In the paper, the WKBZ normal mode approach has been applied to the propagation of the pulsed energy and waveform in ocean channels. The numerical results in two different channels are given. Comparison between the WK...In the paper, the WKBZ normal mode approach has been applied to the propagation of the pulsed energy and waveform in ocean channels. The numerical results in two different channels are given. Comparison between the WKBZ and conventional normal mode codes shows that the WKBZ mode approach is a fast and accurate method and the running time by the WKBZ approach is reduced by about two orders of magnitude.展开更多
In this paper, the ocean acoustic channel is considered as a time-variant channel. In order to analyse the conjoint time-shift - frequency-delay distribution or the fading and spread statistical characteristics of the...In this paper, the ocean acoustic channel is considered as a time-variant channel. In order to analyse the conjoint time-shift - frequency-delay distribution or the fading and spread statistical characteristics of the channel. The TDWVS (Two Dimensional Wigner-Ville Spectrum) of the time - variant channel is defined. The relation between the WVS (Wigner-Ville Spectrum) of the input and the output of the channel is discussed and some examples for the specific channel are shown. Finally, the applications on the detection of signals in noise using the WVS and TDWVS are given and the advantage is obvious, when the detected signal is linear frequency-modulation signal.展开更多
Lag correlations of sea surface temperature anomalies （SSTAs）, sea surface height anomalies （SSHAs）, subsurface temperature anomalies, and surface zonal wind anomalies （SZWAs） produced by the Flexible Global Oce...Lag correlations of sea surface temperature anomalies （SSTAs）, sea surface height anomalies （SSHAs）, subsurface temperature anomalies, and surface zonal wind anomalies （SZWAs） produced by the Flexible Global Ocean-Atmosphere-Land System modeh Grid-point Version 2 （FGOALS-g2） are analyzed and com- pared with observations. The insignificant, albeit positive, lag correlations between the SSTAs in the south- eastern tropical Indian Ocean （STIO） in fall and the SSTAs in the central-eastern Pacific cold tongue in the following summer through fall are found to be not in agreement with the observational analysis. The model, however, does reproduce the significant lag correlations between tile SSHAs in the STIO in fall and those in the cold tongue at the one-year time lag in the observations. These, along with the significant lag correlations between the SSTAs in the STIO in fall and the subsurface temperature anomalies in the equatorial Pacific vertical section in the following year, suggest that the Indonesian Throughflow plays an important role in propagating the Indian Ocean anomalies into the equatorial Pacific Ocean. Analyses of the interannual anomalies of the Indonesian Throughflow transport suggest that the FGOALS-g2 climate system simulates, but underestimates, the oceanic channel dynamics between the Indian and Pacific Oceans. FGOALS-g2 is shown to produce lag correlations between the SZWAs over the western equatorial Pacific in fall and the cold tongue SSTAs at the one-year time lag that are too strong to be realistic in comparison with observations. The analyses suggest that the atmospheric bridge over the Indo-Pacific Ocean is overestimated in the FGOALS-g2 coupled climate model.展开更多
The relationships between the tropical Indian Ocean basin （IOB）/dipole （IOD） mode of SST anomalies （SSTAs） and ENSO phase transition during the following year are examined and compared in observations for the pe...The relationships between the tropical Indian Ocean basin （IOB）/dipole （IOD） mode of SST anomalies （SSTAs） and ENSO phase transition during the following year are examined and compared in observations for the period 1958-2008. Both partial correlation analysis and composite analysis show that both the positive （negative） phase of the lOB and IOD （independent of each other） in the tropical Indian Ocean are possible contributors to the E1 Nino （La Nifia） decay and phase transition to La Nifia （El Nifio） about one year later. However, the influence on ENSO transition induced by the IOB is stronger than that by the IOD. The SSTAs in the equatorial central-eastern Pacific in the coming year originate from subsurface temperature anomalies in the equatorial eastern Indian and western Pacific Ocean, induced by the IOB and IOD through eastward and upward propagation to meet the surface. During this process, however the contribution of the oceanic channel process between the tropical Indian and Pacific oceans is totally different for the IOB and IOD. For the IOD, the influence of the Indonesian Throughflow transport anomalies could propagate to the eastern Pacific to induce the ENSO transition. For the IOB, the impact of the oceanic channel stays and disappears in the western Pacific without propagation to the eastern Pacific.展开更多
An experiment using the Community Climate System Model(CCSM4), a participant of the Coupled Model Intercomparison Project phase-5(CMIP5), is analyzed to assess the skills of this model in simulating and predicting the...An experiment using the Community Climate System Model(CCSM4), a participant of the Coupled Model Intercomparison Project phase-5(CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole(IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the "oceanic channel dynamics" and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.展开更多
