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
The Sea Level Anomaly-Torque(SLAT,relative to a reference location in the Pacific Ocean),which means the total torque of the gravity forces of sea waters with depths equal to the Sea Level Anomaly(S/A)in the tropical ...The Sea Level Anomaly-Torque(SLAT,relative to a reference location in the Pacific Ocean),which means the total torque of the gravity forces of sea waters with depths equal to the Sea Level Anomaly(S/A)in the tropical Pacific Ocean,is defined in this study.The time series of the SLAT from merged altimeter data(1993-2003)had a great meridional variation during the 1997-1998 E1 Nifio event.By using historical upper layer temperature data(1955-2003)for the tropical Pacific Ocean,the temperature-based SLAT is also calculated and the meridional variation can be found in the historical E1 Nifio events(1955-2003),which suggests that the meridional shifts of the sea level anomaly are also intrinsic oscillating modes of the E1 Nifio cycles like the zonal shifts.展开更多
The expansion of river plumes is essential for coastal systems and inner-shelf biogeochemical processes.This investigation employs the Coupled Ocean-Atmosphere-Wave-Sediment Transport(COAWST)modeling system to systema...The expansion of river plumes is essential for coastal systems and inner-shelf biogeochemical processes.This investigation employs the Coupled Ocean-Atmosphere-Wave-Sediment Transport(COAWST)modeling system to systematically analyze the governing mechanisms influencing the Changjiang River plume during winter conditions.Model validation through comparison with the observational datasets demonstrates the system’s capability to accurately reproduce hydrodynamic processes and thermohaline variability.A series of sensitivity experiments was implemented to quantify the relative contributions of distinct forcing mechanisms,including tidal dynamics,wind stress,and waveinduced processes on hydrodynamic patterns and associated temperature-salinity distributions.Numerical simulations reveal that wave-induced vertical mixing generates significant nearshore thermal elevation concurrent with salinity reduction.Tidal residual currents exhibit persistent onshore and northward components,potentially facilitating northward advection of the Changjiang River plume during winter months.Conversely,wind-driven currents impose a constraining effect on plume expansion through the establishment of downwelling-favorable circulation patterns.During extreme wave events,wave-driven current contributions to salinity variance account for 30%−90%,relative to tidal mixing effects.These findings collectively establish wave-current interaction as a critical mechanistic component governing wintertime Changjiang River plume dynamics,with particular relevance to stratification modification and cross-shelf transport processes.展开更多
Typhoon Hinnamnor(2022)was the only tropical cyclone(TC)during 1982-2023 that maintained strong or higher intensity north of 25°N while undergoing two rapid intensification(RI)events under marine heatwave(MHW)con...Typhoon Hinnamnor(2022)was the only tropical cyclone(TC)during 1982-2023 that maintained strong or higher intensity north of 25°N while undergoing two rapid intensification(RI)events under marine heatwave(MHW)conditions.These RI events differed significantly in both duration and intensification rates.This study investigated the role of MHWs in modulating these events,with a focus on variations in ocean stratification and atmospheric circulation.The results revealed that the first RI lasted 18 h,during which typhoon Hinnamnor intensified from a strong tropical storm to a super typhoon,which was driven primarily by oceanic thermal conditions.The anomalous MHW deepened the warm subsurface waters,leading to sustained accumulation of upper ocean heat content(UOHC),which fueled the RI.The cyclone’s rapid movement and moderate intensity helped preserve the abnormally thick barrier layer(BL),which maintained the UOHC via a subsurface“heat pump”effect,thus supporting continued intensification.In contrast,the second RI lasted only 6 h and involved a one-category intensification from a strong typhoon to a super typhoon,influenced by both oceanic and atmospheric factors.The prolonged and intensified MHW maintained a high UOHC,while strong upper-level divergence,increased mid-level moisture and low-level convergence enhanced deep convection,triggering the RI.However,a shallow mixed layer confined warm anomalies to the surface,whereas the cyclone’s slower movement,stronger winds,and thinner BL induced cold water upwelling.This“cold suction”effect depleted the UOHC,prematurely terminating the RI.These findings highlight the complex interplay between oceanic and atmospheric factors in shaping TC intensification under MHW conditions,emphasizing the critical role of upper ocean stratification in improving TC intensity forecasts.展开更多
As a powerful tool to scan the atmosphere, the I idar can derive visibility values by directly collecting the backscattering laser light from the atmosphere. Simultaneous measurements of atmospheric visibility by Micr...As a powerful tool to scan the atmosphere, the I idar can derive visibility values by directly collecting the backscattering laser light from the atmosphere. Simultaneous measurements of atmospheric visibility by Micro-pulsed lidar （MPL） and a commercial visibility meter （VM） NQ-1 have been performed to evaluate the feasibility of the MPL system designed by the Ocean Remote Sensing Laboratory （ORSL） of the Ocean University of China （OUC） from October 21 2005 to November 21 2005 in the Shilaoren Sightseeing Garden on the Qingdao coast. All the 880 data samples obtained by the two instruments have high correlation coefficients （up to 0.86）, which indicates it is feasible to utilize MPL to measure atmospheric visibility.展开更多
Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar （SAR） image of waves. Based on the general dispersion relation of ocean waves the wavelength changes o...Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar （SAR） image of waves. Based on the general dispersion relation of ocean waves the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths.展开更多
Luzon Strait is the main channel connecting the South China Sea(SCS)and the western Pacific,with complex atmospheric and oceanic dynamic processes.Based on 44 days of glider measurements and satellite observations,we ...Luzon Strait is the main channel connecting the South China Sea(SCS)and the western Pacific,with complex atmospheric and oceanic dynamic processes.Based on 44 days of glider measurements and satellite observations,we investigated the temporal and vertical variations of chlorophyll-a(Chl-a)concentration in the Luzon Strait from July 25 to September 6,2019.The Chl a was mainly distributed above 200 m and concentrated in the subsurface chlorophyll maximum(SCM)layer.The depth of SCM ranged between 50 m and 110 m,and the magnitude of SCM varied from 0.42 mg/m3 to 1.12 mg/m3.The variation of Chl a was identified with three stages responding to different dynamic processes.Under the influence of Kuroshio intrusion,the SCM depth sharply deepened,and its magnitude decreased in Stage 1.Afterward,a prominent Chl-a bloom was observed in the SCM layer from August 6 to August 16.The Chl-a bloom in Stage 2 was related to the influence of a cyclonic eddy,which uplifted of the thermocline and thus the deep nutrients.During Stage 3,prolonged heavy rainfall in the northeastern SCS resulted in a significant salinity decrease in the upper ocean.The convergence of upper water deepened the thermocline and the mixed layer.Thus,the Chl a decreased in the SCM layer but increased in the surface layer.In particular,a typhoon passed through the Luzon Strait on August 24,which induced the Chl a increase in the upper 50 m.However,there was little change in the depth-integrated Chl a(0-200 m),indicating that the Chl a increase in the surface layer was likely associated with physical entrainment of SCM caused by strong mixing,rather than the phytoplankton bloom in the upper water column.Underwater gliders provide frequent autonomous observations that help us understand the regional ocean’s complex dynamic processes and biological responses.展开更多
The variability of the air-sea system in the low-frequency time domain can be decomposed into several systematic climate modes, namely, the decadal variability （DV） mode, the El Nino Southem Oscillation （ENSO） mod...The variability of the air-sea system in the low-frequency time domain can be decomposed into several systematic climate modes, namely, the decadal variability （DV） mode, the El Nino Southem Oscillation （ENSO） mode, the annual cycle （AC） mode, the semiannual cycle （ SC ） mode and the intraseasonal variability （ ISV ） mode. The combination of these primary modes in the air - sea system orchestrates a complex climate system. The multi-mode low-frequency variability in SST is investigated based on 22 a SST records from 1982 through 2003. The variation of SST in the past two decades undergoes a different combination of these dominant climate modes over different regions, which leads to an interesting new classification of the global ocean based on the relative importance of these modes. The new classification can provide ideal locations for better monitoring of these low-frequency modes in the scientific proof sense. Moreover, two no-annual variation and 14 no-semiannual variation oceanic points, termed annual and semiannual amphidromes, have been well defined in the AC and SC phase maps. The formation of these nodal points is attributed to the couplings of climate modes in EOF analysis results.展开更多
Numerous published results have showr the importance of the Wcstern Pacific Warm Pool （WPWP）surface centroid movement in ENSO-（EI Nino/Southcrn Oscillation）rclated studies .Howcver,some rccent research conclusions...Numerous published results have showr the importance of the Wcstern Pacific Warm Pool （WPWP）surface centroid movement in ENSO-（EI Nino/Southcrn Oscillation）rclated studies .Howcver,some rccent research conclusions make it necessary to clarify the differenccs of the currently exicing two types of WPWP surface centroid：the geometric centroid and the thermal （heat）centrold.This study analyzes the physical backgrounds of the two typcs of centroid and points out their differenccs.which suggest that different types of ccntroid may scrve different study purposes.This study also shows that the ‘geometric center’of WPWP.actually a close approximation to the mass ccntroid,is more related to the Nino-3 region sca surfacc temperaturc（SST）ancmaly and can also be regarded as an important indicator of ENSO events.展开更多
