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1.
Principal component analysis (PCA) as used by meteorologists and oceanographers is a powerful tool for analysis of the spatial and temporal variability of physical fields.This study was aimed at applying "quasi-local PCA for singular factor" to make the cumulative percentage for the first principal component as great as possible, so that a multi-dimensional problem can be reduced to a single-dimensional one, and then stepwise regression analysis can be used to parameterize the relationship between El Nino events and the hydrographic factor anomalies along 137 癊 in winter.The results show that the salinity anomalies on 30 m level, the sigmat on 250 m level, and the temperature on 300 m level at 8 癗 are most closely related with El Nino events because of thermocline movement caused by enhanced upwelling in this area during El Nino years.  相似文献   

2.
Based on the temperature data along 34°N, 35°N and 36°N sections in August from 1977 to 2003, the structure and formation of the Southern Yellow Sea Cold Water Mass (SYSCWM) and its responses to El Nino events are analyzed. Results show that: (1) There exist double cold cores under the main thermocline along the 35°N and 36°N sections. Also, double warm cores exist above the main thermocline along the 36°N section. (2) Thermocline dome by upwelling separates the upper warm water into two parts, the eastern and western warm waters. Additionally, the circulation structure caused by upwelling along the cold front and northeastward current along the coast in summer is the main reasons of double warm cores along the 36°N section. The intermediate cold water is formed in early spring and moves eastward slowly, which results in the formation of the western one of double cold cores. (3) Position of the thermocline dome and its intensity vary interannually, which is related to El Nino events. However, the  相似文献   

3.
Multi-year SST and NCEP/NCAR reanalyzed wind data were employed to study the impacts of El Nino on the Southeast Asian summer monsoon(SEASM),It was found that the impacts of El Nino on the SEASM differed distinctly from those on the East Asian Summer monsoon (EASM) and the Indian summer monsoon(ISM).Composite analysis indicated that the “gear point“of coupling between the Indo-mosoon circulation and the Pacific-Walker circulation was located in the western margins of Southeast Asia when the developing stage of El Nino events covered the boreal summer.The anomalous circulations in the lower and upper troposphere and divergent circulation are all favorable for the strengthening of the SEASM during this period.Following the evolution of El Nino,the “gear point“ of the two cells shifted eastward to the central Pacific when the mature or decaying period of El Nino events covered the boreal summer.The anomalous circulations are favorable for the weakening of the SEASM ,The anomalous indexes of intenstity of SEASM accord well with the above resultsl.Additionally,the difference of SSTA patterns in the tropical In-do-Pacific OCean between the two stages of the El Nino may play an important role.  相似文献   

4.
Based on the current measurement data from the R/V Ryofu Maru of JMA in the equatorial area along 137°E (1972-83) and 155°E (1972-79) the structures of the zonal velocity of the Equatorial Undercurrent (EUC) and the North Equatorial Countercurrent (NECC) and their variations are systematically analyzed in detail.At 155°E, the current at the equator and 100-300 m depth was a typical eastward EUC, it intensified in 1973-75, i.e., in the non-El Nino period. While the corresponding current at 137°E was mostly westward, and the origin of the EUC shifted to north of the equator around 0.5-1.5°N owing to the influence of the New Guinea Coast. The EUC origin disappeared in early July, 1982. Comparing with the EUC disappearance at 159°W, the average speed of an eastward travelling wave would be~1.1m/s.The velocity core of the NECC at 137 E generally shifted northward in winter and southward in summer, and was stronger in summer and weaker in winter. The fluctuations of the NECC were closely related to thos  相似文献   

5.
Circulation in China Seas has been investigated by Chinese oceanographers in some detail for many years. However, owing to data being sparse and scarce, studies were basically concerned in interseasonal (mainly summer and winter) fluctuations and almost none was in the interannual variability of the circulation in China Seas.It is pointed out that the routine (monthly or bimonthly) hydrographical section data on the continental shelf of China Seas accumulated since 1975, can be used to examine the interannual variability of the shelf circulation. An example is given to show there is interannual variability of shelf circulation in the East China Sea. And what is more, a hypothesis is proposed to describe where the interannual variability comes from and to explain why it is strongly correlated with El Nino events.It is strongly suggested that the interannual variability of the shelf circulation in China Seas be studied, as a strategy, with the routine hydrographical survey, which should be seriously conti  相似文献   

