more attention to,particularly in high latitude ocean regions,where strong winds can amplify its effects.展开更多
In recent years, the coastal region of Southeast China has witnessed a significant increase in the frequency and intensity of extreme rainfall events associated with landfalling typhoons. The hilly and mountainous ter...In recent years, the coastal region of Southeast China has witnessed a significant increase in the frequency and intensity of extreme rainfall events associated with landfalling typhoons. The hilly and mountainous terrain of this area, combined with rapid rainfall accumulation, has led to a surge in flash floods and severe geological hazards. On August 10, 2019, Typhoon Lekima made landfall in Zhejiang Province, China, and its torrential rainfall triggered extensive landslides, resulting in substantial damage and economic losses. Utilizing high-resolution satellite images, we compiled a landslide inventory of the affected area, which comprises a total of 2,774 rainfallinduced landslides over an area of 2965 km2. The majority of these landslides were small to mediumsized and exhibited elongated, clustered patterns. Some landslides displayed characteristics of high-level initiation, obstructing or partially blocking rivers, leading to the formation of debris dams. We used the inventory to analyze the distribution pattern of the landslides and their relationship with topographical, geological, and hydrological factors. The results showed that landslide abundance was closely related to elevation, slope angle, faults, and road density. The landslides were predominantly located in hilly and low mountainous areas, with elevations ranging from 150 to 300 m, slopes of 20 to 30 degrees, and a NE-SE aspect. Notably, we observed the highest Landslide Number Density(LND) and Landslide Area Percentage(LAP) in the rhyolite region. Landslides were concentrated within approximately 4 km on either side of fault zones, with their size and frequency negatively correlated with distances to faults, roads, and river systems. Furthermore, under the influence of typhoons, regions with denser vegetation cover exhibited higher landslide density, reaching maximum values in shrubland areas. In areas experiencing significantly increased concentrated rainfall, landslide density also showed a corresponding rise. In terms of spatial distribution, the rainfall-triggered landslides primarily occurred in the northeastern part of the study area, particularly in regions characterized by complex topography such as Shanzao Village in Yantan Town, Xixia Township, and Shangzhang Township. The research findings offer crucial data on the rainfallinduced landslides triggered by Typhoon Lekima, shedding light on their spatial distribution patterns. These findings provide valuable references for mitigating risks and planning reconstruction in typhoon-affected area.展开更多
The movement speed of Typhoon In-Fa(2021)was notably slow,at 10 km h-1or less,for over 20 hours following its landfall in Zhejiang,China,in contrast to other typhoons that have made landfall.This study examines the fa...The movement speed of Typhoon In-Fa(2021)was notably slow,at 10 km h-1or less,for over 20 hours following its landfall in Zhejiang,China,in contrast to other typhoons that have made landfall.This study examines the factors contributing to the slow movement of Typhoon In-Fa,including the steering flow,diabatic heating,vertical wind shear(VWS),and surface synoptic situation,by comparing it with Typhoons Yagi(2018)and Rumbia(2018)which followed similar tracks.The findings reveal that the movement speed of Typhoons Yagi and Rumbia is most closely associated with their respective 500 h Pa environmental winds,with a steering flow of 10^(-12)m s^(-1).In contrast,Typhoon InFa’s movement speed is most strongly correlated with the 850 h Pa environmental wind field,with a steering flow speed of only 2 m s^(-1).Furthermore,as Typhoon In-Fa moves northwest after landfall,its intensity is slightly greater than that of Typhoons Yagi and Rumbia,and the pressure gradient in front of Typhoon In-Fa is notably smaller,leading to its slow movement.Additionally,the precipitation distribution of Typhoon In-Fa differs from that of the other two typhoons,resulting in a weak asymmetry of wavenumber-1 diabatic heating,which indirectly affects its movement speed.Further analysis indicates that VWS can alter the typhoon’s structure,weaken its intensity,and ultimately impact its movement.展开更多
Highly productive estuaries facilitate intense decomposition of dissolved organic matter(DOM) as a carbon source.However,the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear.To addres...Highly productive estuaries facilitate intense decomposition of dissolved organic matter(DOM) as a carbon source.However,the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear.To address this issue,we investigated the spectral characteristics of DOM before and after Typhoon Ewiniar in Zhanjiang B ay,a eutrophic semi-enclosed bay in the northwestern South China Sea.The results revealed that intense microbial decomposition of DOM occurred during the pre-typhoon period because high nutrient inputs facilitated the mobilization of DOM in the bay.However,the intrusion of external seawater induced by the typhoon diluted the nutrient levels in Zhanjiang B ay,reducing the impact of microbial decomposition on DOM during the post-typhoon perio d.Nevertheless,the net addition of DOM occurred in Zhanjiang Bay during the post-typhoon period,possibly because of the decomposition of particulate organic matter(POM) and desorption of particulate matter.In addition,an increase in apparent oxygen utilization,a decrease in DO saturation and the reduced level of Chl a indicated that organic matter(OM) decomposition was enhanced and OM decomposition shifted to POM decomposition in Zhanjiang Bay after the typhoon.Overall,our study highlighted the shift in the intense OM decomposition from DOM to POM decomposition before and after typhoons in eutrophic bays,providing new insights into the response of typhoons to biogeo chemistry.展开更多
