2017 Vol. 39, No. 11
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2017, 39(11): .
Abstract:
2017, 39(11): 1-13.
doi: 10.3969/j.issn.0253-4193.2017.11.001
Abstract:
Harbor resonance is phenomenon that large oscillations within the harbor are forced at one or more of its natural frequencies. It is crucial in the locally coastal hydrodynamics and ship navigation, and further affect the protection and evaluation of water disaster. This paper presents an overview of harbor resonance and seiches, including resonance mechanism, external forcing and simulation methods. Several typical events in China have been detailed, especially for their resonance characteristics and generation mechanisms. Finally, several prospects are put forward based on the coastal characteristics and current research foundation.
Harbor resonance is phenomenon that large oscillations within the harbor are forced at one or more of its natural frequencies. It is crucial in the locally coastal hydrodynamics and ship navigation, and further affect the protection and evaluation of water disaster. This paper presents an overview of harbor resonance and seiches, including resonance mechanism, external forcing and simulation methods. Several typical events in China have been detailed, especially for their resonance characteristics and generation mechanisms. Finally, several prospects are put forward based on the coastal characteristics and current research foundation.
2017, 39(11): 14-23.
doi: 10.3969/j.issn.0253-4193.2017.11.002
Abstract:
Impact of wind drag coefficients in SWAN model on wave simulation was studied in the paper. Sensitivity experiments were conducted under wind speed 14 m/s, 31.5 m/s and 50 m/s (representing the conditions of strong wind, strong tropical storm and strong typhoon, respectively). Haringvliet in Holland was chosen as experimental area. Results show that in shallow water (shallower than 20 m), the wind drag coefficient has little effect on significant wave height. When the wind speed reaches a certain speed, wave breaking becomes a major factor affecting the significant wave height. In deep water (deeper than 30 m), the effect of wind drag coefficients on significant wave height is still small in condition of strong wind. As the wind speed increases further, the influence of wind drag coefficients on significant wave height becomes obvious gradually. The wind drag coefficient and wind speed have little influence on mean wave period whereas the wave breaking affects it significantly. According to the results of sensitivity experiments, choice of wind drag coefficients in SWAN model is suggested as follows. When the wind waves in shallow water are simulated, the default wind drag coefficient in SWAN can be directly used. As for deep water case, the default wind drag coefficient can be applied in condition of strong wind. When the wind speed is higher, the default wind drag coefficient can be tested firstly, and then it can be modified in terms of the field data if needed.
Impact of wind drag coefficients in SWAN model on wave simulation was studied in the paper. Sensitivity experiments were conducted under wind speed 14 m/s, 31.5 m/s and 50 m/s (representing the conditions of strong wind, strong tropical storm and strong typhoon, respectively). Haringvliet in Holland was chosen as experimental area. Results show that in shallow water (shallower than 20 m), the wind drag coefficient has little effect on significant wave height. When the wind speed reaches a certain speed, wave breaking becomes a major factor affecting the significant wave height. In deep water (deeper than 30 m), the effect of wind drag coefficients on significant wave height is still small in condition of strong wind. As the wind speed increases further, the influence of wind drag coefficients on significant wave height becomes obvious gradually. The wind drag coefficient and wind speed have little influence on mean wave period whereas the wave breaking affects it significantly. According to the results of sensitivity experiments, choice of wind drag coefficients in SWAN model is suggested as follows. When the wind waves in shallow water are simulated, the default wind drag coefficient in SWAN can be directly used. As for deep water case, the default wind drag coefficient can be applied in condition of strong wind. When the wind speed is higher, the default wind drag coefficient can be tested firstly, and then it can be modified in terms of the field data if needed.
2017, 39(11): 24-36.
