2021 Vol. 43, No. 1
Display Method:
2021, 43(1): 1-26.
doi: 10.12284/hyxb2021019
Abstract:
The modern Zhujiang River Delta has experienced the formation and evolution from drowned valley to delta, which is rich in regional characteristics. The research on the Zhujiang River Delta in the past hundred years is summarized into four paradigms: historical description, field investigation-scientific reasoning, instrument applied-discipline theory and “dynamic-sedimentary-morphologic” scale-crossing paradigm. Each illustrated by superb examples and documented. Based on the research of the authors and his team, this paper puts forward several propositions concerning the formation and evolution of the Zhujiang River Delta, which are substantially different from the existing literature, and makes necessary differentiation and analysis from multiple perspectives, including the millennial-scale changes of coastline since the transgression maximum, the mode of formation and evolution of the modern Zhujiang River Delta and the development and its mechanism of the major channels of the network in the delta. Finally, the approache of interdisciplinary, scale-crossing and time-space quantification concerning delta research are briefly discussed.
The modern Zhujiang River Delta has experienced the formation and evolution from drowned valley to delta, which is rich in regional characteristics. The research on the Zhujiang River Delta in the past hundred years is summarized into four paradigms: historical description, field investigation-scientific reasoning, instrument applied-discipline theory and “dynamic-sedimentary-morphologic” scale-crossing paradigm. Each illustrated by superb examples and documented. Based on the research of the authors and his team, this paper puts forward several propositions concerning the formation and evolution of the Zhujiang River Delta, which are substantially different from the existing literature, and makes necessary differentiation and analysis from multiple perspectives, including the millennial-scale changes of coastline since the transgression maximum, the mode of formation and evolution of the modern Zhujiang River Delta and the development and its mechanism of the major channels of the network in the delta. Finally, the approache of interdisciplinary, scale-crossing and time-space quantification concerning delta research are briefly discussed.
2021, 43(1): 27-43.
doi: 10.12284/hyxb2021021
Abstract:
It is no doubt that there is plenty of “water” (existential form: H2O, H2 and (HO)−) existing in the mantle which can either exist in the form of fluids and melts or exist in aqueous minerals, nominally anhydrous minerals (NAMs) and dense hydrous Mg-silicates (DHMS). In this paper, “fluid” mainly refers to water which includes elements and compounds that dissolved in or migrated with it. Fluids, mainly consisting of water, play important roles in major geologic processes such as subduction zone earthquakes, mantle partial melting, magmatism and submarine hydrothermal activities. The subduction zone is a key place where the hydrated oceanic lithospheric plate subducts into the earth’s depth. And it is also an important zone of crust-mantle interaction. In the subduction zone, fluids are carried into the deep earth by the subducting lithospheric plate, part of the fluids are released into the overlying mantle wedge by extrusion, frictional heating and metamorphism, thereby lowering the melting point of mantle materials and causing magmatism; on the one hand, the ascending magma heats seawater that penetrates through cracks or rifts; on the other hand, the heated seawater and post-magmatic fluids generated by magma cooling compose the material basis of modern submarine hydrothermal activities; submarine hydrothermal activities not only affect the material composition of ocean water and ecological environment by importing a large number of underground elements or substances into ocean water, but also lead to the formation of hydrothermal polymetallic ore deposits with important economic value. Therefore, the fluid is a medium in the plate subduction process and the various important geological processes caused by it, thus it is a tracer to study these important geological processes. Based on the analysis of the main geological processes of fluids in the oceanic lithosphere subduction, this paper discussed the roles of fluids in earthquake mechanism, magmatic processes, modern submarine hydrothermal activities and subduction zone fluid mineralization. Furthermore, it is suggested that the recent research work should focus on these four aspects: (1) Making the assessment of the fluid flux subducted into the deep earth more accurate to solve global geochemical or material circulation problems. (2) Describing physical and chemical behaviors of fluids in plate subduction comprehensively and accurately, establishing theoretical models of fluid geological processes in subduction zones. (3) Making full use of modern tests and analysis methods, and obtaining accurate data in terms of in-situ analysis of minerals, testing physical and chemical indexes of fluid inclusions in minerals, stable and radioactive isotope analysis, etc., so as to find out the state and process of substances deep underground which can not be reached by current sampling and observation methods. (4) Developing numerical simulation technique to establish theoretical models of geological processes of fluids in subduction zones.