Synthetic Aperture Radar （SAR） has become one of the important tools for shallow water bathymetry surveys. This has significant economic efficiency compared with the traditional bathymetry surveys. Numerical models ...Synthetic Aperture Radar （SAR） has become one of the important tools for shallow water bathymetry surveys. This has significant economic efficiency compared with the traditional bathymetry surveys. Numerical models have been developed to simulate shallow water bathymetry SAR images. Inversion of these models makes it possible to assess the water depths from SAR images. In this paper, these numerical models of SAR technique are reviewed, and examples are illustrated including in the coastal areas of China. Some issues about SAR technique available and the research orientation in future are also discussed.展开更多
A mobile incoherent Doppler lidar system has been experimentally demonstrated to be able to transmit reliable single frequency operation laser pulse, even after truck transit and in very high vibration environments. T...A mobile incoherent Doppler lidar system has been experimentally demonstrated to be able to transmit reliable single frequency operation laser pulse, even after truck transit and in very high vibration environments. The linewidth of the injection-seeded pulse Nd:YAG laser can be measured by means of an I2 molecular filter. And, lidar validation experiments demonstrated the feasibility and capability of measuring wind field by the Mie-Rayleigh Doppler wind lidar. The un-certainty of measured wind speed is 0.985m/s in the altitude range from 2 to 4 km.展开更多
Usually, lidar detection systems are optimized for the measurement of the low intensity signal using the photon counting technique, but this approach results in the nonlinear signal response for the higher intensity s...Usually, lidar detection systems are optimized for the measurement of the low intensity signal using the photon counting technique, but this approach results in the nonlinear signal response for the higher intensity signal. The problem is successfully solved by the combination of analog-to-digital （AD） and photon- counting （PC） detection. The optimized processing procedure of the signal combination of AD and PC is described, and the corrected result is analyzed and compared with the results by the dealt-time correction method. In this way, the accuracy of wind and aerosol measurement in the nonlinear range is improved. In addition, the signal-to-noise ratios （SNRs） of the two detection methods of AD and PC are compared in the overall dynamic range of signal for the performance analysis.展开更多
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This study is supported by the Doctoral Startup Foundation of 0cean University of China(2003)partly supported by the National Science Foundation of China(40506035)The altimeter products were produced by the CLS Space 0ceanography Division as part of the Environment and Climate EU ENACT project(EVK2-CT2001-00117)and with support from CNES.
文摘The Sea Level Anomaly-Torque(SLAT,relative to a reference location in the Pacific Ocean),which means the total torque of the gravity forces of sea waters with depths equal to the Sea Level Anomaly(S/A)in the tropical Pacific Ocean,is defined in this study.The time series of the SLAT from merged altimeter data(1993-2003)had a great meridional variation during the 1997-1998 E1 Nifio event.By using historical upper layer temperature data(1955-2003)for the tropical Pacific Ocean,the temperature-based SLAT is also calculated and the meridional variation can be found in the historical E1 Nifio events(1955-2003),which suggests that the meridional shifts of the sea level anomaly are also intrinsic oscillating modes of the E1 Nifio cycles like the zonal shifts.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDC0190102the National Key Research and Development Program of China under contract No.2022YFC3105005the Guangdong Key Project under contract No.2019BT02H594.
文摘The expansion of river plumes is essential for coastal systems and inner-shelf biogeochemical processes.This investigation employs the Coupled Ocean-Atmosphere-Wave-Sediment Transport(COAWST)modeling system to systematically analyze the governing mechanisms influencing the Changjiang River plume during winter conditions.Model validation through comparison with the observational datasets demonstrates the system’s capability to accurately reproduce hydrodynamic processes and thermohaline variability.A series of sensitivity experiments was implemented to quantify the relative contributions of distinct forcing mechanisms,including tidal dynamics,wind stress,and waveinduced processes on hydrodynamic patterns and associated temperature-salinity distributions.Numerical simulations reveal that wave-induced vertical mixing generates significant nearshore thermal elevation concurrent with salinity reduction.Tidal residual currents exhibit persistent onshore and northward components,potentially facilitating northward advection of the Changjiang River plume during winter months.Conversely,wind-driven currents impose a constraining effect on plume expansion through the establishment of downwelling-favorable circulation patterns.During extreme wave events,wave-driven current contributions to salinity variance account for 30%−90%,relative to tidal mixing effects.These findings collectively establish wave-current interaction as a critical mechanistic component governing wintertime Changjiang River plume dynamics,with particular relevance to stratification modification and cross-shelf transport processes.