doi: 10.3969/j.issn.0253-4193.2017.11.003
Abstract:
Three sets of mooring Acoustic Doppler Current Profiler (ADCP) data across the continental slope and shelf area in the northern South China Sea are used to study the kinetic energy characteristics of diurnal and semidiurnal coherent and incoherent internal tides (ITs). Research shows that when diurnal ITs spread along continental slope and continental shelf, it is dominated by diurnal coherent ITs kinetic energy generation in the continental slope and the average diurnal coherent ITs kinetic energy generation rate is 2.32 J/(m3·s). It is dominated by diurnal coherent ITs kinetic energy dissipation in the continental shelf and the average diurnal coherent ITs kinetic energy dissipation rate is 0.44 J/(m3·s). The kinetic energy of diurnal incoherent ITs increases in both the continental slope and the continental shelf and the average diurnal incoherent ITs kinetic energy generation rate are 0.39 and 0.03 J/(m3·s). The kinetic energy characteristics of diurnal and semidiurnal coherent ITs are different in the continental slope and continental shelf. It showed that the kinetic energy of diurnal coherent ITs in the continental slope is significantly greater than the kinetic energy of diurnal coherent ITs in the continental shelf, but the kinetic energy of semidiurnal coherent ITs energy had no significant difference in the continental slope and continental shelf. The kinetic energy of diurnal and semidiurnal incoherent ITs in the continental shelf is greater than that in the continental slope.
Three sets of mooring Acoustic Doppler Current Profiler (ADCP) data across the continental slope and shelf area in the northern South China Sea are used to study the kinetic energy characteristics of diurnal and semidiurnal coherent and incoherent internal tides (ITs). Research shows that when diurnal ITs spread along continental slope and continental shelf, it is dominated by diurnal coherent ITs kinetic energy generation in the continental slope and the average diurnal coherent ITs kinetic energy generation rate is 2.32 J/(m3·s). It is dominated by diurnal coherent ITs kinetic energy dissipation in the continental shelf and the average diurnal coherent ITs kinetic energy dissipation rate is 0.44 J/(m3·s). The kinetic energy of diurnal incoherent ITs increases in both the continental slope and the continental shelf and the average diurnal incoherent ITs kinetic energy generation rate are 0.39 and 0.03 J/(m3·s). The kinetic energy characteristics of diurnal and semidiurnal coherent ITs are different in the continental slope and continental shelf. It showed that the kinetic energy of diurnal coherent ITs in the continental slope is significantly greater than the kinetic energy of diurnal coherent ITs in the continental shelf, but the kinetic energy of semidiurnal coherent ITs energy had no significant difference in the continental slope and continental shelf. The kinetic energy of diurnal and semidiurnal incoherent ITs in the continental shelf is greater than that in the continental slope.
2017, 39(11): 37-48.
doi: 10.3969/j.issn.0253-4193.2017.11.004
Abstract:
Under the background of climatic warming, the global ocean temperature increased and the sea level rose significantly, imposing enormous challenges to the sustainable development of human society. The upper ocean heat condition is one of the dominant factors of sea level change. Focusing on the 21st century Silk Road Maritime Region (SRMR), the local spatial and temporal characteristics of the upper ocean heat content were analyzed, furthermore, the change and evolution characteristics of thermosteric sea level and associated impaction were discussed, in order to give the services supporting for marine environment security of "21st century Maritime Silk Road". The analysis results show that, since the 1970s, the upper layer (0-700 m) ocean of SRMR began to warm obviously, and especially presented significant larger warming from the middle of 1990s. Recently 60 years, in tropical oceans of the SRMR, the North Equatorial Current and its north sea area in the western Pacific, the China seas including the north and the south of the South China Sea (SCS) and the Kuroshio valley in East China Sea, the northwest coastal waters in Arabian sea, the sea area of northwest of Malaysia and south part of the Indian Ocean had a long-term heating trend. The warming of the whole region of tropical western Pacific warm pool was not obvious, and presented mainly anti-phase change with the central Indian Ocean, which were modulated by seasonal and interannual variability. The coastal zones of the eastern China seas near the Changjiang River Estuary, the north of the SCS, the southern of Indo-China Peninsula, the northwestern of Arabian Sea had an obviously long-term warming. Since the middle of the 1990s, the thermosteric sea level in costal zones of the east and west of Indo-China Peninsula, the west of Australia and the China seas have rose obviously. The seasonal evolution of thermosteric sea level rising can cause a certain degree of impact on social and economic development in coastal zones. In addition, the East Asian summer monsoon was significantly associated with the thermosteric sea level rising in eastern China seas, at the same time, the ENSO, the PDO and the IOD also related distinctly to the thermosteric sea level rising in coastal zones in China seas and the western Indian Ocean. Particularly, in climate warming scenario, due to the synergy impaction of regional disaster-causing factors and climate variability, the social and economic development and the disaster prevention and mitigation in coastal zones in SRMR would be subject to huge challenges. The study of comprehensive risk of coastal zones by global change has become the top priority.
