Mean Sea Level Variation in the South China Sea from Four Decades of Tidal Records in Hong Kong     

H. Baki Iz  C. K. Shum 《Marine Geodesy》2013,36(4):221-233

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Simulated Heat Content Variability in the Upper Layers of the Tropical Indian Ocean     

Imran M. Momin  Neeraj Agarwal  Rashmi Sharma  Neetu  Sujit Basu  Abhijit Sarkar 《Marine Geodesy》2013,36(1):66-81

Ocean General Circulation Model (OGCM) simulations from 1970–2007 are used to study the upper ocean heat content variability in the Tropical Indian Ocean (TIO). Model computed heat contents up to 50 m (denoted by HC50 m hereafter) representing upper ocean heat content and 300 m (HC300 m) representing heat content up to thermocline depth are first compared with heat contents computed from observations of two buoys in the TIO. It is found that there is good agreement between the model and observations. Fourier analysis of heat content is carried out in different regions of TIO. The amplitudes of semi-annual variability for HC50 m and HC300 m are observed to be greater than those for the annual variability in the Bay of Bengal, while in the Arabian Sea there is a mixed result. Heat content tendency is known to be governed by net surface heat flux and horizontal as well as vertical heat transports. For understanding the relative importance of these processes, a detailed analysis of these terms in the tendency equation is carried out. Rossby wave is observed in the annual mode of heat transport while equatorial jet and Kelvin waves are observed in the semi-annual mode of heart transport. Finally, the correlation between heat content and sea surface temperature (SST) and sea level anomaly (SLA), taken one at a time, is computed. It is found that the correlation improves significantly when both these quantities are together taken into account.  相似文献   

Study the Mechanism of Surface Chlorophyll–a Variability in the Southern Tropical Indian Ocean Using an OGCM     

Aravindakshan Jayakumar  Chellappan Gnanaseelan 《Marine Geodesy》2013,36(3):246-256

Eleven years (1997–2007) of SeaWiFS observations and Ocean General Circulation Model sensitivity experiments are used to understand chlorophyll–a variability in the southern tropical Indian Ocean. The strong offshore Ekman transport forced by anomalous southeasterly winds are responsible for inducing higher chlorophyll-a in the eastern equatorial Indian Ocean. In the case of the southwest tropical Indian Ocean, Rossby waves and local upwelling are responsible for lifting the phytoplankton from deep chlorophyll maxima to the surface. Both intraseasonal dynamical response and interannual forcing are responsible for the phytoplankton blooming in the western basin, whereas the interannual forcing is mainly responsible in the east.  相似文献   

Jacked model pile shafts in offshore calcareous soils     

C. Y. Lee  H. G. Poulous 《Marine Georesources & Geotechnology》2013,31(4):247-274

Abstract

This paper describes the results of laboratory tests carried out on model pile shafts in a variety of reconstituted calcareous sands and on silica sand. The factors influencing both the skin friction under static loading and the degradation of skin friction under cyclic loading have been investigated. The grading and crushability of the particles appears to have a significant influence on both, with less favourable performance being found for uniformly graded crushable particles. Relative density and overconsolidation ratio also have some influence.

Under cyclic loading, the amplitude of cyclic displacement and, more specifically, the cyclic slip displacement, influence the extent of cyclic degradation of skin friction.  相似文献   

基于SPIHT小波的DEM自适应压缩方法研究   总被引：1，自引：0，他引：1  

李毅  龚建华 《地理与地理信息科学》2009,25(4)

海量地形数据给其存储、分发和实时渲染带来了极大的挑战,因此迫切需要适合网络环境下地形可视化的数据压缩方法。该文探讨地形复杂度与DEM压缩方法的关系,研究可视化中地形复杂度的计算方法,并提出一种改进的SPIHT小波压缩方法:采用小波分解后的系数对DEM的地形复杂度进行评估,并针对地形复杂度对编码算法进行自适应调节。实验证明,这种改进的SPIHT小波压缩方法采用合适的压缩比进行DEM数据压缩,能够在满足地形可视化需要的同时提高压缩效率。  相似文献   

Hydrologic modeling of the Heihe watershed by DLBRM in Northwest China     

ChanSheng He  Carlo Demarchi  Thomas E. Croley II  Qi Feng  Tim Hunter 《寒旱区科学》2009,1(5):0432-0442

Water shortage is a chronic problem in arid Northwest China.The rapid population growth and expanding urbanization as well as potential climate change impacts are likely to worsen the situation,threatening domestic,irrigation,and industrial supplies and even the survival of the ecosystems in Northwest China.This paper describes the preliminary work of adapting the Distributed Large Basin Runoff Model(DLBRM) to the Heihe watershed(the second largest inland river in arid Northwestern China,with a drainage area of 128,000 km2) for understanding distribution of glacial-snow melt,groundwater,surface runoff,and evapotranspi-ration,and for assessing hydrological impacts of climate change and glacial recession on water supply in the middle and lower reaches of the watershed.Preliminary simulation results show that the Qilian Mountain in the upper reach area produces most runoff in the Heihe watershed.The simulated daily river flows during the period of 1990-2000 indicate that the Heihe River dis-charges about 1×109 m3 of water from the middle reach(at Zhengyixia Station) to lower reach,with surface runoff and interflow contributing 51 and 49 percent respectively.The sandy lower soil zone in the middle reach has the highest evapotranspiration rate and also contributes nearly half of the river flow.Work underway focuses on the DLBRM model improvement and incorporation of the climate change and management scenarios to the hydrological simulations in the watershed.  相似文献   

