基于不同时间尺度的地质灾害对 气候变化响应研究

地质灾害对气候变化响应关系是近年来研究的热点和焦点,文章以不同时间尺度的地质灾害为研究对象,开展了不同时间尺度下地质灾害诱发因素与气候变化响应关系研究,认为气候变化及气候变化过程中的温暖湿润期与强降水期往往是地质灾害的高群发期。主要取得了如下认识：万年与千年尺度上,黄河上游地区的5个滑坡集中发育期分别对应于黄土高原马兰黄土中的两层弱发育古土壤层L1 4和L1 2、末次冰期晚期/全新世过渡期、全新世适宜期和现代;百年尺度上,全国地质灾害的高发期响应于中世纪暖期和19世纪晚期的季风强盛期;十年尺度上,全国地质灾害的群发期响应于年均降水量;年际尺度上,地质灾害发生数量与年累计极端降水量有很好的响应关系,反映了气候变化对地质灾害发生的制约关系。月份尺度上,我国崩塌、滑坡、泥石流等突发性地质灾害的发生时间主要集中在每年的雨季,地质灾害的高发时段与各地的雨季具有较好的一致性。     

Winkler地基上有限长梁联合共振分析

为进一步完善弹性地基上梁的非线性振动理论以及满足实际工程的需要,本文对三种联合共振情况进行了研究。文中基于已建立的Winkler地基上有限长梁的非线性振动方程,运用Galerkin离散法以及多尺度法推导其稳态运动方程组,分析了主/次联合共振时,结构参数及初始条件对系统幅频响应曲线、调谐-相位曲线的影响,初步探讨了主/超联合共振、次/超联合共振的基本性质。研究结果表明:当且仅当两个激励频率是可公度关系时,联合共振才存在稳态响应;对于一个给定的调谐参数,系统最多存在七个解,而解的最终形式是由初始条件决定;系统参数及初始条件的微小变动,可能会激烈地改变系统的响应;工程中为了较好地抑制结构的振动,必须选择合适的方法提高系统的刚度。     

Interdecadal Variations of Phase Delays Between Two Ni(n)o Indices at Different Time Scales

Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4(1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that thereare two types of period bifurcations in the Nino indices and that period bifurcation points exist only in the region where the wavelet power is small. Interdecadal variation features of phase delays between the two indices vary with different time scales. In the periods of 40-72 months, the phase delay changes its sign in 1977: Nino 1+2 indices are 2-4 months earlier than Nino 3.4 indices before 1977, but 3-6 months later afterwards. In the periods of 20-40 months, however, the phase delay changes its sign in another way:Nino 1+2 indices are 1-4 months earlier before 1980 and during 1986-90, but 1-4 months later during 1980-83 and 1993-2001.     

Fluid flow dynamics under location uncertainty

We present a derivation of a stochastic model of Navier Stokes equations that relies on a decomposition of the velocity fields into a differentiable drift component and a time uncorrelated uncertainty random term. This type of decomposition is reminiscent in spirit to the classical Reynolds decomposition. However, the random velocity fluctuations considered here are not differentiable with respect to time, and they must be handled through stochastic calculus. The dynamics associated with the differentiable drift component is derived from a stochastic version of the Reynolds transport theorem. It includes in its general form an uncertainty dependent subgrid bulk formula that cannot be immediately related to the usual Boussinesq eddy viscosity assumption constructed from thermal molecular agitation analogy. This formulation, emerging from uncertainties on the fluid parcels location, explains with another viewpoint some subgrid eddy diffusion models currently used in computational fluid dynamics or in geophysical sciences and paves the way for new large-scales flow modeling. We finally describe an applications of our formalism to the derivation of stochastic versions of the Shallow water equations or to the definition of reduced order dynamical systems.     

Dependence of radar quantitative precipitation estimation error on the rain intensity in the Cévennes region,France

Abstract

Radar quantitative precipitation estimates (QPEs) were assessed using reference values established by means of a geostatistical approach. The reference values were estimated from raingauge data using the block kriging technique, and the reference meshes were selected on the basis of the kriging estimation variance. Agreement between radar QPEs and reference rain amounts was shown to increase slightly with the space–time scales. The statistical distributions of the errors were modelled conditionally with respect to several factors using the GAMLSS approach. The conditional bias of the errors presents a complex structure that depends on the space–time scales and the considered geographical sub-domains, while the standard deviation of the errors has a more homogeneous behaviour. The estimation standard deviation of the reference rainfall and the standard deviation of the errors between radar and reference rainfall were found to have the same magnitude, indicating the limitations of the available network in terms of providing accurate reference values for the spatial scales considered (5–100 km²).