This study investigates the impact of the salinity barrier layer(BL)on the upper ocean response to Super Typhoon Mangkhut(2018)in the western North Pacific.After the passage of Mangkhut,a noticeable increase(~0.6 psu)...This study investigates the impact of the salinity barrier layer(BL)on the upper ocean response to Super Typhoon Mangkhut(2018)in the western North Pacific.After the passage of Mangkhut,a noticeable increase(~0.6 psu)in sea surface salinity and a weak decrease(<1℃)in sea surface temperature(SST)were observed on the right side of the typhoon track.Mangkhut-induced SST change can be divided into the three stages,corresponding to the variations in BL thickness and SST before,during,and after the passage of Mangkhut.During the pre-typhoon stage,SST slightly warmed due to the entrainment of BL warm water,which suppressed the cooling induced by surface heat fluxes and horizontal advection.During the forced stage,SST cooling was controlled by entrainment,and the preexisting BL reduced the total cooling by 0.89℃ d-1,thus significantly weakening the overall SST cooling induced by Mangkhut.During the relaxation stage,the SST cooling was primarily caused by the entrainment.Our results indicate that a preexisting BL can limit typhoon-induced SST cooling by suppressing the entrainment of cold thermocline water,which contributed to Mangkhut becoming the strongest typhoon in 2018.展开更多
The generation and propagation mechanism of strong nonlinear waves in the South China Sea is an essential research area. In this study, the third-generation wave model WAVEWATCH Ⅲ is employed to simulate wave fields ...The generation and propagation mechanism of strong nonlinear waves in the South China Sea is an essential research area. In this study, the third-generation wave model WAVEWATCH Ⅲ is employed to simulate wave fields under extreme sea states. The model, integrating the ST6 source term, is validated against observed data, demonstrating its credibility. The spatial distribution of the occurrence probability of strong nonlinear waves during typhoons is shown, and the waves in the straits and the northeastern part of the South China Sea show strong nonlinear characteristics. The high-order spectral model HOS-ocean is employed to simulate the random wave surface series beneath five different platform areas. The waves during the typhoon exhibit strong nonlinear characteristics, and freak waves exist. The space-varying probability model is established to describe the short-term probability distribution of nonlinear wave series. The exceedance probability distributions of the wave surface beneath different platform areas are compared and analyzed. The results show that with an increase in the platform area, the probability of a strong nonlinear wave beneath the platform increases.展开更多
The effect of Stokes drift production(SDP),which includes Coriolis-Stokes forcing,Langmuir circulation,and Craik-Lei-bovich vortexes,on the upper ocean during typhoon passage in the Bohai Sea(BS),China,is investigated...The effect of Stokes drift production(SDP),which includes Coriolis-Stokes forcing,Langmuir circulation,and Craik-Lei-bovich vortexes,on the upper ocean during typhoon passage in the Bohai Sea(BS),China,is investigated by using a coupled wave-current model.The role of SDP in turbulent mixing and the further dynamics during the entire typhoon period are comprehensively stud-ied.Experimental results show that SDP greatly increases turbulent mixing at all depths under typhoon conditions by up to seven times that under normal weather conditions.SDP generally strengthens sea surface cooling by more than 0.4℃,with the maximum reduction in sea surface temperature(SST)at the during-typhoon stage exceeding 2℃,which is approximately seven times larger than that under normal weather conditions.The SDP-induced decrease in current speed can exceed 0.2ms^(-1),and the change in current direction is generally opposite the wind direction.These results suggest that Stokes drift depresses the effect of strong winds on currents by intensifying turbulent mixing.Mixed layer depth(MLD)is distinctly increased by O(1)during typhoons due to SDP and can deepen by more than 5m.In addition,the continuous effects of SDP on SST,current,and MLD at the after-typhoon stage indi-cate a hysteretic response between SDP and typhoon actions.展开更多
Typhoons in the western Pacific have a significant impact on the transport of heat,salt and particles through the Luzon Strait.However,there are very limited field observations of this impact because of extreme diffic...Typhoons in the western Pacific have a significant impact on the transport of heat,salt and particles through the Luzon Strait.However,there are very limited field observations of this impact because of extreme difficulties and even dangers for ship-based measurements during the rough weather.Here,we present the preliminary results from analyzing a dataset collected by a glider deployed west of the Luzon Strait a few days prior to the arrival of typhoon MITAG.The gilder data revealed an abnormally salinity(>34.8)subsurface water apparently sourced from Kuroshio intrusion during the typhoon.When typhoon MITAG traveled on the east of the Luzon Strait,the positive wind stress curl strengthened the cyclonic eddy and weakened the anti-cyclonic eddy.This led to a slowdown of Kuroshio and made its intrusion easier.The main axis of the Kuroshio at the northern part of the strait shifted westward after the typhoon and did not return to its original position until a week later.The Ekman transport from persistent northerly wind of typhoon MITAG was significant,but its importance in enhancing the Kuroshio intrusion is only secondary relative to the eddies variations.展开更多