Simultaneous two-way classical and quantum(STCQ)communication combines both continuous classical coherent optical communication and continuous-variable quantum key distribution(CVQKD),which eliminates all detection-re...Simultaneous two-way classical and quantum(STCQ)communication combines both continuous classical coherent optical communication and continuous-variable quantum key distribution(CVQKD),which eliminates all detection-related imperfections by being measurement-device-independent(MDI).In this paper,we propose a protocol relying on STCQ communication on the oceanic quantum channel,in which the superposition-modulation-based coherent states depend on the information bits of both the secret key and the classical communication ciphertext.We analyse the encoding combination in classical communication and consider the probability distribution transmittance under seawater turbulence with various interference factors.Our numerical simulations of various practical scenarios demonstrate that the proposed protocol can simultaneously enable two-way classical communication and CV-MDI QKD with just a slight performance degradation transmission distance compared to the original CV-MDI QKD scheme.Moreover,the asymmetric situation outperforms the symmetric case in terms of transmission distance and optical modulation variance.We further take into consideration the impact of finite-size effects to illustrate the applicability of the proposed scheme in practical scenarios.The results show the feasibility of the underwater STCQ scheme,which contributes toward developing a global quantum communication network in free space.展开更多
The dynamics of the teleconnection between the Indian Ocean Dipole(IOD) in the tropical Indian Ocean and El Ni?o-Southern Oscillation(ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated us...The dynamics of the teleconnection between the Indian Ocean Dipole(IOD) in the tropical Indian Ocean and El Ni?o-Southern Oscillation(ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.The dynamics of the teleconnection between the Indian Ocean Dipole(IOD)in the tropical Indian Ocean and El Ni?o-Southern Oscillation(ENSO)in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations.The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean,which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO.In comparison,lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant,suggesting the short memory of the atmospheric bridge.A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans.The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15%depending on the baroclinic modes.The IOD-ENSO teleconnection is found to get stronger in the past century or so.Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century,which is found sensitive to the global warming forcing.展开更多
The existence of a multi-path channel under the water greatly decreases the accuracy of the short baseline positioning system.In this paper,the application of a time reversal mirror to the short baseline positioning s...The existence of a multi-path channel under the water greatly decreases the accuracy of the short baseline positioning system.In this paper,the application of a time reversal mirror to the short baseline positioning system was investigated.The time reversal mirror technique allowed the acoustic signal to better focus in an unknown environment,which effectively reduced the expansion of multi-path acoustic signals as well as improved the signal focusing.The signal-to-noise ratio（SNR） of the time reversal operator greatly increased and could be obtained by ensonifying the water.The technique was less affected by the environment and therefore more applicable to a complex shallow water environment.Numerical simulations and pool experiments were used to demonstrate the efficiency of this technique.展开更多
基金The project was supported by National Natural Science Foundation of China.
文摘In the paper, the WKBZ normal mode approach has been applied to the propagation of the pulsed energy and waveform in ocean channels. The numerical results in two different channels are given. Comparison between the WKBZ and conventional normal mode codes shows that the WKBZ mode approach is a fast and accurate method and the running time by the WKBZ approach is reduced by about two orders of magnitude.
文摘In this paper, the ocean acoustic channel is considered as a time-variant channel. In order to analyse the conjoint time-shift - frequency-delay distribution or the fading and spread statistical characteristics of the channel. The TDWVS (Two Dimensional Wigner-Ville Spectrum) of the time - variant channel is defined. The relation between the WVS (Wigner-Ville Spectrum) of the input and the output of the channel is discussed and some examples for the specific channel are shown. Finally, the applications on the detection of signals in noise using the WVS and TDWVS are given and the advantage is obvious, when the detected signal is linear frequency-modulation signal.