Editor D. Koutsoyiannis; Guest editor R.J. Moore

Citation Delrieu, G., Bonnifait, L., Kirstetter, P.-E., and Boudevillain, B., 2013. Dependence of radar quantitative precipitation estimation error on the rain intensity in the Cévennes region, France. Hydrological Sciences Journal, 59 (7), 1300–1311. http://dx.doi.org/10.1080/02626667.2013.827337     

论乡村聚居空间结构优化模式——RROD模式

本文受启于TOD理论与实践在城市地域空间结构优化过程中所发挥的重要作用,借鉴以往乡村聚居单元规模与空间结构研究成果,试图提炼出一种乡村聚居空间结构优化模式——乡村公路导向发展模式（Rural Road-Oriented Development Model,简称RROD模式）,并针对概念内涵、构建原则、框架、类型、空间尺度等进行系统分析。同时,重点从设施门槛、耕作半径、邻里交往以及出行距离感知等方面对RROD合理规模与结构进行了综合论证,认为RROD规模半径一般取值范围为450-700m,人口规模一般取值范围为1500-3500人,占地面积一般取值范围为30-75hm²,距离一般取值范围为3.5-5.0km。但由于该取值范围是基于均质地域及一般发展条件假设,其结论具有一般理论指导性,但在具体实践过程中,必须根据实际情况进行适当调整与修正。     

不同蒸散发计算模型在新疆喀什地区的适用性及对比分析研究

为分析不同蒸散发模型在新疆喀什地区的适用性,结合国内常用两种蒸散发计算方法,应用区域实测蒸发数据,按照年、月、季三个时间尺度分析两种方法计算的适用性和精度。结果表明:VIC模型在年尺度上适用性好于P-M模型,但在夏季和秋季尺度上,P-M模型好于VIC模型,各模型在夏季蒸发计算上好于其他季节。研究成果对于喀什地区蒸发计算提供重要的方法参考。     

在EBEX-2000实验资料中湍流耗散率、长度尺度和结构参数特征

采用2000年8月在美国加州棉花地两个高度上应用超声三分量仪、快速响应温度和湿度仪进行的EBEX-2000 (International Energy Balance Experiment, 2000, 简称EBEX-2000) 风速三分量、温度和湿度湍流实验观测数据, 计算分析了在不同稳定度下的湍流能量和热量耗散率和湍流结构参数特征.并与Kansas和长白山原始森林湍流实验得到的结果进行了比较, 得到了一些湍流特征量在不同下垫面情况下的一些有意义的特征.     

Multi-scale study of permeability evolution of a bentonite clay owing to pollutant transport: Part II. Application to an MG-bentonite

This paper is concerned with the application of a multi-scale model of permeability evolution to the simulation of permeation tests of lead nitrate solutions in a compacted natural bentonite. In a previous work, the weathered hydraulic conductivity has been measured for different pollutant concentrations. Textural and structural evolutions induced by heavy metal sorption have also been investigated, therefore giving us information about the various pore spaces that may be encountered during the process of pollutant leaching. Such knowledge has been exploited during the construction of the numerical microstructures. First of all, pure water permeability tests have been simulated, this has allowed us to ascertain the representation of compacted clay before pollutant permeation. For both Prrenjas and Wyoming clays, permeation tests after pollutant permeation have then been simulated, using connected and non-connected macro-voids configurations. Different conclusions have been drawn based on simulation results for the two different clays investigated, which are supported by experimental evidence.     

Internal Resonances for Heave, Roll and Pitch Modes of A Spar Platform Considering Wave and Vortex-Induced Loads in the Main Roll Resonance

We present a study of the nonlinear coupling internal resonance for the heave roll and pitch performance of a spar platform under the wave and vortex-induced loads when the ratio of the frequencies of heave, roll and pitch are approximately 2:1:1. In consideration of varying wet surface, the three DOFs nonlinear coupled equations are established for the spar platform under the effect of the first-order wave loads in the heave and pitch, and vortex-induced loads in the roll. By utilizing the method of multi-scales when the vortex-induced frequency is close to the natural roll frequency, the first-order perturbation solution is obtained analytically and further validated by the numerical integration. Sensitivity analysis is performed to understand the influence of the damping and the internal detuning parameter. Two cases with internal resonance are shown. The first case is that no saturation phenomenon exists under small vortex-induced loads. The first order perturbation solution illustrates that only the vortex-induced frequency motion in roll and the super-harmonic frequency motion in heave are excited. The second case is that the vortex-induced loads are large enough to excite the pitch and a saturation phenomenon in the heave mode follows. The results show that there is no steady response occurrence for some cases. For these cases chaos occurs and large amplitudes response can be induced by the vortex-induced excitation.