The increase in frequency and intensity of Extreme High-temperature Events(EHEs)over Central-Eastern China(CEC)in recent decades has severely impacted social development and livelihoods.Using observation and reanalysi...The increase in frequency and intensity of Extreme High-temperature Events(EHEs)over Central-Eastern China(CEC)in recent decades has severely impacted social development and livelihoods.Using observation and reanalysis datasets,this study explores the effect of the East Asian subtropical westerly jet stream(EAJ)on the CEC EHEs for the summers spanning 1979–2020.Considering its general relative location to the right side of the upper-level jet stream exit region,CEC would theoretically suffer more EHEs with a stronger and northwardly-shifted EAJ in summer due to the likelihood of abnormal subsidence induced by the EAJ.However,such an EAJ–EHE connection has been unstable over the past four decades but has displayed an evident interdecadal change.Before the late 1990s,the interannual variation of the EAJ was manifested mainly by its meridional displacement in the northeastern part of East Asia;thus,the atmospheric responses were essentially located to the east of CEC,exerting less of an influence on the CEC EHEs.However,since the late 1990s,the EAJ variation has featured an intensity change in its center over the northwest portion of the CEC,which has resulted in a westward shift in atmospheric responses to cover the CEC region.Therefore,the EAJ could potentially affect the summer CEC EHEs during 2000–21.Our findings offer support for an in-depth understanding of the formation mechanisms of extreme weather/climate events of this nature and thus provide a scientific reference for seasonal climate predictions.展开更多
Estuaries are key areas for organic carbon cycling,where polymeric carbohydrates are abundant and chemically diverse.The recycling of these polymers by microbes depends on a variety of carbohydrate-active enzymes(CAZy...Estuaries are key areas for organic carbon cycling,where polymeric carbohydrates are abundant and chemically diverse.The recycling of these polymers by microbes depends on a variety of carbohydrate-active enzymes(CAZymes).However,it remains unclear whether other gene traits,particularly those related to cell motility toward polymeric carbohydrates,are intertwined with carbohydrate depolymerization and niche specialization in estuarine sediment soils.In this study,estuarine sediments were incubated with four prevalent polymeric carbohydrates(laminarin,fucan,cellulose,and chitin) under anaerobic conditions.Based on metagenomic analysis,we identified potential responses to the degradation and utilization of polymeric carbohydrate substrates from the perspectives of CAZymes and sugar transporters.The analysis of metagenomic gene data also revealed a positive correlation between chemotaxis and the abundance of CAZymes genes.Furthermore,metagenomes-assembled genomes(MAGs) that exhibited higher abundance in polysaccharide-treated samples compared to controls also featured elevated copies of genes involved in polysaccharide utilization loci(PULs),chemotaxis,as well as those associated with flagellar or gliding movement.SprB and CTDs associated with gliding proteins genes are essential for type Ⅸ secretion system-mediated secretion of CAZymes and gliding motility in Bacteroidota.The enhanced potential for mobility,coupled with the ability to degrade polymeric carbohydrates,may enable these bacteria to exploit nutrients beyond carbon sources,thereby potentially broadening their ecological niches.展开更多
Polygonal fault systems(PFS),characterized by multi-directional fault patterns within layered sequences,are well-documented features in global continental margin basins.While the geometry and formation mechanisms of P...Polygonal fault systems(PFS),characterized by multi-directional fault patterns within layered sequences,are well-documented features in global continental margin basins.While the geometry and formation mechanisms of PFS have been extensively studied in the northern South China Sea,the PFS in the Zhongjiannan Basin(western South China Sea)remain relatively unexplored,with a lack of quantitative analysis regarding their propagation.This study addresses this gap by using high-resolution three-dimensional(3D)seismic data and conducting a quantitative fault analysis to thoroughly examine the planform,cross-sectional geometry,and evolution of PFS in the northern Zhongjiannan Basin.The absence of a dominant strike direction among these polygonal faults suggests that their evolution is not controlled by anisotropic stress.Our interpretation of seismic data,constrained by the spatial relationship among PFS,gullies,and pockmarks,indicates that PFS mainly developed within the Miocene strata,with their initiation occurring during the late Miocene.Furthermore,the PFS act as key conduits connecting gullies to pockmarks in this area.The formation and development of PFS may be primarily driven by thermally triggered processes within siliceous sediments.The necessary heat source is probably associated with the abundant submarine magmatism observed in the Zhongjiannan Basin.To reconstruct the regional geological history,a four-stage evolutionary model,incorporating the formation of PFS,is presented.This research significantly improves our understanding of the regional geological evolution of the Zhongjiannan Basin,providing critical insights into the initiation and development of PFS in the western South China Sea.展开更多
The eddies in the southernmost southern Indian Ocean exert major dynamical and biogeochemical influences on the Earth system.Therefore,disentangling the relative contributions of vertical pumping and horizontal transp...The eddies in the southernmost southern Indian Ocean exert major dynamical and biogeochemical influences on the Earth system.Therefore,disentangling the relative contributions of vertical pumping and horizontal transport to water-property anomalies in the eddy cores is of fundamental importance.Here,the authors introduce a temperaturesalinity gradient-ratio approach(the"R-method")that compares vertical and meridional gradients to quantitatively separate the two processes.Application of the R-method to three-dimensional Argo observations reveals that horizontal transport,rather than vertical pumping,predominantly governs the observed temperature and salinity anomalies within eddy cores in the SIO.Independent theoretical estimations based on background meridional gradients,together with composites formed on isopycnal surfaces,further corroborate this conclusion.The results challenge the conventional assumption that vertical pumping invariably controls eddy-core property anomalies and demonstrate the utility of the R-method for diagnosing eddy impacts in climate and biogeochemical studies.展开更多
The frequency of marine heatwaves(MHWs)in the South China Sea(SCS)has increased recently.However,the relative roles of thermal and dynamic processes regulating the changes of sCs MHWs remain an open question.This stud...The frequency of marine heatwaves(MHWs)in the South China Sea(SCS)has increased recently.However,the relative roles of thermal and dynamic processes regulating the changes of sCs MHWs remain an open question.This study examines all long-lived MHWs(>10 days)in the SCS from 1982 to 2021,categorizing them into intensified and attenuated MHWs based on the overall trend of sea surface temperature during an MHW event.A mixed-layer heat budget analysis reveals that the thermal processes primarily driven by the latent heat flux are crucial in modulating the SCS MHWs,particularly for attenuated MHWs.However,under intensified conditions,the proportions of dynamically dominated MHWs(40%)is approximately comparable to that of thermally dominated ones(47%).This study highlights the significance of dynamic processes in shaping SCS MHWs and discusses the potential impacts induced by tropical cyclones on these MHWs.展开更多
