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1.
It is found that the mud distributions in the Huanghai Sea and East China Sea are extremely identical with the upwelling's in terms of locality and extent. The process of the mud formation is examined. It is concluded that vertical circulation i.e. upwelling plays a determinant role in the: process and furthermore, it is inferred that wherever upwelling occurs on continental shelf, mud should be formed and, conversely, wherever downwelling takes place, mud should not exist, for which coarse: sediment should substitute.  相似文献   

2.
The determinant role of upwelling in fine sediment patches is examined from the view-points of physical process and biological process respectively. It is pointed out that physical and biologicalprocesses are usually coexistent and interact with each other during the sedimentation of suspended mat-ters. This study used available figures showing the circulation pattern and surface sediment distribution inthe whole China Seas, the Gulf of Maine, the Irish Sea and the North Sea, and additional data to verifythat wherever upwelling exists on the continental shelf, mud must occur; and that wherever dowrtwellingoccurs, coarse sediment substitutes for mud.  相似文献   

3.
The article analyses the temporal-spatial changes of profiles by EOF(Emipirical Orthogonal Function)analysis and DTM analysis of GIS.These profiles,which are not affected by engineering,are chosen from the coast with successive field monitoring data from 1990 to 1999.Temporal and spatial EOF indicates the obvious stability of coast profile paramclino with steep slopes flat.In spatial scale,high tidal flats and deep-water terraces are in a balance state while upper clino with steep slopes are sensitive and the stability is easy to be destroyes.In temporal scale,the erosion and deposition in this area are kepy in balance in a whole.There are almost no change below -8-9.5m.At the same time,it is the lower limit of tidal affection and the erosion and deposition process from it to high tidal flat keep in balance for many years.So the closre depth is appointed to from -8m to -9.5m(Wusong datum mark).  相似文献   

4.
In the river systems, the environmental change always undergoes a process from quantitative to qualitative change. The upper limit of the qualitative change is called threshold. When the process reaches or goes beyond the limit, the original event series will be replaced by the other event series. Investigations show that the evolution of the Huanghe River alluvial fan and delta has also under gone a process from quantitative to qualitative change. The geometric forms in each process are roughly the same. This threshold of the geometric forms not only provides us a quantitative index for plotting the periodicity of the alluvial fan and delta, but also is of importance for estimation of the trend of natural environmental change.It is shown that there are three periodic alluvial fans of the Huanghe River since the middle Holocene and four periodic delta since 1855 A.D., the thresholds of their geometric forms are from 0.93 to 0.94 and from 1.2 to 1.21 respectively.The changing trend in the past and the na  相似文献   

5.
The northeast region is one of the principal mire distribution regions in China. According to the process of peat formation and accumulation , middle geomorphology type controlling water source supplement and the plant cover, 2 types, 10 subtypes and 27 mire bodies are divided. The mire area decreases gradually from north to south. There is more peat mire in the mountain and there is mainly gley mire without peat in the plain. The paper also explains the mire types in the principal mire distribution region and the utilization of mire in the fields of agriculture, forest, animal husbandry. The mire is a wetland ecosystem. It can reserve a lot of water, adjust rivers, humidify air. Thereby , attention must be paid to protecting ecological balance in the process of reclaiming mire and the mire protection.  相似文献   

6.
Lanzhou Valley Basin is composed of two smaller diamond-shaped basins striking from NW to SE and including 6 river terraces. The lower terraces remaining even and smooth are main sites for city buildings. The main function of Lanzhou urban settlement is a ferry and transport centre. Lanzhou used to be an im-portant crossing site and post on the "silk road",and then became a transport and trade centre in Northwest China. In the middle part of the 17th century, Lanzhou became the capital of Gansu,a new province. The development process of Lanzhou urban settlement indicates that urban settlement is a system consisting of natural environment and human society based on the former.  相似文献   

7.
The desertification process is rapidly developing at present and 61.5% of the land area in the zone are already desertified.Among the desertified lands, 26.9% are seriously desertified, 25% most seriously desertified and 47.4% are the lands where desertification is under way. They are caused by over-reclamation for farming, over-grazing, unreasonable collection of firewood,the destruction of vegetation and the misuse of water resources. Under the ecological environment in semi-arid zone,the degraded environment process possesses the ability of restoring to its original status as soon as the interruption of excessive human activities are eliminated. The fencing- and-self-cultivating method is an effective measure adopted universally in semi-arid zone to cure the desertified lands.The desertified lands can be readjusted and controlled easily if other controlling measures are supplemented. The fundamental ways to control desertification are to utilize rationally the resources, to readjust the existing land  相似文献   

8.
Model of wind-generated ambient noise in stratified shallow water   总被引：1，自引：0，他引：1  
In order to build a rapid ocean ambient noise model adapted for a stratified shallow water, a hybrid model of normal mode method (for far field) and ray method (for near field) is suggested which combines the advantages of both methods. Since the near field of wind-generated noise is not sensitive to the sound speed profile, the sound speed profile is regarded as a constant; which makes the model rapid and accurate. The simulation results are in agreement with those of the wave model.  相似文献   