基金supported by the China 973 Project (Grant No. 2012CB956000)the NSFC (Grant Nos. 40888001, 41176019, 41005042 and 40975065)
文摘Lag correlations of sea surface temperature anomalies （SSTAs）, sea surface height anomalies （SSHAs）, subsurface temperature anomalies, and surface zonal wind anomalies （SZWAs） produced by the Flexible Global Ocean-Atmosphere-Land System modeh Grid-point Version 2 （FGOALS-g2） are analyzed and com- pared with observations. The insignificant, albeit positive, lag correlations between the SSTAs in the south- eastern tropical Indian Ocean （STIO） in fall and the SSTAs in the central-eastern Pacific cold tongue in the following summer through fall are found to be not in agreement with the observational analysis. The model, however, does reproduce the significant lag correlations between tile SSHAs in the STIO in fall and those in the cold tongue at the one-year time lag in the observations. These, along with the significant lag correlations between the SSTAs in the STIO in fall and the subsurface temperature anomalies in the equatorial Pacific vertical section in the following year, suggest that the Indonesian Throughflow plays an important role in propagating the Indian Ocean anomalies into the equatorial Pacific Ocean. Analyses of the interannual anomalies of the Indonesian Throughflow transport suggest that the FGOALS-g2 climate system simulates, but underestimates, the oceanic channel dynamics between the Indian and Pacific Oceans. FGOALS-g2 is shown to produce lag correlations between the SZWAs over the western equatorial Pacific in fall and the cold tongue SSTAs at the one-year time lag that are too strong to be realistic in comparison with observations. The analyses suggest that the atmospheric bridge over the Indo-Pacific Ocean is overestimated in the FGOALS-g2 coupled climate model.
基金jointly supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA11010102)the NSFC (Grant Nos. 41375094 and 41406028)+1 种基金the "973" project (Grant No. 2012CB956000)the NSFC–Shandong Joint Fund for Marine Science Research Centers (Grant No. U1406401)
文摘The relationships between the tropical Indian Ocean basin （IOB）/dipole （IOD） mode of SST anomalies （SSTAs） and ENSO phase transition during the following year are examined and compared in observations for the period 1958-2008. Both partial correlation analysis and composite analysis show that both the positive （negative） phase of the lOB and IOD （independent of each other） in the tropical Indian Ocean are possible contributors to the E1 Nino （La Nifia） decay and phase transition to La Nifia （El Nifio） about one year later. However, the influence on ENSO transition induced by the IOB is stronger than that by the IOD. The SSTAs in the equatorial central-eastern Pacific in the coming year originate from subsurface temperature anomalies in the equatorial eastern Indian and western Pacific Ocean, induced by the IOB and IOD through eastward and upward propagation to meet the surface. During this process, however the contribution of the oceanic channel process between the tropical Indian and Pacific oceans is totally different for the IOB and IOD. For the IOD, the influence of the Indonesian Throughflow transport anomalies could propagate to the eastern Pacific to induce the ENSO transition. For the IOB, the impact of the oceanic channel stays and disappears in the western Pacific without propagation to the eastern Pacific.
基金the National Basic Research Program of China(973 Program)(No.2012CB956000)the Strategic Priority Project of Chinese Academy of Sciences(No.XDA11010301)+2 种基金the National Natural Science Foundation of China(Nos.41421005,U1406401)the Public Welfare Grant of China Meteorological Administration(No.GYHY201306018)the Global Change and Air-Sea Interactions of State Oceanic Administration(No.GASI-03-01-01-05)
文摘An experiment using the Community Climate System Model(CCSM4), a participant of the Coupled Model Intercomparison Project phase-5(CMIP5), is analyzed to assess the skills of this model in simulating and predicting the climate variabilities associated with the oceanic channel dynamics across the Indo-Pacific Oceans. The results of these analyses suggest that the model is able to reproduce the observed lag correlation between the oceanic anomalies in the southeastern tropical Indian Ocean and those in the cold tongue in the eastern equatorial Pacific Ocean at a time lag of 1 year. This success may be largely attributed to the successful simulation of the interannual variations of the Indonesian Throughflow, which carries the anomalies of the Indian Ocean Dipole(IOD) into the western equatorial Pacific Ocean to produce subsurface temperature anomalies, which in turn propagate to the eastern equatorial Pacific to generate ENSO. This connection is termed the "oceanic channel dynamics" and is shown to be consistent with the observational analyses. However, the model simulates a weaker connection between the IOD and the interannual variability of the Indonesian Throughflow transport than found in the observations. In addition, the model overestimates the westerly wind anomalies in the western-central equatorial Pacific in the year following the IOD, which forces unrealistic upwelling Rossby waves in the western equatorial Pacific and downwelling Kelvin waves in the east. This assessment suggests that the CCSM4 coupled climate system has underestimated the oceanic channel dynamics and overestimated the atmospheric bridge processes.
