2014 Vol. 36, No. 9
Display Method:
2014, 36(9): 1-6.
doi: 10.3969.issn.0253-4193.2014.09.001
Abstract:
Oil spill brings the serious influence to marine ecological environment,fast and accurately detecting the oil spill is of great significance for disaster prevention and mitigation. By making use of satellite remote sensing for the oil spill detection has become the main means of detection,Using the SAR(synthetic aperture radar) data and image processing methods,most scholars carry out a variety of oil spill extraction algorithm research,and get some good results,but there exist some look-alikes,which affect the extract information accuracy. In recent years,from polarization decomposition and a phase,using polarization SAR data in oil spill information extraction,such as the oil spill characteristic analysis,can effectively distinguish between some kind of oil spill phenomenon,and obtain the ideal results. The application of SAR data is analyzed in the oil spill information extraction research,summarized the oil spill polarization SAR detection research is summarized,and the current of the insufficiency in research is pointed out,and the future oil spill polarization SAR remote sensing monitoring.
Oil spill brings the serious influence to marine ecological environment,fast and accurately detecting the oil spill is of great significance for disaster prevention and mitigation. By making use of satellite remote sensing for the oil spill detection has become the main means of detection,Using the SAR(synthetic aperture radar) data and image processing methods,most scholars carry out a variety of oil spill extraction algorithm research,and get some good results,but there exist some look-alikes,which affect the extract information accuracy. In recent years,from polarization decomposition and a phase,using polarization SAR data in oil spill information extraction,such as the oil spill characteristic analysis,can effectively distinguish between some kind of oil spill phenomenon,and obtain the ideal results. The application of SAR data is analyzed in the oil spill information extraction research,summarized the oil spill polarization SAR detection research is summarized,and the current of the insufficiency in research is pointed out,and the future oil spill polarization SAR remote sensing monitoring.
2014, 36(9): 7-17.
doi: 10.3969.issn.0253-4193.2014.09.002
Abstract:
Analyses of sea level anomalies(SLA) from satellite altimetry,ranging from 1992 to 2012,indicate that,as a semi-enclosed narrow water body,the China seas (consisted of the Bohai Sea,the Huanghai Sea,the East China Sea,and the South China Sea) and the Gulf of Thailand are subject to significant meridional sea level oscillation. The north-south SLA seesaw is strongly seasonal,with sea level being high in the south but low in the north during winter seasons,and vise versa in summer. The sea level difference between the Gulf of Bohai and the Gulf of Thailand is taken as a measure of the oscillation,which has a range of over 80 cm and a climatological annual mean of 63 cm. The analysis shows that,in the seasonal time scale,the meridional oscillation is almost totally dominated by variations of the East Asian monsoon,which indicates that monsoon is the main cause of the seasonal seesaw. Further analysis reveals that,in addition to seasonal variation,the meridional sea level oscillation is also subjected to considerable interannual variation. Unlike the oscillation in the seasonal time scale,its interannual variation appears correlated no only with the fluctuations of the East Asian Monsoon but also with the basin scale variation of the Pacific. The influences of remote forcings are comparable with that of the East Asian monsoon,and the seesaw generally lags two months behind the atmospheric forcings. The results from a multi-input,linear partial coherience model shows that,among the mumberous input factors other than the East Asia Monsoon Index,the interannual variation of the sea level oscillation index is correlated with SOI and WP. It is thus suggested that,in addition to the East Asian monsoon,remote forcings are from the tropics as well as the mid-latitude. The east-west sea level seesaw in the tropical Pacific associated with the southern oscillation,and the possible effects of interannual migration of the mid-latitude East Asian jet stream on the sea level,are both possible to cause interannual variation of the north-south sea level seesaw in the area. Further investigation is needed to determine their mechanism.