It is no doubt that there is plenty of “water” (existential form: H2O, H2 and (HO)−) existing in the mantle which can either exist in the form of fluids and melts or exist in aqueous minerals, nominally anhydrous minerals (NAMs) and dense hydrous Mg-silicates (DHMS). In this paper, “fluid” mainly refers to water which includes elements and compounds that dissolved in or migrated with it. Fluids, mainly consisting of water, play important roles in major geologic processes such as subduction zone earthquakes, mantle partial melting, magmatism and submarine hydrothermal activities. The subduction zone is a key place where the hydrated oceanic lithospheric plate subducts into the earth’s depth. And it is also an important zone of crust-mantle interaction. In the subduction zone, fluids are carried into the deep earth by the subducting lithospheric plate, part of the fluids are released into the overlying mantle wedge by extrusion, frictional heating and metamorphism, thereby lowering the melting point of mantle materials and causing magmatism; on the one hand, the ascending magma heats seawater that penetrates through cracks or rifts; on the other hand, the heated seawater and post-magmatic fluids generated by magma cooling compose the material basis of modern submarine hydrothermal activities; submarine hydrothermal activities not only affect the material composition of ocean water and ecological environment by importing a large number of underground elements or substances into ocean water, but also lead to the formation of hydrothermal polymetallic ore deposits with important economic value. Therefore, the fluid is a medium in the plate subduction process and the various important geological processes caused by it, thus it is a tracer to study these important geological processes. Based on the analysis of the main geological processes of fluids in the oceanic lithosphere subduction, this paper discussed the roles of fluids in earthquake mechanism, magmatic processes, modern submarine hydrothermal activities and subduction zone fluid mineralization. Furthermore, it is suggested that the recent research work should focus on these four aspects: (1) Making the assessment of the fluid flux subducted into the deep earth more accurate to solve global geochemical or material circulation problems. (2) Describing physical and chemical behaviors of fluids in plate subduction comprehensively and accurately, establishing theoretical models of fluid geological processes in subduction zones. (3) Making full use of modern tests and analysis methods, and obtaining accurate data in terms of in-situ analysis of minerals, testing physical and chemical indexes of fluid inclusions in minerals, stable and radioactive isotope analysis, etc., so as to find out the state and process of substances deep underground which can not be reached by current sampling and observation methods. (4) Developing numerical simulation technique to establish theoretical models of geological processes of fluids in subduction zones.
2021, 43(1): 44-54.
doi: 10.12284/hyxb2021073
Abstract:
The Okinawa Trough is an initial back arc basin developed on the continental crust due to the subduction of Philippine Sea plate under Eurasian plate. It is a natural laboratory to study the basin evolution, magmatism and crust-mantle interactions in the early stage of back arc expansion. Although a lot of investigations and research works have been done so far, there are still some controversial or urgent scientific problems, such as the genetic relationship between acid pumice and basic basalts in the trough, the control of tectonic background on magmatism in different sections of the trough, the characteristics of magma-derrived mantle, and the influence of subduction plate components (fluid + melt) on the mantle wedge, etc. On the basis of systematically collecting and sorting out (excluding some doubtful data) the major element, trace element (including rare earth elements) and Sr-Nd-Pb isotopic data of volcanic rocks in the Okinawa Trough, the author further confirmed the magma homology of acid pumice and basic basalt through systematic analysis of the data, and believed that the distributions of acid pumice and neutral andesite in the north and middle sections of the trough should be the reflection of regional rift at present, while the basic basalts widely distributed in the south section indicate that they are close to mature back arc basin in structural property. The volcanic magma source area of Okinawa Trough has the characteristics of enriched mantle II (EMII)-type Dupal anomaly, and the magma comes from the source mixed by end-member of prevalent mantle (PREMA) and EMII type mantle end-member, of which the ratio of EMII is about 15% and PREMA about 85%. The addition of fluid/melt from subducted Philippine Sea plate (subducted ocean crust or sediment) is the reason for the EMII type characteristics of magma-derrived mantle beneath the Okinawa Trough, which is different from the viewpoint that the Dupal anomaly originates from the interaction between crust and mantle.
