海南特征文化词及其动态概念化分析

以汉语文化词中专门为表示海南特色民族风俗、区域社会文化信息特征的词语为主要观察对象,文章结合认知语义学基本观点,详尽探讨了这类海南特征文化词的本质属性及其基本特征。对海南特征文化词的动态概念化方式及其动因的分析,论证了从海南特征文化现象或事件,经认知加工,形成象征性语言符号单位的词语及其语义衍生过程。海南特征文化词的认知分析,既是对民族经典文化与汉语传统意义之学的挖掘,更是对文化与海南社会变迁、意识形态的互动关系的语言学理论探讨。

Observed characteristics of atmospheric ducts over the South China Sea in autumn

The observed characteristics of lower atmospheric ducts over the South China Sea(SCS) were analyzed based on Global Position Systerm(GPS) radiosonde data collected four times daily during autumn open cruises from 2006 to 2012.Duct occurrence,thickness,and strength over the SCS were about 40%,150-m thick,and 8 M units,respectively,which were larger than during the summer monsoon period.Most ducts occurred at heights <1 500 m and these ducts easily trap electromagnetic wave clusters with wavelengths <2 m.Diurnal variation of the SCS ducts appeared evident.They occurred more often at midnight at higher altitudes(about 1 100 m),with a thickest layer of about 145 m and less frequently during the evening at lower altitudes(about 800 m),with a thinnest layer of about 125 m.Moreover,ducts during the daytime at a mean height of about 900 m,with the greatest strength of about 10 M units.Furthermore,all duct variables observed over the SCS in autumn decreased from north to south.These findings are useful not only in the design of radar and communication systems,but also for evaluating possible effects of anomalous propagation on meteorological radar and military applications.

The seismic reflecting characteristics of gas hydrate bearing strata and its possible distribution in the South China Sea

The research on gas hydrate is one of the topics of general interest in the field of energy resource and environment. The South China Sea has favorable conditions for the occurrence and formation of gas hydrate. The presence of gas hydrate changes acoustic properties of the sedimentary strata and results in the occurrence of bottom simulating reflectors, which makes the multi-channel seismic investigation an important method to identify gas hydrates. First, the paper, based on results of seismic reflection imaging, analyzes the qualitative seismic reflection characteristics of sedimentary strata containing gas hydrate. Some key seismic imaging techniques are also discussed. Next, a pseudo-well is constructed to perform an impedance inversion to get the quantitative velocity structure of the strata since there is no well in the study area. Finally, the velocity field from geophysical inversion is integrated with the geochemical and geophysical data acquired on the Ocean Drilling Program 184 cruise. All information confirms the presence of gas hydrate and shows its spatial distribution.

Distribution patterns of chlorophyll a in spring and autumn in association with hydrological features in the southern Yellow Sea and northern East China Sea

Two field studies were conducted to measure pigments in the Southern Yellow Sea (SYS) and the northern East China Sea (NECS) in April (spring) and September (autumn) to evaluate the distribution pattern of phytoplankton stock (Chl a concentration) and the impact of hydrological features such as water mass,mixing and tidal front on these patterns.The results indicated that the Chl a concentration was 2.43±2.64 (Mean ± SD) mg m-3 in April (range,0.35 to 17.02 mg m-3) and 1.75±3.10 mg m-3 in September (from 0.07 to 36.54 mg m-3) in 2003.Additionally,four areas with higher Chl a concentrations were observed in the surface water in April,while two were observed in September,and these areas were located within or near the point at which different water masses converged (temperature front area).The distribution pattern of Chl a was generally consistent between onshore and offshore stations at different depths in April and September.Specifically,higher Chl a concentrations were observed along the coastal line in September,which consisted of a mixing area and a tidal front area,although the distributional pattern of Chl a concentrations varied along transects in April.The maximum Chl a concentration at each station was observed in the surface and subsurface layer (0-10 m) for onshore stations and the thermocline layer (10-30 m) for offshore stations in September,while the greatest concentrations were generally observed in surface and subsurface water (0-10 m) in April.The formation of the Chl a distributional pattern in the SYS and NECS and its relationship with possible influencing factors is also discussed.Although physical forces had a close relationship with Chl a distribution,more data are required to clearly and comprehensively elucidate the spatial pattern dynamics of Chl a in the SYS and NECS.

