Implementation of a one-dimensional enthalpy sea-ice model in a simple pycnocline prediction model for sea-ice data assimilation studies

To further explore enthalpy-based sea-ice assimilation, a one-dimensional(1D) enthalpy sea-ice model is implemented into a simple pycnocline prediction model. The 1D enthalpy sea-ice model includes the physical processes such as brine expulsion, flushing, and salt diffusion. After being coupled with the atmosphere and ocean components, the enthalpy sea-ice model can be integrated stably and serves as an important modulator of model variability. Results from a twin experiment show that the sea-ice data assimilation in the enthalpy space can produce smaller root-mean-square errors of model variables than the traditional scheme that assimilates the observations of ice concentration, especially for slow-varying states. This study provides some insights into the improvement of sea-ice data assimilation in a coupled general circulation model.     

Parametric study of the wave-induced residual liquefaction around an embedded pipeline

Wave-induced liquefaction in a porous seabed around submarine pipeline may cause catastrophic consequences such as large horizontal displacements of pipelines on the seabed, sinking or floatation of buried pipelines. Most previous studies in relation to the wave and seabed interactions with embedded pipeline dealt with the wave-induced instaneous seabed response and possible resulting momentary liquefaction (where the soil is liquefied instantaneously during the passage of a wave trough), using theory of poro-elasticity. Studies for the interactions between a buried pipeline and a soil undergoing build-up of pore pressure and residual liquefaction have been comparatively rare. In this paper, this complicated process was investigated by using a new developed integrated numerical model with RANS (Reynolds averaged Navier–Stokes) equations used for governing the incompressible flow in the wave field and Biot consolidation equations used for linking the solid–pore fluid interactions in a porous seabed with embedded pipeline. Regarding the wave-induced residual soil response, a two-dimensional poro-elastoplastic solution with the new definition of the source term was developed, where the pre-consolidation analysis of seabed foundation under gravitational forces including the body forces of a pipeline was incorporated. The proposed numerical model was verified with laboratory experiment to demonstrate its accuracy and effectiveness. The numerical results indicate that residual liquefaction is more likely to occur in the vicinity of the pipeline compared to that in the far-field. The inclusion of body forces of a pipeline in the pre-consolidation analysis of seabed foundation significantly affects the potential for residual liquefaction in the vicinity of the pipeline, especially for a shallow-embedded case. Parametric studies reveal that the gradients of maximum liquefaction depth with various wave and soil characteristics become steeper as pipeline burial depth decreases.     

Structural features of the southern Tulum Fault System,western central Argentina,through gravimetric data and geomorphologic analyses

A gravimetric analysis over the Tulum Valley was made. This data was used to reveal the structural setting of the Tulum Fault System situated in the southeastern part of San Juan province in the arid western part of Argentina. This system is the boundary between two geological provinces, the eastern Precordillera Oriental and the Sierras Pampeanas Occidentales. Gravity data was processed using upward continuation and vertical derivative filters and all the results were compared with the geomorphological and the drainage systems maps of the area. Our assessment confirms the presence of two structures in the Pampeano basement with positive anomalies similar to those found in Valdivia and Barboza hills, two important depocenters with low gravimetric gradients separated by a zone with higher gravity anomalies than the depocenters to the east and west. In view of this, a structural map is proposed for the area. This system is important not only because it is the boundary between two geological provinces and has significance regarding regional tectonic issues but also because it controls the surface drainage, soils distribution and groundwater flow of the Tulum basin conditioning the land use distribution.     

行星波波动对平流层剩余环流的影响

利用ECMWF/ECR-40全球再分析资料,通过计算剩余速度,分析了剩余环流的分布特征,同时利用位势高度场资料做了行星波的谐波分析,计算了行星波1波振幅以及2波振幅.最后通过合成分析、谐波分析等方法,分析了行星波活动强弱不同时期剩余环流的变化以及波动发生转化过程中剩余环流的变化.结果表明,行星波1波、2波振幅与剩余速度三者之间有很好的相关性,2波与剩余速度的相关性要好于1波.此外,波动振幅与(v)*的位相比较一致,超前于(w)*大约1～2个月.当波动较强时,剩余环流也较强.当行星波由1波转化为2波后,剩余环流在平流层50 hPa以下是增强的,在30 hPa以上却是减弱的.当2波转化为1波以后,平流层30 hPa以下的剩余环流减弱,但20 hPa以上却是增强的.     