6.
In this paper, the spreading way in the southern hemisphere that anomalous warm water piled in tropical eastern Pacific is analysed and then impact of E1 Nino on the variability of the Antarctic sea ice extent is investigated by using a dataset from 1970 to 2002. The analysis result show that in E1 Nino event the anomalous warm water piled in tropical eastern Pacific is poleward propagation yet the westward propagation along southern equator current hash “t been discovered . The poleward propagation time of the anomalous warm water is about 1 year or so. E1 Nino event has a close relationship with the sea ice extent in the Amundsen sea , Bellingshausen sea and Antarctic peninsula . After E1 Nino appears , there is a lag of two years that the sea ice in the Amundsen sea , Bellingshausea sea, especially in the Antarctic peninsula decreases obviously. The processes that E1 Nino has influence with Antarctic sea ice extent is the warm water piled in tropical eastern Pacific poleward propagation along off the coast of southern America and cause the anomalous temperature raise in near pole and then lead the sea ice in Amundsen sea , Bellingshausen sea and Antarctic peninsula to decrease where the obvious decrease of the sea ice since 80’ decade has close relation to the frequently appearance of E1 Nino.  相似文献   

7.
Based on the MASNUM wave-tide-circulation coupled numerical model, the temperature structure along 35°N in the Yellow Sea was simulated and compared with the observations. One of the notable features of the temperature structure along 35°N section is the double cold cores phenomena during spring and summer. The double cold cores refer to the two cold water centers located near 122°E and 125°E from the depth of 30m to bottom. The formation, maintenance and disappearance of the double cold cores are discussed. At least two reasons make the temperature in the center (near 123°E) of the section higher than that near the west and east shores in winter. One reason is that the water there is deeper than the west and east sides so its heat content is higher. The other is invasion of the warm water brought by the Yellow Sea Warm Current (YSWC) during winter. This temperature pattern of the lower layer (from 30m to bottom) is maintained through spring and summer when the upper layer (0 to 30m) is heated and s  相似文献   

8.
SEA LEVEL ALONG THE SOUTHEAST COAST OF CHINA DURING EL NINO   总被引：1，自引：0，他引：1  
In El Nino years, along the southeast China coast, the seasonal cycle of sea level variation - low in spring, high in autumn - is attenuated: specifically, the autumn peak is reduced by about 10 cm. This negative anomaly increases toward the south and occurs at the same time as a similar (but five times larger) sea level anomaly at Truk Island (7.5°N) in the western Pacific.  相似文献   

9.
In the summer of 2010/2011 Chile suffered the third most severe energy and water supply crisis in only one decade.This may be surprising as the Andes which accompany the country along 4,200 km are a water tower and could provide more electricity and water than needed.On top of that,it has to be mentioned that Chile also counts with sunny and windy climates and with excellent geothermal energy resources and thus has a huge potential as far as renewable energies are concerned.After analyzing the existing natural conditions,the infrastructure and the present challenges of climate change,it has to be asked in which way Chile can make use of this potential in the near future,considering the legal and political situation and the technological opportunities.It seems that the resources are still hidden in the Andes,and only the key is missing to realize the country’s natural potential.This research has been based on the analysis of existing literature,media,quantitative data from government institutions and other antecedents obtained by the authors in field work done in the South of Chile in 2010.The added value of this compilation lies in the comprehensive perspective,linking the knowledge of climatologists,hydrologists,mountain researchers and energy experts in order to support a sustainable energy and water supply for the future in Chile.From this present research,it can be concluded that Chile necessarilyhas to adopt new energy-related strategies,particularly those aimed at diminishing the strong dependence on traditional sources of energy and establishing new techniques and technologies for generating electricity and utilizing the vast potential that the country is ready to offer,such as that provided by the Andes along 4,200 kilometers.  相似文献   