This study investigates why an extreme hot midsummer occurred in Central and South China(CSC) during 2017. It is shown that the western North Pacific subtropical high(WNPSH) was abnormally intensified and westward-ext...This study investigates why an extreme hot midsummer occurred in Central and South China(CSC) during 2017. It is shown that the western North Pacific subtropical high(WNPSH) was abnormally intensified and westward-extending,resulting in anomalous high pressure and consequent extreme heat over CSC. The abnormal WNPSH was favored by the warming of the western tropical Pacific(WTP), which was unrelated to ENSO and manifested its own individual effect.The WTP warming enhanced the convection in-situ and led to anomalous high pressure over CSC via a local meridional circulation. The influence of the WTP was confirmed by CAM4 model experiments. A comparison between the 2017 midsummer and 2010 midsummer(with a stronger WNPSH but weaker extreme heat) indicated that the influence of the WNPSH on extreme heat can be modulated by the associated precipitation in the northwestern flank.The role of the WTP was verified by regression analyses on the interannual variation of the WTP sea surface temperature anomaly(SSTA). On the other hand, the WTP has undergone prominent warming during the past few decades, resulting from decadal to long-term changes and favoring extreme warm conditions. Through a mechanism similar to the interannual variation, the decadal to long-term changes have reinforced the influence of WTP warming on the temperature over CSC,contributing to the more frequent hot midsummers recently. It is estimated that more than 50% of the temperature anomaly over CSC in the 2017 midsummer was due to the WTP warming, and 40% was related to the decadal to long-term changes of the WTP SSTA.展开更多
Impacts of EI Nino Modoki （ENM）, La Nina Modoki （LNM）, canonical EI Nifio （CEN） and canonical La Nifia （CLN） on tropical cyclones （TCs） that made landfall over China's Mainland during 1951-2011 are analy...Impacts of EI Nino Modoki （ENM）, La Nina Modoki （LNM）, canonical EI Nifio （CEN） and canonical La Nifia （CLN） on tropical cyclones （TCs） that made landfall over China's Mainland during 1951-2011 are analysed using best-track data from China, the USA and Japan. Relative to cold phase years （LNM and CLN）, landfalling TCs in warm years （ENM and CEN） have a farther east genesis location, as well as longer track lengths and durations, both in total and before landfall. ENM demonstrates the highest landfall frequency, most northerly mean landfall position, and shortest after-landfall sustainability （track length and duration）, which indicate a more frequent and extensive coverage of China's Mainland by TCs, but with shorter after-landfall influence. CEN has low landfall frequency and the most southerly mean landfall location. LNM has the most westerly genesis location, being significantly farther west than the 1951-2011 average and leading to short mean track lengths and durations both in total or before landfall, all of which are significantly shorter than the 1951-2011 average. Variations in the low-level wind anomaly, vertical wind shear, mid-level relative humidity, steering flow, the monsoon trough and the western Pacific subtropical high （WPSH） can to some extent account for the features of frequency, location, track length and duration of landfalling TCs. Since ENSO Modoki is expected to become more frequent in the near future, the results for ENSO Modoki presented in this paper are of particular significance.展开更多
Tropical cyclone （TC） genesis over the South China Sea （SCS） during 1965–2004 was analyzed. The locations of TC genesis display evident seasonal changes, with the mean position of formation situated north of 15 &...Tropical cyclone （TC） genesis over the South China Sea （SCS） during 1965–2004 was analyzed. The locations of TC genesis display evident seasonal changes, with the mean position of formation situated north of 15 °N in summer （June–July–August） and south of 15 °N in autumn （September–October–November）. The TC genesis in summer underwent dramatic interdecadal variations, with more and less TC frequency during 1965–1974/1995–2004 and 1979–1993, respectively. In contrast, a significant interannual variation of TC genesis with a period of ～4 years was observed in autumn. This study investigated the relationship of SCS TC genesis to the East Asian jet stream （EAJS） and the western North Pacific subtropical high （WNPSH） on an interdecadal time scale. Analysis and comparison of the impacts of the EAJS and the WNPSH on vertical wind shear changes indicate that changes in the WNPSH and EAJS intensity rather than EAJS meridional location are responsible for changes in TC genesis on an interdecadal time scale. Corresponding to a weaker EAJS, anomalous Rossby wave energy at upper levels displays equatorward propagation at midlatitudes and poleward propagation in the subtropics. This induces anomalous convergence and divergence of wave activity fluxes in East Asia around 30 °N and the SCS, respectively. The anomalous divergence of wave activity fluxes reduces easterlies at upper levels over the SCS, which is favorable to TC genesis.展开更多
Global climate models predict that the increasing Amazoniandeforestation rates cause rising tempera tures （increases of 1.8℃ to 8℃ under different conditions） and Amazonian drying over the 21st century. Observatio...Global climate models predict that the increasing Amazoniandeforestation rates cause rising tempera tures （increases of 1.8℃ to 8℃ under different conditions） and Amazonian drying over the 21st century. Observations in the 20th century also show that over the warmer continent and the nearby western South At lantic Ocean, the lowerlayer equatorial westerly wind （LLEWW） strengthens with the initiation of tropical cyclones （TCs）. The warmercontinentrelated LLEWW can result from the Coriolisforceinduced deflection of the crossequatorial flow （similar to the wellknown heatisland effect on sea breeze） driven by the enhanced landsea contrast between the warmer urbanized continents and relatively cold oceans. This study focuses on the processes relating the warmercontinentrelated LLEWW to the TC initiation and demonstrates that the LLEWW embedded in trade easterlies can directly initiate TCs by creating cyclonic wind shears and forming the intertropical convergence zone. In addition to this direct effect, the LLEWW combined with the rotating Earth can boost additional updraft vapor over the high seasurface temperature region （factor 1）, facilitating a surfacetomidtroposphere moist layer （factor 2） and convective instability （factor 3） followed by diabatic processes. According to previous studies, the diabatic heating in a finite equatorial region also activates TCs （factor 4） on each side of the Equator with weak vertical shear （factor 5）. Factors 1–5 are favorable conditions for the initiation of severe TCs. Statistical analyses show that the earliest signal of sustained LLEWW not only leads the earliest signal of sustained tropical depression by 3 days but also explains a higher percentage of total variance.展开更多
The second-generation Global Ocean Data Assimilation System of the Beijing Climate Center （BCC_GODAS2.0） has been run daily in a pre-operational mode. It spans the period 1990 to the present day. The goal of this pa...The second-generation Global Ocean Data Assimilation System of the Beijing Climate Center （BCC_GODAS2.0） has been run daily in a pre-operational mode. It spans the period 1990 to the present day. The goal of this paper is to introduce the main components and to evaluate BCC_GODAS2.0 for the user community. BCC_GODAS2.0 consists of an observational data preprocess, ocean data quality control system, a three-dimensional variational （3DVAR） data assimilation, and global ocean circulation model [Modular Ocean Model 4 （MOM4）]. MOM4 is driven by six-hourly fluxes from the National Centers for Environmental Prediction. Satellite altimetry data, SST, and in-situ temperature and salinity data are assimilated in real time. The monthly results from the BCC_GODAS2.0 reanalysis are compared and assessed with observations for 1990-201 I. The climatology of the mixed layer depth of BCC_GODAS2.0 is generally in agreement with that of World Ocean Atlas 2001. The modeled sea level variations in the tropical Pacific are consistent with observations from satellite altimetry on interannual to decadal time scales. Performances in predicting variations in the SST using BCC_GODAS2.0 are evaluated. The standard deviation of the SST in BCC_GODAS2.0 agrees well with observations in the tropical Pacific. BCC_GODAS2.0 is able to capture the main features of E1 Nifio Modoki I and Modoki II, which have different impacts on rainfall in southern China. In addition, the relationships between the Indian Ocean and the two types of E1 Nino Modoki are also reproduced.展开更多