Analyses of sea level anomalies(SLA) from satellite altimetry,ranging from 1992 to 2012,indicate that,as a semi-enclosed narrow water body,the China seas (consisted of the Bohai Sea,the Huanghai Sea,the East China Sea,and the South China Sea) and the Gulf of Thailand are subject to significant meridional sea level oscillation. The north-south SLA seesaw is strongly seasonal,with sea level being high in the south but low in the north during winter seasons,and vise versa in summer. The sea level difference between the Gulf of Bohai and the Gulf of Thailand is taken as a measure of the oscillation,which has a range of over 80 cm and a climatological annual mean of 63 cm. The analysis shows that,in the seasonal time scale,the meridional oscillation is almost totally dominated by variations of the East Asian monsoon,which indicates that monsoon is the main cause of the seasonal seesaw. Further analysis reveals that,in addition to seasonal variation,the meridional sea level oscillation is also subjected to considerable interannual variation. Unlike the oscillation in the seasonal time scale,its interannual variation appears correlated no only with the fluctuations of the East Asian Monsoon but also with the basin scale variation of the Pacific. The influences of remote forcings are comparable with that of the East Asian monsoon,and the seesaw generally lags two months behind the atmospheric forcings. The results from a multi-input,linear partial coherience model shows that,among the mumberous input factors other than the East Asia Monsoon Index,the interannual variation of the sea level oscillation index is correlated with SOI and WP. It is thus suggested that,in addition to the East Asian monsoon,remote forcings are from the tropics as well as the mid-latitude. The east-west sea level seesaw in the tropical Pacific associated with the southern oscillation,and the possible effects of interannual migration of the mid-latitude East Asian jet stream on the sea level,are both possible to cause interannual variation of the north-south sea level seesaw in the area. Further investigation is needed to determine their mechanism.
2014, 36(9): 18-29.
doi: 10.3969.issn.0253-4193.2014.09.003
Abstract:
The coupled coastal wave prediction scheme ,which is a combination of a multi-scale numerical model and a statistical method,is proposed in order to avoid the limitations of one single scheme. By ocean wave model,the wave energy density spectrum of the computational grid in the coastal model is forecasted. We have defined a transfer coefficient matrix for thewave energy density spectrum between the computational grid and the coastal forecasting point. A statistical model for the prediction of this transfer coefficient is established using empirical orthogonal function (EOF) and Kalman filtering method. This statistical model is then coupled with the numerical model. The wave energy density spectrum of computational grid is optimized using the observed coastal buoy data. The coastal wave forecasting are validated by the observations of NAHA station for one year,indicating that this coupled method significantly improved the prediction power compared with the numerical model on its own. The rootmeansquare error of the significant wave height reduces about 0.16mand the average relative error is reduced by about 9%. It is also found that the forecasting accuracy of this method is limited within 24 hours; the principal components decomposed from the wave energy density spectrum reflect the main characteristics of local wave climate; and the change transfer coefficient of the spectrum reflects the seasonal variation of the wave climate.
The coupled coastal wave prediction scheme ,which is a combination of a multi-scale numerical model and a statistical method,is proposed in order to avoid the limitations of one single scheme. By ocean wave model,the wave energy density spectrum of the computational grid in the coastal model is forecasted. We have defined a transfer coefficient matrix for thewave energy density spectrum between the computational grid and the coastal forecasting point. A statistical model for the prediction of this transfer coefficient is established using empirical orthogonal function (EOF) and Kalman filtering method. This statistical model is then coupled with the numerical model. The wave energy density spectrum of computational grid is optimized using the observed coastal buoy data. The coastal wave forecasting are validated by the observations of NAHA station for one year,indicating that this coupled method significantly improved the prediction power compared with the numerical model on its own. The rootmeansquare error of the significant wave height reduces about 0.16mand the average relative error is reduced by about 9%. It is also found that the forecasting accuracy of this method is limited within 24 hours; the principal components decomposed from the wave energy density spectrum reflect the main characteristics of local wave climate; and the change transfer coefficient of the spectrum reflects the seasonal variation of the wave climate.
2014, 36(9): 30-36.
doi: 10.3969.issn.0253-4193.2014.09.004
Abstract:
Marine oil spill often forms oil droplets in stormy conditions.. Based on the dimensional analysis Rayleigh method,the relationship is established between entrainment rate of oil droplet and statistical physical quantities such as the energy dissipation rate,intrusion depth et al. An expression of size spectrum of oil droplets is derived based on Π theorem and relationship between capillary number,the dimensionless intrusion time and viscosity ratio. Preliminary results show that the slope of the derived spectrum is-2.29,which agrees well with the measured slope-2.3 in laboratory. Shear rate,surface tension,droplet radius,oil and water viscosity is the main factors controlling the total number of the oil droplets.