On the Scale-dependence of the Gradient Richardson Number in the Residual Layer

We present results of a technique for examining the scale-dependence of the gradient Richardson number, Ri, in the nighttime residual layer. The technique makes use of a series of high-resolution, in situ, vertical profiles of wind speed and potential temperature obtained during CASES-99 in south-eastern Kansas, U.S.A. in October 1999. These profiles extended from the surface, through the nighttime stable boundary layer, and well into the residual layer. Analyses of the vertical gradients of both wind speed, potential temperature and turbulence profiles over a wide range of vertical scale sizes are used to estimate profiles of the local Ri and turbulence structure as a function of scale size. The utility of the technique lies both with the extensive height range of the residual layer as well as with the fact that the sub-metre resolution of the raw profiles enables a metre-by-metre ‘sliding’ average of the scale-dependent Richardson number values over hundreds of metres vertically. The results presented here show that small-scale turbulence is a ubiquitous and omnipresent feature of the residual layer, and that the region is dynamic and highly variable, exhibiting persistent turbulent structure on vertical scales of a few tens of metres or less. Furthermore, these scales are comparable to the scales over which the Ri is less than or equal to the critical value of Ri _c of 0.25, although turbulence is also shown to exist in regions with significantly larger Ri values, an observation at least consistent with the concept of hysteresis in turbulence generation and maintenance. Insofar as the important scale sizes are comparable to or smaller than the resolution of current models, it follows that, in order to resolve the observed details of small Ri values and the concomitant turbulence generation, future models need to be capable of significantly higher resolutions.     

Residual and Fully Softened Strength Evaluation of Soils using Artificial Neural Networks

A backpropagation artificial neural network (ANN) model is developed to predict the secant friction angle of residual and fully softened soils, using data reported by Stark et al. (J Geotech Geoenviron Eng ASCE 131:575–588, 2005). In the ANN model, index properties such as liquid limit, plastic limit, activity, clay fraction and effective normal stress are used as input variables while secant residual friction angle is used as output variable. The model is verified using data that were not used for model training and testing. The results also indicate that the secant residual friction angle of cohesive soils can be predicted quite accurately using liquid limit, clay fraction and effective normal stress as input variables with R ² = 0.93. The sensitivity analysis results indicate that plastic limit and activity have no appreciable effect on ANN predicted secant friction angles. The secant friction angle predictions of the ANN model were also compared with those of Stark’s et al. (2005) curves and the empirical formulas suggested for the same data sets by Wright (Evaluation of soil shear strengths for slope and retaining wall stability with emphasis on high plasticity clays, 2005). The comparison shows that the ANN model predictions are very close to those suggested by the Stark et al. (2005) curves but much better than the prediction of Wright’s (2005) empirical equations. The results also show that ANN is an alternative powerful tool to predict the secant friction angle of soils.     

CROSS-VALIDATION, INFLUENTIAL OBSERVATIONS AND SELECTION OF VARIABLES IN CHEMOMETRIC STUDIES OF WINES BY PRINCIPAL COMPONENTS ANALYSIS

Cross-validatory estimation of the bilinear model based on principal components is reviewed andKrzanowski's modification of Wold's procedure is described. Two different types of residuals useful forchecking model adequacy are defined and indices measuring the influence of each observed unit on theestimates of the parameters are discussed. A method for the selection of variables derived from Procrustesanalysis is described. Results arising from the study of two sets of enological data are given.     

花岗岩残积土浅层地基承载力评价方法探讨

花岗岩残积土是一种特殊性土体, 是混粒土的一种特殊类型, 从而导致浅层地基承载力也具有特殊性。作者首先分析了现行实验评价方法的利弊关系, 以大量的野外实验和室内实验资料为依据, 确定了其它测试方法评价该类土体浅层地基承载力的可行性, 并提出了利用标准贯入试验击数确定浅层地基承载力的修改方案。并探讨了土体含水量和浅层地基承载力和这些影响因素之间的相互关系。     

三种算法联合迭代反演求取最佳剩余静校正量

估算剩余静校正量可看作是以激发点及接收点剩余静校正量为模型参数的、以叠加能量为目标函数的全局最优值的搜索问题．当地震记录的剩余静校正量大而信噪比较低时，应用相关统计法不能有效地拾取静校正量．本文分别采用了ＣＭＰ道集内道间互相关法、图像边缘提取的Ｌａｐｌａｃｉａｎ算法及ＤＦＰ算法，三种不同算法联合迭代反演可求取最佳的模型参数，使目标函数值达到或接近于全局最优．理论试算及实际资料处理效果表明，这种方法能够解决低信噪比及大静校正量造成的周期跳跃等静校正问题．     

滑带土结构强度再生研究

滑带土抗剪强度参数的正确选取，是没坡稳定性评价和 抗没工程设计中的关键问题。本文在现场调研和室内试验基础上，揭示了只要具有一定滑体厚度的滑带，没滑面具有强度再现象，在抗剪强度参数中尤其存在一定量值的结构强度。