Under the background of climatic warming, the global ocean temperature increased and the sea level rose significantly, imposing enormous challenges to the sustainable development of human society. The upper ocean heat condition is one of the dominant factors of sea level change. Focusing on the 21st century Silk Road Maritime Region (SRMR), the local spatial and temporal characteristics of the upper ocean heat content were analyzed, furthermore, the change and evolution characteristics of thermosteric sea level and associated impaction were discussed, in order to give the services supporting for marine environment security of "21st century Maritime Silk Road". The analysis results show that, since the 1970s, the upper layer (0-700 m) ocean of SRMR began to warm obviously, and especially presented significant larger warming from the middle of 1990s. Recently 60 years, in tropical oceans of the SRMR, the North Equatorial Current and its north sea area in the western Pacific, the China seas including the north and the south of the South China Sea (SCS) and the Kuroshio valley in East China Sea, the northwest coastal waters in Arabian sea, the sea area of northwest of Malaysia and south part of the Indian Ocean had a long-term heating trend. The warming of the whole region of tropical western Pacific warm pool was not obvious, and presented mainly anti-phase change with the central Indian Ocean, which were modulated by seasonal and interannual variability. The coastal zones of the eastern China seas near the Changjiang River Estuary, the north of the SCS, the southern of Indo-China Peninsula, the northwestern of Arabian Sea had an obviously long-term warming. Since the middle of the 1990s, the thermosteric sea level in costal zones of the east and west of Indo-China Peninsula, the west of Australia and the China seas have rose obviously. The seasonal evolution of thermosteric sea level rising can cause a certain degree of impact on social and economic development in coastal zones. In addition, the East Asian summer monsoon was significantly associated with the thermosteric sea level rising in eastern China seas, at the same time, the ENSO, the PDO and the IOD also related distinctly to the thermosteric sea level rising in coastal zones in China seas and the western Indian Ocean. Particularly, in climate warming scenario, due to the synergy impaction of regional disaster-causing factors and climate variability, the social and economic development and the disaster prevention and mitigation in coastal zones in SRMR would be subject to huge challenges. The study of comprehensive risk of coastal zones by global change has become the top priority.
2017, 39(11): 49-60.
doi: 10.3969/j.issn.0253-4193.2017.11.005
Abstract:
On September 16, 2015, at 19:54 (local time) a magnitude Mw 8.3 earthquake took place off the coast of central Chile, focal depth of 25 km. Meanwhile, the earthquake with rupture zone 200 km long and 100 km wide triggered moderate intensity teletsunami. The tsunami impacted approximately 700 km of the coast of Chile, some areas tsunami reached amplitudes near 5 m and tsunami run-up exceeded 13 m. Tsunami waves were subsequently recorded by more than 40 Deep-ocean Assessment and Reporting of Tsunami (DART) buoys in the Pacific Ocean and more than 200 tide gauges throughout the Pacific Ocean, a rich supply of data which study the tsunami propagation scenarios in near-filed and deep-water. This paper used the finite fault models and adaptive refinement algorithms to build a well computational efficiency and high resolution numerical tsunami model. We analyzed the teletsunami propagation characteristics. The results show that by using the established model can well reproduce the far-field and near-field tsunami process, especially on the near-field the simulation results fit well with the observational data. It indicates that the finite fault model can better depict the near-field, especially the rupture characteristics and provide more accurate source information. The fine prediction of tsunami propagation characteristics can be achieved by the finite fault model and high resolution numerical tsunami model. In this paper, using the observation data and simulation results, analyzed the frequency dispersion of the tsunami wave and its influence on the model. Meanwhile, carried out a brief summary of the typical characteristics of the tsunami wave. The wavelet analysis show that the tsunami energy is concentrated in the period band of around 10-50 min. These wave characteristics are not involved in the current tsunami warning information, but they are very important parameters. Further research on these characteristics will provide technical support for the improvement of tsunami warning information and warning products.
