2009 No. 3
Display Method:
2009, (3): 1-6.
Abstract(
PDF 1828KB
Abstract:
The characteristics of growth, reproduction of Corophium acherusicum and its sensitivity to pollutant in sediment were studied in this paper to assess its suitability as an standard organism in sediment toxicity tests. The results showed that corophium acherusicum are easy to culture and capable of quick reproduction , and their wild caught have high tocicological sensitivities. The results may provide useful information on the culture of marine benthic Amphipods in lab and sediment toxicity tests.
The characteristics of growth, reproduction of Corophium acherusicum and its sensitivity to pollutant in sediment were studied in this paper to assess its suitability as an standard organism in sediment toxicity tests. The results showed that corophium acherusicum are easy to culture and capable of quick reproduction , and their wild caught have high tocicological sensitivities. The results may provide useful information on the culture of marine benthic Amphipods in lab and sediment toxicity tests.
2009, (3): 7-16.
Abstract:
The acute toxic effects of No.0 diesel oil wateraccomodated fractions(WAFs) and dispersed oil (disWAFs) on sea urchin were studied, and the response of antioxidase(superoxide dismutase, SOD; catalase, CAT; glutathione Stransferase,GST) in digestive gland to disWAFs were tested. Hemicentrotus pulcherrimus was exposed to different concentrations of disWAFs (0.5,1,2 mg/L) for 13 days, and then transferred into clean sea water for 11d restoring experiment. The results showed that the disWAFs was more toxic, with 24, 48, 72, 96h LC50 values of 11.7,9.1,7.4 and 5.1 mg/L respectively. The activity of antioxidase was statistically significant doserelated effect in different disWAFs concentrations. Under the same doseconcentration exposure, SOD, CAT and GST activities increased first and then decreased with the prolonged exposure time. This trend was most significant in GST activity. The activities of SOD, CAT and GST of all concentration groups recovered to the corresponding control level after recovery experiment. According to the data, SOD, CAT and GST can be taken as biomarkers to monitor benthic marine oil pollution and provide.
The acute toxic effects of No.0 diesel oil wateraccomodated fractions(WAFs) and dispersed oil (disWAFs) on sea urchin were studied, and the response of antioxidase(superoxide dismutase, SOD; catalase, CAT; glutathione Stransferase,GST) in digestive gland to disWAFs were tested. Hemicentrotus pulcherrimus was exposed to different concentrations of disWAFs (0.5,1,2 mg/L) for 13 days, and then transferred into clean sea water for 11d restoring experiment. The results showed that the disWAFs was more toxic, with 24, 48, 72, 96h LC50 values of 11.7,9.1,7.4 and 5.1 mg/L respectively. The activity of antioxidase was statistically significant doserelated effect in different disWAFs concentrations. Under the same doseconcentration exposure, SOD, CAT and GST activities increased first and then decreased with the prolonged exposure time. This trend was most significant in GST activity. The activities of SOD, CAT and GST of all concentration groups recovered to the corresponding control level after recovery experiment. According to the data, SOD, CAT and GST can be taken as biomarkers to monitor benthic marine oil pollution and provide.
2009, (3): 17-27.
Abstract:
Benthic nutrient fluxes and early diagentic processes were investigated in the east Chongming tidal flat of Yangtze estuary in winter. 〖JP2〗Significantly nutrient influxes from water column to sediment are observed in high marsh: benthic fluxes of NO-3, NO-2, NH+4, PO3-4 and SiO2-3 are (-0.896±0.540) mmol/m2/d,(-0.089±0.049) mmol/m2/d,〖JP〗(-2.002±0.642) mmol/m2/d,(-0.068±0.006) mmol/m2/d and (-1.334±0.381) mmol/m2/d individually (negative indicate nutrient absorption from water column to sediment and positive indicate nutrient release from sediment to water column). The exflux of NO-3 ((0.203±0.112) mmol/m2/d) and influxes of NO-2 ((-0.010±0.005) mmol/m2/d) and PO3-4 ((-0.005±0.002) mmol/m2/d) are observed in middle marsh. In low marsh, only PO3-4 ((-0.047±0.009) mmol/m2/d) influx is significant and there are large uncertainty in other nutrient fluxes due to strong wave disturbance. Diffusional nutrient fluxes contribute to the benthic nutrient fluxes slightly. Due to benthic flux differences among nutrients, benthic nutrient exchanges promote the growths of N/P and Si/P ratios in water column.