基金National Natural Science Foundation of China(42375012)China Meteorological Administration Foundation(CXFZ2025J023)。
文摘Understanding the factors that control typhoon rainfall distribution is critical for improving rainfall forecasting,especially for landfall typhoons. This study investigated the impact of typhoon size on rainfall characteristics at landfall in eastern coast of China. Typhoons Ampil(2018) and Rumbia(2018), which had similar intensities, were investigated to explore the connection between storm size and rainfall. The larger cyclonic wind field in Typhoon Rumbia led to greater vorticity and broader convergence compared to Typhoon Ampil, along with an ascending region outside the eyewall, which promoted more vigorous rainbands. Rumbia′s larger size exhibited greater outer-core radial vorticity advection relative to Ampil. This maintained its extensive outer-core wind field and intensified outer rainband development. Consequently,Rumbia generated more extensive and prolonged rainfall post-landfall compared to Ampil. A composite analysis of typhoons making landfall in eastern China(2001-2021) further examines the statistical correlation between typhoon size and rainfall distribution. Results indicate that larger typhoons are more likely to generate heavier and more spatially extensive rainfall in regions beyond their eyewalls. These findings highlight that typhoon size significantly regulates rainfall evolution during landfall, underscoring the necessity of incorporating this parameter into operational rainfall forecasting models for landfalling typhoons.
基金supported in part by the National Natural Science Foundation of China under Grant 42374037 and 41404031in part by the State Key Laboratory of Geodesy and Earth's Dynamics, Innovation Academy for Precision Measurement Science and Technology under Grant SKLGED2022-3-5
文摘Previous studies have revealed that typhoons can affect the ionosphere.This paper uses GNSS observations provided by GNSS tracking stations of Taiwan region,ERA5 gravity wave dissipation products,and Himawari-8 band 07 brightness temperature observation data to analyze the impact of Typhoon Meranti on Taiwan region's ionosphere from September 13 to 15,2016.In addition to the daily effects of traveling ionospheric disturbances(TIDs),TIDs of various intensities caused by Meranti-induced gravity waves were observed during this period,which is inseparable from the state of the typhoon and the topographic features during its progress.The ionospheric disturbance caused by the edge of a typhoon is usually larger than that at the typhoon eye.When the typhoon approached Taiwan region with high intensity on September 14,it was observed that the gravity waves caused by the typhoon had a wavelength of about 174-293 km,a period of 13.5-23.5 min,and a propagation speed of 142-302 m/s.When the vortex structure of a typhoon interacts with complex surfaces such as mountains,it is easier to excite more medium-scale gravity waves.The origin that excites gravity waves and causes ionospheric anomalies is different from the location of the typhoon eye and changes over time.The gravity waves caused by the typhoon lasted for three days in the central mountains of Taiwan region.Still,background wind conditions restricted the propagation of gravity waves from the mesosphere to the thermosphere and led to TID predominantly concentrated between 06:00 and 13:00 UT each day.
基金supported by the National Natural Science Foundation of China(Grant No.U2142201)the Fengyun Application Pion eering Project(Grant No.FY-APP-ZX-2022.01)。
文摘Measurements from a hyperspectral infrared(HIR) sounder onboard a satellite in geostationary orbit not only provide atmospheric thermodynamic information,but also can be used to infer dynamic information with high temporal resolution.Radiance measurements from the Geostationary Interferometric Infrared Sounder(GIIRS),obtained with 15-min temporal resolution during Typhoon Maria(2018) and 30-min temporal resolution during Typhoon Lekima(2019),were used to derive three-dimensional(3D) horizontal winds by tracking the motion of atmospheric moisture.This work focused on the impact of assimilation of 3D winds on typhoon analyses and forecasts using the operational NWP model of the China Meteorological Administration(CMA-MESO),and improved understanding of the potential benefits of assimilating dynamic information from geostationary sounder data with higher temporal resolution.The standard deviation of the observations minus simulations revealed that the accuracy of the derived 3D winds with 15-min resolution was higher than that of derived winds with 30-min resolution.Experiments showed that the assimilation system can effectively absorb the information of the derived 3D winds,and that dynamic information from clear-sky areas can be transferred to typhoon areas.In typhoon prediction,assimilation of the derived 3D winds had greatest influence on the typhoon track,and less influence on the maximum wind speed.Assimilation of the derived 3D winds reduced the average track error by 17.4% for Typhoon Maria(2018) and by 3.5% for Typhoon Lekima(2019) during their entire 36-h forecasts initiated at different times.Assimilation of GIIRS dynamic information can substantially improve forecasts of heavy precipitation by CMAMESO.Results indicate that the assimilation of dynamic information from high-temporal-resolution geostationary HIR sounder data adds value for improved numerical weather prediction.