中国旅游业发展空间差异的综合评判   总被引：2，自引：0，他引：2  

杨建明 《地理科学》2009,29(4)

从旅游收入、游客人数、旅游交通和旅游接待设施4个方面寻找评价旅游业发展空间差异的相对性指标,构建了一种中国旅游业发展空间差异的综合评判模型.评判结果表明,在31个省级行政区中,旅游业的发达程度具有从沿海向内陆、从东、南部向西、北部逐渐减弱的趋势,这与从沿海向内陆逐步对外开放的步伐以及经济发展的客观规律是一致的.研究还表明,旅游业最发达的地区是北京、上海和天津传统直辖市,这与以往认为广东省居于旅游业发展之首的结论有所不同.  相似文献   

Evaluating and comparing methods of sinkhole susceptibility mapping in the Ebro Valley evaporite karst (NE Spain)     

J.P. Galve  F. Gutirrez  J. Remondo  J. Bonachea  P. Lucha  A. Cendrero 《Geomorphology》2009,111(3-4):160-172

Multiple sinkhole susceptibility models have been generated in three study areas of the Ebro Valley evaporite karst (NE Spain) applying different methods (nearest neighbour distance, sinkhole density, heuristic scoring system and probabilistic analysis) for each sinkhole type separately (cover collapse sinkholes, cover and bedrock collapse sinkholes and cover and bedrock sagging sinkholes). The quantitative and independent evaluation of the predictive capability of the models reveals that: (1) The most reliable susceptibility models are those derived from the nearest neighbour distance and sinkhole density. These models can be generated in a simple and rapid way from detailed geomorphological maps. (2) The reliability of the nearest neighbour distance and density models is conditioned by the degree of clustering of the sinkholes. Consequently, the karst areas in which sinkholes show a higher clustering are a priori more favourable for predicting new occurrences. (3) The predictive capability of the best models obtained in this research is significantly higher (12.5–82.5%) than that of the heuristic sinkhole susceptibility model incorporated into the General Urban Plan for the municipality of Zaragoza. Although the probabilistic approach provides lower quality results than the methods based on sinkhole proximity and density, it helps to identify the most significant factors and select the most effective mitigation strategies and may be applied to model susceptibility in different future scenarios.  相似文献   

Response spectra for the deep sediment-filled Rhône Valley in the Swiss Alps     

Hans-Balder Havenith  Donat Fäh  Sonia Alvarez-Rubio  Daniel Roten 《Soil Dynamics and Earthquake Engineering》2009

We present numerical modeling of earthquake ground motion for various profiles across the Swiss Rhône Valley and characterize the seismic response in terms of spectral acceleration. First, we evaluate the relative amplification of 2D with respect to 1D response. Then, we show how the selected bedrock spectrum influences the response spectra of the valley sites. Particular attention is paid to how the internal sediment structure and the often weakly constrained Q-factor shape the seismic response. Results obtained for the different profiles are compared with reference spectra (Swiss building code and Eurocode 8) and for one profile with recorded data as well. From this comparison, we infer that the surficial layer strongly influences spectral acceleration values between 0.1 and 1 s. The total thickness of sediments significantly affects the seismic response at longer periods around the fundamental period of the studied valley sections between 1.8 and 3.6 s.  相似文献   

Simulated multi-scale watershed runoff and sediment production based on GeoWEPP model   总被引：5，自引：2，他引：3  

YU Xinxiao  ZHANG Xiaoming  NIU Lili Prof. Dr.  Key Laboratory of Soil  Water Conservation  Desertification Combating  Ministry of Education  School of Soil  Water Conservation  Beijing Forestry University  Beijing  China  Dr. China Institute of Water Resource  Hydropower Research  Beijing  China Dr.  ... 《国际泥沙研究》2009,24(4):465-478

The runoff and sediment yield data from the Qiaozidonggou, Qiaozixigou, and Lu＇ergou watersheds, in the Loess Plateau of China are used to calibrate and validate the runoff and sediment yield simulated by GeoWEPP model of the WEPP Model at watershed scale. The indices of relative error, R, correlation coefficient, Re, and Nash-Suttcliffe efficiency coefficient Ens are used to evaluate the model fit. The eco-hydrological responses in the Luoyugou and Lu＇ergou watersheds are also forecast based on the WEPP Model. Meanwhile, the relation between vegetation pattern changes and sediment yield in the watershed is discussed, and the responses of runoff and sediment yield in the watersheds concerning forest growth stages are studied. The results show that the relative errors of simulated values of runoff and sediment yield are below 30%, the correlation coefficients axe above 0.90, and the Nash-Suttcliffe efficiency coefficients axe above 0.80. The simulation results present satisfactory performance, thus, the model could be used to simulate the runoff and sediment yield in these small watersheds. It is also observed that soil erosion tended to become severe as precipitation increased in the watershed, while soil erosion has a decreasing trend as forest cover increases and vegetation pattern is optimized. When the watershed is fully covered by forest, erosion and sediment yield are minimized. When the forest cover is about 30% and evenly distributed in the watershed, the erosion intensity is lower than if the forest cover is collectively distributed in the watershed. Erosion varies with different forest growth stages in the watershed; it is more serious at the young and near planting stage and is the smallest at the mature forest stage.  相似文献