10.
Sediment delivery ratio can be used as a measure of sediment connectivity and it can be linked to the structural connectivity(morphological unit, slope length, slope steepness, travel time) of a basin and to the functional connectivity(rainfall-runoff processes at morphological unit scale). In this paper the sediment connectivity approach was applied at basin scale both using Sediment Delivery Distributed(SEDD) model, which takes into account the hillslope sediment transport, and sediment yield measurements carried out at SPA2 experimental basin(Sicily, Italy). The expression of the sediment delivery ratio SDRi of a morphological unit was modified for highlighting two components corresponding to the structural(SDR_(L,i)) and functional(SDR_(F,i)) sediment connectivity, respectively. For SPA2 basin the frequency distribution of the travel time of each morphological unit was used to estimate the coefficient βL of the structural component of the sediment delivery ratio of each morphological unit. Then, using the sediment yield measurements carried out at the outlet of the experimental SPA2 basin in the period April 2000-March 2015, the SEDD model was calibrated at event scale for estimating the coefficient βF of the functional component of the sediment delivery ratio. At event scale the developed analysis stated that the functional connectivity is dependent on the magnitude of erosion events. Intermediate and high events, which were characterized by the lowest values of the functional coefficient, determine a more high functional connectivity and are characterized by a more efficient sediment transport along the hillslopes. Finally, at annual scale, the model was calibrated for the period 2000-2015 and relationships for estimating the coefficient βF,a of the functional component of the sediment delivery ratio taking into account the intensity of erosion events occurring in each year were determined. At annual scale, the analysis demonstrated that the functional coefficient was always greater than the landscape coefficient and the sediment connectivity was always controlled by the low values of the functional component.  相似文献   

11.
This paper investigates the response of the thermocline depth(TD) in the South China Sea(SCS) to the El Ni?o-Southern Oscillation(ENSO) events using 51-year(from 1960 to 2010) monthly seawater temperature and surface wind stress data acquired from the Simple Ocean Data Assimilation(SODA), together with heat flux data from the National Centers for Environmental Prediction(NCEP), precipitation data from the National Oceanic and Atmospheric Administration(NOAA) and evaporation data from the Woods Hole Oceanographic Institution(WHOI). It is indicated that the response of the SCS TD to the El Ni?o or La Ni?a events is in opposite phase. On one hand, the spatial-averaged TDs in the SCS(deeper than 200 m) appear as negative and positive anomalies during the mature phase of the El Ni?o and La Ni?a events, respectively. On the other hand, from June of the El Ni?o year to the subsequent April, the spatial patterns of TD in the north and south of 12°N appear as negative and positive anomalies, respectively, but present positive and negative anomalies for the La Ni?a case. However, positive and negative TD anomalies occur almost in the entire SCS in May of the subsequent year of the El Ni?o and La Ni?a events, respectively. It is suggested that the response of the TD in the SCS to the ENSO events is mainly caused by the sea surface buoyancy flux and the wind stress curl.  相似文献   

12.
A framework is proposed to characterize and forecast the displacement trends of slow-moving landslides, defined as the reactivation stage of phenomena in rocks or fine-grained soils, with movements localized along one or several existing shear surfaces. The framework is developed based on a thorough analysis of the scientific literature and with reference to significant reported case studies for which a consistent dataset of continuous displacement measurements is available. Three distinct trends of movement are defined to characterize the kinematic behavior of the active stages of slow-moving landslides in a velocity-time plot： a linear trend-type I, which is appropriate for stationary phenomena; a convex shaped trend-type II, which is associated with rapid increases in pore water pressure due to rainfall, followed by a slow decrease in the groundwater level with time; and a concave shaped trend-type III, which denotes a non-stationary process related to the presence of new boundary conditions such as those associated with the development of a newly formed local slip surface that connects with the main existing slip surface. Within the proposed framework, a model is developed to forecast future displacements for active stages of trend-type II based on displacement measurements at the beginning of the stage. The proposed model is validated by application to two case studies.  相似文献   

13.
The three dimensional structure of the western boundary current east of the Vietnam coast was determined from measurements by Argo profiling floats which deployed near the east of the Vietnam Coast in October 2007. The trajectories of the Argo floats provided robust evidence that there does exist southward flowing current along the Vietnam coast. The southward current begins at about 15°N, 111°E, flowing along the 1 000 m isobath and extending to 5°N south. The estimated surface and parking depth velocities obtained from the floats suggest that this southward current can extend to 1 000 m depth. The mean surface velocity of the western boundary current is about 49 cm/s, with the maximum speed exceeding 100 cm/s occurring at 11.6°N, 109.5°E in the direction of 245°. The mean parking depth (1 000 m) velocity is 12–16 cm/s with the maximum speed of 36 cm/s occurring at 12.1°N, 109.7°E in the direction of 239°. The water mass analysis suggests that the Kuroshio surface water and NPIW are not apparent in the western boundary current although this time was the favored season for the Kuroshio intrusion into Luzon Strait. The mean geostrophic currents suggest that the Kuroshio intrusion into Luzon Strait during October to December 2007 is very weak, as most of the intruding water was carried eastward at 14°N near the western boundary and little flowed southward along the western boundary, providing an explanation for the absence of Kuroshio surface water and NPIW in the water mass analysis. There is a strong cyclonic circulation in the SSCS during this time, which induces a strong mixing in the western boundary companied by a homogeneous salinity layer between 300–600 m in the salinity vertical distribution. No reversal undercurrent occurred at the intermediate depth along the western boundary east of the Vietnam coast during October to December 2007.  相似文献   