9.
The investigation shows that the concentrations of nutrients are high in estuarine and coastal waters and low in offshore waters. The concentration of nitrate in estuaries is controlled through a physical mixing process and is also affected by hiotic activity. The annual transport of total inorganic nitrogen and dissolved phosphate-phosphorus from the Huanghe River water to the sea is about 8.45×104 and 1.45×103 tons respectively. The distributions of inorganic nitrogen and silicate in interstitial water of surface sediments are similar to those in surface and bottom sea water. Their contents in interstitial water are227 552μmol/l (average 375) for ammonia, 0.31 -9.0μmol/l (average 1.6) for nitrite, 0 41μmol/1 (average 6.0) for nitrate, and 41 139μmol/l (average 77) for silicate. The average concentrations of phosphate in the surveyed area are 0.64μmol/l for seawater and 1.2μmol/l for interstitial water. A cycle of phosphate in the estuary is also suggested in this paper.  相似文献   

10.
With the astounding development and gradual improvement of remote sensing technology, as an advancedscience technology, it is used to provide multi-temporal, large scope real-time information for land-use dynamic change,and also is one of the best efficient methods for studying the earth resources and environment. Remote sensing image hasits characteristics of ample information and reflecting the objective realities. The paper uses multi-temporal TM images in1986, 1996 and 2000, and relevant statistic data to analyze land-use changes of Dalian City in Liaoning Province of Chi-na over ten years by means of the correlation analysis method. The results have shown that two methods could con-formably reflect the present land-use change. Urbanization is closely correlative to natural factors and economic develop-ment. Especially in recent 20 years, under the influence of the reform and open-up policy, Dalian, as a specific coastcity, is becoming an international metropolis.  相似文献   

11.
In the present paper a three-dimensional model has been used to calculate the vertical structure of the current generated by typhoon surge. The aim of this work is to obtain support for the depth-averaged model, which is based upon two basic assumptions. One of them is that the current has a negligible vertical structure and the other is that the velocity veering angle is small. Our results show that, in most of the real storm surge cases, these two assumptions are quite good approximations of the real situation, especially when water is shallow, and the locations are near the shore. These features are usually encountered in the real storm surges with which we are concerned. Therefore, we can expect that the two-dimensional depth-averaged model will give satisfactory results. The experiments carried out by using a straight coastline and uniform depth give vertical structures which are compatible with the conclusions previously reached by other authors.  相似文献   

12.
AGGLOMERATION AND RADIATION EFFECT OF THE PULL OF URBANIZATION   总被引：2，自引：1，他引：1  
In order to explore the train of thought for China‘s urbanizing development and coordinated rural eco-nomic development, and to find good ways of solving rural problems through urbanization, this paper absorbs the push-and-pull forces theory and the systematic dynamic theory in the traditional population migration theories, views urbanization as a dynamic system, makes research on the push-and-pull mechanism of urbanization. The pulling power of urbanization is analyzed according to two aspects, the agglomeration effect and the radiation effect of cities. The agglomeration effect provides continuous propelling force for urbanization, and the radiation effect further accelerates the urbanization process by pushing forward the development of rural economy. Of course, the slow de-velopment of urbanization can result in the hindrance to rural economic development.  相似文献   

13.
The Green Corridor in the lower reaches of the Tarim River is not only a unique natural landscape in desert but also an important passageway. Nowadays, the ecologic environment of the corridor is getting worse and worse due to man's economic activities and the lack of knowledge of the importance of the environment, which is one of is the three environment problems in Xinjiang. The corridor is in great need of planning and managing.  相似文献   

14.
The area of the intermontane basins in the Xuefeng Mountain region is 4,000 km2. These basins are the most favourable area for agriculture in the mountainous region. Unfortunately, in each basin the eco-environment has gradually worsened because of the irrational utilization of natural resources. A rational model of agro-ecologic- economic system of intermontane basin must be formed so as to exploit and utilize rationally the natural resources. The intermontane basins may be divided into 3 ecologic belts of agriculture. Here are some ecologic-economic problems in the development: The resources of the outer mountains lie waste, but the valley basins in centre are over-development; the low mountains and hillocks are cultivated for dry crops so that the water and soil losses are serious and the natural disasters are frequent. Therefore, the agro-economic, agro-biologic and eco-environmental subsystems form a complete agro-ecologic-economic system of intermontane basins. Developing rationally the resources  相似文献   

15.
Volume transport fluctuations of the Florida Current (Gulf Stream), generated within the Straits of Florida by local meridional wind stress, is investigated. A simple coastal response model was applied to the Straits of Florida and forced by along-channel winds only. The predicted volume transports were in good agreement with transport estimates derived from moored current meters and cable voltages for winter winds. Surprisingly, good agreement was also found for the annual transport cycle for the two years of available data, suggesting that the seasonal change in local along-channel wind forcing provides a significant contribution to the annual transport cycle of the Gulf Stream.  相似文献   