The Okinawa Trough is an initial back arc basin developed on the continental crust due to the subduction of Philippine Sea plate under Eurasian plate. It is a natural laboratory to study the basin evolution, magmatism and crust-mantle interactions in the early stage of back arc expansion. Although a lot of investigations and research works have been done so far, there are still some controversial or urgent scientific problems, such as the genetic relationship between acid pumice and basic basalts in the trough, the control of tectonic background on magmatism in different sections of the trough, the characteristics of magma-derrived mantle, and the influence of subduction plate components (fluid + melt) on the mantle wedge, etc. On the basis of systematically collecting and sorting out (excluding some doubtful data) the major element, trace element (including rare earth elements) and Sr-Nd-Pb isotopic data of volcanic rocks in the Okinawa Trough, the author further confirmed the magma homology of acid pumice and basic basalt through systematic analysis of the data, and believed that the distributions of acid pumice and neutral andesite in the north and middle sections of the trough should be the reflection of regional rift at present, while the basic basalts widely distributed in the south section indicate that they are close to mature back arc basin in structural property. The volcanic magma source area of Okinawa Trough has the characteristics of enriched mantle II (EMII)-type Dupal anomaly, and the magma comes from the source mixed by end-member of prevalent mantle (PREMA) and EMII type mantle end-member, of which the ratio of EMII is about 15% and PREMA about 85%. The addition of fluid/melt from subducted Philippine Sea plate (subducted ocean crust or sediment) is the reason for the EMII type characteristics of magma-derrived mantle beneath the Okinawa Trough, which is different from the viewpoint that the Dupal anomaly originates from the interaction between crust and mantle.
2021, 43(1): 93-101.
doi: 10.12284/hyxb2021023
Abstract:
The risk assessment and zoning of submarine landslides can guide the site selection and risk prevention of offshore engineering facilities. In this paper, an unsupervised machine learning spectral analysis algorithm was used to evaluate the risk of submarine landslides in the Chengdao sea area of the Yellow River Estuary. A model of submarine landslides risk assessment with 9 input parameters, 4 output parameters and 0.08 as kernel function parameters is constructed. By using this model, the study area can be divided into 4 parts: high, quite high, quite low and low risk of submarine landslide. The comparison between the evaluation results and the distribution characteristics of geological environment factors show that the most important factors are the type of seafloor sediment and hydrodynamic action, and the most important trigger factor is liquefaction. The analysis results of model parameters present that the evaluation results with slightly lower accuracy can be obtained by reasonably simplifying the input factors, and the kernel function parameter is important index affecting the evaluation accuracy. The above research shows that the unsupervised machine learning algorithm can be well used in the risk assessment of submarine landslides, and the richness and accuracy of data categories are important factors affecting the assessment accuracy.
The risk assessment and zoning of submarine landslides can guide the site selection and risk prevention of offshore engineering facilities. In this paper, an unsupervised machine learning spectral analysis algorithm was used to evaluate the risk of submarine landslides in the Chengdao sea area of the Yellow River Estuary. A model of submarine landslides risk assessment with 9 input parameters, 4 output parameters and 0.08 as kernel function parameters is constructed. By using this model, the study area can be divided into 4 parts: high, quite high, quite low and low risk of submarine landslide. The comparison between the evaluation results and the distribution characteristics of geological environment factors show that the most important factors are the type of seafloor sediment and hydrodynamic action, and the most important trigger factor is liquefaction. The analysis results of model parameters present that the evaluation results with slightly lower accuracy can be obtained by reasonably simplifying the input factors, and the kernel function parameter is important index affecting the evaluation accuracy. The above research shows that the unsupervised machine learning algorithm can be well used in the risk assessment of submarine landslides, and the richness and accuracy of data categories are important factors affecting the assessment accuracy.
2021, 43(1): 102-109.
doi: 10.12284/hyxb2021017
Abstract:
The occurrence of phosphatization will lead to the dilution of major ore-forming elements in polymetallic crusts and thus inhibit the growth of crusts in general. Phosphatization occurred in the Pacific Ocean in an episodic manner, and the occurrence periods correspond to the phosphatization layers in crusts and the geochemical characteristics of P, Ca and other elements, providing evidence for the dating of crusts. However, due to the frequent occurrence of phosphatization in multiple layers of crusts, a more reliable age frame needs to be determined before it can be mutually corroborated with phosphatization events. In this study, the Co-Os dating system with large dating range and the ability to determine hiatus was applicated in dating for the crust samples from central Pacific and western Pacific. With the naked eye identification of phosphatization mineralization features and geochemical profile characteristics, the age frames were proved and the effect of phosphatization on crust mineralization were discussed. The two large-scale phosphatization phases of 39–34 Ma and 27–21 Ma all correspond to the large-scale discontinuous phases of the crusts, while most small-scale phosphatization events in 71 Ma, 55 Ma and 31 Ma can be identified in the layers and geochemical profiles, corresponding to the rising and peak characteristics of P and Ca content. On the one hand, it is confirmed that the occurrence of phosphatization inhibits the growth of crusts, and has a wide range of influence area and a clear time interval in Pacific. On the other hand, it proves the accuracy of the chronological framework of polymetallic crusts.