Marine oil spill often forms oil droplets in stormy conditions.. Based on the dimensional analysis Rayleigh method,the relationship is established between entrainment rate of oil droplet and statistical physical quantities such as the energy dissipation rate,intrusion depth et al. An expression of size spectrum of oil droplets is derived based on Π theorem and relationship between capillary number,the dimensionless intrusion time and viscosity ratio. Preliminary results show that the slope of the derived spectrum is-2.29,which agrees well with the measured slope-2.3 in laboratory. Shear rate,surface tension,droplet radius,oil and water viscosity is the main factors controlling the total number of the oil droplets.
2014, 36(9): 37-44.
doi: 10.3969.issn.0253-4193.2014.09.005
Abstract:
A model of a semi-enclosed rectangular basin with a coastal barrier is schematized from the Bohai Sea, the Huanghai Sea and Shandong Peninsula. Using the DELFT3D-FLOW numerical model, we have conducted the analyses of the tidal characteristics of the M2 constituent , the formation mechanism of the amphidromic points and the radial tidal current field in the basin. The results show that,due to the Coriolis force and the barrier reflection, there will always present an amphidromic point in front of the coastal barrier. However, the radial tidal field is absent in the case of uniform water depth with an exception of the existence of mild slope in the nearshore topography. It is found that the locations of the focal point of the radial tidal current field and the amphidromic point are affected by the mean water depth. With the increase of the mean water depth, the location of the amphidromic point will shift to the entrance and the central axis of the basin, while the focal point of the radial tidal current field will move towards the entrance of the basin. The findings in the paper will facilitate the understanding of the formation mechanism and dynamic characteristics of stationary tidal wave in this type of the basin.
A model of a semi-enclosed rectangular basin with a coastal barrier is schematized from the Bohai Sea, the Huanghai Sea and Shandong Peninsula. Using the DELFT3D-FLOW numerical model, we have conducted the analyses of the tidal characteristics of the M2 constituent , the formation mechanism of the amphidromic points and the radial tidal current field in the basin. The results show that,due to the Coriolis force and the barrier reflection, there will always present an amphidromic point in front of the coastal barrier. However, the radial tidal field is absent in the case of uniform water depth with an exception of the existence of mild slope in the nearshore topography. It is found that the locations of the focal point of the radial tidal current field and the amphidromic point are affected by the mean water depth. With the increase of the mean water depth, the location of the amphidromic point will shift to the entrance and the central axis of the basin, while the focal point of the radial tidal current field will move towards the entrance of the basin. The findings in the paper will facilitate the understanding of the formation mechanism and dynamic characteristics of stationary tidal wave in this type of the basin.
2014, 36(9): 45-55.
doi: 10.3969.issn.0253-4193.2014.09.006
Abstract:
The satellite gravity mission GRACE (gravity recovery and climate experiment) has greatly improved the accuracy and resolution of the gravity field model of the earth,particularly in long-wave components. It can determine the characteristics of large scale global ocean surface currents combining satellite altimetry. In addition,the new generation GOCE (gravity field and steady-state ocean circulation explorer) mission was successfully launched in 2009 using gravity gradient measurements,which is very sensitive to the high-frequency part of the gravity field. Therefore,the GOCE is capable to determine the ocean surface currents with high spatial resolution. In this paper,the global surface geostrophic currents are determined from three models: (1)the gravity field model derived from 1 to 7 years of GRACE observations;(2)the gravity field model GO_CONS_GCF_2_TIM_R3 derived from one and half years of GOCE observations; (3) the mean sea surface topography model MSS_CNES_CLS_11 derived from satellite altimetry. It has shown that the gravity field model based on GOCE satellite gravity observations has a higher spatial resolution and can reflect more details and characteristics of the surface geostrophic currents with high accuracy and spatial resolution,e.g.,the medium and small-scale Mexico Gulf currents. Furthermore,the predictions are consistent with the in-situ drifters buoy data. However,the gravity model from 1 to 4 years of GRACE observations cannot predict global geostrophic currents accurately,and even the model from 7 years of GRACE observations is still less accurate than that from the one and half years of GOCE observations; the former one cannot reveal the details of current at the medium and small scales and has larger noises.