基金Supported by the Foundation Enhancement Program Project"Key Technologies for Analytical Traceability and Numerical Modeling of Fluctuations in the Middle and Upper Atmosphere"(2022-JCJQ-JJ-0882).
文摘Typhoons,as strong convective systems,can excite multi-scale atmospheric gravity waves that travel long distances,and play an important role in momentum and energy transmission between the middle and upper atmosphere.In this paper,the research progress in the observation techniques,generation mechanism and propagation characteristics of typhoon-induced gravity waves were systematically reviewed.These studies show that based on the combined application of ground-based and space-based observation(sounding balloons,airglow imaging,and satellite remote sensing)and reanalysis data(such as ERA5),with the aid of ray tracing theory and numerical simulation technology,the mechanism of typhoon induced gravity waves and its dynamic characteristics in the middle and upper atmosphere have been better revealed.At present,there are still some insufficiencies in the fields of propagation path tracking of gravity waves,terrain multi-scale effect modeling and parameterization of inertial gravity waves,which need to be further studied in the future.
基金supported by the National Science and Technology Council(NSTC),Taiwan(NSTC 114-2119-M-019-003).
文摘Amid growing typhoon risks driven by climate change with projected shifts in precipitation intensity and temperature patterns,Taiwan faces increasing challenges in flood risk.In response,this study proposes a geographic information system(GIS)-based artificial intelligence(AI)model to assess flood susceptibility in Keelung City,integrating geospatial and hydrometeorological data collected during Typhoon Krathon(2024).The model employs the random forest(RF)algorithm,using seven environmental variables excluding average elevation,slope,topographic wetness index(TWI),frequency of cumulative rainfall threshold exceedance,normalized difference vegetation index(NDVI),flow accumulation,and drainage density,with the number of flood events per unit area as the output.The RF model demonstrates high accuracy,achieving the accuracy of 97.45%.Feature importance indicates that NDVI is the most critical predictor,followed by flow accumulation,TWI,and rainfall frequency.Furthermore,under the IPCC AR5 RCP8.5 scenarios,projected 50-year return period rainfall in Keelung City increases by 42.40%-64.95%under+2℃to+4℃warming.These projections were integrated into the RF model to simulate future flood susceptibility.Results indicate two districts in the study area face the greatest increase in flood risk,emphasizing the need for targeted climate adaptation in vulnerable urban areas.
基金supported by the National Natural Science Foundation of China(Nos.42122049 and 42377104)the Basic Strengthening Research Program(No.2021-JCJQ-JJ-1058)+1 种基金the Strategy Priority Research Programof Chinese Academy of Sciences(No.XDB0760403)the National Key Scientific and Technological Infrastructure project"Earth System Science Numerical Simulator Facility"(EarthLab)the Innovation Foundation of CPML/CMA(No.2024CPML-C027).
文摘The extraordinary Super Typhoon(STY)Muifa(2022)made landfall four times and had a significant impact on the coastal regions from south to north of China.Although previous studies have demonstrated the‘pumping effect'of typhoons on the enhancement of reactive nitrogen(Nr)wet deposition over the ocean,it is uncertain how Nr deposition is influenced by typhoons thatmake prolonged mechanism due tomultiple landfalls.In this study,theNr wet deposition induced by STYMuifawas investigated fromthe perspective of in-and below-cloud processes based on the Nested Air Quality Prediction Modeling System with an online tracer-tagging module.High volume of Nr wet deposition caused by Muifa migrated from south to north,passing over half of China's coastal cities.Compared to the typhoon generated vicinity,both mean values of the oxidized and reduced nitrogen wet deposition over the Typhoon affected regions were increased about 20.4 and 66.1 times after landfall even with the similar rainfall.Emissions from the four landfall areas of China contributed to the majority of Nr wet deposition with significantly enhanced proportion of in-cloud deposition.The strong pumping effect of typhoon to the Nr deposition along the coastal areas and the risk of ecosystem effects requires further researches and higher demands on the control of nitrogen emissions of National Industrial Park,which usually located in China's coastal cities.
