Sea Surface Height Variability in the Indian Ocean from TOPEX/POSEIDON Altimetry and Model Simulations

Sea Surface Height (SSH) variability in the Indian Ocean during 1993-1995 is studied using TOPEX/POSEIDON (T/P) altimetry data. Strong interannual variability is seen in the surface circulation of the western Arabian Sea, especially in the Somali eddy structure. During the Southwest (SW) monsoon, a weak monsoon year is characterized by a single eddy system off Somalia, a strong or normal monsoon year by several energetic eddies. The Laccadive High (LH) and Laccadive Low (LL) systems off southwest India are observed in the altimetric SSH record. The variability of the East India Coastal Current (EICC), the western boundary current in the Bay of Bengal, is also detected. Evidence is found for the propagation of Kelvin and Rossby waves across the northern Indian Ocean; these are examined in the context of energy transfer to the western boundary currents, and associated eddies. A simple wind-driven isopycnal model having three active layers is implemented to simulate the seasonal changes of surface and subsurface circulation in the North Indian Ocean and to examine the response to different wind forcing. The wind forcing is derived from the ERS-1 scatterometer wind stress for the same period as the T/P altimeter data, enabling the model response in different (active/weak) monsoon conditions to be tested. The model output is derived in 10-day snapshots to match the time period of the T/P altimeter cycles. Complex Principal Component Analysis (CPCA) is applied to both altimetric and model SSH data. This confirms that long Rossby waves are excited by the remotely forced Kelvin waves off the southwest coast of India and contribute substantially to the variability of the seasonal circulation in the Arabian Sea.     

Effect of Salinity and Currents on Sea Level Variation Along the Indian Coast: A Numerical Study

The process of upwelling/sinking and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. Further,precipitation and monsoonal floods, apart from the marine meteorological parameters, are expected to influence the sea level fluctuations along the coast. This study comprises determining the sea level from the various parameters together with the pure wind stress forcing, which is compared with the observed cycle. However, it is found that there is considerable difference between the computations and observations. This suggests that the sea level is dependent not just on the local forcing alone, but also on the induced background circulation as well. For example, the sea level changes along the east coast of India, particularly the northern region, are more sensitive to freshwater discharge from various rivers joining the Bay of Bengal. This is due to more frequently occurring pre- and postmonsoon cyclonic storms and the associated surges in the Bay of Bengal as compared to the Arabian Sea. Hence the salinity effects are particularly important in the coastal waters off the east coast of India during monsoon months (June-September). For the west coast of India, however, it is expected that the large-scale coastal circulation may play a role in determining sea level changes in addition to other forcings. The salinity effects are negligible along the west coast in the absence of any major river systems that join the Arabian Sea. The local advection currents caused by the offshore directed freshwater discharge from various estuaries joining the coastal bay also seemed to influence the sea level. In order to elucidate the essential dynamics involved and to study the effect of the remote forcing, a three-dimensional baroclinic, nonlinear numerical model is used with appropriate open boundary conditions. The local effect of the current has been incorporated in the west coast model by means of opening a channel at Cochin through which the rainwater is carried away to the model ocean. The low saline plume, cascading from north along the east cost of India, has been incorporated in the east coast model through a proper forcing applied at the northern boundary of the model. With the inclusion of these remote forcings in the models, the disagreement between the simulations and the observations is minimized.     

Recent Sea Level and Sea Surface Temperature Trends Along the Bangladesh Coast in Relation to the Frequency of Intense Cyclones

The French Transportable Laser Ranging System (FTLRS) was deployed in the calibration site of satellite radar altimeters in Corsica over the 2002 and 2005 campaigns. The paper describes the different steps of SLR data processing. The average arcs RMS obtained are about 1–2 cm for Lageos-1&;-2, Starlette and Stella satellites; it is shown that the best results of satellite orbits determination and geocentric positioning are obtained with Eigen-Grace03s gravity model. The difference of FTLRS absolute 3D positioning, between 2002 and 2005, of about 7.7 mm (i.e., 2.6 mm/yr) is less than residual errors of ITRF2005 velocities (of about 4.3 mm/yr).     

Sea Levels and Western Boundary Flow Near a Tectonic Zone in the Northern Pacific

This article concerns an interrelation between the sea levels and the western boundary flow near a tectonic boundary in a local zone in the Northwestern Pacific. In this zone, sea level variations at stations located on the coast facing the Pacific are studied to find the interrelation between variations of the Kurosio flow as an index of the distance of the flow axis off a specific coast. The result is discussed after data processing of the monthly means of the sea levels, and a notice is taken of variations caused by active crustal upheavals during a seismic event, a local earthquake.     