On September 16, 2015, at 19:54 (local time) a magnitude Mw 8.3 earthquake took place off the coast of central Chile, focal depth of 25 km. Meanwhile, the earthquake with rupture zone 200 km long and 100 km wide triggered moderate intensity teletsunami. The tsunami impacted approximately 700 km of the coast of Chile, some areas tsunami reached amplitudes near 5 m and tsunami run-up exceeded 13 m. Tsunami waves were subsequently recorded by more than 40 Deep-ocean Assessment and Reporting of Tsunami (DART) buoys in the Pacific Ocean and more than 200 tide gauges throughout the Pacific Ocean, a rich supply of data which study the tsunami propagation scenarios in near-filed and deep-water. This paper used the finite fault models and adaptive refinement algorithms to build a well computational efficiency and high resolution numerical tsunami model. We analyzed the teletsunami propagation characteristics. The results show that by using the established model can well reproduce the far-field and near-field tsunami process, especially on the near-field the simulation results fit well with the observational data. It indicates that the finite fault model can better depict the near-field, especially the rupture characteristics and provide more accurate source information. The fine prediction of tsunami propagation characteristics can be achieved by the finite fault model and high resolution numerical tsunami model. In this paper, using the observation data and simulation results, analyzed the frequency dispersion of the tsunami wave and its influence on the model. Meanwhile, carried out a brief summary of the typical characteristics of the tsunami wave. The wavelet analysis show that the tsunami energy is concentrated in the period band of around 10-50 min. These wave characteristics are not involved in the current tsunami warning information, but they are very important parameters. Further research on these characteristics will provide technical support for the improvement of tsunami warning information and warning products.
2017, 39(11): 61-74.
doi: 10.3969/j.issn.0253-4193.2017.11.006
Abstract:
Based on extended SST data (ERSST V3b) from NOAA Climate Prediction Center(CPC), monthly China 160 stations' precipitation data from National Climate Center(NCC) and monthly mean horizontal wind velocity, vertical velocity and humidity data at pressure level from the National Center for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR), the impacts of two types of El Niño events over South China precipitation in autumn was discussed. And the focus was on the impacts of different sea surface temperature anomaly modes in Indian Ocean on the relationship between two types of El Niño Events and South China autumn rainfall. The results show that during the EP(CP) El Niño autumn, precipitation in south of the Changjiang River in China is more (less).When EP El Niño and India Ocean dipole (IOD) occur simultaneously, rainfall in autumn over South China is much more than that of not considering SST of India Ocean. When CP El Niño and IOD occur simultaneously, precipitation in Southwest China is more and that in Southeast China is less. When CP El Niño and India Ocean Basin Warming (IOB) occur at the same time, rainfall over South China in autumn is less, and the less degree is greater than that without considering SST anomaly of India Ocean. In addition, the circulation cause of the Indian Ocean SST's impacrtcs was analyzed.
Based on extended SST data (ERSST V3b) from NOAA Climate Prediction Center(CPC), monthly China 160 stations' precipitation data from National Climate Center(NCC) and monthly mean horizontal wind velocity, vertical velocity and humidity data at pressure level from the National Center for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR), the impacts of two types of El Niño events over South China precipitation in autumn was discussed. And the focus was on the impacts of different sea surface temperature anomaly modes in Indian Ocean on the relationship between two types of El Niño Events and South China autumn rainfall. The results show that during the EP(CP) El Niño autumn, precipitation in south of the Changjiang River in China is more (less).When EP El Niño and India Ocean dipole (IOD) occur simultaneously, rainfall in autumn over South China is much more than that of not considering SST of India Ocean. When CP El Niño and IOD occur simultaneously, precipitation in Southwest China is more and that in Southeast China is less. When CP El Niño and India Ocean Basin Warming (IOB) occur at the same time, rainfall over South China in autumn is less, and the less degree is greater than that without considering SST anomaly of India Ocean. In addition, the circulation cause of the Indian Ocean SST's impacrtcs was analyzed.