Tropical cyclone （TC） Nargis （2008） made landfall in Myanmar on 02 May 2008, bringing a storm surge, major flooding, and resulting in a significant death toll. TC Nargis （2008） displayed abnormal features, inclu...Tropical cyclone （TC） Nargis （2008） made landfall in Myanmar on 02 May 2008, bringing a storm surge, major flooding, and resulting in a significant death toll. TC Nargis （2008） displayed abnormal features, including rare eastward motion in its late stage, rapid intensification before landing. Using reanalysis data and a numerical model, we investigated how a low-latitude westerly wind modulated TC Nargis’ （2008） track and provided favorable atmospheric conditions for its rapid intensification. More importantly, we found a possible counterbalance effect of flows from the two hemispheres on the TC track in the Bay of Bengal. Our analysis indicates that a strong westerly wind burst across the Bay of Bengal, resulting in TC Nargis’ （2008） eastward movement after its recurvature. This sudden enhancement of westerly wind was mainly due to the rapidly intensified mid-level cross-equatorial flow. Our results show that a high-pressure system in the Southern Hemisphere induced this strong, mid-level, cross-equatorial flow. During the rapid intensification period of TC Nargis （2008）, this strong and broad westerly wind also transported a large amount of water vapor to TC Nargis （2008）. Sufficient water vapor gave rise to continuously high and increased mid-level relative humidity, which was favorable to TC Nargis’ （2008） intensification. Condensation of water vapor increased the energy supply, which eventuated the intensification of TC Nargis （2008） to a category 4 on the Saffir-Simpson scale.展开更多
Tropical cyclone （TC） genesis in the South China Sea （SCS） during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that ...Tropical cyclone （TC） genesis in the South China Sea （SCS） during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that during 1979-1993 （27）. During the TC peak season （July-September, JAS）, there were 43 TCs fi＇om 1994-2008, but only 17 during 1979-1993. For July in particular, 13 TCs formed from 1994-2008, but there were none during 1979-1993. The change in TC number is associated with changes of key environmental conditions in atmosphere and ocean. Compared to 1979-1993, the subtropical high was significantly weaker and was displaced more eastward during 1994-2008. In the former period, a stronger subtropical high induced downward flow, inhibiting TC formation. In the latter period, vertical wind shear and outgoing longwave radiation all weakened. Mid-level （850-500 hPa） humidity, and relative vorticity were higher. Sea surface temperature and upper layer heat content were also higher in the area. All these factors favor TC genesis during the latter period. The decadal change of TC genesis led to more landfalling TCs in Southern China during the period 1994-2008, which contributed to an abrupt increase in regional rainfall.展开更多
High-frequency oscillations, with periods of about 2 hours, are first identified by applying wavelet analysis to observed minutely wind speeds around the eye and eyewall of tropical cyclones（TCs）. Analysis of a mode...High-frequency oscillations, with periods of about 2 hours, are first identified by applying wavelet analysis to observed minutely wind speeds around the eye and eyewall of tropical cyclones（TCs）. Analysis of a model simulation of Typhoon Hagupit（2008） shows that the oscillations also occur in the TC intensity, vertical motion, convergence activity and air density around the eyewall. Sequences of oscillations in these variables follow a certain order.展开更多
The temporal variations in the frequency of tropical cyclones (TCs) traversing the Taiwan and Hainan Islands (TH islands), were analyzed using a best-track TC dataset from the Joint Typhoon Warning Center for the peri...The temporal variations in the frequency of tropical cyclones (TCs) traversing the Taiwan and Hainan Islands (TH islands), were analyzed using a best-track TC dataset from the Joint Typhoon Warning Center for the period 1945-2007. Results show that the oscillations were interannual and interdecadal on the timescales of 2-8 and 8-12 years, respectively. It is also shown that the number of TCs formed in the western North Pacific basin (WNP) and of those traversing the TH islands varied intraseasonally. These results also held for typhoons traversing the TH islands, although the oscillations were less apparent. This study identified interrelationships between the frequency of TCs making landfall on the TH islands and the East Asia summer monsoon (EASM), the South Asia summer monsoon (SASM), and the South China Sea summer monsoon (SCSSM). The SCSSM significantly influenced the number of TCs traversing Hainan Island, but had little influence on the number of TCs traversing Taiwan Island. By contrast, the SASM influenced the numbers of TCs traversing both of the TH islands, shown by correlation coefficients of 0.41 for Taiwan Island and -0.25 for Hainan Island. In addition, the frequency of TC landfall on Taiwan Island increased during years of enhanced EASM, as indicated by a correlation coefficient of 0.4.展开更多
The modulation of tropical cyclogenesis over the southern South China Sea （SSCS） by the El Nin o- Southern Oscillation （ENSO） is examined in October–December （OND）, when tropical cyclone （TC） activities are m...The modulation of tropical cyclogenesis over the southern South China Sea （SSCS） by the El Nin o- Southern Oscillation （ENSO） is examined in October–December （OND）, when tropical cyclone （TC） activities are most active in this region. The results reveal that there were more TCs formed over the SSCS during La Nin a years and less TCs during El Nin o years. How different environmental factors （including low-level vorticity, mid-level relative humidity, vertical wind shear, and potential intensity） contribute to this influence is investigated, using a genesis potential （GP） index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for El Nin o and La Nin a years separately, which could account for the changes of TC frequency over the SSCS in different ENSO phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results show that the mid-level relative humidity makes the largest contribution to the ENSO modulation of tropical cyclogenesis over the SSCS. Although warmer sea surface temperatures （SSTs） and larger amount of evaporation from the ocean surface were observed over the SSCS during El Nin o years, anomalous descending motions due to the anomalous Walker circulations inhibited the upward transports of water vapor and led to less moisture contents in the middle troposphere, which suppressed TC formations.展开更多
This study examines the modulation of tropical cyclogenesis over the South China Sea （SCS） by the E1 Nifio-Southem Oscillation （ENSO） Modoki during the boreal summer. Results reveal that there were more tropical c...This study examines the modulation of tropical cyclogenesis over the South China Sea （SCS） by the E1 Nifio-Southem Oscillation （ENSO） Modoki during the boreal summer. Results reveal that there were more tropical cyclones （TCs） formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors （including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity） contribute to this influence is investigated, using a genesis potential （GP） index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modold-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC fre-quency over the SCS by the ENSO Modold during the boreal summer.展开更多