Tectonic Evolution and Geological Characteristics of Hydrocarbon Reservoirs in Marine Mesozoic-Paleozoic Strata in the South Yellow Sea Basin

The South Yellow Sea Basin is the main body of the lower Yangtze area in which marine Mesozoic–Paleozoic strata are widely distributed.The latest geophysical data were used to overcome the limitation of previous poor-quality deep data.Meanwhile,the geological characteristics of hydrocarbon reservoirs in the marine Mesozoic–Paleozoic strata in the South Yellow Sea Basin were analyzed by comparing the source rocks and the reservoir and utilizing drilling and outcrop data.It is believed that the South Yellow Sea Basin roughly underwent six evolutionary stages:plate spreading,plate convergence,stable platform development,foreland basin development,faulted basin development,and depression basin development.The South Yellow Sea Basin has characteristics of a composite platform-fault depression geological structure,with a half-graben geological structure and with a ‘sandwich structure' in the vertical direction.Four sets of hydrocarbon source rocks developed – the upper Permian Longtan–Dalong formation,the lower Permian Qixia formation,the lower Silurian Gaojiabian formation,and the lower Cambrian Hetang formation/Mufushan formation,giving the South Yellow Sea Basin relatively good hydrocarbon potential.The carbonate is the main reservoir rock type in the South Yellow Sea area,and there are four carbonate reservoir types:porous dolomitic,reef-bank,weathered crust,and fractured.There are reservoir-forming horizons similar to the typical hydrocarbon reservoirs in the Yangtze land area developed in the South Yellow Sea,and there are three sets of complete source-reservoir-cap rock assemblages developed in the marine strata,with very good hydrocarbon potential.

Vertical structure and evolution of the Luzon Warm Eddy

Eddies are frequently observed in the northeastern South China Sea （SCS）. However, there have been few studies on vertical structure and temporal-spatial evolution of these eddies. We analyzed the seasonal Luzon Warm Eddy （LWE） based on Argo float data and the merged data products of satellite altimeters of Topex/Poseidon, Jason-1 and European Research Satellites. The analysis shows that the LWE extends vertically to more than 500 m water depth, with a higher temperature anomaly of 5℃ and lower salinity anomaly of 0.5 near the thermocline. The current speeds of the LWE are stronger in its uppermost 200 m, with a maximum speed of 0.6 m/s. Sometimes the LWE incorporates mixed waters from the Kuroshio Current and the SCS, and thus has higher thermohaline characteristics than local marine waters. Time series of eddy kinematic parameters show that the radii and shape of the LWE vary during propagation, and its eddy kinetic energy follows a normal distribution. In addition, we used the empirical orthogonal function （EOF） here to analyze seasonal characteristics of the LWE. The results suggest that the LWE generally forms in July, intensifies in August and September, separates from the coast of Luzon in October and propagates westward, and weakens in December and disappears in February. The LWE＇s westward migration is approximately along 19°N latitude from northwest of Luzon to southeast of Hainan, with a mean speed of 6.6 cm/s.

An Analysis of the Characteristics of Monsoon Onset over the Bay of Bengal and the South China Sea in 2010

Based on NCEP/NCAR daily reanalysis and the Tropical Rainfall Measuring Mission data, the back- ground atmospheric circulation and the characteristics of meteorological elements during the period of the Bay of Bengal monsoon （BOBM） and the South China Sea （SCS） monsoon （SCSM） in 2010 are studied. The impacts of the BOBM onset on the SCSM onset and the relationship between the two monsoons are also analyzed. The two main results are as follows： （l） The BOBM onset obvi- ously occurs earlier than the SCSM onset in 2010, which is a typical onset process of the Asian monsoon. During the BOBM＇s onset, northward jump, and eastward expansion, convective precipitation and southwest winds occurred over the SCS, which resulted in the onset of the SCSM. （2） The relationship among strong convection, heavy rainfall, and vertical circulation configuration is obtained during the monsoon onsets over the BOB and SCS, and it is concluded that the South Asian High plays an important role in this period.