14.
Using interpolation and averaging methods, we analyzed the sea surface wind data obtained from December 1992 to November 2008 by the scatterometers ERS-1, ERS-2, and QuikSCAT in the area of 2°N–39 °N, 105°E–130°E, and we reported the monthly mean distributions of the sea surface wind field. A vector empirical orthogonal function (VEOF) method was employed to study the data and three temporal and spatial patterns were obtained. The first interannual VEOF accounts for 26% of the interannual variance and displays the interannual variability of the East Asian monsoon. The second interannual VEOF accounts for 21% of the variance and reflects the response of China sea winds to El Nio events. The temporal mode of VEOF-2 is in good agreement with the curve of the Nio 3.4 index with a four-month lag. The spatial mode of VEOF-2 indicates that four months after an El Nio event, the southwesterly anomalous winds over the northern South China Sea, the East China Sea, the Yellow Sea, and the Bohai Sea can weaken the prevailing winds in winter, and can strengthen the prevailing winds in summer. The third interannual VEOF accounts for 10% of the variance and also reflects the influence of the ENSO events to China Sea winds. The temporal mode of VEOF-3 is similar to the curve of the Southern Oscillation Index. The spatial mode of VEOF-3 shows that the northeasterly anomalous winds over the South China Sea and the southern part of the East China Sea can weaken the prevailing winds, and southwesterly anomalous winds over the northern part of the East China Sea, the Yellow Sea, and the Bohai Sea can strengthen the prevailing winds when El Nio occurs in winter. If El Nio happens in summer, the reverse is true.  相似文献   

15.
The vegetation and soil are mutual environmental factors, soil characteristics, such as chemical properties and microorganism that affect the vegetation occurrence, development and succession speed. In this study, we evaluated the structure of microbial communities of rhizosphere of Cowskin Azalea(Rhododendron aureum Georgi) populations and compared with non-rhizosphere soils at four sample sites of the Changbai Mountains, China, and analyzed the correlation between chemical properties of soil and microbial communities. The results showed that microbial structure and soil chemical properties are significant superior to non-rhizosphere at all four sample sites. The rhizosphere microorganisms are mainly composed of bacteria, actinomycetes, followed by fungi least. The principal component analysis(PCA) biplot displayed that there are differences between rhizosphere and non-rhizosphere soils for microflora; Through correlation analysis, we found that the bacteria is clearly influenced by p H on the Changbai Mountains, besides p H, other soil features such as NO3–-N. These data highlight that R. aureum as the dominant vegetation living in the alpine tundra is a key factor in the formation of soil microorganism and improving soil fertility, and is of great significance for the maintenance of alpine tundra ecosystem.  相似文献   

16.
Sea surface temperature （SST） variation in the Subei coastal waters, East China, which is important for the ecological environment of the Yellow Sea where Enteromorphaprolifera blooms frequently, is affected by the East Asian winter monsoon （EAWM）, El Nifio-Southem Oscillation （ENSO）, and Pacific Decadal Oscillation （PDO）. In this study, correlations between climatic events and SST anomalies （SSTA） around the Subei （North Jiangsu Province, East China） Coast from 1981-2012 are analyzed, using empirical orthogonal function （EOF） and correlation analyses. First, a key region was determined by EOF analysis to represent the Subei coastal waters. Then, coherency analyses were performed on this key region. According to the correlation analysis, the EAWM index has a positive correlation with the spring and summer SSTA of the key region. Furthermore, the Nifio3.4 index is negatively correlated with the spring and summer SSTA of the key region 1 year ahead, and the PDO has significant negative coherency with spring SSTA and negative coherency with summer SSTA in the key region 1 year ahead. Overall, PDO exhibits the most significant impact on SSTA of the key region. In the key region, all these factors are correlated more significantly with SSTA in spring than in summer. This suggests that outbreaks ofEnteromorpha prolifera in the Yellow Sea are affected by global climatic changes, especially the PDO.  相似文献   