This study examines the seasonal variations of tropical cyclogenesis over the South China Sea (SCS) using a genesis potential (GP) index developed by Emanuel and Nolan. How different environmental factors (including l...This study examines the seasonal variations of tropical cyclogenesis over the South China Sea (SCS) using a genesis potential (GP) index developed by Emanuel and Nolan. How different environmental factors (including low-level vorticity, mid-level relative humidity, vertical wind shear, and potential intensity) contribute to these variations is investigated. Composite anomalies of the GP index are produced for the summer and winter monsoons separately. These composites replicate the observed seasonal variations of the observed frequency and location of tropical cyclogenesis over the SCS. The degree of contribution by each factor in different regions is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. Over the northern SCS, potential intensity makes the largest contributions to the seasonal variations in tropical cyclogenesis. Over the southern SCS, the low-level relative vorticity plays the primary role in the seasonal modulation of tropical cyclone (TC) genesis frequency, and the vertical wind shear plays the secondary role. Thermodynamic factors play more important roles for the seasonal variations in tropical cyclogenesis over the northern SCS, while dynamic factors are more important in the seasonal modulation of TC genesis frequency over the southern SCS.展开更多
Variations in the high-frequency oscillations of tropical cyclones （TCs） over the western North Pacific （WNP） are studied in numerical model simulations. Power spectrum analysis of maximum wind speeds at 10 m （MW...Variations in the high-frequency oscillations of tropical cyclones （TCs） over the western North Pacific （WNP） are studied in numerical model simulations. Power spectrum analysis of maximum wind speeds at 10 m （MWS10） from an ensemble of 15 simulated TCs shows that oscillations are significant for all TCs. The magnitudes of oscillations in MWS10 are similar in the WNP and South China Sea （SCS）; however, the mean of the averaged significant periods in the SCS （1.93 h） is shorter than that in the open water of the WNP （2.83 h）. The shorter period in the SCS is examined through an ensemble of simulations, and a case simulation as well as a sensitivity experiment in which the continent is replaced by ocean for Typhoon Hagupit （2008）. The analysis of the convergence efficiency within the boundary layer suggests that the shorter periods in the SCS are possibly due to the stronger terrain effect, which intensifies convergence through greater friction. The enhanced convergence strengthens the disturbance of the gradient and thermal wind balances, and then contributes to the shorter oscillation periods in the SCS.展开更多
This study, using laboratory experiments and scaling analysis, evaluates the influence of geothermal heating on global oceanic circulation. Upon a well-developed large-scale convective flow, an additional heat flux pe...This study, using laboratory experiments and scaling analysis, evaluates the influence of geothermal heating on global oceanic circulation. Upon a well-developed large-scale convective flow, an additional heat flux perturbation 5F/F is employed. The increments of flow and thermal properties, including eddy diffusivity K7, flow velocity Vand bottom temperature Tb, are found to be independent of the applied heat flux F. Together with the scaling analysis of convective flow at different configurations, where the flow is thermally driven in the relatively low or extremely high turbulent thermal convections or the horizontal convection, the variances of flow properties, 6KT/KTand 6V/V, are found to be close to 0.5% and 0.75% at 5F/F=2%. This means that the small heat flux perturbation plays a negligible role in the global convective flow. However, 6Tb/ATis found to be 1.5% at 8F/F=2%, which would have a significant effect in the local region. The results might provide a clue to understanding the influence of geothermal heating on global oceanic circulation. It is expected that geothermal heating will contribute less than 1% in turbulent mixing and volume flux to global oceanic circulation, so its influence can be negligible in this situation. However, when it comes to the local environment, the influence of geothermal heating cannot be ignored. For example, temperature increases of about 0.5℃ with geothermal heating would have a significant effect on the physical environments within the benthic boundary layer.展开更多
Shipboard radiosonde soundings are important for detecting and quantifying the multiscale variability of atmosphere-ocean interactions associated with mass exchanges.This study evaluated the accuracies of shipboard Gl...Shipboard radiosonde soundings are important for detecting and quantifying the multiscale variability of atmosphere-ocean interactions associated with mass exchanges.This study evaluated the accuracies of shipboard Global Positioning System(GPS)soundings in the eastern tropical Indian Ocean and South China Sea through a simultaneous balloon-borne inter-comparison of different radiosonde types.Our results indicate that the temperature and relative humidity(RH)measurements of GPS-TanKong(GPS-TK)radiosonde(used at most stations before 2012)have larger biases than those of ChangFeng-06-A(CF-06-A)radiosonde(widely used in current observation)when compared to reference data from Vaisala RS92-SGP radiosonde,with a warm bias of 5℃and dry bias of 10%during daytimes,and a cooling bias of-0.8℃and a moist bias of 6%during nighttime.These systematic biases are primarily attributed to the radiation effects and altitude deviation.An empirical correction algorithm was developed to retrieve the atmospheric temperature and RH profiles.The corrected profiles agree well with that of RS92-SGP,except for uncertainties of CF-06-A in the stratosphere.These correction algorithms were applied to the GPS-TK historical sounding records,reducing biases in the corrected temperature and RH profiles when compared to radio occultation data.The correction of GPS-TK historical records illustrated an improvement in capturing the marine atmospheric structure,with more accurate atmospheric boundary layer height,convective available potential energy,and convective inhibition in the tropical ocean.This study contributes significantly to improving the quality of GPS radiosonde soundings and promotes the sharing of observation in the eastern tropical Indian Ocean and South China Sea.展开更多
基金supported by the Natural Science Foundation of China(Grant No:42105025,42075189,42275036,and 42430610)the National Key R&D Program of China under Grant 2021YFA0718000+3 种基金the China Meteorological Administration Youth Innovation Team(CMA2023QN15)China Meteorological Administration Key Innovation Team(CMA2024ZD07)the development fund of South China Sea Institute of Oceanology of the Chinese Academy of Sciences(SCSIO202203 and SCSIO202208)the Open Research Fund of the State Key Laboratory of Tropical Oceanography(South China Sea Institute of Oceanology,Chinese Academy of Sciences)(LTO2110)。
文摘The increase in frequency and intensity of Extreme High-temperature Events(EHEs)over Central-Eastern China(CEC)in recent decades has severely impacted social development and livelihoods.Using observation and reanalysis datasets,this study explores the effect of the East Asian subtropical westerly jet stream(EAJ)on the CEC EHEs for the summers spanning 1979–2020.Considering its general relative location to the right side of the upper-level jet stream exit region,CEC would theoretically suffer more EHEs with a stronger and northwardly-shifted EAJ in summer due to the likelihood of abnormal subsidence induced by the EAJ.However,such an EAJ–EHE connection has been unstable over the past four decades but has displayed an evident interdecadal change.Before the late 1990s,the interannual variation of the EAJ was manifested mainly by its meridional displacement in the northeastern part of East Asia;thus,the atmospheric responses were essentially located to the east of CEC,exerting less of an influence on the CEC EHEs.However,since the late 1990s,the EAJ variation has featured an intensity change in its center over the northwest portion of the CEC,which has resulted in a westward shift in atmospheric responses to cover the CEC region.Therefore,the EAJ could potentially affect the summer CEC EHEs during 2000–21.Our findings offer support for an in-depth understanding of the formation mechanisms of extreme weather/climate events of this nature and thus provide a scientific reference for seasonal climate predictions.