Theoretical Analysis of Coral Reef Stability in South Sea

In this paper,we utilize the variational limiting equilibrium(LE) procedure to theoretically determine the slope stability of homogeneous coral sand in the South China Sea.By establishing a reasonable functional and calculating its extremum,we can deduce the stability factor of a coral reef identical to that obtained by upper bound analysis.To determine the accuracy of the results obtained using the variational LE procedure,we present some classical examples of homogeneous sand slopes without a hard shell and compare our results with those obtained by the upper bound theorem of plasticity.A series of extensive calculations and comparisons reveal that the results obtained by our proposed analysis method and those obtained using classical methods are slightly different,but the variational results are believable.On the other hand,our method solves some stability factors for reef slopes covered with a hard shell,which indicates that the existence of a hard reef shell may significantly enhance the stability of a reef slope,and that there is strong nonlinear relationship between reef stability and the mechanical characteristics of the reef shell,such as its thickness and strength.Finally,based on the variational results presented in this paper,we present a useful chart that offers a convenient and straightforward way to determine the maximum stability factor of reef slopes.Taking into account the influence of the hard reef shell,we found that,in some limit equilibrium cases,the limit stability factor and critical height of a coral slope could be improved significantly.Therefore,this issue deserves careful attention in engineering practice.

Climate change trend and causes of tropical cyclones affecting the South China Sea during the past 50 years

Tropical cyclones(TCs)in the South China Sea(SCS)cause serious disasters and loss every year to the coastal and inland areas of southern China.The types of TCs are usually difficult to forecast,and studies on the understanding of the TCs affecting the SCS are lacking.In this study,the authors use the TC data during 1965–2017 from two best-track datasets to analyse the climatic characteristics in terms of the frequency,the track activity,and the influencing indexes of the TCs affecting the SCS and investigate the possible causes.The results show that,during 1965–2017,there were 535 TCs affecting the SCS,mainly occurring from June to November of each year,with the annual average frequency exhibiting a significant downward trend.Meanwhile,the frequency of the track activity in most areas of the SCS also demonstrate a remarkable decreasing trend but an increase in the Gulf of Tonkin and the Taiwan Strait.The large-scale environmental anomalous westerlies and the decrease of humidity in the mid-and low-level over the northern part of the SCS are likely the main causes for the decrease in frequency and the track activity.In addition,the analysis using the cyclone activity index shows that the influence of the before mentioned TCs in southern China gradually decreases,while the influence of TCs in the SCS show a decreasing trend during past decades.

3-D BAROCLINIC NUMERICAL SIMULATION OF THE SOUTH CHINA SEA I. UPPER CIRCULATION

A three dimensional baroclinic shelf sea model was employed to simulate the seasonal characteristics of the South China Sea (SCS) upper circulation. The results showed that: in summer, an anticyclonic eddy, after its formation between the Bashi Channel and Dongsha Islands in the northeastern SCS, moves southwestward until it disperses slowly. There exists a northward western boundary current along the east shore of the Indo China Peninsula in the western SCS and an anticyclonic gyre in the southern SCS. But at the end of summer and beginning of autumn, a weak local cyclonic eddy forms in the Nansha Trough, then grows slowly and moves westward till it becomes a cyclonic gyre in the southern SCS in autumn. At the beginning of winter, there exists a cyclonic gyre in the northern and southern SCS, and there is a southward western boundary current along the east shore of the Indo China Peninsula. But at the end of winter, an anticyclonic eddy grows and moves toward the western boundary after forming in the Nansha Trough. The eddy’s movement induces a new opposite sign eddy on its eastern side, while the strength of the southward western boundary current gets weakened. This phenomenon continues till spring and causes eddies in the southern SCS.