Benthic nutrient fluxes and early diagentic processes were investigated in the east Chongming tidal flat of Yangtze estuary in winter. 〖JP2〗Significantly nutrient influxes from water column to sediment are observed in high marsh: benthic fluxes of NO-3, NO-2, NH+4, PO3-4 and SiO2-3 are (-0.896±0.540) mmol/m2/d,(-0.089±0.049) mmol/m2/d,〖JP〗(-2.002±0.642) mmol/m2/d,(-0.068±0.006) mmol/m2/d and (-1.334±0.381) mmol/m2/d individually (negative indicate nutrient absorption from water column to sediment and positive indicate nutrient release from sediment to water column). The exflux of NO-3 ((0.203±0.112) mmol/m2/d) and influxes of NO-2 ((-0.010±0.005) mmol/m2/d) and PO3-4 ((-0.005±0.002) mmol/m2/d) are observed in middle marsh. In low marsh, only PO3-4 ((-0.047±0.009) mmol/m2/d) influx is significant and there are large uncertainty in other nutrient fluxes due to strong wave disturbance. Diffusional nutrient fluxes contribute to the benthic nutrient fluxes slightly. Due to benthic flux differences among nutrients, benthic nutrient exchanges promote the growths of N/P and Si/P ratios in water column.
2009, (3): 28-37.
Abstract:
Eleven groups of results on activities of 210Pb from IAEA（International Atomic Energy Agency）for international comparison were analyzed to discuss the difference between two methods for 210Pb analysis: alpha and gamma spectrometry techniques. Consistence of the results by two techniques was discussed through linear regression analysis; consistence of the results by the same technique among different laboratories was also discussed; their availabilities and utilization ratios were compared, and then factors that influenced consistence and availabilities were discussed. Results showed that, there was a good agreement and strong linear correlation in the average results using two different techniques; however, there was significant difference among laboratories even using the same technique. Relatively, availability of results using alpha technique was higher than that of gamma spectrometry technique, but laboratories using gamma techniques were increasing annually. Low activity of 210Pb would affect consistence among laboratories negatively, especially for gamma techniques. Therefore, it was suggested that laboratory quality controls should be enhanced and comparisons among international and national laboratories should be put in an important place in order to improve the analysis quality of 210Pb and comparability among laboratories.
Eleven groups of results on activities of 210Pb from IAEA（International Atomic Energy Agency）for international comparison were analyzed to discuss the difference between two methods for 210Pb analysis: alpha and gamma spectrometry techniques. Consistence of the results by two techniques was discussed through linear regression analysis; consistence of the results by the same technique among different laboratories was also discussed; their availabilities and utilization ratios were compared, and then factors that influenced consistence and availabilities were discussed. Results showed that, there was a good agreement and strong linear correlation in the average results using two different techniques; however, there was significant difference among laboratories even using the same technique. Relatively, availability of results using alpha technique was higher than that of gamma spectrometry technique, but laboratories using gamma techniques were increasing annually. Low activity of 210Pb would affect consistence among laboratories negatively, especially for gamma techniques. Therefore, it was suggested that laboratory quality controls should be enhanced and comparisons among international and national laboratories should be put in an important place in order to improve the analysis quality of 210Pb and comparability among laboratories.
2009, (3): 38-47.
Abstract:
Based on historical and 2005-2006 field survey data, environmental impact assessment of Qingcaosha Reservoir construction project in the Yangtze Estuary was carried out. Results show that water quality in Qingcaosha is good, and the main indicators of water quality can meet the class Ⅱ of national surface water standard. There are 22 common types of plants in the study area with a vegetation cover of 11.3 km2. The aquatic biodiversity is high, and freshwater species are the main types of aquatic ecology. River basin pollution emissions, upstream runoff water quality deterioration, major construction projects and estuarine saltwater invasion may impact water quality of the reservoir. Reservoir operations optimization, delineation of source water protected areas, environmental pollution control and compensation strategy should be taken to protect the Qingcaosha area.
