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  • 1993 Volume 48 Issue 5
    Published: 15 September 1993
      
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  • RELATIVER SEA LEVEL RISE IN HUANGHE CHANGJIANG AND ZHUJIANG (YELLOW，YANGTZE AND PEARL RIVER)DELTA OVER THE LAST 30 YEARS AND PREDICATION FOR THE NEXT 40 YEARS (2030)
    Ren Mei-e
    1993, 48(5): 385-393. https://doi.org/10.11821/xb199305001
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    In Huanghe Changjiang and Zhujiang(Ye11ow,Yangtze and Pearl River)Delta,China,owing to tectonic sinking,sediment compaction and man-induced land subsidence (chiefly due to over-pumping of ground water) ,relative sea level rise over the last 30 years is much greater than mean rate of sea level rise of the world and China. In Tianjin coast , rate of relative sea level rise is more than 10 times that of the global and China's mean rate. For the next century，according to the best estimate of IPCC.global sea level rise in 2030 will be 18cm .In the three Chinese deltas,considering local land subsidence and the current and projected mitigation measures of the local authorities,lt is estimated that relative sea level rise in 2030 will he 60cm，in Old Huanghe Delta (Tianjin area)，30一40cm in Changjiang Delta (Shanghaiarea)and 20一25cm in Zhujiang Delta. It is hoped that these estimates of relative sea level rise in 2030 may be useful to policy makers in formulating future coastal management plans and development policies.
  • NUMERICAL SIMULATION OF INFLUENCE OF ANTARCTIC LAND ICE-SNOW COVER DISAPPEARANCE ON ATMOSPHERIC GENERAL CIRCULATION AND CLIMATE
    Yang Xiuqun, Xie Qian, Huang Shisong
    1993, 48(5): 394-402. https://doi.org/10.11821/xb199305002
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    By using a perpetual July，nine-level general circulation spectral model with rhomboidal truncation at wavenumber 15，incorporated with a comprehensive set of physical processes，two numerical experiments,i. e. one with normal Antarctic land ice-snow cover and the other without Antarctic land ice-snow cover,were conducted to study the influence of the removal of Antarctic land ice-snow cover on general circulation of atmosphere and global climate. The results exhibit that the removal of Antarctic land ice-snow cover may induce global atmospheric anomalies， which is characterized by}l)The increase of air temperature with a maximum abnormal center ex- ceeding 6. 0 degree in the Antarctic land areas and the weakening of Antarctic polar vortex and westerlies at the high latitudes of Southern Hemisphere，2)The anomalies of ultra-long waves es-pecially those at wavenumber 3 in the Southern Hemisphere，3)The intensification of summer monsoon circulation of east Asia and the weakening of equatorial Walker circulation，4 ) The in-crease of precipitation over east Asia and the coast areas and the decrease of that over equatorial western Pacific，5)The exciting of the two leading wavetrains of the east Asian and the Eurasian patterns in the Northern Hemisphere，6)Climatic anomalies in China with decrease of air tempera-ture in northeastern China and with increase of precipitation in southern China. Therefore，the Antarctic land ice-snow cover plays an important role in the formation of general circulation and climate. The removal of it may lead a serious consequence for global climate. The dynamical mechanism of climatic effect of Antarctic land ice-snow cover is also discussed in this paper.
  • AIRFLOW OVER MOUNTAIN AND DAXINGANLING FOEHN
    Qi Ying,, Fu Baopu
    1993, 48(5): 403-411. https://doi.org/10.11821/xb199305003
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    In China，Daxinganling foehn results in a long"warm ridge" ,which stretches from 40°N to 52°N in the Northeast region ,in the distribution of sea-level average air temperatures in winter. Therefore.Daxinganling foehn seriously influences the climate of China. In this paper , a mesoscale numerical model，which has the ability to simulate the mesoscale mountain climates such as Boulder downslope windstorm in America ,is used. By using this model， the foehn on the eastern slope of Daxinganling Mountains in the Northeast China in the winter is successfully simulated. The cause of formation for this foehn is discussed,and the following con-elusions are obtained: (I)The Daxinganling foehn"warm ridge"at the east slope is due to the intense adiabatic sub-sidence of the strong downslope wind at the eastern steep slope. (2)The wave-breaking region over the Daxinganling eastern steep slope results in the strong downslope wind of the foehn., (3)The static hydraulic jump at the foot of the Daxinganling eastern steep slope makes the foelw occur only at the steep slope.