CLIMATIC CHARACTERISTICS OF THE ONSET OF SOUTH CHINASEA SUMMERMONSOON II.INTER-DECADAL VARIATION

By using the 40-year NCEP (1958-1997) grid point reanalysis meteorological data, we analyzed the inter-decadal variation on the climatic characteristics of the onset of South China Sea summer monsoon. The results are as follows. (1) There was great difference on the onset date of the SCS summer monsoon between the first two decades and the last two decades. It was late on the 6th pentad of May for the first two decades and was on the 4th and 5th pentad of May for the next two decades. (2) Except for the third decade (1978-1987), the establishment of the monsoon rainfall was one to two pentads earlier than the onset of the summer monsoon in all other three decades. (3) The onset of the SCS monsoon is the result of the abrupt development and eastward advancement of the southwesterly monsoon over the Bay of Bengal. The four-decade analysis shows that there were abrupt development of the southwesterly monsoon over the Bay of Bengal between the 3rd and 4th pentad of May, but there was great difference between its eastward movement and its onset intensity. These may have important effect to the earlier or later onset of the SCS summer monsoon. (4) During the onset of the SCS summer monsoon, there were great difference in the upper and lower circulation feature between the first two and the next two decades. At the lower troposphere of the first two decades, the Indian-Burma trough was stronger and the center of the subtropical high was located more eastward. At the upper troposphere, the northward movement of the center of subtropical high was large and located more northward after it landed on the Indo-China Peninsula. After comparison, we can see that the circulation feature of the last two decades was favorable to the establishment and development of the SCS summer monsoon.

STATISTICAL CHARACTERISTICS AND NUMERICAL SIMULATION OF SEA-LAND BREEZES IN HAINAN ISLAND

The sea-land breeze circulation(SLBC) occurs regularly at coastal locations and influences the local weather and climate significantly. In this study, based on the observed surface wind in 9 conventional meteorological stations of Hainan Island, the frequency of sea-land breeze(SLB) is studied to depict the diurnal and seasonal variations. The statistics indicated that there is a monthly average of 12.2 SLB days and an occurrence frequency of about 40%, with the maximum frequency(49%) in summer and the minimum frequency(29%) in autumn. SLB frequencies(41%) are comparable in winter and spring. A higher frequency of SLB is present in the southern and central mountains due to the enhancement effect of the mountain-valley breeze. Due to the synoptic wind the number of SLB days in the northern hilly area is less than in other areas. Moreover, the WRF model, adopted to simulate the SLBC over the island for all seasons, performs reasonably well reproducing the phenomenon, evolution and mechanism of SLBC. Chiefly affected by the difference of temperature between sea and land, the SLBC varies in coverage and intensity with the seasons and reaches the greatest intensity in summer. The typical depth is about 2.5 km for sea breeze circulation and about 1.5 km for land breeze circulation. A strong convergence zone with severe ascending motion appears on the line parallel to the major axis of the island, penetrating 60 to 100 km inland. This type of weak sea breeze convergence zone in winter is north-south oriented. The features of SLBC in spring are similar both to that in summer with southerly wind and to that in winter with easterly wind. The coverage and intensity of SLBC in autumn is the weakest and confined to the southwest edge of the central mountainous area. The land breeze is inherently very weak and easily affected by the topography and weather. The coverage and intensity of the land breeze convergence line is significantly less than those of the sea breeze. The orographic forcing of the central mountain exhibits significant impacts on low-level airflow. A windward land breeze front usually occurs along the coastline between the wee hours and the morning in summer, with an arc-shaped convergence zone about 10 to 30 km off shore. In winter the arc-shaped convergence zone is weak and appears only in the southeast coastal area. Landing on the flat regions of northern to western parts of the island and going inland from there, the sea breeze front at the leeward side meets with that at the windward side in the centre of the island when sea breeze fully develops, causing an intense convergence zone throughout the whole island. Consistent with prevailing winds in direction, the windward sea breeze and leeward land breeze develop quickly but are not distinguishable from background winds.

INTENSITY INDEX OF SOUTH CHINA SEA MONSOON AND ITS VARIATION CHARACTERISTICS

According to the basic characteristics of the activities of summer monsoon in the South China Sea, a standardized index, sI, has been designed that integrates a dynamic factor (southwesterly component) and a thermodynamic factor (OLR) for the indication of summer monsoon in the South China Sea. With the index determined for individual months of June, July and August and the entire summertime from 1975 to 1999, specific months and years are indicated that are either strong or weak in monsoon intensity. The variation is studied for the patterns and sI抯 relationship is revealed with the onset of summer monsoon and the precipitation in Guangdong province and China. The results show that there are quasi-10 and quasi-3-4 year cycles in the interannual variation of the monsoon over the past 25 years. When it has an early (late) onset, the summer monsoon is usually strong (weak). In the strong (weak) monsoon years, precipitation tends to be more (less) in the first raining season of the year but normal or less (normal) in the second, in the province, but it would be more (less) in northeastern China and most parts of the northern China and south of the lower reaches of the Changjiang River and less (more) in the middle and lower reaches of the river, western part of northern China and western China.