2017, 39(11): 75-84.
doi: 10.3969/j.issn.0253-4193.2017.11.007
Abstract:
The total organic carbon (TOC), total nitrogen (TN), C/N ratios and the stable carbon isotope of bulk sediment organic matter (δ13Corg) in the GHE27L and GHE24L cores, collected from Shenhu area in the northern South China Sea (NSCS), were analyzed to reveal the composition of sedimentary organic matter (OM) and the paleoclimate changes since the Last Maximum Glacial (LMG). The values of TOC, TN, C/N, and δ13Corg ranged from 0.53% to 1.81%, 0.07% to 0.18%, 8.2 to 16.0 and-23.6‰ to 20.3‰ in Core GHE27L, and 0.45% to 1.65%, 0.09% to 0.24%, 5.3 to 12.2 and-22.6‰ to-20.4‰ in Core GHE24L, respectively. The profiles of bulk OM indicated that the OM mixed origins from both terrigenous and marine OM, and that marine OC was the major source of OC in the NSCS since the LGM. The relative contribution of terrigenous OM in the glaciation was higher than that in the Holocene. The climate was dry and C4 plants were to thrive in the NSCS during the last glaciation. The precipitation enhanced due to the strong summer Asian Monsoon in the NSCS during the Holocene. However, it seems that the primary productivity in the NSCS was impacted by the anthropogenic activities since the last 2.0 ka BP.
The total organic carbon (TOC), total nitrogen (TN), C/N ratios and the stable carbon isotope of bulk sediment organic matter (δ13Corg) in the GHE27L and GHE24L cores, collected from Shenhu area in the northern South China Sea (NSCS), were analyzed to reveal the composition of sedimentary organic matter (OM) and the paleoclimate changes since the Last Maximum Glacial (LMG). The values of TOC, TN, C/N, and δ13Corg ranged from 0.53% to 1.81%, 0.07% to 0.18%, 8.2 to 16.0 and-23.6‰ to 20.3‰ in Core GHE27L, and 0.45% to 1.65%, 0.09% to 0.24%, 5.3 to 12.2 and-22.6‰ to-20.4‰ in Core GHE24L, respectively. The profiles of bulk OM indicated that the OM mixed origins from both terrigenous and marine OM, and that marine OC was the major source of OC in the NSCS since the LGM. The relative contribution of terrigenous OM in the glaciation was higher than that in the Holocene. The climate was dry and C4 plants were to thrive in the NSCS during the last glaciation. The precipitation enhanced due to the strong summer Asian Monsoon in the NSCS during the Holocene. However, it seems that the primary productivity in the NSCS was impacted by the anthropogenic activities since the last 2.0 ka BP.
2017, 39(11): 85-96.
doi: 10.3969/j.issn.0253-4193.2017.11.008
Abstract:
Ability of marine multi-electrode resisitivity method to detect the process of cold spring gas leakage in seabed sediment would been analysed and evaluated in this paper. In order to meet this object, on the base of predecessors' research results and some concrete examples, the geoelectric models of sediments were built, then theoretical electrical resisitivity sections were calculated while marine multi-electrode resisitivity method was used to detect the gathering, leaking and erupting of fast or slow cold spring gas in seabed sediment. Compare the numerical simulation resisitivity images and experimental ones, some results have been generalized. In the detected section images of rapid cold spring. Gas bearing layer and leakage passages in different phases of leakage performanced for different anomaly resistivity image characteristics, but they were easy to identify. In the detected section images of slow cold spring, gas enrichment region in shallow sediment showed obvious high resistivity anomaly. As the gas leaked, abnormal area gradually disappeared. Two types of landforms formed by gas eruption process could also be reflected in the detected images. Marine multi-electrode resisitivity method was proved to be an effective method which could describe the gas bearing layer, leakage passage and spatial distribution of gas and liquid interface position with measured anomaly images.
Ability of marine multi-electrode resisitivity method to detect the process of cold spring gas leakage in seabed sediment would been analysed and evaluated in this paper. In order to meet this object, on the base of predecessors' research results and some concrete examples, the geoelectric models of sediments were built, then theoretical electrical resisitivity sections were calculated while marine multi-electrode resisitivity method was used to detect the gathering, leaking and erupting of fast or slow cold spring gas in seabed sediment. Compare the numerical simulation resisitivity images and experimental ones, some results have been generalized. In the detected section images of rapid cold spring. Gas bearing layer and leakage passages in different phases of leakage performanced for different anomaly resistivity image characteristics, but they were easy to identify. In the detected section images of slow cold spring, gas enrichment region in shallow sediment showed obvious high resistivity anomaly. As the gas leaked, abnormal area gradually disappeared. Two types of landforms formed by gas eruption process could also be reflected in the detected images. Marine multi-electrode resisitivity method was proved to be an effective method which could describe the gas bearing layer, leakage passage and spatial distribution of gas and liquid interface position with measured anomaly images.