17.
Current data from three moored Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea at sites A (1-24.17°E, 34.82°N), B (122.82°E, 35.65°N) in summer 2001 and site C (120.85°E, 34.99°N) in summer 2003 were analyzed in this paper. Features of the tidal and residual currents were studied with rotary spectral and cross-spectral methods. Main achievements were as follows: 1) Tides dominated the currents. At sites A and B, the semidiurnal tidal current was basically homogeneous in the whole depth, taking a clockwise rotation at site A, and near-rectilinear counterclockwise rotation at site B; while the diurnal tidal current was strong and clockwise near the surface, but decreased and turned counterclockwise with depth; at site C, semidiurnal tidal current dominated and diurnal current took the second, both of which were counterclockwise and vertically homogeneous. Inertial motion contributed to the clockwise component of diurnal fluctuations; 2) The 3-5d fluctuation of residual current w  相似文献   

18.
Based on Hagget's theory of spatial structure,researches on the nodes and field of tourist origins to Huang-cheng Village in Shanxi Province of China have been explored.Nodal hierarchy structure of tourist origins is analyzed with cluster analysis and the gravity model.And field of tourist origins is analyzed with attraction radius index(R)and geography concentration index(G).In the field analysis,R and G of Huangcheng Village are compared with Xidi Village that is a world heritage located in Huangshan City of Anhui Province in China.According to comparison of loca-tions of two areas,influential factors for field area of Huangcheng Village are identified.It is concluded that:1)cluster analysis and gravity model can be complementary methods to each other for nodal hierarchy structure analysis of tour-ist origins;and 2)as far as location is concerned,the weak intensity effect of tourism resources in the tourist region is a major cause for explaining why tourist origins to Huangcheng Village are mainly its neighboring areas.Moreover,it is suggested that the regional effect of tourist resources should be regarded as a component of destination attractiveness when applying gravity model.  相似文献   

19.
Coral bleaching, caused by elevated sea surface temperature(SST), is occurring more frequently and seriously worldwide. Due to the lack of field observations, we understand little about the large-scale variability of thermal stress in the South China Sea(SCS) and its effect on China’s coral reefs. This paper used 4-km high resolution gap-filled SST(Filled SST) data and thermal stress data related to coral bleaching derived from Coral Reef Temperature Anomaly Database(Co RTAD) to quantify the spatial and temporal characteristics of chronic thermal stress and acute thermal stress to China’s coral reefs in SCS from 1982 to 2009. We analyzed the trend of SST in summer and the thermal stress frequency, intensity and duration during this period. The results indicate that, as a chronic thermal stress, summer mean SST in SCS shows an average upward trend of 0.2℃/decade and the spatial pattern is heterogeneous. Waters of Xisha Islands and Dongsha Islands of the northern SCS are warming faster through time compared to Zhongsha Islands and Nansha Islands sea areas of the southern SCS. High frequency bleaching related thermal stress events for these reefs are seen in the area to the northwest of Luzon Island. Severe anomaly thermal stress events are more likely to occur during the subsequent year of the El Nino year for these coral reefs. Besides, the duration of thermal stress varies considerably by anomaly year and by region.  相似文献   

20.
Morphometric analysis is an indispensable tool for hydrological investigation that involves the development and management of drainage basin. This study characterizes the micro watersheds in the Palar sub-watershed using morphometric analysis and assesses its risk by land use and land cover features in a particular micro watershed. Palar sub-watershed is divided into 6 micro watersheds for prioritization based on morphometric and land use analysis. Several morphometric parameters （linear, shape and relief） are determined from the drainage map; ranks are assigned based on their capacity to induce erodability and degradation. Final ranking is based on the composite index calculated from the sum of the ranks of each morphometric parameter. Morphometric analysis reveals micro watersheds 5 and 6 as most susceptible and 2 and 3 as low susceptible. Land use is mapped using IRS ID LISS III satellite data. The risk in terms of watershed degradation involved to each micro watershed is based on the ranks of each land use feature, obtained from a similar composite index as that of morphometric analysis. Land use analysis shows that micro watersheds 2 and 4 fall under high priority category while 5 and 6 under low priority category. Integration of the morphometric and land use analysis shows that only microwatershed 1 falls under the same category in both analyses. Control measures are suggested to contain degradation depending on its specific land use pattern and morphometric features. This study ean be used to prepare a comprehensive watershed plan for the development or for planning resource conservation strategies, by integrating land use features with the drainage characteristics of the region, in particular for a hill ecosystem as the prioritization is at micro level.  相似文献   

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