The satellite gravity mission GRACE (gravity recovery and climate experiment) has greatly improved the accuracy and resolution of the gravity field model of the earth,particularly in long-wave components. It can determine the characteristics of large scale global ocean surface currents combining satellite altimetry. In addition,the new generation GOCE (gravity field and steady-state ocean circulation explorer) mission was successfully launched in 2009 using gravity gradient measurements,which is very sensitive to the high-frequency part of the gravity field. Therefore,the GOCE is capable to determine the ocean surface currents with high spatial resolution. In this paper,the global surface geostrophic currents are determined from three models: (1)the gravity field model derived from 1 to 7 years of GRACE observations;(2)the gravity field model GO_CONS_GCF_2_TIM_R3 derived from one and half years of GOCE observations; (3) the mean sea surface topography model MSS_CNES_CLS_11 derived from satellite altimetry. It has shown that the gravity field model based on GOCE satellite gravity observations has a higher spatial resolution and can reflect more details and characteristics of the surface geostrophic currents with high accuracy and spatial resolution,e.g.,the medium and small-scale Mexico Gulf currents. Furthermore,the predictions are consistent with the in-situ drifters buoy data. However,the gravity model from 1 to 4 years of GRACE observations cannot predict global geostrophic currents accurately,and even the model from 7 years of GRACE observations is still less accurate than that from the one and half years of GOCE observations; the former one cannot reveal the details of current at the medium and small scales and has larger noises.
2014, 36(9): 56-64.
doi: 10.3969.issn.0253-4193.2014.09.007
Abstract:
Decadal change characteristics of the intermediate water at 18°N in the South China Sea during 1965 and 2012 were investigated using the historical temperature and salinity profile data from SCSIO (South China Sea Institute of Oceanology) and WOD09 (World Ocean Database 2009). This study revealed the significant decadal changes of the intermediate water based on the analysis of its decadal averaged salinity. The salinity was 34.432 on average in the period of 1965 to 1977 and increased to 34.440 in the 1980s, followed by an evident decrease after the 1990s. Modulated by the decadal scale changes, the salinity variation presented different trends in different periods. There was a significant decrease trend from 1967 to 1977, followed by a further decrease from 34.450 to 34.414 during 1990 and 1997. Thereafter there appeared a significant increase. Meanwhile, the temperature presented the same changing trends. Both temperature and salinity decreased in the 21st century with smaller amplitude of variation compared those in 1990s. The decadal changes of the intermediate water at 18°N were found to present different characteristics than those of Indian Ocean and the Pacific Ocean. In addition, the significant decadal changes of the intermediate water have greater amplitudes than those of the decadal scale variations. In addition, it is found that the salinity was closely related with ENSO that it reached its minimum in El Niño years.
Decadal change characteristics of the intermediate water at 18°N in the South China Sea during 1965 and 2012 were investigated using the historical temperature and salinity profile data from SCSIO (South China Sea Institute of Oceanology) and WOD09 (World Ocean Database 2009). This study revealed the significant decadal changes of the intermediate water based on the analysis of its decadal averaged salinity. The salinity was 34.432 on average in the period of 1965 to 1977 and increased to 34.440 in the 1980s, followed by an evident decrease after the 1990s. Modulated by the decadal scale changes, the salinity variation presented different trends in different periods. There was a significant decrease trend from 1967 to 1977, followed by a further decrease from 34.450 to 34.414 during 1990 and 1997. Thereafter there appeared a significant increase. Meanwhile, the temperature presented the same changing trends. Both temperature and salinity decreased in the 21st century with smaller amplitude of variation compared those in 1990s. The decadal changes of the intermediate water at 18°N were found to present different characteristics than those of Indian Ocean and the Pacific Ocean. In addition, the significant decadal changes of the intermediate water have greater amplitudes than those of the decadal scale variations. In addition, it is found that the salinity was closely related with ENSO that it reached its minimum in El Niño years.