DIFFERENCES OF SOUTH CHINA SEA SUMMER MONSOON DERIVED BY NCEP AND ECMWF REANALYSIS DATA

Due to long-term time series and many elements, reanalysis data of National Centers for Environmental Prediction （NCEP） and European Center for MediumRange Weather Forecasts （ECMWF） are widely used in present climate studies. Even so, there are discrepancies between NCEP and ECMWF reanalysis. Some climate fields may be better reproduced by NCEP than by ECMWF. On the other hand, ECMWF may describe some climate characteristics more realistically than NCEP. Xu et al.pointed out that NCEP data are of uncertainty when used for studying long-term trends of climate change. By comparing temperatures and pressures from NCEP and observation, it can be seen that NCEP data show higher reliability in the east and lower-latitudes of China than in its west and higher latitudes, NCEP temperature is of more reality than pressure and NCEP data after 1979 are closer to the observations than before. Yang et al.also revealed some serious problems of NCEP data in the north of subtropical Asia. Regional differences of NCEP data in representation are also explored by other studiest. As for seasonal variability, NCEP simulates relatively real conditions of Chinese summer and annual mean but winter data are relatively bad, as in comparisons of NCEP data wity China surface station observations by Zhao et al.Moreover, Trenberth and Stepaniak showed that ECMWF data had better energy budgets than NCEP data for pure pressure coordinates are adopted by ECMWF. Renfrew et al. compared NCF, P data to ECMWF data in terms of surface fluxes and the results indicate that the time series of surface sensible and latent heating fluxes from ECMWF are 13% and 10% larger than the observations and those from NCEP would be 51% and 27% larger than the observations, respectively. So, Renfrew et al. suggested that it be more appropriate to drive ocean models by ECMWF data. Based on comparisons of multiple elements by some scientists, it seems that ECMWF data are better than NCEP data on global, hemispheric and regional scales. Whereas, reanalysis have big errors in some regions in contrast to observations, especially the variables related to humidity. Since that, researchers should compare the two sets of data and select a better one according to specific problems.

Sedimentary Characteristics of Relict Deposits on the Western South Yellow Sea

Integrated studies of vertical sedimentary sequences, grain sizes, and benthic foraminifera and ostracoda, in combination with AMS 14C dating, and 210pb and 137Cs analysis were carried out in three vibracores taken from the area of relict deposits on the western South Yellow Sea. The relict sands, which are about 0.4 m thick, overlie on the Early Holocene coastal marsh or tidal fiat deposits with an evident erosional interface in between. The middle and upper parts or sometimes the whole of the relict sands have been reworked under the modern dynamic environment. The sedimentation rate varies between 0.204）.30 cmyear-l. The relict sands show a bimodal grain-size distribution pattern in frequency curves, with a sharp peak in the coarse fraction between 3（I） and 4（I） and a secondary peak in the fine fraction of about 7（I）. Of the benthic foraminiferal and ostracod assemblages, the reworked relict sands are characterized by the mixing of the nearshore euryhaline shallow-water species and deeper water species. The erosional interface at the bottom of the relict sands is considered as a regional ravinement surface formed during the transgression in the Early Holocene due to shoreface retreating landwards. The relict sands were accumulated on the ravinement surface during the transgression in the deglaciation period as lag deposits after winnowing and reworking by marine dynamic processes. And the secondary peak of fine fraction in the frequency curve for the relict sands suggests the input of fine-grained sediments during the reworking process. As the conclusion, the relict sands in the study area are interpreted as a type of reworked relict sediments.