16.
The removal of bed material from active river channels usually affects the bed profile of the streambed, causing progressive degradation upstream and downstream of the extraction site. These effects can extend for kilometers affecting hydraulic structures located in the vicinity of the river reach. In this paper, the geomorphic effects of gravel mining are reviewed and summarized. Some cases in Venezuelan streams are presented to illustrate the problem. To describe the processes of erosion and sedimentation in a gravel extraction pit, a recent developed mathematical model for the simulation of flow and sediment transport in gravel-cobble bed streams is applied to a hypothetical case of gravel mining in a river channel. A simple rectangular dredge pit is imposed as initial condition in the channel bed, and changes in bed elevations and grain size distribution of bed material are calculated by using the numerical model. The process of deposition within the pit, and the downstream and upstream migration of the erosion wave are well simulated by the model and closely resemble the phenomena observed in laboratory experiments. The response of the friction coefficient to the changes in flow and bed elevations shows the importance in modeling adequately flow resistance and sediment transport in gravel-cobble bed streams.  相似文献   

17.
A two and a half layer oceanic model of wind-driven, thermodynamical general circulation is appliedto study the interannual oscillation of sea surface temperature (SST) in the South China Sea (SCS). Themodel consists of two active layers: the upper mixed layer (UML) and the seasonal thermocline, with themotionless abyss beneath them. The governing equations which include momentum, continuity and sea.temperature for each active layer, can describe the physics of Boussinseq approximation, reduced gravityand equatorial β-plane. The formulas for the heat flux at the surface and at the interface between twoactive layers are designed on the Haney scheme. The entrainment and detrainment at the bottom of theUML induces vertical transport of mass,momentum and heat, and couples of dynamic andthermodynamic effect.Using leap-frog integrating scheme and the Arakawa-C grid the model is forced bya time-dependent wind anomaly stress pattern obtained from category analysis of COADS. The numerical results indicate that t  相似文献   

18.
THE WESTERN BOUNDARY CURRENT OF THE PACIFIC AND ITS ROLE IN THE CLIMATE   总被引：1，自引：0，他引：1  
On the basis of the CTD data gathered by the-R / V Science I in each Oct. of 1986-1988 and the winter averaged temperature anomaly in southeast China, the interannual variability of the Western Boundary Current (WBC) is examined in terms of volume transport by inverse calculation and its role in the climate is studied by statistical method.The estimated transport is 50,20, and 33 x 106 m3 / s for the Kuroshio and 24,34, and 36 x 106 m3 / s for the Mindanao Current (MC)in October of 1986,1987, and 1988, respectively.The WBC is the biggest channel in the ocean for transporting heat poleward and plays an extremely important role in establishing and maintaining the global heat balance. Results showed that meridional heat transport by the Kuroshio northeast of Luzon apparently dominates coldness or warmness in winter in southeast China.Two phenomena observed in the western Pacific but not in the western Atlantic are the warm pool and the equatorward flowing MC which, together with the North Equatorial Counte  相似文献   

19.
An important raw material for making agar-agar is the seaweed Gracilaria, which is distributed worldwide but grows mostly in the natural state in warm tropic and subtropic zones. Some countries have tried in small scale to cultivate the seaweed, but only along the coasts of South China has it been done successfully on a large commercial scale (in pond and raft culture).  相似文献   

20.
Jiaozhou Bay data collected from May 1991 to February 1994, in 12 seasonal investigations, and provided the authors by the Ecological Station of Jiaozhou Bay, were analyzed to determine the spatiotemporal variations in temperature, light, nutrients (NO3^--N, NO2^--N, NH4^ -N, SIO3^2--Si, PO4^3--P), phytoplankton, and primary production in Jiaozhou Bay. The results indicated that only silicate correlated well in time and space with, and had important effects on, the characteristics, dynamic cycles and trends of, primary production in Jiaozhou Bay. The authors developed a corresponding dynamic model of primary production and silicate and water temperature. Eq. ( 1 ) of the model shows that the primary production variation is controlled by the nutrient Si and affected by water temperature; that the main factor controlling the primary production is Si; that water temperature affects the composition of the structure of phytoplankton assemblage; that the different populations of the phytoplankton assemblage occupy different ecological niches for C, the apparent ratio of conversion of silicate in seawater into phytoplankton biomas and D, the coefficient of water temperature‘s effect on phytoplankton biomass. The authors researched the silicon source of Jiaozhou Bay, the biogeochemical sediment process of the silicon, the phytoplankton predominant species and the phytoplankton structure. The authors considered silicate a limiting factor of primary production in Jiaozhou Bay, whose decreasing concentration of silicate from terrestrial source is supposedly due to dilution by current and uptake by phytoplankton; quantified the silicate assimilated by phytoplankton, the intrinsic ratio of conversion of silicon into phytoplankton biomass, the proportion of silicate uptaken by phytoplankton and diluted by current; and found that the primary production of the phytoplankton is determined by the quantity of the silicate assimilated by them. The phenomenon of apparently high plant-nutrient concentTations but low phytoplankton biomass in some waters is reasonably explained in this paper.  相似文献   

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