The occurrence of phosphatization will lead to the dilution of major ore-forming elements in polymetallic crusts and thus inhibit the growth of crusts in general. Phosphatization occurred in the Pacific Ocean in an episodic manner, and the occurrence periods correspond to the phosphatization layers in crusts and the geochemical characteristics of P, Ca and other elements, providing evidence for the dating of crusts. However, due to the frequent occurrence of phosphatization in multiple layers of crusts, a more reliable age frame needs to be determined before it can be mutually corroborated with phosphatization events. In this study, the Co-Os dating system with large dating range and the ability to determine hiatus was applicated in dating for the crust samples from central Pacific and western Pacific. With the naked eye identification of phosphatization mineralization features and geochemical profile characteristics, the age frames were proved and the effect of phosphatization on crust mineralization were discussed. The two large-scale phosphatization phases of 39–34 Ma and 27–21 Ma all correspond to the large-scale discontinuous phases of the crusts, while most small-scale phosphatization events in 71 Ma, 55 Ma and 31 Ma can be identified in the layers and geochemical profiles, corresponding to the rising and peak characteristics of P and Ca content. On the one hand, it is confirmed that the occurrence of phosphatization inhibits the growth of crusts, and has a wide range of influence area and a clear time interval in Pacific. On the other hand, it proves the accuracy of the chronological framework of polymetallic crusts.
2021, 43(1): 110-121.
doi: 10.12284/hyxb2021009
Abstract:
As a kind of coastal accumulation body in high-energy environment, natural gravel beach is a good coastal protection barrier due to its coarse particle size and large porosity. The gravel morphology is an important parameter to understand the gravel formation process, but it is difficult to obtain the quantitative parameters of a large number of gravels quickly and accurately. In this study, we surveyed three gravel beaches (Jiuzhangya, Yueyawan, Changtan) in the Beichangshan Island, four gravel beaches (Xianjingyuan, Linhai, Changshanwei and Mingzhuguangchang) in the Nanchangshan Island in the Shandong Province. We measured beach profile, collected gravel samples and took gravel images. Using the software ImageJ for digital image measurement in situ without interference, we can quickly obtain a large number of gravel morphologic parameters, including particle size, grinding roundness and shape ratio. The results show that the range of the particle size is 4−79 mm, which was mainly pebbles. The average particle size of the beach in the Beichangshan Island is slightly smaller than that in the Nanchangshan Island, with the largest average particle size of gravels in the Jiuzhangya Beach of the Beichangshan Island and the smallest one in the Xianjingyuan Beach of the Nanchangshan Island. From beach berm to the high tidal line, the average particle size decreases gradually, but increases at waterline. The range of roundness of gravel is 0.59–0.75, and the grade is round. The gravel beaches have reached a relatively mature stage based on roundness, with the best roundness in the Yueyawan Beach and the worst roundness in the Changtan Beach of the Beichangshan Island. The gravel roundness increases from land to sea. The shape ratio ranges from 1.36 to 1.77, which is negatively correlated with the gravel roundness (R2=0.98). The gravel gradually changed from long strip to elliptic shape from land to sea. The gravel beaches morphology of the Changshan Island is affected by the provenances, dynamic conditions and human activities. The slope range of the gravel beach in the study area is 16%−35%, and they are positively correlated with the gravel particle size.
As a kind of coastal accumulation body in high-energy environment, natural gravel beach is a good coastal protection barrier due to its coarse particle size and large porosity. The gravel morphology is an important parameter to understand the gravel formation process, but it is difficult to obtain the quantitative parameters of a large number of gravels quickly and accurately. In this study, we surveyed three gravel beaches (Jiuzhangya, Yueyawan, Changtan) in the Beichangshan Island, four gravel beaches (Xianjingyuan, Linhai, Changshanwei and Mingzhuguangchang) in the Nanchangshan Island in the Shandong Province. We measured beach profile, collected gravel samples and took gravel images. Using the software ImageJ for digital image measurement in situ without interference, we can quickly obtain a large number of gravel morphologic parameters, including particle size, grinding roundness and shape ratio. The results show that the range of the particle size is 4−79 mm, which was mainly pebbles. The average particle size of the beach in the Beichangshan Island is slightly smaller than that in the Nanchangshan Island, with the largest average particle size of gravels in the Jiuzhangya Beach of the Beichangshan Island and the smallest one in the Xianjingyuan Beach of the Nanchangshan Island. From beach berm to the high tidal line, the average particle size decreases gradually, but increases at waterline. The range of roundness of gravel is 0.59–0.75, and the grade is round. The gravel beaches have reached a relatively mature stage based on roundness, with the best roundness in the Yueyawan Beach and the worst roundness in the Changtan Beach of the Beichangshan Island. The gravel roundness increases from land to sea. The shape ratio ranges from 1.36 to 1.77, which is negatively correlated with the gravel roundness (R2=0.98). The gravel gradually changed from long strip to elliptic shape from land to sea. The gravel beaches morphology of the Changshan Island is affected by the provenances, dynamic conditions and human activities. The slope range of the gravel beach in the study area is 16%−35%, and they are positively correlated with the gravel particle size.