2017, 39(11): 97-105.
doi: 10.3969/j.issn.0253-4193.2017.11.009
Abstract:
The photosynthetically active radiation (PAR) is one of the most important factors driving the variations in ocean primary productivity, implying that the PAR may have potential influence on the abundance and spatial distribution of pelagic fish species. In this study, the catch per unit effort (CPUE) and the latitudinal gravity center (LATG) of CPUE was used to indicate the squid abundance and spatial distribution of fishing ground, respectively, we evaluated the influence of PAR on stock variation of jumbo flying squid Dosidicus gigas in the Southeast Pacific Ocean off Peru, based on the fishery data during 2006-2015 obtained from the Chinese squid-jigging Science and Technology Group as well as the remotely satellite data. The results indicated that the catch, fishing effort, CPUE and PAR exhibited significant monthly variations. The CPUE and PAR showed the similar trend, decreasing from January to June and increasing from July to December. The correlation analysis suggested that positive relationship was found between the CPUE and the PAR. However, the correlation was significant in July and August, but was not significant in other months. Based on the histogram analysis, the monthly suitable and the most preferred PAR for Dosidicus gigas were evaluated. Significantly positive relationship was found between the monthly percentages of suitable PAR accounting for the fishing ground and the CPUE over 2006-2015, suggesting that the abundance of Dosidicus gigas off Peruvian waters was determined by the monthly suitable PAR area. Meanwhile, the latitudinal gravity center of CPUE was positively related to the mean latitude of the most preferred PAR, indicating that the locations of fishing ground of Dosidicus gigas were strongly affected by the latitudinal distribution of the most favorable PAR. Furthermore, the suitable PAR area in La Niña years was much larger than that in El Niño years. Our findings suggested that the abundance and spatial distribution of Dosidicus gigas in the Southeast Pacific Ocean off Peru were significantly influenced by the PAR, the regulation process tended to be different under different climate variability.
The photosynthetically active radiation (PAR) is one of the most important factors driving the variations in ocean primary productivity, implying that the PAR may have potential influence on the abundance and spatial distribution of pelagic fish species. In this study, the catch per unit effort (CPUE) and the latitudinal gravity center (LATG) of CPUE was used to indicate the squid abundance and spatial distribution of fishing ground, respectively, we evaluated the influence of PAR on stock variation of jumbo flying squid Dosidicus gigas in the Southeast Pacific Ocean off Peru, based on the fishery data during 2006-2015 obtained from the Chinese squid-jigging Science and Technology Group as well as the remotely satellite data. The results indicated that the catch, fishing effort, CPUE and PAR exhibited significant monthly variations. The CPUE and PAR showed the similar trend, decreasing from January to June and increasing from July to December. The correlation analysis suggested that positive relationship was found between the CPUE and the PAR. However, the correlation was significant in July and August, but was not significant in other months. Based on the histogram analysis, the monthly suitable and the most preferred PAR for Dosidicus gigas were evaluated. Significantly positive relationship was found between the monthly percentages of suitable PAR accounting for the fishing ground and the CPUE over 2006-2015, suggesting that the abundance of Dosidicus gigas off Peruvian waters was determined by the monthly suitable PAR area. Meanwhile, the latitudinal gravity center of CPUE was positively related to the mean latitude of the most preferred PAR, indicating that the locations of fishing ground of Dosidicus gigas were strongly affected by the latitudinal distribution of the most favorable PAR. Furthermore, the suitable PAR area in La Niña years was much larger than that in El Niño years. Our findings suggested that the abundance and spatial distribution of Dosidicus gigas in the Southeast Pacific Ocean off Peru were significantly influenced by the PAR, the regulation process tended to be different under different climate variability.
2017, 39(11): 106-114.
doi: 10.3969/j.issn.0253-4193.2017.11.010
Abstract:
Bathymetry accuracy evaluation of multibeam echo sounder is an important aspect of water depth measurement quality control. It is an effective method using the static data accuracy evaluation and cross line coverage data accuracy evaluation to estimate the depth samples error. In the actual investigation of the water depth, there is no data of the true water depth, so it is difficult to make statistics of the depth error. The depth data collected by Kongsberg EM120 is used to analysis, the static measurement statistics is calculated using the central beam data, then a grid method is applied to make statistics using the cross line coverage depth data. In addition, the distribution of the sample data total error is showed by the cross line coverage depth deviation. In conclusion, it is an effective way to using the statistics central beam data and the cross line coverage depth data for the water depth accuracy evaluation of multibeam echo sounder.