Based on historical and 2005-2006 field survey data, environmental impact assessment of Qingcaosha Reservoir construction project in the Yangtze Estuary was carried out. Results show that water quality in Qingcaosha is good, and the main indicators of water quality can meet the class Ⅱ of national surface water standard. There are 22 common types of plants in the study area with a vegetation cover of 11.3 km2. The aquatic biodiversity is high, and freshwater species are the main types of aquatic ecology. River basin pollution emissions, upstream runoff water quality deterioration, major construction projects and estuarine saltwater invasion may impact water quality of the reservoir. Reservoir operations optimization, delineation of source water protected areas, environmental pollution control and compensation strategy should be taken to protect the Qingcaosha area.
2009, (3): 48-55.
Abstract:
The progress in the research of the statistical distribution of wave crest characteristics and the mechanism of synthetic aperture radar (SAR) wave image were reviewed in this paper, and the information of crest length were obtained by applying the linear accumulative method to the simulation of random wave crest. The comparison of crest length distribution shows there is a goodness of fit between numerical simulation and the observation of SAR. It validates the technique of numerical simulation and deduces a probability equation of crest above certain length.
The progress in the research of the statistical distribution of wave crest characteristics and the mechanism of synthetic aperture radar (SAR) wave image were reviewed in this paper, and the information of crest length were obtained by applying the linear accumulative method to the simulation of random wave crest. The comparison of crest length distribution shows there is a goodness of fit between numerical simulation and the observation of SAR. It validates the technique of numerical simulation and deduces a probability equation of crest above certain length.
2009, (3): 56-62.
Abstract:
Taking the vertical densitystratified ambient fluid into consideration, a vertical twodimensional model for buoyant jet was established based on a kε turbulent model. Finite volume method and SIMPLE algorithm were used to obtain the solution of the model. Numerical simulation of vertical buoyant jet in linearly densitystratified ambient fluid was simulated, and the distribution of density, trajectory, dilution and width of the jet were obtained. The numerical simulation results were in good agreement with the experimental results, which means that the vertical twodimensional buoyant jet model can exactly simulate the behavior of buoyant jet and the mixture of the buoyant jet and ambient fluid.
Taking the vertical densitystratified ambient fluid into consideration, a vertical twodimensional model for buoyant jet was established based on a kε turbulent model. Finite volume method and SIMPLE algorithm were used to obtain the solution of the model. Numerical simulation of vertical buoyant jet in linearly densitystratified ambient fluid was simulated, and the distribution of density, trajectory, dilution and width of the jet were obtained. The numerical simulation results were in good agreement with the experimental results, which means that the vertical twodimensional buoyant jet model can exactly simulate the behavior of buoyant jet and the mixture of the buoyant jet and ambient fluid.
2009, (3): 63-71.
Abstract:
This paper picked up the impact factors of road distance, NDBI (Normalized Difference Buildup Index), NDVI(Normalized Difference Vegetation Index) and so on by means of analyzing the TM RS images and land use map digitally in Zhangjiagang city. In order to figure the effect of road to cropland in urbanization quantificationally, BP ANN (Back Propagation Artificial Neural Networks) was used to simulate the process of invasion and occupation of urban expansion in Zhangjiagang city. The results indicated that the probability of change from cropland to urban increased as high as 12% inside the range of 500 m around the road, and the impact of road to surrounding cropland reach the farthest to 2 000 m away. When -0.3NDBI0.5,the cropland neighboring the road was more easily transformed to urban. Finally, increasing training points of BP ANN could avoid the network to get into local minimum point defects.