2021, 43(1): 55-60.
doi: 10.12284/hyxb2021031
Abstract:
A submarine mooring system was deployed in the east of the Luzon Strait and the vertical distribution of high frequency (mostly tidal) variations of ocean currents were analyzed in the paper. Several features were revealed that the tidal kinetic energy of the middle (1 550 m) and the deep layers（2 560 m） was one to two orders smaller than that of the subsurface layers (100−160 m) , and slightly smaller than that of the near-bottom layers (4 040 m); the tidal currents were irregular semi-diurnal in the subsurface layers and were irregular diurnal in the middle and deep layers; the tidal kinetic energy was larger in summer (June to September) and winter (February to March) , which mainly caused by enhancement of M2 and K1 tidal components in corresponding periods; the high frequency fluctuations in all layers were mainly in clockwise rotation; the near-inertial frequency in the upper layers (middle and deep layers) were close to (slightly smaller than) the local inertial frequency.
A submarine mooring system was deployed in the east of the Luzon Strait and the vertical distribution of high frequency (mostly tidal) variations of ocean currents were analyzed in the paper. Several features were revealed that the tidal kinetic energy of the middle (1 550 m) and the deep layers（2 560 m） was one to two orders smaller than that of the subsurface layers (100−160 m) , and slightly smaller than that of the near-bottom layers (4 040 m); the tidal currents were irregular semi-diurnal in the subsurface layers and were irregular diurnal in the middle and deep layers; the tidal kinetic energy was larger in summer (June to September) and winter (February to March) , which mainly caused by enhancement of M2 and K1 tidal components in corresponding periods; the high frequency fluctuations in all layers were mainly in clockwise rotation; the near-inertial frequency in the upper layers (middle and deep layers) were close to (slightly smaller than) the local inertial frequency.
2021, 43(1): 61-68.
doi: 10.12284/hyxb2021013
Abstract:
Based on the hybrid detection method for ocean mesoscale eddy, this paper uses the measured data to verify the detected boundary and center of eddy, and draws the following conclusions. (1) By diagnosing the angle between the detected boundary and the measured current vector, the results show that the detected boundary of eddy can basically reflect the current state of the actual eddy. (2) The center of detected eddy is compareed with the center that inversed by the measured current and temperature data. The results show that the detected center of eddy is basically consistent with the inversed center. Furthermore, by comparing the fitting effect of circle and ellipse to the detected boundary of eddy, the results show that the fitting accuracy of ellipse is higher than that of circle.
Based on the hybrid detection method for ocean mesoscale eddy, this paper uses the measured data to verify the detected boundary and center of eddy, and draws the following conclusions. (1) By diagnosing the angle between the detected boundary and the measured current vector, the results show that the detected boundary of eddy can basically reflect the current state of the actual eddy. (2) The center of detected eddy is compareed with the center that inversed by the measured current and temperature data. The results show that the detected center of eddy is basically consistent with the inversed center. Furthermore, by comparing the fitting effect of circle and ellipse to the detected boundary of eddy, the results show that the fitting accuracy of ellipse is higher than that of circle.
2021, 43(1): 69-81.
doi: 10.12284/hyxb2021075
Abstract:
Based on the WRF (Weather Research and Forecasting Model) and its three-dimensional variational data assimilation system, the numerical simulation and Doppler radar data assimilation are conducted with the data of GFS (Global Forecasting System) and JMA (Japan Meteorological Agency) reanalyses as the initial conditions respectively. The impact of assimilation radar data in different background fields on the initial typhoon field, internal structure and forecast were investigated based on the super typhoon case Saomai in 2006. The results show that, both experiments with GFS and JMA data are able to enhance the typhoon initial winds field at 700 hPa and geopotential height field at 500 hPa after assimilating radar observations. The improvements in terms of the root-mean-square error during the 3 h during the data assimilation cycling, the minimum sea level pressure, and the thermal and dynamic structure from the JMA tests are more significant than that with GFS data. The forecast skills for the precipitation, the typhoon track, and the intensity are also noticeable with JMA data by correctly predicting the precipitation location in the front of typhoon.