Bathymetry accuracy evaluation of multibeam echo sounder is an important aspect of water depth measurement quality control. It is an effective method using the static data accuracy evaluation and cross line coverage data accuracy evaluation to estimate the depth samples error. In the actual investigation of the water depth, there is no data of the true water depth, so it is difficult to make statistics of the depth error. The depth data collected by Kongsberg EM120 is used to analysis, the static measurement statistics is calculated using the central beam data, then a grid method is applied to make statistics using the cross line coverage depth data. In addition, the distribution of the sample data total error is showed by the cross line coverage depth deviation. In conclusion, it is an effective way to using the statistics central beam data and the cross line coverage depth data for the water depth accuracy evaluation of multibeam echo sounder.
2017, 39(11): 115-127.
doi: 10.3969/j.issn.0253-4193.2017.11.011
Abstract:
Snow and sea ice in the polar regions react strongly to the climate change. Sea ice thickness is also a critical parameter for navigation in the polar oceans. In this paper, we present measurements taken using a high-resolution thermistor chain (SIMBA) to monitor snow and ice thickness in the land-fast ice zone in winters 2014 and 2015 in the Prydz Bay outside Zhongshan Station, Antarctic. SIMBA measures vertical temperature profiles 4 times a day as well as two daily sensor heating temperature profiles in 60 s and 120 s. Snow and ice thickness were derived (a) manually on the basis of different linear temperature gradients in air, snow, ice, and water, and (b) applying an automatic algorithm based on temporal variation of the temperature gradients associated with analyses of heating temperature response statistics. Compared with borehole in situ measurements, the manually estimated ice thickness had a mean bias and RMSE of 2.1 cm and 6.4 cm in 2014, 4.3 cm and 6.5 cm in 2015. The mean bias and RMSE of algorithm-based ice thickness was-6.8 cm and 6.4 cm in 2014, 4.5 cm and 6.6 cm in 2015. The snow thickness was estimated only for winter 2015, and the mean bias and RMSE of manual and algorithm methods were 0.5 cm and 8.5 cm, 4.7 cm and 10.8 cm, respectively. The manual estimation, in general, yielded better results. Our results reveal that SIMBA is capable to monitor snow and ice thickness in the Prydz Bay, Antarctic.
Snow and sea ice in the polar regions react strongly to the climate change. Sea ice thickness is also a critical parameter for navigation in the polar oceans. In this paper, we present measurements taken using a high-resolution thermistor chain (SIMBA) to monitor snow and ice thickness in the land-fast ice zone in winters 2014 and 2015 in the Prydz Bay outside Zhongshan Station, Antarctic. SIMBA measures vertical temperature profiles 4 times a day as well as two daily sensor heating temperature profiles in 60 s and 120 s. Snow and ice thickness were derived (a) manually on the basis of different linear temperature gradients in air, snow, ice, and water, and (b) applying an automatic algorithm based on temporal variation of the temperature gradients associated with analyses of heating temperature response statistics. Compared with borehole in situ measurements, the manually estimated ice thickness had a mean bias and RMSE of 2.1 cm and 6.4 cm in 2014, 4.3 cm and 6.5 cm in 2015. The mean bias and RMSE of algorithm-based ice thickness was-6.8 cm and 6.4 cm in 2014, 4.5 cm and 6.6 cm in 2015. The snow thickness was estimated only for winter 2015, and the mean bias and RMSE of manual and algorithm methods were 0.5 cm and 8.5 cm, 4.7 cm and 10.8 cm, respectively. The manual estimation, in general, yielded better results. Our results reveal that SIMBA is capable to monitor snow and ice thickness in the Prydz Bay, Antarctic.