基金supported by the National Natural Science Foundation of China(Nos.42073078,U1901211 and 41876126)the National Key Research and Development Program of China(Nos.2023YFC3905003,2023-67 and 2017FY100700)+4 种基金the Hainan Province Science and Technology Special Fund(ZDYF2023SHFZ172)the Natural Science Foundation of Guangdong Province(Nos.2020A1515011137,2023A1515012004 and 2024A1515011203)Nansha District High-Level Talent Innovation Team Project in 2021(Mangrove Wetland Blue Carbon Sequestration Technology Innovation Team)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA19060204)the Key Tasks Guarantee Special Fund Project for Green-Beautiful Guangdong Ecological Construction in 2024(Precise Restoration and Ecological Function Evaluation of Mangroves).
文摘Estuaries are key areas for organic carbon cycling,where polymeric carbohydrates are abundant and chemically diverse.The recycling of these polymers by microbes depends on a variety of carbohydrate-active enzymes(CAZymes).However,it remains unclear whether other gene traits,particularly those related to cell motility toward polymeric carbohydrates,are intertwined with carbohydrate depolymerization and niche specialization in estuarine sediment soils.In this study,estuarine sediments were incubated with four prevalent polymeric carbohydrates(laminarin,fucan,cellulose,and chitin) under anaerobic conditions.Based on metagenomic analysis,we identified potential responses to the degradation and utilization of polymeric carbohydrate substrates from the perspectives of CAZymes and sugar transporters.The analysis of metagenomic gene data also revealed a positive correlation between chemotaxis and the abundance of CAZymes genes.Furthermore,metagenomes-assembled genomes(MAGs) that exhibited higher abundance in polysaccharide-treated samples compared to controls also featured elevated copies of genes involved in polysaccharide utilization loci(PULs),chemotaxis,as well as those associated with flagellar or gliding movement.SprB and CTDs associated with gliding proteins genes are essential for type Ⅸ secretion system-mediated secretion of CAZymes and gliding motility in Bacteroidota.The enhanced potential for mobility,coupled with the ability to degrade polymeric carbohydrates,may enable these bacteria to exploit nutrients beyond carbon sources,thereby potentially broadening their ecological niches.
基金financially supported by the National Key Research and Development Program of China(No.2021YFC3100700)the National Natural Science Foundation of China(No.42376070)+1 种基金the Natural Science Foundation of Guangdong Province(No.2024A1515012371)the Rising Star Foundation of the South China Sea Institute of Oceanology(No.NHXX2019DZ0201)。
文摘Polygonal fault systems(PFS),characterized by multi-directional fault patterns within layered sequences,are well-documented features in global continental margin basins.While the geometry and formation mechanisms of PFS have been extensively studied in the northern South China Sea,the PFS in the Zhongjiannan Basin(western South China Sea)remain relatively unexplored,with a lack of quantitative analysis regarding their propagation.This study addresses this gap by using high-resolution three-dimensional(3D)seismic data and conducting a quantitative fault analysis to thoroughly examine the planform,cross-sectional geometry,and evolution of PFS in the northern Zhongjiannan Basin.The absence of a dominant strike direction among these polygonal faults suggests that their evolution is not controlled by anisotropic stress.Our interpretation of seismic data,constrained by the spatial relationship among PFS,gullies,and pockmarks,indicates that PFS mainly developed within the Miocene strata,with their initiation occurring during the late Miocene.Furthermore,the PFS act as key conduits connecting gullies to pockmarks in this area.The formation and development of PFS may be primarily driven by thermally triggered processes within siliceous sediments.The necessary heat source is probably associated with the abundant submarine magmatism observed in the Zhongjiannan Basin.To reconstruct the regional geological history,a four-stage evolutionary model,incorporating the formation of PFS,is presented.This research significantly improves our understanding of the regional geological evolution of the Zhongjiannan Basin,providing critical insights into the initiation and development of PFS in the western South China Sea.
基金supported by the National Natural Science Foundation of China [grant number 42176001]the State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences [grant number LTO2106]the STU Scientific Research Foundation for Talents [grant number NTF21009]。
文摘The eddies in the southernmost southern Indian Ocean exert major dynamical and biogeochemical influences on the Earth system.Therefore,disentangling the relative contributions of vertical pumping and horizontal transport to water-property anomalies in the eddy cores is of fundamental importance.Here,the authors introduce a temperaturesalinity gradient-ratio approach(the"R-method")that compares vertical and meridional gradients to quantitatively separate the two processes.Application of the R-method to three-dimensional Argo observations reveals that horizontal transport,rather than vertical pumping,predominantly governs the observed temperature and salinity anomalies within eddy cores in the SIO.Independent theoretical estimations based on background meridional gradients,together with composites formed on isopycnal surfaces,further corroborate this conclusion.The results challenge the conventional assumption that vertical pumping invariably controls eddy-core property anomalies and demonstrate the utility of the R-method for diagnosing eddy impacts in climate and biogeochemical studies.
基金supported by the National Key R&D Program of China[grant number 2022YFF0801400]the National Natural Science Foundation of China [grant numbers 42376027 and W2441014]+2 种基金the Development Fund of the South China Sea Institute of Oceanology of the Chinese Academy of Sciences [grant number SCSIO202208]the Special Fund of the South China Sea Institute of Oceanology of the Chinese Academy of Sciences [grant number SCSIO2023QY01]the Science and Technology Projects in Guangzhou [grant number 202201010367]。
文摘The frequency of marine heatwaves(MHWs)in the South China Sea(SCS)has increased recently.However,the relative roles of thermal and dynamic processes regulating the changes of sCs MHWs remain an open question.This study examines all long-lived MHWs(>10 days)in the SCS from 1982 to 2021,categorizing them into intensified and attenuated MHWs based on the overall trend of sea surface temperature during an MHW event.A mixed-layer heat budget analysis reveals that the thermal processes primarily driven by the latent heat flux are crucial in modulating the SCS MHWs,particularly for attenuated MHWs.However,under intensified conditions,the proportions of dynamically dominated MHWs(40%)is approximately comparable to that of thermally dominated ones(47%).This study highlights the significance of dynamic processes in shaping SCS MHWs and discusses the potential impacts induced by tropical cyclones on these MHWs.