基金The National Natural Science Foundation of China under contract Nos 42275024,42405063,42575023,W2441014,and 42176001the Guangdong Basic and Applied Basic Research Foundation under contract Nos 2023B1515020009 and 2024B1515040024+1 种基金the Special Fund of the South China Sea Institute of Oceanology,Chinese Academy of Sciences,under contract Nos SCSIO2023QY01 and SCSIO2023HC07the Science and Technology Planning Project of Guangzhou under contract No.2024A04J6275.
文摘Typhoon Hinnamnor(2022)was the only tropical cyclone(TC)during 1982-2023 that maintained strong or higher intensity north of 25°N while undergoing two rapid intensification(RI)events under marine heatwave(MHW)conditions.These RI events differed significantly in both duration and intensification rates.This study investigated the role of MHWs in modulating these events,with a focus on variations in ocean stratification and atmospheric circulation.The results revealed that the first RI lasted 18 h,during which typhoon Hinnamnor intensified from a strong tropical storm to a super typhoon,which was driven primarily by oceanic thermal conditions.The anomalous MHW deepened the warm subsurface waters,leading to sustained accumulation of upper ocean heat content(UOHC),which fueled the RI.The cyclone’s rapid movement and moderate intensity helped preserve the abnormally thick barrier layer(BL),which maintained the UOHC via a subsurface“heat pump”effect,thus supporting continued intensification.In contrast,the second RI lasted only 6 h and involved a one-category intensification from a strong typhoon to a super typhoon,influenced by both oceanic and atmospheric factors.The prolonged and intensified MHW maintained a high UOHC,while strong upper-level divergence,increased mid-level moisture and low-level convergence enhanced deep convection,triggering the RI.However,a shallow mixed layer confined warm anomalies to the surface,whereas the cyclone’s slower movement,stronger winds,and thinner BL induced cold water upwelling.This“cold suction”effect depleted the UOHC,prematurely terminating the RI.These findings highlight the complex interplay between oceanic and atmospheric factors in shaping TC intensification under MHW conditions,emphasizing the critical role of upper ocean stratification in improving TC intensity forecasts.
基金supported by the National Natural Science Foundation of China(Nos.40275009 and 40405005).
文摘As a powerful tool to scan the atmosphere, the I idar can derive visibility values by directly collecting the backscattering laser light from the atmosphere. Simultaneous measurements of atmospheric visibility by Micro-pulsed lidar （MPL） and a commercial visibility meter （VM） NQ-1 have been performed to evaluate the feasibility of the MPL system designed by the Ocean Remote Sensing Laboratory （ORSL） of the Ocean University of China （OUC） from October 21 2005 to November 21 2005 in the Shilaoren Sightseeing Garden on the Qingdao coast. All the 880 data samples obtained by the two instruments have high correlation coefficients （up to 0.86）, which indicates it is feasible to utilize MPL to measure atmospheric visibility.
基金Supported by the Fund of the Second Institute of Oceanography,SOA (No.1403-40 and 1426-40)
文摘Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar （SAR） image of waves. Based on the general dispersion relation of ocean waves the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths.
基金Supported by the Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.2019BT02H594)the Chinese Academy of Sciences(Nos.XDB42010305,XDA15020901,133244KYSB20190031,SCSIO202201,SCSIO202204)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA13010500)the National Natural Science Foundation of China(No.41976024)the Independent Research Project Program of State Key Laboratory of Tropical Oceanography(No.LTOZZ2101)。
文摘Luzon Strait is the main channel connecting the South China Sea(SCS)and the western Pacific,with complex atmospheric and oceanic dynamic processes.Based on 44 days of glider measurements and satellite observations,we investigated the temporal and vertical variations of chlorophyll-a(Chl-a)concentration in the Luzon Strait from July 25 to September 6,2019.The Chl a was mainly distributed above 200 m and concentrated in the subsurface chlorophyll maximum(SCM)layer.The depth of SCM ranged between 50 m and 110 m,and the magnitude of SCM varied from 0.42 mg/m3 to 1.12 mg/m3.The variation of Chl a was identified with three stages responding to different dynamic processes.Under the influence of Kuroshio intrusion,the SCM depth sharply deepened,and its magnitude decreased in Stage 1.Afterward,a prominent Chl-a bloom was observed in the SCM layer from August 6 to August 16.The Chl-a bloom in Stage 2 was related to the influence of a cyclonic eddy,which uplifted of the thermocline and thus the deep nutrients.During Stage 3,prolonged heavy rainfall in the northeastern SCS resulted in a significant salinity decrease in the upper ocean.The convergence of upper water deepened the thermocline and the mixed layer.Thus,the Chl a decreased in the SCM layer but increased in the surface layer.In particular,a typhoon passed through the Luzon Strait on August 24,which induced the Chl a increase in the upper 50 m.However,there was little change in the depth-integrated Chl a(0-200 m),indicating that the Chl a increase in the surface layer was likely associated with physical entrainment of SCM caused by strong mixing,rather than the phytoplankton bloom in the upper water column.Underwater gliders provide frequent autonomous observations that help us understand the regional ocean’s complex dynamic processes and biological responses.