基金supported by the National Natural Science Foundation of China[grant numbers 42192553 and 41922036]the Fundamental Research Funds for the Central Universities–Cemac“GeoX”Interdisciplinary Program[grant number 020714380207]。
文摘While steady improvements have been achieved for the track forecasts of typhoons,there has been a lack of improvement for intensity forecasts.One challenge for intensity forecasts is to capture the rapid intensification(RI),whose nonlinear characteristics impose great difficulties for numerical models.The ensemble sensitivity analysis(ESA)method is used here to analyze the initial conditions that contribute to typhoon intensity forecasts,especially with RI.Six RI processes from five typhoons(Chaba,Haima,Meranti,Sarika,and Songda)in 2016,are applied with ESA,which also gives a composite initial condition that favors subsequent RI.Results from individual cases have generally similar patterns of ESA,but with different magnitudes,when various cumulus parameterization schemes are applied.To draw the initial conditions with statistical significance,sample-mean azimuthal components of ESA are obtained.Results of the composite sensitivity show that typhoons that experience RI in 24 h favor enhanced primary circulation from low to high levels,intensified secondary circulation with increased radial inflow at lower levels and increased radial outflow at upper levels,a prominent warm core at around 300 hPa,and increased humidity at low levels.As the forecast lead time increases,the patterns of ESA are retained,while the sensitivity magnitudes decay.Given the general and quantitative composite sensitivity along with associated uncertainties for different cumulus parameterization schemes,appropriate sampling of the composite sensitivity in numerical models could be beneficial to capturing the RI and improving the forecasting of typhoon intensity.
基金supported by the project of National Natural Science Foundation of China(Grant No.42371203 and U21A2032)the project Financial Fund of Sichuan Institute of Geological Survey(SCIGSCZDXM-2024008)+1 种基金Sichuan Provincial Science and Technology Department Program Funding(No.2025YFHZ0010)Science and Technology Program of Aba City(NO.R24YYJSYJ0001)。
文摘The 2019 Typhoon Lekima triggered extensive landslides in Zhejiang Province.To explore the impact of typhoon paths on the distribution of landslide susceptibility,this study proposes a spatiotemporal zoning assessment framework based on typhoon paths and inner rainbands.According to the typhoon landing path and its rainfall impact range,the study area is divided into the typhoon event period(TEP)and the annual non-typhoon period(ANP).The model uses 14 environmental factors,with the only difference between TEP and ANP being the rainfall index:TEP uses 48-hour rainfall during the typhoon,while ANP uses multi-year average annual rainfall.Modeling and comparative analysis were conducted using six machine learning models including random forest(RF)and support vector machine(SVM).The results show that the distribution pattern of high-risk landslide areas during TEP is significantly correlated with typhoon intensity:when the intensity is level 12,high-risk areas are radially distributed;at levels 10-11,they tend to concentrate asymmetrically along the coast;and when the intensity drops to below level 9,the overall susceptibility decreases significantly.During ANP,the distribution of landslides is relatively uniform with no obvious spatial concentration.Analysis on the factor contribution rate indicates that the rainfall weight in TEP is as high as 32.1%,making it the dominant factor;in ANP,the rainfall weight drops to 13.6%while the influence of factors such as slope and topographic wetness index increases,revealing differences in landslide formation mechanisms between the two periods.This study demonstrates that the spatiotemporal zoning method based on typhoon paths can effectively characterize the spatial susceptibility patterns of landslides and improve disaster identification capabilities under extreme weather conditions.The finally generated annual susceptibility zoning map divides the study area into four types of risk regions,providing a reference for dynamic monitoring and differentiated risk management of landslides in typhoon-prone areas.
基金supported by the Yantai Science,Technology and Innovation Development Programme(Nos.2023 JCYJ094,2023JCYJ097)the Major Research Grant from the Natural Science Foundation of China(NSFC)(No.42330406)。
文摘To investigate the effect of typhoon path translation on storm surge augmentation,the storm surge during Typhoon 1909 Lekima in the East China Sea is simulated using Delft 3D.The model sets up three scenarios to analyze the path’s effect on storm surge in the Shandong Peninsula Sea by shifting the typhoon path to the east and west.Results show that the areas of maximum storm surge in each scenario are located on both sides of the typhoon path and shift along with its movement.When the typhoon path shifts eastward,the maximum storm surge intensifies at Zhifu Island station 8 hours earlier.Conversely,a westward shift in the typhoon track leads to a maximum storm surge increase at Shidao Island station 12 hours earlier.Other scenarios exhibit minimal deviation from the original route.Typhoons penetrating deep inland can induce substantial storm surges,with the most extensive surge area situated in the western part of the Shandong Peninsula.
基金supported in part by the National Natural Science Foundation of China(No.51761165022)the Natural Science Foundation of Jiangsu Province(No.BK20210309)the Jiangsu Graduate Research and Practice Innovation Program(No.KYCX21_0234)。
文摘An analysis is conducted on the hydrodynamic response law of a single module maritime airport,considering the atmospheric variables of the wind and wave field.The analysis is based on hydroelastic theory and focuses on the typhoon-driven very large floating structures(VLFS)configuration of the maritime airport.The findings indicate that the proposed method enables efficient information exchange between the fluid and structure domains through the coupling interface.The displacement of the maritime airport affected by the typhoon’s wave field is mostly determined by the direction of the flow.The wave loads acting on the floating body also influence the wave profile of the irregular wave and the deformation of the floating body.The von Mises stress distribution is not significant in all parts of the floating body.