基金supported by National Key R&D Program of China (Grant No. 2016YFA0600601)the National Natural Science Foundation of China (Grant Nos. 41605027, 41721004, 41530530 and 41731173)+1 种基金the Leading Talents of Guangdong Province Program, the Pioneer Hundred Talents Program of the Chinese Academy of Sciencesthe Fundamental Research Funds for the Central Universities
文摘This study investigates why an extreme hot midsummer occurred in Central and South China(CSC) during 2017. It is shown that the western North Pacific subtropical high(WNPSH) was abnormally intensified and westward-extending,resulting in anomalous high pressure and consequent extreme heat over CSC. The abnormal WNPSH was favored by the warming of the western tropical Pacific(WTP), which was unrelated to ENSO and manifested its own individual effect.The WTP warming enhanced the convection in-situ and led to anomalous high pressure over CSC via a local meridional circulation. The influence of the WTP was confirmed by CAM4 model experiments. A comparison between the 2017 midsummer and 2010 midsummer(with a stronger WNPSH but weaker extreme heat) indicated that the influence of the WNPSH on extreme heat can be modulated by the associated precipitation in the northwestern flank.The role of the WTP was verified by regression analyses on the interannual variation of the WTP sea surface temperature anomaly(SSTA). On the other hand, the WTP has undergone prominent warming during the past few decades, resulting from decadal to long-term changes and favoring extreme warm conditions. Through a mechanism similar to the interannual variation, the decadal to long-term changes have reinforced the influence of WTP warming on the temperature over CSC,contributing to the more frequent hot midsummers recently. It is estimated that more than 50% of the temperature anomaly over CSC in the 2017 midsummer was due to the WTP warming, and 40% was related to the decadal to long-term changes of the WTP SSTA.
基金supported by The National Natural Science Foundation of China(Grant No.40976011)the Public Science and Technology Research Funds Projects of Ocean(Grant No.201105018)the National Key Basic Research Program of China(Grant No.2013CB430300)
文摘Impacts of EI Nino Modoki （ENM）, La Nina Modoki （LNM）, canonical EI Nifio （CEN） and canonical La Nifia （CLN） on tropical cyclones （TCs） that made landfall over China's Mainland during 1951-2011 are analysed using best-track data from China, the USA and Japan. Relative to cold phase years （LNM and CLN）, landfalling TCs in warm years （ENM and CEN） have a farther east genesis location, as well as longer track lengths and durations, both in total and before landfall. ENM demonstrates the highest landfall frequency, most northerly mean landfall position, and shortest after-landfall sustainability （track length and duration）, which indicate a more frequent and extensive coverage of China's Mainland by TCs, but with shorter after-landfall influence. CEN has low landfall frequency and the most southerly mean landfall location. LNM has the most westerly genesis location, being significantly farther west than the 1951-2011 average and leading to short mean track lengths and durations both in total or before landfall, all of which are significantly shorter than the 1951-2011 average. Variations in the low-level wind anomaly, vertical wind shear, mid-level relative humidity, steering flow, the monsoon trough and the western Pacific subtropical high （WPSH） can to some extent account for the features of frequency, location, track length and duration of landfalling TCs. Since ENSO Modoki is expected to become more frequent in the near future, the results for ENSO Modoki presented in this paper are of particular significance.
基金sponsored by the National Basic Research Program of China (also called 973 Program, Grant Nos 2011CB403504 and 2010CB950400)National Natural Science Foundation of China (Grant Nos U0833602, U0733002 and 40906010)+2 种基金Hong Kong Croucher Foundation (Grant No 9220055)City University of Hong Kong (Strategic Research Grant No 7002717)Key Laboratory of Tropical Marine Environmental Dynamics (LED), Chinese Academy of Sciences (Grant No LED0804)
文摘Tropical cyclone （TC） genesis over the South China Sea （SCS） during 1965–2004 was analyzed. The locations of TC genesis display evident seasonal changes, with the mean position of formation situated north of 15 °N in summer （June–July–August） and south of 15 °N in autumn （September–October–November）. The TC genesis in summer underwent dramatic interdecadal variations, with more and less TC frequency during 1965–1974/1995–2004 and 1979–1993, respectively. In contrast, a significant interannual variation of TC genesis with a period of ～4 years was observed in autumn. This study investigated the relationship of SCS TC genesis to the East Asian jet stream （EAJS） and the western North Pacific subtropical high （WNPSH） on an interdecadal time scale. Analysis and comparison of the impacts of the EAJS and the WNPSH on vertical wind shear changes indicate that changes in the WNPSH and EAJS intensity rather than EAJS meridional location are responsible for changes in TC genesis on an interdecadal time scale. Corresponding to a weaker EAJS, anomalous Rossby wave energy at upper levels displays equatorward propagation at midlatitudes and poleward propagation in the subtropics. This induces anomalous convergence and divergence of wave activity fluxes in East Asia around 30 °N and the SCS, respectively. The anomalous divergence of wave activity fluxes reduces easterlies at upper levels over the SCS, which is favorable to TC genesis.
基金sponsored by the National Key Basic Research Project of China (2009CB421404)the key project of National Natural Science Foundation of China (Grant No 40730951)National Natural Science Foundation of China (Grant No 40575021)
文摘Global climate models predict that the increasing Amazoniandeforestation rates cause rising tempera tures （increases of 1.8℃ to 8℃ under different conditions） and Amazonian drying over the 21st century. Observations in the 20th century also show that over the warmer continent and the nearby western South At lantic Ocean, the lowerlayer equatorial westerly wind （LLEWW） strengthens with the initiation of tropical cyclones （TCs）. The warmercontinentrelated LLEWW can result from the Coriolisforceinduced deflection of the crossequatorial flow （similar to the wellknown heatisland effect on sea breeze） driven by the enhanced landsea contrast between the warmer urbanized continents and relatively cold oceans. This study focuses on the processes relating the warmercontinentrelated LLEWW to the TC initiation and demonstrates that the LLEWW embedded in trade easterlies can directly initiate TCs by creating cyclonic wind shears and forming the intertropical convergence zone. In addition to this direct effect, the LLEWW combined with the rotating Earth can boost additional updraft vapor over the high seasurface temperature region （factor 1）, facilitating a surfacetomidtroposphere moist layer （factor 2） and convective instability （factor 3） followed by diabatic processes. According to previous studies, the diabatic heating in a finite equatorial region also activates TCs （factor 4） on each side of the Equator with weak vertical shear （factor 5）. Factors 1–5 are favorable conditions for the initiation of severe TCs. Statistical analyses show that the earliest signal of sustained LLEWW not only leads the earliest signal of sustained tropical depression by 3 days but also explains a higher percentage of total variance.
基金supported by the National Natural Science Foundation of China (Grant No. 41306005)the National Basic Research Program of China (Grant No. 2012CB955903)the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘The second-generation Global Ocean Data Assimilation System of the Beijing Climate Center （BCC_GODAS2.0） has been run daily in a pre-operational mode. It spans the period 1990 to the present day. The goal of this paper is to introduce the main components and to evaluate BCC_GODAS2.0 for the user community. BCC_GODAS2.0 consists of an observational data preprocess, ocean data quality control system, a three-dimensional variational （3DVAR） data assimilation, and global ocean circulation model [Modular Ocean Model 4 （MOM4）]. MOM4 is driven by six-hourly fluxes from the National Centers for Environmental Prediction. Satellite altimetry data, SST, and in-situ temperature and salinity data are assimilated in real time. The monthly results from the BCC_GODAS2.0 reanalysis are compared and assessed with observations for 1990-201 I. The climatology of the mixed layer depth of BCC_GODAS2.0 is generally in agreement with that of World Ocean Atlas 2001. The modeled sea level variations in the tropical Pacific are consistent with observations from satellite altimetry on interannual to decadal time scales. Performances in predicting variations in the SST using BCC_GODAS2.0 are evaluated. The standard deviation of the SST in BCC_GODAS2.0 agrees well with observations in the tropical Pacific. BCC_GODAS2.0 is able to capture the main features of E1 Nifio Modoki I and Modoki II, which have different impacts on rainfall in southern China. In addition, the relationships between the Indian Ocean and the two types of E1 Nino Modoki are also reproduced.