基金supported by the National Natural Science Foundation of China (Grant No. 61871407)the Natural Science Foundation of Hunan Province (Grant No. 2021JJ30878)+2 种基金the Key Project of Research and Development Plan of Hunan Province (Grant Nos. 2020GK4063, 2022GK2016)the support from the Optoelectronic Information Center of Central South UniversityHunan Railway Engineering Machinery Electrohydraulic Control Engineering Technology Research Center
文摘Simultaneous two-way classical and quantum(STCQ)communication combines both continuous classical coherent optical communication and continuous-variable quantum key distribution(CVQKD),which eliminates all detection-related imperfections by being measurement-device-independent(MDI).In this paper,we propose a protocol relying on STCQ communication on the oceanic quantum channel,in which the superposition-modulation-based coherent states depend on the information bits of both the secret key and the classical communication ciphertext.We analyse the encoding combination in classical communication and consider the probability distribution transmittance under seawater turbulence with various interference factors.Our numerical simulations of various practical scenarios demonstrate that the proposed protocol can simultaneously enable two-way classical communication and CV-MDI QKD with just a slight performance degradation transmission distance compared to the original CV-MDI QKD scheme.Moreover,the asymmetric situation outperforms the symmetric case in terms of transmission distance and optical modulation variance.We further take into consideration the impact of finite-size effects to illustrate the applicability of the proposed scheme in practical scenarios.The results show the feasibility of the underwater STCQ scheme,which contributes toward developing a global quantum communication network in free space.
基金Supported by the National Basic Research Program of China(973 Program)(No.2012CB956001)the CMA(No.GYHY201306018)+4 种基金the State Oceanic Administration(SOA)(No.GASI-03-01-01-05)the National Natural Science Foundation of China(NSFC)(Nos.41421005,41176019,U1406401)the Shandong Provincial Project(No.2014GJJS0101)the Strategic Priority Project of CAS(Nos.XDA11010301,XDA11010102,XDA11010205)the QNLM Project(No.2016ASKJ04)
文摘The dynamics of the teleconnection between the Indian Ocean Dipole(IOD) in the tropical Indian Ocean and El Ni?o-Southern Oscillation(ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.The dynamics of the teleconnection between the Indian Ocean Dipole(IOD)in the tropical Indian Ocean and El Ni?o-Southern Oscillation(ENSO)in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations.The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean,which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO.In comparison,lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant,suggesting the short memory of the atmospheric bridge.A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans.The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%–15%depending on the baroclinic modes.The IOD-ENSO teleconnection is found to get stronger in the past century or so.Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century,which is found sensitive to the global warming forcing.
基金Supported by the National Defense Basic Foundation of China B2420710007
文摘The existence of a multi-path channel under the water greatly decreases the accuracy of the short baseline positioning system.In this paper,the application of a time reversal mirror to the short baseline positioning system was investigated.The time reversal mirror technique allowed the acoustic signal to better focus in an unknown environment,which effectively reduced the expansion of multi-path acoustic signals as well as improved the signal focusing.The signal-to-noise ratio（SNR） of the time reversal operator greatly increased and could be obtained by ensonifying the water.The technique was less affected by the environment and therefore more applicable to a complex shallow water environment.Numerical simulations and pool experiments were used to demonstrate the efficiency of this technique.