基金jointly supported by the National Natural Science Foundation of China[grant numbers U2342202 and 42175005]the Qing Lan Project[grant number R2023Q06]。
文摘In 2021,Cempaka,a tiny tropical cyclone,made landfall in China.As the TC intensified prior to landfall,the tropical cyclone size measured with precipitation decreased significantly.A numerical simulation was conducted to examine the possible processes modulating the storm size.Azimuthally mean potential vorticity(PV)was found to decrease mainly in the middle to upper troposphere between 50-and 80-km radii.The PV budget results indicate that the advection and generation of mean PV associated with asymmetric processes,rather than the symmetric processes,primarily contributed to the decrease in mean PV.These asymmetric processes leading to a negative PV tendency were likely associated with inactive outer rainbands.In contrast,the tangential winds simultaneously expanded radially outward,possibly related to inner-core diabatic heating.The findings here emphasize the importance of outer rainband activity in tropical cyclone size change.
基金Supported by the National Natural Science Foundation of China(Nos.42006018,42276009,42376199)the Open Fund Project of the Key Laboratory of Ocean Observation and Information of Hainan Province(No.HKLOOI-OF-2023-03)the Tianjin Natural Science Foundation(Nos.21JCYBJC00500,21JCQNJC00590)。
文摘Frequent typhoons can significantly change the temperature,nutrient availability,and phytoplankton biomass in marginal seas.The oceanic response to typhoons is usually influenced by the features of the typhoon,among which the translational speed is critically important.By using a high resolution coupled physical-biological model,we investigated the response of the Yellow and East China seas(YECS)to two typhoons at different translational speeds,Muifa in August 2011 and Bolaven in August 2012.The model well reproduced the spatial and temporal variations of temperature,chlorophyll-a concentration over the YECS.Results show that typhoons with slower translational speeds uplift more deep water,leading to a more significant oceanic response.Divergence and convergence caused nutrient fluxes in opposite directions in the surface and bottom layers.Moreover,the nutrient flux in the bottom layer was greater than that in the surface layer.These phenomena are closely related to the spatial distribution of nutrients.Further studies show that the degree of ocean response to typhoons is highly correlated with the initial conditions of physical and biological elements of the upper ocean before the typhoon,as well as with ocean structure.Pretyphoon initial conditions of oceanic physical and ecological elements,mixed layer depth,and potential energy anomalies can all alter the degree of typhoon-induced oceanic response.This study emphasizes the important roles of the translational speed of typhoons and the initial oceanic conditions in the oceanic response to typhoons.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFB2601100)the National Natural Science Foundation of China(Grant No.52171246)+4 种基金The Belt and Road Special Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2019491911)the Open Research Foundation of the State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology(Grant No.LP2005)the Science and Technology Innovation Program of Hunan Province(Grant No.2023RC3136)the Natural Science Foundation of Hunan Province(Grant No.2022JJ20041)Educational Science Foundation of Hunan Province(Grant No.23A0265)。
文摘Ocean waves and Stokes drift are generated by typhoons.This study investigated the characteristics of ocean waves and wave-induced Stokes drift and their effects during Typhoon Mangkhut using European Centre for MediumRange Weather Forecasts(ECMWF)ERA5 datasets and observational data.The results revealed that the typhoon generated intense cyclones and huge typhoon waves with a maximum wind speed of 45 m/s,a minimum pressure of955 h Pa,and a maximum significant wave height of 12 m.The Stokes drift caused by typhoon waves exceeded 0.6m/s,the Stokes depth scale exceeded 18 m,and the maximum Stokes transport reached 6 m^(2)/s.The spatial distribution of 10-m wind speed,typhoon wave height,Stokes drift,Stokes depth,and Stokes transport during the typhoon was highly correlated with the typhoon track.The distribution along the typhoon track showed significant zonal asymmetry,with greater intensity on the right side of the typhoon track than on the left side.These findings provide important insights into the impact of typhoons on ocean waves and Stokes drift,thus improving our understanding of the interactions between typhoons and the ocean environment.This study also investigated the contribution of Stokes transport to the total net transport during typhoons using Ekman-Stokes Numbers as a comparative measure.The results indicated that the ratio of Stokes transport to the total net transport reached up to 50%within the typhoon radius,while it was approximately 30%outside the radius.Strong Stokes transport induced by typhoon waves led to divergence in the transport direction,which resulted in upwelling of the lower ocean as a compensation current.Thus,Stokes transport played a crucial role in the vertical mixing of the ocean during typhoons.The findings suggested that Stokes transport should be paid more attention to,particularly in high latitude ocean regions,where strong winds can amplify its effects.