基金supportedby a grant from the Major State Basic Research Development Program of China(973Program)(No2011CB403500)the National Natural Science Foundation of China(NSFC)(NoU0733002)the Natural Science Foundation of Guangdong Province,China(No8351030101000002)
文摘Tropical cyclone （TC） Nargis （2008） made landfall in Myanmar on 02 May 2008, bringing a storm surge, major flooding, and resulting in a significant death toll. TC Nargis （2008） displayed abnormal features, including rare eastward motion in its late stage, rapid intensification before landing. Using reanalysis data and a numerical model, we investigated how a low-latitude westerly wind modulated TC Nargis’ （2008） track and provided favorable atmospheric conditions for its rapid intensification. More importantly, we found a possible counterbalance effect of flows from the two hemispheres on the TC track in the Bay of Bengal. Our analysis indicates that a strong westerly wind burst across the Bay of Bengal, resulting in TC Nargis’ （2008） eastward movement after its recurvature. This sudden enhancement of westerly wind was mainly due to the rapidly intensified mid-level cross-equatorial flow. Our results show that a high-pressure system in the Southern Hemisphere induced this strong, mid-level, cross-equatorial flow. During the rapid intensification period of TC Nargis （2008）, this strong and broad westerly wind also transported a large amount of water vapor to TC Nargis （2008）. Sufficient water vapor gave rise to continuously high and increased mid-level relative humidity, which was favorable to TC Nargis’ （2008） intensification. Condensation of water vapor increased the energy supply, which eventuated the intensification of TC Nargis （2008） to a category 4 on the Saffir-Simpson scale.
基金Supported by the National Basic Research Program of China (973 Program)(No.2011CB403500)the Knowledge Innovation Program of Chinese Academy of Sciences (Nos. KZCX2-YW-Q11-02, XDA05090404)+1 种基金the National Basic Research Program of China (973 Program) (No. 2010CB950302)the Qianren and Changjiang Scholar Projects, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)and SOEST-8711 & IPRC-901
文摘Tropical cyclone （TC） genesis in the South China Sea （SCS） during 1979-2008 underwent a decadal variation around 1993. A total of 55 TCs formed in the SCS from May to September during 1994- 2008, about twice that during 1979-1993 （27）. During the TC peak season （July-September, JAS）, there were 43 TCs fi＇om 1994-2008, but only 17 during 1979-1993. For July in particular, 13 TCs formed from 1994-2008, but there were none during 1979-1993. The change in TC number is associated with changes of key environmental conditions in atmosphere and ocean. Compared to 1979-1993, the subtropical high was significantly weaker and was displaced more eastward during 1994-2008. In the former period, a stronger subtropical high induced downward flow, inhibiting TC formation. In the latter period, vertical wind shear and outgoing longwave radiation all weakened. Mid-level （850-500 hPa） humidity, and relative vorticity were higher. Sea surface temperature and upper layer heat content were also higher in the area. All these factors favor TC genesis during the latter period. The decadal change of TC genesis led to more landfalling TCs in Southern China during the period 1994-2008, which contributed to an abrupt increase in regional rainfall.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41375050, 41405048 and 41205032)the China National Basic Research Program (Grant Nos. 2011CB403500 and 2014CB953904)
文摘High-frequency oscillations, with periods of about 2 hours, are first identified by applying wavelet analysis to observed minutely wind speeds around the eye and eyewall of tropical cyclones（TCs）. Analysis of a model simulation of Typhoon Hagupit（2008） shows that the oscillations also occur in the TC intensity, vertical motion, convergence activity and air density around the eyewall. Sequences of oscillations in these variables follow a certain order.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-Q11-02)
文摘The temporal variations in the frequency of tropical cyclones (TCs) traversing the Taiwan and Hainan Islands (TH islands), were analyzed using a best-track TC dataset from the Joint Typhoon Warning Center for the period 1945-2007. Results show that the oscillations were interannual and interdecadal on the timescales of 2-8 and 8-12 years, respectively. It is also shown that the number of TCs formed in the western North Pacific basin (WNP) and of those traversing the TH islands varied intraseasonally. These results also held for typhoons traversing the TH islands, although the oscillations were less apparent. This study identified interrelationships between the frequency of TCs making landfall on the TH islands and the East Asia summer monsoon (EASM), the South Asia summer monsoon (SASM), and the South China Sea summer monsoon (SCSSM). The SCSSM significantly influenced the number of TCs traversing Hainan Island, but had little influence on the number of TCs traversing Taiwan Island. By contrast, the SASM influenced the numbers of TCs traversing both of the TH islands, shown by correlation coefficients of 0.41 for Taiwan Island and -0.25 for Hainan Island. In addition, the frequency of TC landfall on Taiwan Island increased during years of enhanced EASM, as indicated by a correlation coefficient of 0.4.
基金The National Basic Research Program of China under contract No. 2011CB403500the fund from the State Key Laboratory of Satellite Ocean Environmental Dynamics (Second Institute of Oceanography) under contract No. SOED1108+1 种基金the fund from the State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology) under contract No. LED1002the tropical marine meteorology fund from the Institute of Tropical and Marine Meteorology and the Fundamental Research Funds for the Central Universities under contract No. 111gpy13
文摘The modulation of tropical cyclogenesis over the southern South China Sea （SSCS） by the El Nin o- Southern Oscillation （ENSO） is examined in October–December （OND）, when tropical cyclone （TC） activities are most active in this region. The results reveal that there were more TCs formed over the SSCS during La Nin a years and less TCs during El Nin o years. How different environmental factors （including low-level vorticity, mid-level relative humidity, vertical wind shear, and potential intensity） contribute to this influence is investigated, using a genesis potential （GP） index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for El Nin o and La Nin a years separately, which could account for the changes of TC frequency over the SSCS in different ENSO phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results show that the mid-level relative humidity makes the largest contribution to the ENSO modulation of tropical cyclogenesis over the SSCS. Although warmer sea surface temperatures （SSTs） and larger amount of evaporation from the ocean surface were observed over the SSCS during El Nin o years, anomalous descending motions due to the anomalous Walker circulations inhibited the upward transports of water vapor and led to less moisture contents in the middle troposphere, which suppressed TC formations.