This paper picked up the impact factors of road distance, NDBI (Normalized Difference Buildup Index), NDVI(Normalized Difference Vegetation Index) and so on by means of analyzing the TM RS images and land use map digitally in Zhangjiagang city. In order to figure the effect of road to cropland in urbanization quantificationally, BP ANN (Back Propagation Artificial Neural Networks) was used to simulate the process of invasion and occupation of urban expansion in Zhangjiagang city. The results indicated that the probability of change from cropland to urban increased as high as 12% inside the range of 500 m around the road, and the impact of road to surrounding cropland reach the farthest to 2 000 m away. When -0.3NDBI0.5,the cropland neighboring the road was more easily transformed to urban. Finally, increasing training points of BP ANN could avoid the network to get into local minimum point defects.
2009, (3): 72-82.
Abstract:
The Yangshan deepwater harbor locates in the Qiqu Archipelago with many islands and tidal channels. The cyclic tidal flow with strong velocity of 1.0m/s is the major dynamic force for maintaining the stability of the way and the sediment in flow is always under the combining action of waves and tidal currents. The seabed evolution is aroused by suspended sediment transport. The suspended sediment concentration is more 1.0 kg/m3. Based on the measured data of Oct. 1996, 1999, 2004 and 2006, and the measured surface suspended sediment concentration data from 1998 to 2007, the change characteristic of suspended sediment concentration was analyzed. Moreover, it was discussed to the causes of the variation of suspended sediment concentration, 〖JP2〗the effect of suspended sediment diffusion of Changjiang river mouth to Yangshan, and the “channel effect” to high suspended sediment concentration in Yangshan sea areas.
The Yangshan deepwater harbor locates in the Qiqu Archipelago with many islands and tidal channels. The cyclic tidal flow with strong velocity of 1.0m/s is the major dynamic force for maintaining the stability of the way and the sediment in flow is always under the combining action of waves and tidal currents. The seabed evolution is aroused by suspended sediment transport. The suspended sediment concentration is more 1.0 kg/m3. Based on the measured data of Oct. 1996, 1999, 2004 and 2006, and the measured surface suspended sediment concentration data from 1998 to 2007, the change characteristic of suspended sediment concentration was analyzed. Moreover, it was discussed to the causes of the variation of suspended sediment concentration, 〖JP2〗the effect of suspended sediment diffusion of Changjiang river mouth to Yangshan, and the “channel effect” to high suspended sediment concentration in Yangshan sea areas.
2009, (3): 83-89.
Abstract:
The study was carried out based on CPT data. Firstly, the soil nonuniformity of Chengdao Sea at Yellow River estuary was discussed. Then one model for analyzing the liquefaction based on CPT data was established, and the liquefaction degree of Chengdao Sea was calculated. Results show that, liquefaction does not always begin from surface of seabed to down expansion, but easily appear at the weak layer. The soil horizontal nonuniformity induced different liquefaction depths, and can reach 3.65.0 m under 10th storm waves. Under the water and gravity force, the liquefied soil could fail and form rugged topography.
The study was carried out based on CPT data. Firstly, the soil nonuniformity of Chengdao Sea at Yellow River estuary was discussed. Then one model for analyzing the liquefaction based on CPT data was established, and the liquefaction degree of Chengdao Sea was calculated. Results show that, liquefaction does not always begin from surface of seabed to down expansion, but easily appear at the weak layer. The soil horizontal nonuniformity induced different liquefaction depths, and can reach 3.65.0 m under 10th storm waves. Under the water and gravity force, the liquefied soil could fail and form rugged topography.
2009, (3): 90-97.
Abstract:
Three oil spill models were briefly reviewed. And based on the analysis of problems and defects existing in “Oil Particle” approach, a “TwoStep” method was put forward for oil spill simulation. The method divides oil spill movement into two steps: selfexpansion and turbulent expansion. The former step was handled by refinement of Fay’s equations, while the latter was handled by “Oil Particle” approach. Numerical experiment results show the “TwoStep” method can make up the shortcomings of “Oil Particle” approach and accords with the reality that spilled oil has different diffusion mechanism in the process of movement.