Automatic detection of oceanic mesoscale eddies in the South China Sea

This study focuses on the spatial and temporal distribution characteristics of mesoscale eddies in the South China Sea(SCS). An automatic eddy detection method,based on the geometry of velocity vectors,was adopted to obtain an eddy dataset from 21 years of satellite altimeter data. Analysis revealed that the number of anticyclonic eddies was nearly equal to cyclonic eddies; in the SCS,cyclonic eddies are generally stronger than anticyclonic eddies and anticyclonic eddies are larger and longer-lived than cyclonic eddies. Anticyclonic eddies tend to survive longer in the spring and summer,while cyclonic eddies have longer lifetimes in the autumn and winter. The characteristics and seasonal variations of eddies in the SCS are strongly related to variations in general ocean circulation,in the homogeneity of surface wind stress,and in the unevenness of bottom topography in the SCS. The spatial and temporal variation of mesoscale eddies in the SCS could,therefore,be an important index for understanding local hydrodynamics and regional climate change.

Spatial Distribution Characteristics of Surface Tidal Currents in the Southwest of Taiwan Strait

This study was conducted on the spatial distribution characteristics of surface tidal currents in the southwestern Taiwan Strait based on the quasi-harmonic analysis of current data obtained by two high frequency surface wave radar(HFSWR) systems. The analysis shows that the tidal current pattern in the southwestern Taiwan Strait is primarily semi-diurnal and influenced significantly by shallow water constituents. The spatial distribution of tidal current ellipses of M2 is probably affected by the interaction between two different systems of tide wave, one from the northern mouth of Taiwan Strait and the other from the Bashi Channel. The directions of the major axes of M2 tidal current ellipses coincide roughly with the axis of the Taiwan Strait. The spatial distribution of the magnitudes of the probable maximum current velocity(PMCS) shows gradual increase of the velocity from northeast to southwest, which is in accordance with the spatial distribution of the measured maximum current velocity(MMCS). The directions of the residual currents are in accordance with the direction of the prevailing monsoon wind at the Taiwan Strait and the direction of the Taiwan warm current during summer. The bathymetry also shows a significant effect on the spatial distribution characteristics of tidal currents.

Decadal variability of chlorophyll α in the South China Sea: a possible mechanism

Four climatologies on a monthly scale (January, April, May and November) of chlorophyll a within the South China Sea (SCS) were calculated using a Coastal Zone Color Scanner (CZCS) (1979-1983) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (1998-2002). We analyzed decadal variability of chlorophyll a by comparing the products of the two observation periods. The relationships of variability in chlorophyll a with sea surface wind speed (SSW), sea surface temperature (SST), wind stress (WS), and mixed layer depth (MLD) were determined. The results indicate that there is obvious chlorophyll a decadal variability in the SCS. The decadal chlorophyll a presents distinct seasonal variability in characteristics, which may be as a result of various different dynamic processes. The negative chlorophyll a concentration anomaly in January was associated with the warming of SST and a shallower MLD. Generally, there were higher chlorophyll a concentrations in spring during the SeaWiFS period compared with the CZCS period. However, the chlorophyll a concentration exhibits some regional differences during this season, leading to an explanation being difficult. The deepened MLD may have contributed to the positive chlorophyll a concentration anomalies from the northwestern Luzon Island to the northeastern region of Vietnam during April and May. The increases of chlorophyll a concentration in northwestern Borneo during May may be because the stronger SSW and higher WS produce a deeper mixed layer and convective mixing, leading to high levels of nutrient concentrations. The higher chlorophyll a off southeastern Vietnam may be associated with the advective transport of the colder water extending from the Karimata Strait to southeastern Vietnam.

Morphology, sedimentary characteristics, and origin of the Dongsha submarine canyon in the northeastern continental slope of the South China Sea