2014, 36(9): 65-74.
doi: 10.3969.issn.0253-4193.2014.09.008
Abstract:
Based on the tide level data of tide gauge stations and satellite altimeter,sea surface temperature,air pressure ,wind etc hydrological and meteorological data in the region of eastern equatorial Pacific,the relationship between the sea level change of China coastal area and ENSO are investigated. The research results show that the sea level of China coastal area is affected by ENSO obviously. Annual and semiannual amplitude of tide level decreased significantly in El Niño events. The minimum value of annual amplitude all appeared in El Niño years,but different regions happened in different years. In addition,the Sa tidal amplitude of China coastal in response to El Niño events related its strength. Response area and magnitude is bigger in strong events,response area and magnitude is smaller in weak events. In El Niño events,the sea level was lower than adjacent years,the MSL also shows prominent inter-annual and inter-decade variation besides the seasonal variation,the prominent terms are 2~3 a,4~7 a,9 a,11 a and 19 a,the oscillation of 4~7 a is the most prominent. There is a significant negative correlation between the MSL in China coastal area and SST in the central and eastern equatorial Pacific,it also shows negative correlation with Niño4 and Niño3.4 indices prominently. In typical El Niño event,the winter monsoon is strong in the winter half year before the occurrence of El Niño event,the pressure gradient is strengthened and the sea level is low in China coastal area. on the contrary,in the winter half year before the occurrence of La Niña event,the winter monsoon is weak,the pressure gradient is weaken and the sea level is high in the coast of China.
Based on the tide level data of tide gauge stations and satellite altimeter,sea surface temperature,air pressure ,wind etc hydrological and meteorological data in the region of eastern equatorial Pacific,the relationship between the sea level change of China coastal area and ENSO are investigated. The research results show that the sea level of China coastal area is affected by ENSO obviously. Annual and semiannual amplitude of tide level decreased significantly in El Niño events. The minimum value of annual amplitude all appeared in El Niño years,but different regions happened in different years. In addition,the Sa tidal amplitude of China coastal in response to El Niño events related its strength. Response area and magnitude is bigger in strong events,response area and magnitude is smaller in weak events. In El Niño events,the sea level was lower than adjacent years,the MSL also shows prominent inter-annual and inter-decade variation besides the seasonal variation,the prominent terms are 2~3 a,4~7 a,9 a,11 a and 19 a,the oscillation of 4~7 a is the most prominent. There is a significant negative correlation between the MSL in China coastal area and SST in the central and eastern equatorial Pacific,it also shows negative correlation with Niño4 and Niño3.4 indices prominently. In typical El Niño event,the winter monsoon is strong in the winter half year before the occurrence of El Niño event,the pressure gradient is strengthened and the sea level is low in China coastal area. on the contrary,in the winter half year before the occurrence of La Niña event,the winter monsoon is weak,the pressure gradient is weaken and the sea level is high in the coast of China.
2014, 36(9): 75-83.
doi: 10.3969.issn.0253-4193.2014.09.009
Abstract:
The empirical mode decomposition (EMD) method is introduced to analyze the stability of turbulence for the first time and is compared with the traditional detrending methods,like linear detrending(LDT) and running mean filtering (RMF). The results show that EMD is the most reliable method to obtain momentum flux at the air-sea surface. Based on about two years of data from Flux Observation on Platform in South China Sea (FOPSCS) project,22 476 friction velocities were obtained. It was found that when the wind speed is less than 5 m/s,the drag coefficient decreases with the increase of wind speed; whereas,the trend is opposite when wind speed is greater than 5 m/s. These two different cases reflect the contribution to the wind stress from the roughness generated by viscous boundary-layer and wave-induced form drag,respectively. Further analysis shows that the drag coefficient with limited fetch condition is larger than that with unlimited fetch,which revealed the wave age can also influence the momentum exchange at the air-sea surface.