Three oil spill models were briefly reviewed. And based on the analysis of problems and defects existing in “Oil Particle” approach, a “TwoStep” method was put forward for oil spill simulation. The method divides oil spill movement into two steps: selfexpansion and turbulent expansion. The former step was handled by refinement of Fay’s equations, while the latter was handled by “Oil Particle” approach. Numerical experiment results show the “TwoStep” method can make up the shortcomings of “Oil Particle” approach and accords with the reality that spilled oil has different diffusion mechanism in the process of movement.
2009, (3): 98-107.
Abstract:
The study was carried out using the Hybrid Coordinate Ocean Model. Both climatological and 10year (1990-1999) simulating results were used. According to the climatological results, the heat transport from Kuroshio to the East China Sea is maximum in winter, and minimum in summer. The transport to the South China Sea is always positive except in summer. The annual mean of heat transport to the East China Sea and South China sea is 1.67×1014 W and 1.5×1014 W. The salt transport changing trend is similar to the heat. According to the wavelet analysis of 1990-1999 simulating results, the transport to the East China Sea has a period of 4 to 7 years, and is negatively correlated with the nino 3.4 index. While the South China Sea transport’s period is 3 to 4 years, and also shows certain correlation with EL Nino.
The study was carried out using the Hybrid Coordinate Ocean Model. Both climatological and 10year (1990-1999) simulating results were used. According to the climatological results, the heat transport from Kuroshio to the East China Sea is maximum in winter, and minimum in summer. The transport to the South China Sea is always positive except in summer. The annual mean of heat transport to the East China Sea and South China sea is 1.67×1014 W and 1.5×1014 W. The salt transport changing trend is similar to the heat. According to the wavelet analysis of 1990-1999 simulating results, the transport to the East China Sea has a period of 4 to 7 years, and is negatively correlated with the nino 3.4 index. While the South China Sea transport’s period is 3 to 4 years, and also shows certain correlation with EL Nino.
2009, (3): 108-119.
Abstract:
Base on the Hybrid Coordinate Ocean Model (HYCOM), this paper simulated the three dimensional dynamic and thermologic structure of the North Pacific Ocean from 1981 to 2001. After verifying the validation of the model results, the mixed layer depth (MLD) field and its seasonal variation in Japan/East Sea (JES) as well as the interannual variation were analyzed. The analysis shows that there exists strong seasonal and interannual variations of MLD in JES; which can be seen as one of the noticeable hydrological phenomena there. The MLD is deeper in winter and shallower in summer. The variable range is from 10 meters to 100 meters. There exists both similarity and difference between seasonal and interannual variations of MLD in JES. The analysis shows that the topography, the current, the monsoon and the temperature gradient in JES work together, making the variation of MLD in JES.
Base on the Hybrid Coordinate Ocean Model (HYCOM), this paper simulated the three dimensional dynamic and thermologic structure of the North Pacific Ocean from 1981 to 2001. After verifying the validation of the model results, the mixed layer depth (MLD) field and its seasonal variation in Japan/East Sea (JES) as well as the interannual variation were analyzed. The analysis shows that there exists strong seasonal and interannual variations of MLD in JES; which can be seen as one of the noticeable hydrological phenomena there. The MLD is deeper in winter and shallower in summer. The variable range is from 10 meters to 100 meters. There exists both similarity and difference between seasonal and interannual variations of MLD in JES. The analysis shows that the topography, the current, the monsoon and the temperature gradient in JES work together, making the variation of MLD in JES.
2009, (3): 120-126.
Abstract:
Insitu measurements of settling velocities were conducted at Xuliujing in Changjiang Estuary during a flood tidal and medium tidal from Sept. 2007 to Oct. 2007. An OBS3A and a LISST100 (Type B) were used together with sufficient water samples to estimate the settling velocity of suspended sediments. Based on the results of measured relationship between the average floc size and floc density, improvement on the original approach was implemented to relax the basic assumption: (1) floc density are the same for all floc size; (2) the volume of void water was included. Thus a better settling velocity of suspended sediment can be estimated.