Based on the WRF (Weather Research and Forecasting Model) and its three-dimensional variational data assimilation system, the numerical simulation and Doppler radar data assimilation are conducted with the data of GFS (Global Forecasting System) and JMA (Japan Meteorological Agency) reanalyses as the initial conditions respectively. The impact of assimilation radar data in different background fields on the initial typhoon field, internal structure and forecast were investigated based on the super typhoon case Saomai in 2006. The results show that, both experiments with GFS and JMA data are able to enhance the typhoon initial winds field at 700 hPa and geopotential height field at 500 hPa after assimilating radar observations. The improvements in terms of the root-mean-square error during the 3 h during the data assimilation cycling, the minimum sea level pressure, and the thermal and dynamic structure from the JMA tests are more significant than that with GFS data. The forecast skills for the precipitation, the typhoon track, and the intensity are also noticeable with JMA data by correctly predicting the precipitation location in the front of typhoon.
2021, 43(1): 82-92.
doi: 10.12284/hyxb2021007
Abstract:
In the present study, the connection between the Arctic Oscillation (AO) in May and the following summer (June to September) western North Pacific tropical cyclone genesis frequency is investigated based on NCEP/NCAR reanalysis data and tropical cyclone data from China Meteorological Administration for the period 1950–2018. A statistically significant positive correlation is found between the late spring AO and summer tropical cyclone genesis frequency. The diagnosis results show that the low-level relative vorticity, high-level divergence, vertical wind shear and the mid-low level relative humidity are all beneficial for the genesis of the western North Pacific tropical cyclones during the positive AO years. Moreover, the western Pacific subtropical high shifts eastward and northward and tends to be much weaker. On the contrary, during the negative AO years, the tropical cyclone formation is reduced because of the strengthened western Pacific subtropical high combined with an anticyclonic vorticity in the lower troposphere. The possible mechanism involved the variations of the storm track in the North Pacific. It is showed that during the positive (negative) AO years the storm track is moving northward (southward) and there is a cyclonic (an anticyclonic) vorticity anomaly in the lower troposphere in the western North Pacific in the subsequent summer through the interaction between the synoptic-scale eddies and low-frequency mean flow. The resulting anomalous local Hadley circulation could lead to the change of the western Pacific subtropical high and further contribute to the western North Pacific tropical cyclogenesis.
In the present study, the connection between the Arctic Oscillation (AO) in May and the following summer (June to September) western North Pacific tropical cyclone genesis frequency is investigated based on NCEP/NCAR reanalysis data and tropical cyclone data from China Meteorological Administration for the period 1950–2018. A statistically significant positive correlation is found between the late spring AO and summer tropical cyclone genesis frequency. The diagnosis results show that the low-level relative vorticity, high-level divergence, vertical wind shear and the mid-low level relative humidity are all beneficial for the genesis of the western North Pacific tropical cyclones during the positive AO years. Moreover, the western Pacific subtropical high shifts eastward and northward and tends to be much weaker. On the contrary, during the negative AO years, the tropical cyclone formation is reduced because of the strengthened western Pacific subtropical high combined with an anticyclonic vorticity in the lower troposphere. The possible mechanism involved the variations of the storm track in the North Pacific. It is showed that during the positive (negative) AO years the storm track is moving northward (southward) and there is a cyclonic (an anticyclonic) vorticity anomaly in the lower troposphere in the western North Pacific in the subsequent summer through the interaction between the synoptic-scale eddies and low-frequency mean flow. The resulting anomalous local Hadley circulation could lead to the change of the western Pacific subtropical high and further contribute to the western North Pacific tropical cyclogenesis.
2021, 43(1): 122-136.
doi: 10.12284/hyxb2021015
Abstract:
It is a common ocean phenomenon that eddies attract each other and propagate in the form of dipole mode, and these dipoles play an important role in transporting seawater, nutrients and other substances. In this paper, a global dipole pair automatic recognition method based on the eddy trajectory data is proposed. By using the K–D tree for cutting space, the eddy trajectory data are calculated from January 1993 to September 2016, and a total of 86 662 westward moving dipoles and 30 590 eastward moving dipoles with a life cycle of more than 60 days are found. The global characteristics of the dipole that we detected are analyzed, and the reliability of the automatic recognition algorithm is verified by the comparison and test with sea surface temperature anomaly and sea surface salinity anomaly. Finally in this paper, the transmission modes and characteristics of dipoles are analyzed, including the characteristics of long life, high propagation speed and entanglement trajectory.