The empirical mode decomposition (EMD) method is introduced to analyze the stability of turbulence for the first time and is compared with the traditional detrending methods,like linear detrending(LDT) and running mean filtering (RMF). The results show that EMD is the most reliable method to obtain momentum flux at the air-sea surface. Based on about two years of data from Flux Observation on Platform in South China Sea (FOPSCS) project,22 476 friction velocities were obtained. It was found that when the wind speed is less than 5 m/s,the drag coefficient decreases with the increase of wind speed; whereas,the trend is opposite when wind speed is greater than 5 m/s. These two different cases reflect the contribution to the wind stress from the roughness generated by viscous boundary-layer and wave-induced form drag,respectively. Further analysis shows that the drag coefficient with limited fetch condition is larger than that with unlimited fetch,which revealed the wave age can also influence the momentum exchange at the air-sea surface.
2014, 36(9): 84-93.
doi: 10.3969.issn.0253-4193.2014.09.010
Abstract:
The sea spray flux parameterization scheme is incorporated into a high resolution and non-hydrostatic weather research and forecasting (WRF) model to simulate tropical cyclone (TC) Morakot (0908),and to study the effect of sea spray on boundary layer structure and intensity of Morakot. The results show that the intensity prediction of Morakot has been improved by using the new scheme,while there is no any impact on its track forecasting. Moreover,the averaged elements,such as radial wind,tangential wind,temperature,relative humidity,vertical wind,heat flux and precipitation in TC inner core region are increase by improving TC boundary layer processes. That means the contributions of all the elements have play important roles on Morakot structure and intensity change.
The sea spray flux parameterization scheme is incorporated into a high resolution and non-hydrostatic weather research and forecasting (WRF) model to simulate tropical cyclone (TC) Morakot (0908),and to study the effect of sea spray on boundary layer structure and intensity of Morakot. The results show that the intensity prediction of Morakot has been improved by using the new scheme,while there is no any impact on its track forecasting. Moreover,the averaged elements,such as radial wind,tangential wind,temperature,relative humidity,vertical wind,heat flux and precipitation in TC inner core region are increase by improving TC boundary layer processes. That means the contributions of all the elements have play important roles on Morakot structure and intensity change.
2014, 36(9): 94-102.
doi: 10.3969.issn.0253-4193.2014.09.011
Abstract:
Acoustical propagation features caused by subtropical mode water (STMW) of Northwestern Pacific during seasonal transition are analyzed by Argo profile data and acoustic numerical model. The results of sound filed show that the main propagating pattern of STMW formed region is a combination of surface or subsurface duct and convergence zone (CZ). The CZ exists all the year round, but the surface duct appears in a growing mixed-layer environment in autumn and winter, and the subsurface duct appears only in a STMW subduction environment in summer. Two types of duct propagation show an inverse pattern of sound energy distribution, and the difference can be around 10 to 15 dB between the internal and the external of the duct (sound frequency is 1 kHz). Seasonal transition of STMW can also lead to the change of CZ positions. The changes are influenced by the source depth. When the source locates at 20 m, the CZ position reaches its furthest in the summer, remains medium in the spring, and arrives its nearest in the winter, where the maximum difference can be 6.6 km. When the source locates at 150 m, the CZ reduces 3.1 km in summer and shows no distinct changes in other seasons.
Acoustical propagation features caused by subtropical mode water (STMW) of Northwestern Pacific during seasonal transition are analyzed by Argo profile data and acoustic numerical model. The results of sound filed show that the main propagating pattern of STMW formed region is a combination of surface or subsurface duct and convergence zone (CZ). The CZ exists all the year round, but the surface duct appears in a growing mixed-layer environment in autumn and winter, and the subsurface duct appears only in a STMW subduction environment in summer. Two types of duct propagation show an inverse pattern of sound energy distribution, and the difference can be around 10 to 15 dB between the internal and the external of the duct (sound frequency is 1 kHz). Seasonal transition of STMW can also lead to the change of CZ positions. The changes are influenced by the source depth. When the source locates at 20 m, the CZ position reaches its furthest in the summer, remains medium in the spring, and arrives its nearest in the winter, where the maximum difference can be 6.6 km. When the source locates at 150 m, the CZ reduces 3.1 km in summer and shows no distinct changes in other seasons.