Insitu measurements of settling velocities were conducted at Xuliujing in Changjiang Estuary during a flood tidal and medium tidal from Sept. 2007 to Oct. 2007. An OBS3A and a LISST100 (Type B) were used together with sufficient water samples to estimate the settling velocity of suspended sediments. Based on the results of measured relationship between the average floc size and floc density, improvement on the original approach was implemented to relax the basic assumption: (1) floc density are the same for all floc size; (2) the volume of void water was included. Thus a better settling velocity of suspended sediment can be estimated.
2009, (3): 127-135.
Abstract:
A 2-D horizontal model with generalized curvilinear coordinates was applied to simulate flow and sediment transports in the Tianxingzhou reach of the Yangtze River. The model was first calibrated and verified using field data. The variations in the velocity distribution and water surface level were then simulated for the conditions of different flow discharges and different depths of sand mining. The model was also used to forecast the change of the reach and the sedimentation efficiency in mining areas after sand mining through selected typical flow and sediment conditions. The results provide necessary information for quantifying effects of sand mining at different scales.
A 2-D horizontal model with generalized curvilinear coordinates was applied to simulate flow and sediment transports in the Tianxingzhou reach of the Yangtze River. The model was first calibrated and verified using field data. The variations in the velocity distribution and water surface level were then simulated for the conditions of different flow discharges and different depths of sand mining. The model was also used to forecast the change of the reach and the sedimentation efficiency in mining areas after sand mining through selected typical flow and sediment conditions. The results provide necessary information for quantifying effects of sand mining at different scales.
2009, (3): 136-145.
Abstract:
Reclamations in a hilly, fluvial and macrotidal estuary will narrow flood channels. Consequently, it may reduce the safety and stability of hydraulic structures downstream. For this, the paper calculated the maximum scour depth of piers of Yundan Bridge in Fujian province through a 2D numerical model, the semiempire and semitheory formulae about general scour and localized scour. The results indicate that, during flooding period, the scour depth of piers of Yudang Bridge is comparatively serious; so it is necessary to take protecting measures for piers. In addition, influence factors about the maximum scour depth of bridge piers are discussed, and then the conclusion is put forward that actual scour depth of piers hardly reach the calculated amount.
Reclamations in a hilly, fluvial and macrotidal estuary will narrow flood channels. Consequently, it may reduce the safety and stability of hydraulic structures downstream. For this, the paper calculated the maximum scour depth of piers of Yundan Bridge in Fujian province through a 2D numerical model, the semiempire and semitheory formulae about general scour and localized scour. The results indicate that, during flooding period, the scour depth of piers of Yudang Bridge is comparatively serious; so it is necessary to take protecting measures for piers. In addition, influence factors about the maximum scour depth of bridge piers are discussed, and then the conclusion is put forward that actual scour depth of piers hardly reach the calculated amount.
2009, (3): 146-152.
Abstract:
By indoor experiments about the silt in the Yellow River Delta, the characteristics of the silt’s preconsolidation pressure were studied from points of soil genesis, structure and component, and sedimentary environment. The studies show that, the silt in the Yellow River Delta, as a special regional soil, has a different trend of the preconsolidation from the traditional theory. And the preconsolidation of silt is most constrained by soil genesis, structure and component, and is affected by the overlying pressure in little degree.
By indoor experiments about the silt in the Yellow River Delta, the characteristics of the silt’s preconsolidation pressure were studied from points of soil genesis, structure and component, and sedimentary environment. The studies show that, the silt in the Yellow River Delta, as a special regional soil, has a different trend of the preconsolidation from the traditional theory. And the preconsolidation of silt is most constrained by soil genesis, structure and component, and is affected by the overlying pressure in little degree.
2009, (3): 153-159.
Abstract:
In this paper, the nonparametric MannKendallSneyers test was used to analyze the stationarity of the annual streamflow records of Baoqing hydrological station and Caizuizi hydrological station in Naoli River watershed from 1956 to 2005. The empirical model which shows the relationship between rainfall and streamflow was established, and the model was used to assess the impacts of climate changes and human activities on annual streamflows. The result shows that the whole period of annual streamflows from 1956 to 2005 can be divided into two phases: baseline period (1956—1967) and changed period (1968—2005). During the changed period，the interannual and intraannual variability of streamflows changed significantly, and the interannual variability of streamflows was mainly caused by human activities, about 40 percent was caused by climate changes.