The Dongsha submarine canyon is a large canyon belonging to a group of canyons on the northeastern South China Sea margin Investigation of the Dongsha canyon is important for understanding the origin of this canyon group as well as the transport mechanism of sediments on the margin, and the evolution of the Taixinan foreland basin and the associated Taiwan orogenic belt. In this study, the morphology, sedimentary characteristics, and origin of the Dongsha canyon were investigated by inte- grating high-resolution multi-channel seismic reflection profiles and high-precision multibeam bathymetric data. This is a slope-confined canyon that originates in the upper slope east of the Dongsha Islands, extends downslope in the SEE direction, and finally merges with the South Taiwan Shoal canyon at a water depth of 3000 m. The total length and average width of the canyon are around 190 and 10 km, respectively. Eleven seismic sequence boundaries within the canyon fills were identified and interpreted as incision surfaces of the canyon. In the canyon fills, four types of seismic facies were defined： parallel onlap fill, chaotic fill, mounded divergent facies, and migrated wavy facies. The parallel onlap fill facies is interpreted as altemating coarser turbidites or other gravity-flow deposits and fine hemipelagic sediments filling the canyon valley. The chaotic fill faci- es is presumed to be debrites and/or basal lag deposits filling the thalwegs. The mounded divergent and migrated wavy seismic facies can be explained as canyon levees consisting mainly of overspilled fine turbidites and sediment waves on the levees or on the canyon-mouth submarine fans. Age correlation between the sequence boundaries and the ODP Site 1144 data suggests that the Dongsha canyon was initiated at approximately 0.9 Ma in the middle Pleistocene. Mapping of the canyon indicates that the canyon originated at the upstream portion of the middle reach of the modem canyon, and has been continuously expanding both upstream and downstream by retrogressive erosion, incision, and deposition of turbidity currents and other gravity transport processes. The ages of the sequence boundaries representing major canyon incision events are in good agreement with those of global sea-level lowstands, indicating that sea-level changes may have played an important role in the canyon＇s development. The Dongsha canyon developed in a region with an active tectonic background characterized by the Taiwan up- lifting and the development of the Taixinan foreland basin. However, no evidence suggests that the canyon formation is directly associated with local or regional faulting and magmatic activities. Turbidity currents and other gravity transport processes （includ- ing submarine slides and slumps） may have had an important influence on the formation and evolution of the canyon.

Intraseasonal oscillation features of the South China Sea summer monsoon and its response to abnormal Madden and Julian Oscillation in the tropical Indian Ocean

By applying the OLR and wind data, rainfall data and the Madden and Julian Oscillation （MJO） index, the paper deals with in traseasonal oscillation features and interannual differences of the South China Sea （SCS） summer monsoon, distribution of its LF circulation and convection fields and rainfall, and path of summer monsoon ISO spreading, as well as impact of tropical IndoMJO on SCS summer monsoon ISO during 19792008. It is found that （1） there are three intraseasonal oscillations of the SCS summer monsoon Intraseasonal Oscillation （ISO） in summer （from May to August） in the climate normal. The SCS summer monsoon ISO goes through six phases （exclusive of weak phase） at every complete fluctuation： developing, the strongest, weakening, restraining, the weakest, and recovering. Due to tropical LC convection spreading to the east and north, the LR convection and circulation fields in the lst3rd and 4th6th phases present the antiphase in the Arabian SeaWest Pa cific latitudinal band. Its corresponding rain bands in the lst3rd and 4th6th phases als present antiphase roughly. The rain band, mainly in tropical regions in the south of 20N, moves eastward with LR convection shifting eastward, while the rain band moves northward with LR convection shifting northward in East Asia （EA） subtropical regions in the north of 20N. （2） The SCS summer monsoon ISO presents significant interannual variations in intensity. There are three stronger monsoon in traseasonal oscillations in summer in the strong SCS monsoon ISO year. The first two oscillations from the tropical Indian Ocean ISO spread northward to the Bay of Bengal first, and then to the South China Sea （SCS） along the 10-20N latitudinal band. They are strengthened there and stimulate the ISO moving to the north to form the tropical IndoISO. Finally they spread to South China （SC） by relay way in the longitudelatitude direction. Moreover, in the weaker SCS summer monsoon ISO, the oscillation weakens greatly and irregularly in intensity with the weaker ISO spreading in the longitudelatitude direction. In average conditions, the tropical Indian ISO spreads to the SCS by about 20 days （one half ISO periods）. （3） MJO1 （the first modal of MJO index provided by the CPC） averaged value in the lst2nd pentads of April has the negative correlation with the SCS monsoon ISO intensity. The tropical IndoMJO is slightly stronger in the subsequent May to August when it is more ac tive in the lst2nd pentads of April, and the ISO also spreads strongly to the SCS, so that the SCS summer monsoon ISO strengthens. Conversely, the SCS summer monsoon ISO weakens. The abnormal MJO in the lst2nd pentads of April contrib utes to a certain theory basis for us to predict the subsequent SCS summer monsoon ISO intensity and analyze the related re gions＇ abnormal rainfall.