基金This research was jointly supported by the National Basic Research Program of China under contract N0.2005CB422308the National Natural Science Foundation of China under Contract N0.40545018the National Key laboratory of Remote Sensing Sciences.
文摘The variability of the air-sea system in the low-frequency time domain can be decomposed into several systematic climate modes, namely, the decadal variability （DV） mode, the El Nino Southem Oscillation （ENSO） mode, the annual cycle （AC） mode, the semiannual cycle （ SC ） mode and the intraseasonal variability （ ISV ） mode. The combination of these primary modes in the air - sea system orchestrates a complex climate system. The multi-mode low-frequency variability in SST is investigated based on 22 a SST records from 1982 through 2003. The variation of SST in the past two decades undergoes a different combination of these dominant climate modes over different regions, which leads to an interesting new classification of the global ocean based on the relative importance of these modes. The new classification can provide ideal locations for better monitoring of these low-frequency modes in the scientific proof sense. Moreover, two no-annual variation and 14 no-semiannual variation oceanic points, termed annual and semiannual amphidromes, have been well defined in the AC and SC phase maps. The formation of these nodal points is attributed to the couplings of climate modes in EOF analysis results.
基金This study has been supported by the Doctoral Startup Foundation of 0cean University of China(2003)partly by the Natural Science Foundation of China(No.40506035).The author is thankful to the NCDC for the SST data.The author also thanks the reviewers for their very valuable suggestions.
文摘Numerous published results have showr the importance of the Wcstern Pacific Warm Pool （WPWP）surface centroid movement in ENSO-（EI Nino/Southcrn Oscillation）rclated studies .Howcver,some rccent research conclusions make it necessary to clarify the differenccs of the currently exicing two types of WPWP surface centroid：the geometric centroid and the thermal （heat）centrold.This study analyzes the physical backgrounds of the two typcs of centroid and points out their differenccs.which suggest that different types of ccntroid may scrve different study purposes.This study also shows that the ‘geometric center’of WPWP.actually a close approximation to the mass ccntroid,is more related to the Nino-3 region sca surfacc temperaturc（SST）ancmaly and can also be regarded as an important indicator of ENSO events.
文摘Synthetic Aperture Radar （SAR） has become one of the important tools for shallow water bathymetry surveys. This has significant economic efficiency compared with the traditional bathymetry surveys. Numerical models have been developed to simulate shallow water bathymetry SAR images. Inversion of these models makes it possible to assess the water depths from SAR images. In this paper, these numerical models of SAR technique are reviewed, and examples are illustrated including in the coastal areas of China. Some issues about SAR technique available and the research orientation in future are also discussed.
基金This work was supported by the National 863 Project of Information Acquisition and Processing Technology 2002 AA135286 and the National Natural Science Foundation of China (Grant Nos. 40176011,60178017).
文摘A mobile incoherent Doppler lidar system has been experimentally demonstrated to be able to transmit reliable single frequency operation laser pulse, even after truck transit and in very high vibration environments. The linewidth of the injection-seeded pulse Nd:YAG laser can be measured by means of an I2 molecular filter. And, lidar validation experiments demonstrated the feasibility and capability of measuring wind field by the Mie-Rayleigh Doppler wind lidar. The un-certainty of measured wind speed is 0.985m/s in the altitude range from 2 to 4 km.
基金supported bythe National Natural Science Foundation of China under Grant Nos.60578038 and 40427001
文摘Usually, lidar detection systems are optimized for the measurement of the low intensity signal using the photon counting technique, but this approach results in the nonlinear signal response for the higher intensity signal. The problem is successfully solved by the combination of analog-to-digital （AD） and photon- counting （PC） detection. The optimized processing procedure of the signal combination of AD and PC is described, and the corrected result is analyzed and compared with the results by the dealt-time correction method. In this way, the accuracy of wind and aerosol measurement in the nonlinear range is improved. In addition, the signal-to-noise ratios （SNRs） of the two detection methods of AD and PC are compared in the overall dynamic range of signal for the performance analysis.
