2003年7月8日安徽系列龙卷的新一代天气雷达分析

利用合肥新一代天气雷达资料对2003年7月8日夜间发生在安徽庐江和无为县的龙卷过程进行了简要的分析。7月8日夜间至9日凌晨，与一条自西向东移动的、被包裹在大片层状雨区中的带状对流(飑线)相联系，先后有4个径向速度场上明显的小尺度涡旋特征出现在飑线的前沿。其中一个小尺度涡旋特征持续了大约2小时30分，先后在庐江和无为县产生了龙卷。特别是在无为产生的龙卷，造成了严重的生命和财产损失，其级别为F2～F3，属于较强龙卷。分析表明，此次龙卷为非超级单体龙卷，在反射率因子图上几乎没有任何特征，而在径向速度图上呈现为明显的小尺度涡旋特征，说明新一代天气雷达的使用大大增强了对龙卷的探测能力。     

安徽省县级大雾预报业务系统

分析安徽省多年大雾的天气气候特征和形成的天气学条件,并利用3年T106资料,经相关性检验,基于最优表征大雾形成的天气学特征的因子建立了多元回归方程,用1年T213资料进行检验,最终确定了可用于实时业务MICAPS格式的安徽省县级24h、48h和72h大雾预报的预报业务系统。     

Application of the patient rule induction method to detect hydrologic model behavioural parameters and quantify uncertainty

Finding an operational parameter vector is always challenging in the application of hydrologic models, with over‐parameterization and limited information from observations leading to uncertainty about the best parameter vectors. Thus, it is beneficial to find every possible behavioural parameter vector. This paper presents a new methodology, called the patient rule induction method for parameter estimation (PRIM‐PE), to define where the behavioural parameter vectors are located in the parameter space. The PRIM‐PE was used to discover all regions of the parameter space containing an acceptable model behaviour. This algorithm consists of an initial sampling procedure to generate a parameter sample that sufficiently represents the response surface with a uniform distribution within the “good‐enough” region (i.e., performance better than a predefined threshold) and a rule induction component (PRIM), which is then used to define regions in the parameter space in which the acceptable parameter vectors are located. To investigate its ability in different situations, the methodology is evaluated using four test problems. The PRIM‐PE sampling procedure was also compared against a Markov chain Monte Carlo sampler known as the differential evolution adaptive Metropolis (DREAM_ZS) algorithm. Finally, a spatially distributed hydrological model calibration problem with two settings (a three‐parameter calibration problem and a 23‐parameter calibration problem) was solved using the PRIM‐PE algorithm. The results show that the PRIM‐PE method captured the good‐enough region in the parameter space successfully using 8 and 107 boxes for the three‐parameter and 23‐parameter problems, respectively. This good‐enough region can be used in a global sensitivity analysis to provide a broad range of parameter vectors that produce acceptable model performance. Moreover, for a specific objective function and model structure, the size of the boxes can be used as a measure of equifinality.     

Three‐dimensional numerical analysis of concrete‐faced rockfill dam using dual‐mortar finite element method with mixed tangential contact constraints

Concrete‐faced rockfill dam (CFRD) is a popular alternative to traditional dam types in the last two decades. The modelling of CFRD involves complex multi‐body contact and strong geometry and material nonlinearities. We present a numerical approach for the modelling of CFRDs in this paper. Based on the dual‐mortar finite element method, the presented approach considers different parts of rockfill and all concrete slabs as independent deformable continuum. The multi‐body contacts are modelled using Lagrange multipliers with a weak form segment‐to‐segment contact strategy. To alleviate instability induced by strong geometry nonlinearity in the slab–slab contact, we propose a mixed type of constraints for the tangential contact. A general transformation scheme is introduced to simplify the implementation of contact constraints. Three‐dimensional analysis of Tianshengqiao‐1 CFRD is performed. The nonlinear and time‐dependent deformation of the rockfill is considered. We study the influence of the rockfill deformation on the reliability of the concrete face. Three major concerns of the face, that is, the axial compression, the slab–slab separation and the face‐rockfill separation, are discussed in detail. The numerical results are compared with data from in‐situ observation. Copyright © 2016 John Wiley & Sons, Ltd.     