徐州市公交便捷度分析

通过公式计算了徐州市区的各公交站点功能分,在此基础上运用ArcGIS软件将徐州市区地冈进行单元划分,形成公交站区;然后将各公交站区的功能分进行属性赋值,并进行空间分析,得出徐州市区公交分布南公交便捷度大致从市中心及火车站向外扩展为四级,并且公交站点的便捷度均由站点向外呈衰减趋势,且衰减程度越来越明显,尤其是位于公交便捷度低的区域更为明显;最后将公交便捷度泰森多边形分布图与人口密度泰森多边形分布图进行叠加分析．得出目前徐州市公交便捷度与人口密度分布的匹配适应性以主城区向外围逐渐增强．一些地区的公交便捷度还不能满足人口密度分布的状况。     

2003年7～9月固原地电阻率异常变化分析

针对固原台视电阻率2003年7月出现的趋势上升变化,在环境、气候调查的基础上,利用水平层状介质模型反演固原台电性分层结构,计算了降雨量和地下水对其视电阻率的影响,认为大量降雨和地下水上升造成了该台视电阻率的上升。     

Influences of reservoir water level drawdown on slope stability and reliability analysis

To investigate the influences of reservoir water level drawdown on slope stability, a series of numerical simulations were carried out to examine the impacts of slope angle, slope permeability and water drawdown speed on the pore water pressure (PWP) change during seepage, as well as the factor of safety (Fs) of the slope. Based on the numerical results, an estimation model relating the factor of safety to the influential factors mentioned above was developed. The model expression indicates that there are interaction effects between the slope angle, the drawdown speed and the slope permeability, with regard to the influences on slope stability. Furthermore, in view of the uncertainty characteristics of the slope permeability, reliability assessment was performed to examine the influences of those key parameters mentioned above on the probability of slope failure.     

井筒水位预报的一种新方法

数值法预报出抽水井处的水位是均衡域的平均值，它既不代表抽水井井壁水位，更不代表抽水井井筒水位。在数值法拟合、预报结果的基础上，若以抽水井处拟合水位与实抽水位之差作为由计算方法和井的作用共同产生的附加除深（△hf），以附加降深（△hf）与实际单井涌水量（Q实）之比作为附加降深系数（β）；多个抽水井时，可取其算术平均值作为平均附加降深系数（β），附加降深系数（β或β）与设计单井开采量（Q设）之积则是设计开采条件下抽水井的附加降深（△hf），再以抽水井处的预报水位（hj）减去该附加降深（△hf），便可得到抽水井井筒水位（hn）。     

Improvement Of The Mellor–Yamada Turbulence Closure Model Based On Large-Eddy Simulation Data

On the basis of data constructed with large-eddy simulation (LES), an attempt is made to improve the Mellor–Yamada (M–Y) turbulence closure model. Firstly, stably-stratified and convective planetary boundary layers without moisture are simulated by a LES model to obtain a database for the improvement. Secondly, based on the LES data, closure constants are re-evaluated and a new diagnostic equation for the master length scale L is proposed. The new equation is characterized by allowing L in the surface layer to vary with stability instead of constant kz, where k is the von Kármán constant, and z is height.The non-dimensional eddy-diffusivity coefficients calculated from the modifiedM–Y model are in satisfactory agreement with those from the LES data. It isfound that the modified M–Y model improves the original one largely, and thatthe improvement is achieved by considering buoyancy effects on the pressurecovariances andby using the newly proposed equation for L.     

论成矿台阶

成矿台阶系指同一成矿区，同一成矿系列的同一类型矿床的主要矿体赋存在相应的标高范围内，湘南－粤北地区，铌钽矿床的成矿台阶为640－980m;石英脉－黑钨矿床600－1400m，石英脉一白钨矿床100－400m，矽卡岩型白钨矿床100－860m;浅源重熔岩浆系列铅锌矿床600－1100m，深源同熔岩浆系列铅锌矿床－200－100m，最深可达－700m;石英脉型锡石矿床650－1400m，锡石－硫化物，蚀变花岗岩型，云英岩型锡矿床450－650m，香花岭，界牌岭锡多金属矿床－200－270m，利用成矿台阶新理念，指导上述矿床的勘查，可以收到事半功倍的探矿效果。