It is a common ocean phenomenon that eddies attract each other and propagate in the form of dipole mode, and these dipoles play an important role in transporting seawater, nutrients and other substances. In this paper, a global dipole pair automatic recognition method based on the eddy trajectory data is proposed. By using the K–D tree for cutting space, the eddy trajectory data are calculated from January 1993 to September 2016, and a total of 86 662 westward moving dipoles and 30 590 eastward moving dipoles with a life cycle of more than 60 days are found. The global characteristics of the dipole that we detected are analyzed, and the reliability of the automatic recognition algorithm is verified by the comparison and test with sea surface temperature anomaly and sea surface salinity anomaly. Finally in this paper, the transmission modes and characteristics of dipoles are analyzed, including the characteristics of long life, high propagation speed and entanglement trajectory.
2021, 43(1): 137-146.
doi: 10.12284/hyxb2021011
Abstract:
Himawari-8 is a new generation geostationary meteorological satellite launched by the Japan Meteorological Agency, and provides the important observation data for merging hourly sea surface temperature (SST). This paper uses the optimal interpolation method to provide the hourly Northwest Pacific SST based on the Advanced Himawari Imagery(AHI) SST, the Global Change Observation Mission-Water (GCOM-W1) Advanced Microwave Scanning Radiometer 2 (AMSR2) SST and North-East Asian Regional–Global Ocean Observing System (NEAR-GOOS) SST. The diurnal SST variation and the bias between multi-source SSTs are the two significant factors affecting the accuracy of hourly SST fusion products. In order to make full use of SST at the adjacent time and improve the accuracy, a diurnal variation model of Himawari-8 AHI SST is established by using the matchup data set, which contains simultaneous Himawari-8 AHI SST and European Centre for Medium-Range Weather Forecasts wind data at the same location. In addition, a bias correction method based on Poisson’s equation is applied to correct GCOM-W1 AMSR2 SST biases relative to the AHI SST. The experimental results show that the diurnal warming calculated by the hourly SST fusion product is closely related to sea surface wind speed, which indirectly confirms the accuracy of the hourly SST fusion products. The root mean square difference and bias between the hourly SST fusion product and NEAR-GOOS SST are 0.89℃ and 0.09℃, respectively. The results show that the hourly SST fusion product is basically consistent with the in situ SST.
Himawari-8 is a new generation geostationary meteorological satellite launched by the Japan Meteorological Agency, and provides the important observation data for merging hourly sea surface temperature (SST). This paper uses the optimal interpolation method to provide the hourly Northwest Pacific SST based on the Advanced Himawari Imagery(AHI) SST, the Global Change Observation Mission-Water (GCOM-W1) Advanced Microwave Scanning Radiometer 2 (AMSR2) SST and North-East Asian Regional–Global Ocean Observing System (NEAR-GOOS) SST. The diurnal SST variation and the bias between multi-source SSTs are the two significant factors affecting the accuracy of hourly SST fusion products. In order to make full use of SST at the adjacent time and improve the accuracy, a diurnal variation model of Himawari-8 AHI SST is established by using the matchup data set, which contains simultaneous Himawari-8 AHI SST and European Centre for Medium-Range Weather Forecasts wind data at the same location. In addition, a bias correction method based on Poisson’s equation is applied to correct GCOM-W1 AMSR2 SST biases relative to the AHI SST. The experimental results show that the diurnal warming calculated by the hourly SST fusion product is closely related to sea surface wind speed, which indirectly confirms the accuracy of the hourly SST fusion products. The root mean square difference and bias between the hourly SST fusion product and NEAR-GOOS SST are 0.89℃ and 0.09℃, respectively. The results show that the hourly SST fusion product is basically consistent with the in situ SST.
2021, 43(1): 147-154.
doi: 10.12284/hyxb2021005
Abstract:
The diffuse attenuation coefficient (Kd) is an important marine optical parameter, which can provide the basic data for the water environment change, the water quality analysis and the aquaculture. There are some limitations of the traditional methods, such as the low efficiency and resolution of the traditional shipborne field measurement and the rough inversion accuracy and spatial resolution of the satellite remote sensing. Therefore, an extraction method for diffuse attenuation coefficient based on airborne LiDAR bathymetric water column waveform is proposed in this paper. Firstly, the water column contribution is decomposed by the waveform decomposition algorithm for airborne LiDAR bathymetry based on the layered heterogeneous model. Then, according to the attenuation characteristics of laser in water, the diffuse attenuation coefficient extraction model is constructed. Finally, the diffuse attenuation coefficient spatial distribution in a large area of water is obtained. The performance of the proposed method was verified by the measured data from the Ganquan Island in the Xisha Archipelago and the Lianyungang’s seacoast. The experimental results demonstrated that the proposed method could obtain the diffuse attenuation coefficient without the water bottom contribution intensity and depth information for each bathymetric point. And the good results were also achieved in turbid waters. Meanwhile, the proposed method showed the feasibility of employing the ALB system to obtain the high-precision diffuse attenuation coefficient in China coastal waters.