A dual mortar contact method for porous media and its application to clay-core rockfill dams

The clay-core rockfill dam is a multibody contact system in which the hydromechanical response of the clay core plays a crucial role. This complex problem is highly challenging to model numerically. We present a numerical approach that considers the multibody contact, consolidation, and strong geometric and material nonlinearities for the modeling of clay-core rockfill dams. Within the framework of the dual mortar finite element method, the presented approach considers the contact bodies as independent porous media continuums. The nonlinear contact conditions are derived based on the effective contact traction on contact interfaces and pore pressure continuity. The weak forms are obtained by introducing Lagrange multipliers as additional unknowns, which are then condensed through an extended general transformation. The presented method is first validated with a patch test considering the contact between two porous media. Then, a three-dimensional analysis of the Rumei clay-core rockfill dam is performed. The main numerical analysis concerns are the two observation galleries planned for construction inside the clay core. The galleries consist of dozens of tunnel-like concrete blocks, giving rise to complex concrete-concrete and concrete-clay contacts. The discontinuous separation and sliding between concrete blocks are investigated. For the concrete-concrete contact, both hard and soft joint approaches are evaluated and compared. The pore pressure results of the concrete structures are also analyzed.     

古尔班通古特沙漠蜂窝状沙丘沉积物理化特征及沉积环境

采样分析了古尔班通古特沙漠蜂窝状沙丘表层沉积物的粒度、元素和微形态特征,讨论了其沉积环境.结果表明:(1)古尔班通古特沙漠蜂窝状沙丘表层沉积物以细沙为主;与上部陆壳平均化学组成(UCC)比,常量元素产生亏损,微量元素Co富集明显;化学蚀变指数(CIA)与上部陆壳平均值接近;石英沙颗粒磨圆度适中,微形态特征以碟形坑与不规...     

Response of Callovo-Oxfordian claystone during drying tests: unsaturated hydromechanical behavior

The French National Agency for Nuclear Waste Management is currently studying the Callovo-Oxfordian claystone as a potential repository for nuclear waste. This study focuses on the hydromechanical (HM) unsaturated response of the rock subjected to hydraulic loading. Static atmosphere drying tests highlighted the HM coupling and mechanical anisotropy of the samples. A coupled poroelastic model was proposed, involving highly nonlinear equations. Numerical simulations were performed using the finite element code Code_Aster. Through a sensitivity analysis, the most suitable parameters for estimation were found to be the Biot coefficient and 3 of the 4 independent parameters of the Van Genuchten?CMualem relations. The parameters were estimated according to an inverse procedure that minimizes a cost functional. The estimates could not outline any hysteretic behavior, but they appeared to be divided into two groups (depending on their fitted values). The convergence and stability of the inverse algorithm were studied, and the results showed that direct computations must be run prior to the inversion to ensure its convergence. No plasticity occurred in the samples (according to the model), whereas irreversible phenomena do take place in situ.     

Evolution of the angrite parent body: Implications of metamorphic coronas in NWA 3164

Northwest Africa 3164 is a coarse‐grained angrite that shows reaction coronas, a unique character among achondrites. Olivine (Fo₅₇; 1.2 wt% CaO), fassaitic clinopyroxene, anorthite, and spinel account for 46–47, 28–29, 8–13, and 4–8 vol%, respectively; kamacite is an accessory phase. The spinel grains in contact with clinopyroxene are bounded by discontinuous 20 μm thick coronas of anorthite and olivine, indicating the reaction Cpx + Spl → Ol + An (R1). In addition, irregular coronas of clinopyroxene and spinel developed around the primary anorthite in contact with primary olivine, during the reaction Ol + An → Cpx + Spl (R2). R2 also generated clinopyroxene and spinel films between the secondary olivine and anorthite coronas produced during R1, implying that R1 preceded R2. Both are metamorphic reactions that developed in the solid state. Finally, the coronas are cross cut by μm‐thick veinlets due to a late shock. A mass‐balance study shows that R2 is almost the reverse of R1. The P–T metamorphic evolution of the rock, modeled by calculating a P–T isochemical diagram, indicates an equilibrium T of 940 ± 120 °C at P < 0.9 GPa for the initial assemblage, followed by an increase of T up to approximately 1000–1200 °C during reaction R1 and a subsequent cooling during R2. Several causes are envisaged to account for this metamorphic evolution. Contact metamorphism due to a hot magmatic intrusion in the angrite parent body is favored, as similar metamorphic coronas are well known in metamorphic terrestrial rocks. In addition to differentiation and magmatism, there is now evidence for metamorphism in the angrite parent body, which would have been a large asteroid or a planetary‐sized body.