In this paper, the nonparametric MannKendallSneyers test was used to analyze the stationarity of the annual streamflow records of Baoqing hydrological station and Caizuizi hydrological station in Naoli River watershed from 1956 to 2005. The empirical model which shows the relationship between rainfall and streamflow was established, and the model was used to assess the impacts of climate changes and human activities on annual streamflows. The result shows that the whole period of annual streamflows from 1956 to 2005 can be divided into two phases: baseline period (1956—1967) and changed period (1968—2005). During the changed period，the interannual and intraannual variability of streamflows changed significantly, and the interannual variability of streamflows was mainly caused by human activities, about 40 percent was caused by climate changes.
2009, (3): 160-169.
Abstract:
Two kinds of snows, called systematic snow and cold outbreak snow, at northern Shandong Peninsula were identified by using EOF (empirical orthogonal function). Forming mechanism of coldoutbreak snow, namely cold snow, discussed climatically. The favorable circulation pattern is lowlevel strong cold advection accompanied by deepening trough with NNW flow strengthening. Then heat flux and water vapour from the sea, as well as lowlevel stratification instability play an important role. The results show that thermal regime and evaporation in December in a year provide more advantaged capability for local snow, as accords with the observational facts. It is baroclinic boundary layer and land friction and orographic forcing that strengthen convection, so that peculiar spacial snow pattern forms at Shandong Peninsula. Further study shows that lowfrequent inner gravity wave is one of important dynamical factors which are able to inspire convection and organize snow.
Two kinds of snows, called systematic snow and cold outbreak snow, at northern Shandong Peninsula were identified by using EOF (empirical orthogonal function). Forming mechanism of coldoutbreak snow, namely cold snow, discussed climatically. The favorable circulation pattern is lowlevel strong cold advection accompanied by deepening trough with NNW flow strengthening. Then heat flux and water vapour from the sea, as well as lowlevel stratification instability play an important role. The results show that thermal regime and evaporation in December in a year provide more advantaged capability for local snow, as accords with the observational facts. It is baroclinic boundary layer and land friction and orographic forcing that strengthen convection, so that peculiar spacial snow pattern forms at Shandong Peninsula. Further study shows that lowfrequent inner gravity wave is one of important dynamical factors which are able to inspire convection and organize snow.
2009, (3): 170-178.
Abstract:
In this paper, in case of fractal properties of river bed and the calculation method of fractal dimension, the fractal principle, technology of Geography Information System (GIS) and theory of river bed evolution were combined. Firstly, the attitude data was automatic extracted from the underwater geographical map by the programming, and the GIS software was used to build the river bed surface DEM. Then the Projection Covering Method was improved to calculate fractal dimension of the bed surface with the DEM. At last, the physics conception was discussed by the comparison among the fractal dimensions of each reach in different periods. This research show that this calculated method is effective and accurate, and supplies a new way to calculate fractal dimension of bed surface. Meanwhile, the bed surface fractal dimension varies with the time and space. It can be used to describe the undulating degree of bed scouring and sedimentation quantitatively, and the fractal dimension is correlation with river regime and pattern. This method and conclusion are valuable to river evolution and river mechanics.
In this paper, in case of fractal properties of river bed and the calculation method of fractal dimension, the fractal principle, technology of Geography Information System (GIS) and theory of river bed evolution were combined. Firstly, the attitude data was automatic extracted from the underwater geographical map by the programming, and the GIS software was used to build the river bed surface DEM. Then the Projection Covering Method was improved to calculate fractal dimension of the bed surface with the DEM. At last, the physics conception was discussed by the comparison among the fractal dimensions of each reach in different periods. This research show that this calculated method is effective and accurate, and supplies a new way to calculate fractal dimension of bed surface. Meanwhile, the bed surface fractal dimension varies with the time and space. It can be used to describe the undulating degree of bed scouring and sedimentation quantitatively, and the fractal dimension is correlation with river regime and pattern. This method and conclusion are valuable to river evolution and river mechanics.