The diffuse attenuation coefficient (Kd) is an important marine optical parameter, which can provide the basic data for the water environment change, the water quality analysis and the aquaculture. There are some limitations of the traditional methods, such as the low efficiency and resolution of the traditional shipborne field measurement and the rough inversion accuracy and spatial resolution of the satellite remote sensing. Therefore, an extraction method for diffuse attenuation coefficient based on airborne LiDAR bathymetric water column waveform is proposed in this paper. Firstly, the water column contribution is decomposed by the waveform decomposition algorithm for airborne LiDAR bathymetry based on the layered heterogeneous model. Then, according to the attenuation characteristics of laser in water, the diffuse attenuation coefficient extraction model is constructed. Finally, the diffuse attenuation coefficient spatial distribution in a large area of water is obtained. The performance of the proposed method was verified by the measured data from the Ganquan Island in the Xisha Archipelago and the Lianyungang’s seacoast. The experimental results demonstrated that the proposed method could obtain the diffuse attenuation coefficient without the water bottom contribution intensity and depth information for each bathymetric point. And the good results were also achieved in turbid waters. Meanwhile, the proposed method showed the feasibility of employing the ALB system to obtain the high-precision diffuse attenuation coefficient in China coastal waters.
2021, 43(1): 155-164.
doi: 10.12284/hyxb2021035
Abstract:
In order to find an effective way to reverse the decline in the health of the oceans, the United Nations has decided to launch the "United Nations Decade of Ocean Science for Sustainable Development" (hereinafter referred to as the "Ocean Decade") since 2021. The Implementation Plan of Ocean Decade, which has been aceepted by the United Nations General Assembly on September 31, 2020, outlines the Ocean Decade’s vision of “building the science we need and the ocean we want”, and sets out the outcomes, challenges and objectives of the Ocean Decade, as well as mechanisms for implementation, governance, coordination, financing, monitoring and review. Described by the United Nations as a “once in a lifetime” programme, the Ocean Decade is a comprehensive United Nations-sponsored capstone programme for Ocean Megasciences that will build stronger science and technology innovation-based governance system at the global and national levels by inspiring and driving change in marine science. This will profoundly change human cognition and behavioural patterns towards the oceans, profoundly influence and even guide the evolution of the marine order, and have a great impact on the overall layout of regional cooperation in the oceans. It is suggested that China, guided by the concept of the “Marine Community with Shared Future”, actively participate in the Ocean Decade as a core means of deepening its participation in global ocean governance, and establish the Ocean Decade National Committee as soon as possible, and develop a Chinese programme of action to advance the sustainable development of the oceans and seas together with the international community.
In order to find an effective way to reverse the decline in the health of the oceans, the United Nations has decided to launch the "United Nations Decade of Ocean Science for Sustainable Development" (hereinafter referred to as the "Ocean Decade") since 2021. The Implementation Plan of Ocean Decade, which has been aceepted by the United Nations General Assembly on September 31, 2020, outlines the Ocean Decade’s vision of “building the science we need and the ocean we want”, and sets out the outcomes, challenges and objectives of the Ocean Decade, as well as mechanisms for implementation, governance, coordination, financing, monitoring and review. Described by the United Nations as a “once in a lifetime” programme, the Ocean Decade is a comprehensive United Nations-sponsored capstone programme for Ocean Megasciences that will build stronger science and technology innovation-based governance system at the global and national levels by inspiring and driving change in marine science. This will profoundly change human cognition and behavioural patterns towards the oceans, profoundly influence and even guide the evolution of the marine order, and have a great impact on the overall layout of regional cooperation in the oceans. It is suggested that China, guided by the concept of the “Marine Community with Shared Future”, actively participate in the Ocean Decade as a core means of deepening its participation in global ocean governance, and establish the Ocean Decade National Committee as soon as possible, and develop a Chinese programme of action to advance the sustainable development of the oceans and seas together with the international community.
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