基金supported by National Natural Science Foundation of China (42277136)Natural Science Research Project of Anhui Educational Committee (2023AH030041)National Key Research and Development Program of China (2021YFB3901205)。
文摘In recent years, the coastal region of Southeast China has witnessed a significant increase in the frequency and intensity of extreme rainfall events associated with landfalling typhoons. The hilly and mountainous terrain of this area, combined with rapid rainfall accumulation, has led to a surge in flash floods and severe geological hazards. On August 10, 2019, Typhoon Lekima made landfall in Zhejiang Province, China, and its torrential rainfall triggered extensive landslides, resulting in substantial damage and economic losses. Utilizing high-resolution satellite images, we compiled a landslide inventory of the affected area, which comprises a total of 2,774 rainfallinduced landslides over an area of 2965 km2. The majority of these landslides were small to mediumsized and exhibited elongated, clustered patterns. Some landslides displayed characteristics of high-level initiation, obstructing or partially blocking rivers, leading to the formation of debris dams. We used the inventory to analyze the distribution pattern of the landslides and their relationship with topographical, geological, and hydrological factors. The results showed that landslide abundance was closely related to elevation, slope angle, faults, and road density. The landslides were predominantly located in hilly and low mountainous areas, with elevations ranging from 150 to 300 m, slopes of 20 to 30 degrees, and a NE-SE aspect. Notably, we observed the highest Landslide Number Density(LND) and Landslide Area Percentage(LAP) in the rhyolite region. Landslides were concentrated within approximately 4 km on either side of fault zones, with their size and frequency negatively correlated with distances to faults, roads, and river systems. Furthermore, under the influence of typhoons, regions with denser vegetation cover exhibited higher landslide density, reaching maximum values in shrubland areas. In areas experiencing significantly increased concentrated rainfall, landslide density also showed a corresponding rise. In terms of spatial distribution, the rainfall-triggered landslides primarily occurred in the northeastern part of the study area, particularly in regions characterized by complex topography such as Shanzao Village in Yantan Town, Xixia Township, and Shangzhang Township. The research findings offer crucial data on the rainfallinduced landslides triggered by Typhoon Lekima, shedding light on their spatial distribution patterns. These findings provide valuable references for mitigating risks and planning reconstruction in typhoon-affected area.
基金Natural Science Foundation of Shandong Province(ZR2021MD012)CMA Special Fund for Innovation and Development(CXFZ2023J015)。
文摘The movement speed of Typhoon In-Fa(2021)was notably slow,at 10 km h-1or less,for over 20 hours following its landfall in Zhejiang,China,in contrast to other typhoons that have made landfall.This study examines the factors contributing to the slow movement of Typhoon In-Fa,including the steering flow,diabatic heating,vertical wind shear(VWS),and surface synoptic situation,by comparing it with Typhoons Yagi(2018)and Rumbia(2018)which followed similar tracks.The findings reveal that the movement speed of Typhoons Yagi and Rumbia is most closely associated with their respective 500 h Pa environmental winds,with a steering flow of 10^(-12)m s^(-1).In contrast,Typhoon InFa’s movement speed is most strongly correlated with the 850 h Pa environmental wind field,with a steering flow speed of only 2 m s^(-1).Furthermore,as Typhoon In-Fa moves northwest after landfall,its intensity is slightly greater than that of Typhoons Yagi and Rumbia,and the pressure gradient in front of Typhoon In-Fa is notably smaller,leading to its slow movement.Additionally,the precipitation distribution of Typhoon In-Fa differs from that of the other two typhoons,resulting in a weak asymmetry of wavenumber-1 diabatic heating,which indirectly affects its movement speed.Further analysis indicates that VWS can alter the typhoon’s structure,weaken its intensity,and ultimately impact its movement.
基金The National Natural Science Foundation of China under contract Nos 42276047, 92158201 and U1901213the Entrepreneurship Project of Shantou under contract No.2021112176541391the Scientific Research Start-Up Foundation of Shantou University under contract No.NTF20006。
文摘Highly productive estuaries facilitate intense decomposition of dissolved organic matter(DOM) as a carbon source.However,the specific impacts of typhoons on DOM decomposition in eutrophic bays remain unclear.To address this issue,we investigated the spectral characteristics of DOM before and after Typhoon Ewiniar in Zhanjiang B ay,a eutrophic semi-enclosed bay in the northwestern South China Sea.The results revealed that intense microbial decomposition of DOM occurred during the pre-typhoon period because high nutrient inputs facilitated the mobilization of DOM in the bay.However,the intrusion of external seawater induced by the typhoon diluted the nutrient levels in Zhanjiang B ay,reducing the impact of microbial decomposition on DOM during the post-typhoon perio d.Nevertheless,the net addition of DOM occurred in Zhanjiang Bay during the post-typhoon period,possibly because of the decomposition of particulate organic matter(POM) and desorption of particulate matter.In addition,an increase in apparent oxygen utilization,a decrease in DO saturation and the reduced level of Chl a indicated that organic matter(OM) decomposition was enhanced and OM decomposition shifted to POM decomposition in Zhanjiang Bay after the typhoon.Overall,our study highlighted the shift in the intense OM decomposition from DOM to POM decomposition before and after typhoons in eutrophic bays,providing new insights into the response of typhoons to biogeo chemistry.