2014, 36(9): 103-105.
doi: 10.3969.issn.0253-4193.2014.09.012
Abstract:
Oil spilling is one of the major sources for in marine pollutions,which are widely distributed and can bring cause terrible significant environmental damages. In recent years,due to the increase in offshore human activities and development of petroleum processing industries,oil spill accidents are also increasing,which are mostly caused by well blowouts,explosions of drilling platforms and ship collisions. Therefore,monitoring oil spilling has important significance in both economical and social aspects. As an all-weather high-resolution active microwave imaging sensor,Synthetic Aperture Radar (SAR) can greatly improve the resolution of images and the accuracy of forecasts,and thus takes an important role in oil spill monitoring. This paper aims to realize the semi-automatic identification of various targets on SAR images. We have conducted a convincing contrast of different neural networks,using Matlab as the tool through image preprocessing (image correction and enhancement),feature extraction and neural network recognition. First,oil spilli images are preliminarily manually identified,followed by image preprocessing (such as geometric correction,filtering,etc.) and feature extraction based on gray level co-occurrence matrix. Then,two types of neural networks,namely RBF and BP ,are introduced to classify the oil spill area and other suspected areas. Finally,the processed images are analyzed,indicating the capability in classifying oil,sea water,and land targets. The results reveal that the outputs from the RBF neural network are more accurate compared to those from the BP neural network.
2014, 36(9): 112-120.
doi: 10.3969.issn.0253-4193.2014.09.013
Abstract:
Darwin firstly developed the coral reef morphological type and discussed its genetic mechanism, after he performed a global survey for coral reefs in tropical oceans during 1832 to 1836. The overall morphology of coral reef in his model looks like a wholly or partly truncated cone-shape, which is called as "the truncated taper" type in this paper. Subsequent several-generation researchers accepted his model. In recent time some workers have put forward another type for coral reefs after studying on geomorphologic characteristics of coral reefs in the South China Sea (SCS). In this new model, the outer reef slope takes on a concave curve and the reef’s shape is mushroom-like, and the model is called as mushroom-like type in this paper. Based on the measured data and references in geomorphology, we confirmed that the morphological type of coral reefs in the SCS is not the mushroom-like type but the truncated cone-shape, because the former one didn’t match the rules for the formation and evolution of coral reefs in nature.
Darwin firstly developed the coral reef morphological type and discussed its genetic mechanism, after he performed a global survey for coral reefs in tropical oceans during 1832 to 1836. The overall morphology of coral reef in his model looks like a wholly or partly truncated cone-shape, which is called as "the truncated taper" type in this paper. Subsequent several-generation researchers accepted his model. In recent time some workers have put forward another type for coral reefs after studying on geomorphologic characteristics of coral reefs in the South China Sea (SCS). In this new model, the outer reef slope takes on a concave curve and the reef’s shape is mushroom-like, and the model is called as mushroom-like type in this paper. Based on the measured data and references in geomorphology, we confirmed that the morphological type of coral reefs in the SCS is not the mushroom-like type but the truncated cone-shape, because the former one didn’t match the rules for the formation and evolution of coral reefs in nature.
2014, 36(9): 121-131.
doi: 10.3969.issn.0253-4193.2014.09.014
Abstract:
The mass-dependent magnetic susceptibility (χ) with low and high frequency, anhysteretic susceptibility (χARM) and temperature-dependent susceptibility (k-T) of 61 surface sediment samples obtained from Bering Sea and western Arctic Ocean were measured with an attempt to find the composition, province and transport of magnetic minerals, which is helpful to accurately decipher the paleo-climate and environmental information recorded by the magnetic parameters in Arctic area. The results show that the χ values of surface sediments have an evident regional difference. The χ values are commonly higher in Bering Sea than that in Chukchi Sea, and they are the lowest in the plains and ridges of high western Arctic Ocean. The χ values are the highest off the Yukon River estuary and to the south of St. Lawrence Island in Bering Sea shelf, decreasing northward and south-westward. The χ values are relatively higher in the central-eastern Chukchi Sea shelf than that off the Alaskan coast. The χARM share the common variation trends of χ, however, the frequency-dependent susceptibility changes oppositely to that of χ. The analysis of k-T shows that the magnetic mineral in surface sediments in Aleutian Basin is maghemite, and off the Yukon River estuary and to the south of St. Lawrence Island is magnetite, and both maghemite and magnetite occur in the western shelf of Bering Sea and central-eastern shelf of Chukchi Sea. The magnetic mineral of surface sediment off the Alaskan coast is pyrite, while in the slope, plains and ridges of high western Arctic Ocean, the magnetic minerals are greigite and pyrite, but the content of greigite is higher in high latitude. The regional distribution of magnetic minerals in surface sediments is controlled by the sources of sediments, currents and bottom environments. The maghemite in the shelf of Bering Sea and Chukchi Sea is from the Asian main land, and the magnetite in eastern Bering Sea shelf is from the watershed of Yukon River. Pyrite off the Alaskan coast may be terrigenous or formed during the early diagenesis, while the greigite in high western Arctic Ocean is biogenous.