  • A PHENOMENOLOGICAL STUDY ON TIDAL VARIATION OF TURBIDITY IN THE SOUTH PASSAGE OF THE CHANGJIANG ESTUARY
    Shi Weirong
    1993, 48(5): 412-420. https://doi.org/10.11821/xb199305004
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    The characteristic variation pattern of the near bottom suspended sediment concentration has been identified for the first time during the hydrographic survey of the turbidity maximum in the South Passage of the Changjiang Estuary. In most of the monitoring periods (each generally ex-seeding 25 hours)there are peak values in one to three hours after the reversal of the tidal cur-rent，moreover the concentration decreases sharply thereafter. The origination of those peak values have been analysed based on the diffusion equation. The eddy diffusion coefficients Kz are calcu-lated by using the field data. Meanwhile the vertical profiles of velocity have been fitted in calcu-lation in order to get insight into its tidal variation. The Kz so calculated show a tidal variation course similar to that of the near bottom concentration，i. e. the maximum values occur in the midway of the current speed acceleration phase，1t is indeed closely related to the tidal variations of the vertical gradient of velocity which have large initial values. On the other hand,the longitu-dinal section on the distribution of concentration shows that there is a foreward and backward movement of near bottom turbide water during a certain tidal period. The conclusion is that those peak values of concentration occurring soon after the slack-water are mainly caused by the strongest diffusion of the settled suspended materials due to the largest gradient of velocity at the same time. The resuspension takes place in relative short time since the amount of settled sediments seems to be limited. It disappears before the arrival of the full current，which restrains effectively the further increase of near bottom concentration and explains why the turbidity max-imum in the Changjiang estuary is developed near the bottom.
  • A STUDY ON THE FORMATION AND EVOLUTION OF OASES IN TARIM BASIN
    Fan Zili
    1993, 48(5): 421-427. https://doi.org/10.11821/xb199305005
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    According to the history,the oases in Tarim Basin can be divided into ancient oases,old oasis and new oases. Based on landform they can be classified as valleys,alluvial fans,alluvial plains and river terminus. The formation is affected by hydrology，landform，soil，vegetation and other natural factors，and it is also affected by the enhancement of water conservancy technique，the improvement of productive tool and the growth of population. The development and evolution of oases is mainly decided by the human utilization of water resources. The ancient small oases are mostly distributed in the lower reaches of rivers. Along with the development of agriculture and the enlargement of oases，water becomes insufficient in the lower reaches,which causes the oases moving towards the piedmont area. As a result,the oases in the lower reaches were compelled to be abandoned due to the shortage of water. The further enlargement of oases can not be satisfied by using the water from river channels hence the plain reserviors should be constructed to regulate runoff. That is the reason why the new oases irrigated by using reservoirs are mostly located around the old piedmont oases. Strong winds and sands,serious salinization and river course change are the natural causes for the disappearance of ancient oases. The main human cause is the agricultural irrigation which results in temporal and spatial changes of the distribution of surface water.
  • AN ANALYSIS OF THE ECOLOGICAL CONDITIONS IN THE XINYANG TEA-PRODUCING AREA
    Wang Yinfeng, Zhang Jihong, Zhai Haiguo
    1993, 48(5): 428-436. https://doi.org/10.11821/xb199305006
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    Comparing the ecological conditions of the tea-producing area in Xinyang with that in the other places in China，we have obtained the following conclusions:(1)The temperature is one of the most important factors that affect the tea quality，and the temperature of the Northern Sub-tropical Zone is one of the best for high quality teas. (2)The Xinyang tea-producing area which is located in the Northern Subtropical Zone has favourable moisture condition and fogs，and is a suitable area for high quality tea production.(3)The landforms in Xinyang tea-producing area are mostly low-mountains and hills;the area of land suitable for growing tea is large and the farming intensity of land is low. Therefore,the Xinyang tea-producing area is a high quality tea-producing area. (
  • ON LICHEN KARST EROSION—A MICROMORPHOLOGICAL APPROACH
    Zhang Jie
    1993, 48(5): 437-446. https://doi.org/10.11821/xb199305007