基金supported by the National Natural Science Foundation of China(Grant No.42176015)the National Natural Science Foundation of China(Grant No.41605070)+3 种基金the National Key Research and Development Program(Grant No.2021YFC3101500)the Hunan Provincial Natural Science Outstanding Youth Fund(Grant No.2023JJ10053)the Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.311022001)a project of the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.SML2021SP207)。
文摘This study investigates the impact of the salinity barrier layer(BL)on the upper ocean response to Super Typhoon Mangkhut(2018)in the western North Pacific.After the passage of Mangkhut,a noticeable increase(~0.6 psu)in sea surface salinity and a weak decrease(<1℃)in sea surface temperature(SST)were observed on the right side of the typhoon track.Mangkhut-induced SST change can be divided into the three stages,corresponding to the variations in BL thickness and SST before,during,and after the passage of Mangkhut.During the pre-typhoon stage,SST slightly warmed due to the entrainment of BL warm water,which suppressed the cooling induced by surface heat fluxes and horizontal advection.During the forced stage,SST cooling was controlled by entrainment,and the preexisting BL reduced the total cooling by 0.89℃ d-1,thus significantly weakening the overall SST cooling induced by Mangkhut.During the relaxation stage,the SST cooling was primarily caused by the entrainment.Our results indicate that a preexisting BL can limit typhoon-induced SST cooling by suppressing the entrainment of cold thermocline water,which contributed to Mangkhut becoming the strongest typhoon in 2018.
基金financially supported by the National Key R&D Program of China(No.2022YFC3104205)the National Natural Science Foundation of China(No.42377457).
文摘The generation and propagation mechanism of strong nonlinear waves in the South China Sea is an essential research area. In this study, the third-generation wave model WAVEWATCH Ⅲ is employed to simulate wave fields under extreme sea states. The model, integrating the ST6 source term, is validated against observed data, demonstrating its credibility. The spatial distribution of the occurrence probability of strong nonlinear waves during typhoons is shown, and the waves in the straits and the northeastern part of the South China Sea show strong nonlinear characteristics. The high-order spectral model HOS-ocean is employed to simulate the random wave surface series beneath five different platform areas. The waves during the typhoon exhibit strong nonlinear characteristics, and freak waves exist. The space-varying probability model is established to describe the short-term probability distribution of nonlinear wave series. The exceedance probability distributions of the wave surface beneath different platform areas are compared and analyzed. The results show that with an increase in the platform area, the probability of a strong nonlinear wave beneath the platform increases.
基金supported by the National Natural Science Foundation of China(No.42176020)the National Key Research and Development Program(No.2022 YFC3105002).
文摘The effect of Stokes drift production(SDP),which includes Coriolis-Stokes forcing,Langmuir circulation,and Craik-Lei-bovich vortexes,on the upper ocean during typhoon passage in the Bohai Sea(BS),China,is investigated by using a coupled wave-current model.The role of SDP in turbulent mixing and the further dynamics during the entire typhoon period are comprehensively stud-ied.Experimental results show that SDP greatly increases turbulent mixing at all depths under typhoon conditions by up to seven times that under normal weather conditions.SDP generally strengthens sea surface cooling by more than 0.4℃,with the maximum reduction in sea surface temperature(SST)at the during-typhoon stage exceeding 2℃,which is approximately seven times larger than that under normal weather conditions.The SDP-induced decrease in current speed can exceed 0.2ms^(-1),and the change in current direction is generally opposite the wind direction.These results suggest that Stokes drift depresses the effect of strong winds on currents by intensifying turbulent mixing.Mixed layer depth(MLD)is distinctly increased by O(1)during typhoons due to SDP and can deepen by more than 5m.In addition,the continuous effects of SDP on SST,current,and MLD at the after-typhoon stage indi-cate a hysteretic response between SDP and typhoon actions.
基金The fund from Science,Technology and Innovation Commission of Shenzhen Municipality under contract No.JCYJ20210324105211031the National Natural Science Foundation of China under contract No.41720104001.
文摘Typhoons in the western Pacific have a significant impact on the transport of heat,salt and particles through the Luzon Strait.However,there are very limited field observations of this impact because of extreme difficulties and even dangers for ship-based measurements during the rough weather.Here,we present the preliminary results from analyzing a dataset collected by a glider deployed west of the Luzon Strait a few days prior to the arrival of typhoon MITAG.The gilder data revealed an abnormally salinity(>34.8)subsurface water apparently sourced from Kuroshio intrusion during the typhoon.When typhoon MITAG traveled on the east of the Luzon Strait,the positive wind stress curl strengthened the cyclonic eddy and weakened the anti-cyclonic eddy.This led to a slowdown of Kuroshio and made its intrusion easier.The main axis of the Kuroshio at the northern part of the strait shifted westward after the typhoon and did not return to its original position until a week later.The Ekman transport from persistent northerly wind of typhoon MITAG was significant,but its importance in enhancing the Kuroshio intrusion is only secondary relative to the eddies variations.