2017, 39(11): 128-140.
doi: 10.3969/j.issn.0253-4193.2017.11.012
Abstract:
Based on the monthly ocean temperature reanalysis data from SODA datasets, this paper makes a statistical analysis on the temporal and spatial characteristic of the thermal energy in the Pacific Ocean and the sea area surrounding China during January 1971 to December 2010. The main conclusions are as follows: (1) the temperature difference between the upper and deep layer has obvious seasonal variations; from boreal winter to summer, the 20℃ iso-temperature-difference line extend from 20°N to 40°N in the Northern Hemisphere, while the variation in the Southern Hemisphere is relatively small; the efficient exploiting area ranges from 30°S to 40°N, of which the zonal distribution isn't even; the climatology 20℃ iso-temperature-difference line can be approximately the boundary of the all-time exploiting area. (2) The equivalent head of thermal energy tends to grow yearly in most areas of the Pacific Ocean with the maximum growth rate of 2 m/a; the variable coefficient of thermal energy has obvious seasonal variations but remains at low level, which is basically lower than 0.1 in the efficient exploiting area regardless of the season. (3) The thermal energy resource in the sea area surrounding China is most abundant in South China Sea and the east of Taiwan Island, where the temperature difference maintains at high level and the energy density is on rise year by year, where the stability of energy is satisfactory and the efficient exploiting time is the whole year, where the best exploiting time is May to July. (4) The available exploitation amount in the Pacific Ocean is on the order of TW and has a rising trend of 2.83 GW/a.
Based on the monthly ocean temperature reanalysis data from SODA datasets, this paper makes a statistical analysis on the temporal and spatial characteristic of the thermal energy in the Pacific Ocean and the sea area surrounding China during January 1971 to December 2010. The main conclusions are as follows: (1) the temperature difference between the upper and deep layer has obvious seasonal variations; from boreal winter to summer, the 20℃ iso-temperature-difference line extend from 20°N to 40°N in the Northern Hemisphere, while the variation in the Southern Hemisphere is relatively small; the efficient exploiting area ranges from 30°S to 40°N, of which the zonal distribution isn't even; the climatology 20℃ iso-temperature-difference line can be approximately the boundary of the all-time exploiting area. (2) The equivalent head of thermal energy tends to grow yearly in most areas of the Pacific Ocean with the maximum growth rate of 2 m/a; the variable coefficient of thermal energy has obvious seasonal variations but remains at low level, which is basically lower than 0.1 in the efficient exploiting area regardless of the season. (3) The thermal energy resource in the sea area surrounding China is most abundant in South China Sea and the east of Taiwan Island, where the temperature difference maintains at high level and the energy density is on rise year by year, where the stability of energy is satisfactory and the efficient exploiting time is the whole year, where the best exploiting time is May to July. (4) The available exploitation amount in the Pacific Ocean is on the order of TW and has a rising trend of 2.83 GW/a.
2017, 39(11): 141-147.
doi: 10.3969/j.issn.0253-4193.2017.11.013
Abstract:
Scholars have done a lot of work in the assessment and validation of SMOS sea surface salinity (SSS) data since SMOS satellite data released, but rarely work have done in the Western Pacific Ocean(WPO) influenced by radio frequency interference (RFI), it will be of important significance on understanding of RFI influence on SMOS SSS date. The main method is matching the WOD13 in-situ SSS data with SMOS half-orbit SSS data, assessing the accuracy of SMOS data by statistics method. Results suggest that since SMOS is polluted by RFI sources located in west coast of the WPO, the RMSE of SMOS L2 SSS data in high risk area of RFI pollution is relatively low, and the highest RMSE can be achieved on 3.45, thus it can be seen that the RFI have a significant influence on SMOS satellite in the WPO, this has resulted in the loss of significant amount of data, especially in the China sea, how to detect and mitigate RFI is a scientific problem to be solved.
Scholars have done a lot of work in the assessment and validation of SMOS sea surface salinity (SSS) data since SMOS satellite data released, but rarely work have done in the Western Pacific Ocean(WPO) influenced by radio frequency interference (RFI), it will be of important significance on understanding of RFI influence on SMOS SSS date. The main method is matching the WOD13 in-situ SSS data with SMOS half-orbit SSS data, assessing the accuracy of SMOS data by statistics method. Results suggest that since SMOS is polluted by RFI sources located in west coast of the WPO, the RMSE of SMOS L2 SSS data in high risk area of RFI pollution is relatively low, and the highest RMSE can be achieved on 3.45, thus it can be seen that the RFI have a significant influence on SMOS satellite in the WPO, this has resulted in the loss of significant amount of data, especially in the China sea, how to detect and mitigate RFI is a scientific problem to be solved.
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