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    Calcarous lichen is a very common biokarst erosional agent. Lichens on limestone sculpture relicts may be the significant destroyers. Although there are some papers on lichen erosion of calcarous rocks,it seems that there is still a lack of work on the relation between erosional forms and lichen tissues. The forms of Lichen erosion on karst rocks are mainly at micro scale. 1n order to collect sam-ples，I did field work on the limestone-built Rome arena in Pula,the limestone bedrock in the karst valley in Plitvice and the limestone karren in Postojna Pojie，former Yugoslavia in 1989. I also did some field work in China ,included Nanjing and Yixing in Jiangsu Province，the Stone Forest of Yongan in Fulian Province.Jiuzhaigou District in Sichuan Province and the limestone hillside in Tibet. From these areas，I collected the lichen erosion samples of limestone under various climatic conditions, including Medeteranean , Northern and Mid-humid Subtropic, and high-altitu- de and semi-arid climatic environments. According to the geometric feature of lichen erosional re- lieves found in research areas，I classified them into dotted，linear，and patched types. There are four basic lichen karst erosional forms named as pinprick , microgroove , ultra borehole and patched etosional nit and related micro-terrace. Pin-prick is a kind of very common microrelieves on the lichen covered limestone. It is a pin- head hole in a scale of 10-4一10-3m，which is bored by lichen fruiting body. There are two types of substrate surface among pinpricks. One is smooth surface which lacks organistns,and another is greyish in colour because of the covering of chasmolithic algae. Section observation under SEM shows that the wall of pinprick is bored by mycobiont hyphae,especial at the bottom of pinprick. In the substrate beneath lichen thallus,it is easy to find some embryonic fruiting bodies，which are composed of weaved micoboint hyphea. They were formed as the result of the gethering of boring hyphea. It showed the genetic roles played by mycobiont boring in the formation of pinprick. Lichen erosional microgrooves are zigzag linear erosional relieves with a width of about 0. 2mm. They are normally ocupied by dark oranic matter and micobiont hyphae. With SEM ob- servation,it shows that the prothallus or hypothalus may be the genetic agent for their formation. As we know ,there are dark edges around lichen thallus named as prothallus or hypothallus. They are composed of densely gethered mycobiont hyphae on which crustose lichen thallus develop. While two or more communities of lichen thallus gethered,the mycobiont hyphae will be strengt- hened. Under SEM observation，Some ultral erosional relieves on the substrate beneath lichen thallus can be observed,including ultra borehole and solutionsal concaved pits. Mycobiont borehole is a kind of ultral endolithic erosional relieves of lichen. Mycobiont hyphea can penetrate calcite crystals. The walls of boreholes can be both smooth and rough，de- pending on the kinds of substrates. Patched erosional pits on the lichen covered limestone surface are also common. Their forma- tion is due to the lichen thallus even effect on the limestone substrate. The edge of patched pits of- ten resembles relict microterrace. Patched erosional pits are greyish with hand specimen. Mechanisms of lichen karst erosion can basically be classified into three groups，i. e. chemi- cal，physical and biological ones. The chemical processe is the essential one. A compound biological process is composed of one or both of the former two processes. Chemical erosion,i. e. ,lichen affected solution on limestone substrate can be observed under SEM. There are both epilithic and endolithic micro solutional features，including at least three types:1)Boreholes formed by fungal hyphae and algal cells;2)Micro etched pyramids on the surf- ace of substrate which is directly touched by lichen thallus;3)Concaved solutional pits on calcite spar of limestone surface beneath lichen thallus. There are two possible chemical processes related to lichen secreted substance (lichenic acids and j or other organic acids ). Mechanical processes of lichen erosion can cause the calcite spar coming off. Micro-fissues and boreholes formed by lichen may benifit the mechanical weathering of limestone substrate. Crustosae endolithic lichen is the one that part of it may grow in the substrate. While the endolith- is part of crustose lichen thallus grows,it may cause the top layer of substrate limestone peeled off. Biological process is a synthetic process influenced by the lichen physiological processes. Pinpricks and micro-grooves are related to certain lichen tissues. They were formed during the processes of lichen growth or reproduction. Respiration of lichen thallus during the night may produce CO2 which is a significant erosional agent. The CO2 exchange of lichen thallus is related to the water content of lichen thallus so it seems that the water content of lichen thallus may further effect on the solution process. To conclude ,lichen karst erosion is a significant biokarst process which exist under various climatic conditions. There are epi-and endolithic lichen karst erosional relieves in micro scale in-eluding pinpricks,microgroovs,ultral boreholes and the patched pits and the related micro-terrace. Lichen karst erosional relieves may related to certain special tissues of lichen. There are three kinds of mechanisms of lichen karst erosion，i. e.，chemical，physical and biological ones. The chemical processes is the basic process. Micromorphology of lichen karst erosion may indicate the special genetic process of itself.