The mass-dependent magnetic susceptibility (χ) with low and high frequency, anhysteretic susceptibility (χARM) and temperature-dependent susceptibility (k-T) of 61 surface sediment samples obtained from Bering Sea and western Arctic Ocean were measured with an attempt to find the composition, province and transport of magnetic minerals, which is helpful to accurately decipher the paleo-climate and environmental information recorded by the magnetic parameters in Arctic area. The results show that the χ values of surface sediments have an evident regional difference. The χ values are commonly higher in Bering Sea than that in Chukchi Sea, and they are the lowest in the plains and ridges of high western Arctic Ocean. The χ values are the highest off the Yukon River estuary and to the south of St. Lawrence Island in Bering Sea shelf, decreasing northward and south-westward. The χ values are relatively higher in the central-eastern Chukchi Sea shelf than that off the Alaskan coast. The χARM share the common variation trends of χ, however, the frequency-dependent susceptibility changes oppositely to that of χ. The analysis of k-T shows that the magnetic mineral in surface sediments in Aleutian Basin is maghemite, and off the Yukon River estuary and to the south of St. Lawrence Island is magnetite, and both maghemite and magnetite occur in the western shelf of Bering Sea and central-eastern shelf of Chukchi Sea. The magnetic mineral of surface sediment off the Alaskan coast is pyrite, while in the slope, plains and ridges of high western Arctic Ocean, the magnetic minerals are greigite and pyrite, but the content of greigite is higher in high latitude. The regional distribution of magnetic minerals in surface sediments is controlled by the sources of sediments, currents and bottom environments. The maghemite in the shelf of Bering Sea and Chukchi Sea is from the Asian main land, and the magnetite in eastern Bering Sea shelf is from the watershed of Yukon River. Pyrite off the Alaskan coast may be terrigenous or formed during the early diagenesis, while the greigite in high western Arctic Ocean is biogenous.
2014, 36(9): 132-141.
doi: 10.3969.issn.0253-4193.2014.09.015
Abstract:
Coastal erosion and accretion has always existed in the coastal zone systems,and sculptured the present coastlines. However,with increasing human activities and ongoing global climate change,the coasts have been suffering more and more erosion,leading to severe land loss and aggravating financial burden. This study presented an integrated methodology for risk assessment of coastal erosion,and described the methods for coastal erosion risk assessment,and provided some helpful guidances for coastal erosion risk management. The analytic hierarchy process and the fuzzy set theory were adopted in the study to establish the methodology. Taking the Fujian coast as an example,this study assessed its coastal erosion risk and compiled the risk map,and the results obtained were consistent with the actual situation and confirmed the applicability of the method mentioned above. The system established for coastal erosion risk assessment in this study can be applied to other regions after slightly adjusting the values of the assessment indicators.
Coastal erosion and accretion has always existed in the coastal zone systems,and sculptured the present coastlines. However,with increasing human activities and ongoing global climate change,the coasts have been suffering more and more erosion,leading to severe land loss and aggravating financial burden. This study presented an integrated methodology for risk assessment of coastal erosion,and described the methods for coastal erosion risk assessment,and provided some helpful guidances for coastal erosion risk management. The analytic hierarchy process and the fuzzy set theory were adopted in the study to establish the methodology. Taking the Fujian coast as an example,this study assessed its coastal erosion risk and compiled the risk map,and the results obtained were consistent with the actual situation and confirmed the applicability of the method mentioned above. The system established for coastal erosion risk assessment in this study can be applied to other regions after slightly adjusting the values of the assessment indicators.
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