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences with Grant No.XDA11010000the National Natural Science Foundation of China (No.41205026)+6 种基金the National Basic Research Program of China (2011CB403500)the Innovation Group Program of State Key Laboratory of Tropical Oceanography (LTOZZ1201)Dr.Lei Wang was also sponsored by the Knowledge Innovation Program of the Chinese Academy of Sciences (SQ201208)the foundation for returned scholars of Ministry of Education of Chinathe specialized research fund for the doctoral program of Higher Education for Youthsthe foundation of Guangdong Educational Committee for Youths (2012 LYM_0008)the open fund of the Key Laboratory of Ocean Circulation and Waves of Chinese Academy of Sciences (KLOCAW1309)
文摘This study examines the modulation of tropical cyclogenesis over the South China Sea （SCS） by the E1 Nifio-Southem Oscillation （ENSO） Modoki during the boreal summer. Results reveal that there were more tropical cyclones （TCs） formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors （including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity） contribute to this influence is investigated, using a genesis potential （GP） index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modold-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC fre-quency over the SCS by the ENSO Modold during the boreal summer.
基金funded by the tropical marine meteorology fund from the Institute of Tropical and Marine Meteorology CMAthe National Basic Research Program of China(2011CB403500)+2 种基金SOED1108LED1002the Fundamental Research Funds for the Central Universities (No.11lgpy13)
文摘This study examines the seasonal variations of tropical cyclogenesis over the South China Sea (SCS) using a genesis potential (GP) index developed by Emanuel and Nolan. How different environmental factors (including low-level vorticity, mid-level relative humidity, vertical wind shear, and potential intensity) contribute to these variations is investigated. Composite anomalies of the GP index are produced for the summer and winter monsoons separately. These composites replicate the observed seasonal variations of the observed frequency and location of tropical cyclogenesis over the SCS. The degree of contribution by each factor in different regions is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. Over the northern SCS, potential intensity makes the largest contributions to the seasonal variations in tropical cyclogenesis. Over the southern SCS, the low-level relative vorticity plays the primary role in the seasonal modulation of tropical cyclone (TC) genesis frequency, and the vertical wind shear plays the secondary role. Thermodynamic factors play more important roles for the seasonal variations in tropical cyclogenesis over the northern SCS, while dynamic factors are more important in the seasonal modulation of TC genesis frequency over the southern SCS.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41405048, 41675043, 41375050, 41205032 and 41775094)Independent Research Project Program of State Key Laboratory of Tropical Oceanography (Grant No. LTOZZ1603)
文摘Variations in the high-frequency oscillations of tropical cyclones （TCs） over the western North Pacific （WNP） are studied in numerical model simulations. Power spectrum analysis of maximum wind speeds at 10 m （MWS10） from an ensemble of 15 simulated TCs shows that oscillations are significant for all TCs. The magnitudes of oscillations in MWS10 are similar in the WNP and South China Sea （SCS）; however, the mean of the averaged significant periods in the SCS （1.93 h） is shorter than that in the open water of the WNP （2.83 h）. The shorter period in the SCS is examined through an ensemble of simulations, and a case simulation as well as a sensitivity experiment in which the continent is replaced by ocean for Typhoon Hagupit （2008）. The analysis of the convergence efficiency within the boundary layer suggests that the shorter periods in the SCS are possibly due to the stronger terrain effect, which intensifies convergence through greater friction. The enhanced convergence strengthens the disturbance of the gradient and thermal wind balances, and then contributes to the shorter oscillation periods in the SCS.
基金The National Natural Science Foundation(NSF)of China under contract Nos 41176027 and 11072253the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11030302the State Key Laboratory of Tropical Oceanography(LTO)grant,South China Sea Institute of Oceanography,Chinese Academy of Sciences,under contract No.LTOZZ1304
文摘This study, using laboratory experiments and scaling analysis, evaluates the influence of geothermal heating on global oceanic circulation. Upon a well-developed large-scale convective flow, an additional heat flux perturbation 5F/F is employed. The increments of flow and thermal properties, including eddy diffusivity K7, flow velocity Vand bottom temperature Tb, are found to be independent of the applied heat flux F. Together with the scaling analysis of convective flow at different configurations, where the flow is thermally driven in the relatively low or extremely high turbulent thermal convections or the horizontal convection, the variances of flow properties, 6KT/KTand 6V/V, are found to be close to 0.5% and 0.75% at 5F/F=2%. This means that the small heat flux perturbation plays a negligible role in the global convective flow. However, 6Tb/ATis found to be 1.5% at 8F/F=2%, which would have a significant effect in the local region. The results might provide a clue to understanding the influence of geothermal heating on global oceanic circulation. It is expected that geothermal heating will contribute less than 1% in turbulent mixing and volume flux to global oceanic circulation, so its influence can be negligible in this situation. However, when it comes to the local environment, the influence of geothermal heating cannot be ignored. For example, temperature increases of about 0.5℃ with geothermal heating would have a significant effect on the physical environments within the benthic boundary layer.
基金The Second Tibetan Plateau Scientific Expedition and Research Program under contract No.2019QZKK0102-02the National Natural Science Foundation of China under contract Nos 42230402,92158204,42176026,42076201,41049903,41149908,41249906,41249907,and 41249910+2 种基金the Guangdong Basic and Applied Basic Research Foundation under contract No.2022A1515240069the Marine Economic Development Special Program of Guangdong Province(Six Major Marine Industries):Research and Demonstration of Critical Technologies for Comprehensive Prevention and Control of Natural Disaster in Offshore Wind Farms,China under contract No.29[2023]the Fund of Fujian Provincial Key Laboratory of Marine Physical and Geological Processes under contract No.KLMPG-22-02.
文摘Shipboard radiosonde soundings are important for detecting and quantifying the multiscale variability of atmosphere-ocean interactions associated with mass exchanges.This study evaluated the accuracies of shipboard Global Positioning System(GPS)soundings in the eastern tropical Indian Ocean and South China Sea through a simultaneous balloon-borne inter-comparison of different radiosonde types.Our results indicate that the temperature and relative humidity(RH)measurements of GPS-TanKong(GPS-TK)radiosonde(used at most stations before 2012)have larger biases than those of ChangFeng-06-A(CF-06-A)radiosonde(widely used in current observation)when compared to reference data from Vaisala RS92-SGP radiosonde,with a warm bias of 5℃and dry bias of 10%during daytimes,and a cooling bias of-0.8℃and a moist bias of 6%during nighttime.These systematic biases are primarily attributed to the radiation effects and altitude deviation.An empirical correction algorithm was developed to retrieve the atmospheric temperature and RH profiles.The corrected profiles agree well with that of RS92-SGP,except for uncertainties of CF-06-A in the stratosphere.These correction algorithms were applied to the GPS-TK historical sounding records,reducing biases in the corrected temperature and RH profiles when compared to radio occultation data.The correction of GPS-TK historical records illustrated an improvement in capturing the marine atmospheric structure,with more accurate atmospheric boundary layer height,convective available potential energy,and convective inhibition in the tropical ocean.This study contributes significantly to improving the quality of GPS radiosonde soundings and promotes the sharing of observation in the eastern tropical Indian Ocean and South China Sea.