  • SPATIAL STRUCTURE OF SOIL WATER CONTENT AND SAMPLING NUMBER DETERMINATION IN THE FIELD
    Yang Shixiu, Lei Zhidong
    1993, 48(5): 447-456. https://doi.org/10.11821/xb199305008
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    This paper deals with spatial variation and spatial structure of soil一water content based on the test data in the field. 100 sampling sites were arranged along a line with one meter interval locat-ed at the Experimental Station of Guan County in Shandong Province. 505 samples were taken at depths of lOcm，3Ocm，5Ocm，7Ocm，9Ocm，89 samples for bulk density were taken in correspon-deuce with the samples for soil-water content. The analysis of statistical parameter，autocor-relation，and semivariogram have been done for the soil-water contents at different depths the avarage 0-100cm soil-water contente Field data obtained form the study area show that the co- efficient of soil-water content CVs is about 0. 1一0. 25. The values are similar to the CVs from 78 series(5000 samples)，which we were taken form Shanxi，Inner Mongolia，and Hebei Provences. The coefficient of avarage soil-water content CV at 0一1 OOcm is smaller than that of the soil-water content CVs at different depths. 1t is possible to calculate soil-water storage capaci-ty for one meter depth by using average soil-water content and average bulk density. The spatial relationship among the field soil-water contents is of little Significance. Samples which have a certain distance can be treated as random variables. Then the number of samples necessary for various probability level (or confidence level) PI and specified limit (or certain es- timation error )\Can be determined. A method of computer-similitude have been applied to check the necessary number of samples otained form the table. In general ,sampling for soil-water content with specified limit of A=10一l5% at confide-nce level of PI=90一95% is acceptable in practic.
  • NUMERICAL STUDY ON EVAPORATION OF LAND SURFACE IN AKSUO REGION
    Sheng Weaning, Yao Deliang, Li Jiachun
    1993, 48(5): 457-467. https://doi.org/10.11821/xb199305009
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    The study carries out a numerical simulation of land evaporation in arsuo region. Because the region is extremely dry with limited rainfall, the paper introduces in detail the computation mel:hod for evaporation under the condition of shortage of water. Because of artificid irrigation by Xu.jiang Geographical Institute，the underground water level is raised to 1. 5一2. 0m. In order to study the evaporation in wheat fields，we do not adopt completely computational formulae of eva- poration under the condition of drought. Because climate changes are very abnormal，the author adopts aerodynamics method with the resistances in turbulent ABL to carry out numerical simula- tiori. The vegetation in the model is wheat，and the soil is sandy loam. The date is 15一23， June，1992. The soil suface is covered with wheat completely，therefore the model do not consider the condition of bared soils. The author gives the hourly change trend of the field evapo- transpiration by the comparison with measured data. The author studies the heat transport of the soil，emphasizes particularly on the temperature change between soil and the vezetation layer .and deals with the radiation balance.
  • COASTAL EROSION IN CHINA
    Xia Dongxing, Wang Wenhai, Wu Guiqiu, Cui Jinrui, Li Fulin
    1993, 48(5): 468-476. https://doi.org/10.11821/xb199305010
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    Since the end of the 1950s', coastal erosion has taken place extensively in China and has been accelerated. At present，nearly all of the muddy coasts and 70% of the Snady coasts are subject to erosion. Coastal erosion has threatened villages，roads，factories coast-protection forests and tourism resources. The speed of erosion of muddy coasts changes considerably from place to place while that of the sandy coasts ranges between 1 and 2 m/ yr in general. The coral- reef coasts and platform coasts are subject to serious erosions too. The coasts located to the north of the Yangtze River are more seriously eroded than those to the south of the river. Intense coastal erosion has taken place in the provinces of Jiangsu,Shandong,Hebei and Liaoning and in Tianjing Municipality，all of them are located to the north of the Yangtze River. While to the south of the river，strong coastal erosion occurs only along the coasts in Fujian and Hainan provinces. The main causes of coastal erosion in China are the quarrying of sands and the decrease of sediment discharges of the rivers into the sea. It is estimated that about 4000 million tons of beach sands have been exploited annual throughout the country，while the decreased amount of river sediment discharge into the sea is much larger than the amount of beach sands exploitation. The annual sediment discharge of the Huanghe River in the 1980s' was decreased over 300 million tons compared to the average. Sea level rise and ground subsidence in the future 50一100 years will cause the lowlying coastal areas in China to be subject to seawater transgression，and coastal erosion will cause a great loss of land area in China.