结合实地观测和STEREO/HI图像观测分析2010年CME事件

本文使用了基于单颗STEREO卫星日球层成像仪(Heliospheric Imager,HI)图像的固定Φ角拟合法(Fixed-Φ,FΦ)和调和均值拟合法(Harmonic-mean,HM),结合STEREO和ACE卫星的太阳风实地观测数据,深入分析了2010年15个日冕物质抛射(CME)事件,对比讨论了这两种方法在提取CME参数如太阳赤道平面的主传播方向、传播速度的效果,其中FΦ拟合法假设CME是固定方向传播的小质点,HM拟合法假设CME为具有球形前沿的通量绳结构,结果发现:(1)使用HM拟合法分析得到的CME主传播方向与太阳-实地观测点的夹角平均值是9.5°,小于FΦ拟合法的19.7°;(2)HM拟合法分析的预计到达时间与实测ICME起始时间的平均误差和最大误差分别为0.282天和0.805天,明显小于FΦ拟合法.本文也使用结合STEREO两颗卫星HI图像的直接三角法(Direct-triangulation,DT)和球面切线法(Tangent-to-a-sphere,TS),深入分析了5个朝向地球的CME事件,其中,DT和FΦ拟合法的假设相同,TS和HM拟合法的假设相同,结果发现:(1)这两种方法分析的CME主传播方向与日地连线的夹角最大值分别是13.2°和21.1°,明显小于单颗卫星观测的20.7°和27.5°;(2)其中4个CME事件使用方法得到的线性拟合加速度不超过0.4 m·s-2,这说明CME在主传播方向上的速度变化在1AU内不超过100 km·s-1;(3)使用TS方法得到的预计到达时间与实测ICME起始时间的绝对误差最小,平均值和最大值分别是2.3 h和5.8 h.可见,利用HI图像提取CME传播参数时,加入CME前沿结构假设和结合多角度观测都能够有效地减小拟合误差.     

上海佘山(SSE)地震台站下方170km深度低速界面研究

利用接收函数多次波研究了上海SSE台站下方170 km深度低速界面.通过全波场理论接收函数模拟,对观测资料进行了合理解释.结合该区域已有研究成果,推断该低速界面可能由软流圈中的低速异常体引起.另一方面,该结果也和面波层析成像结果相一致.     

中低纬地区电离层对CIR和CME响应的统计分析

本文利用中低纬日本地区(131°E, 35°N)GPS-TEC格点化数据,分析了2001—2009年间109个共转相互作用区(CIR)事件、45个日冕物质抛射 (CME)事件引起的地磁扰动期间电离层的响应.结果表明,电离层暴的类型随太阳活动的变化而有不同的变化,CIR事件引发的电离层正相暴、正负双相暴多发生在太阳活动下降年,负相暴多发生在高年,负正双相暴多发生在低年;CME事件引发的电离层正相暴和负相暴多发生在高年.CIR和CME引发的不同类型的电离层暴的季节性差异不大,在夏季多发生正负双相暴.电离层暴发生时间相对地磁暴的时延大部分在-6~6 h之间,但CIR引发的电离层暴时延范围更广,在-12~24 h之间,而CME引发的电离层暴时延主要在-6~6 h之间.中低纬的电离层暴多发生在主相阶段,其中CIR引发的双相暴也会发生在初相阶段.电离层负暴多发生在AE最大值为800~1200 nT之间.CIR引起的电离层扰动持续时间较长,一般在1~6天左右,而CME引起的电离层扰动持续时间一般在1~4天左右.     

地形对碎屑流冲出的影响作用(英文)

传统的碎屑流冲出预测经验模型主要基于冲出物体积与冲出物到达角的假设关系式,并没有考虑地形的影响,其中到达角指滑坡后壁顶点与堆积体末端点连线的角度。本文通过小尺寸模型槽实验研究不同地形条件对碎屑流冲出的影响,发现冲出路径上的缓地形将增加到达角,对近期的两个地震诱发型碎屑流场点的调查结果也表明了缓地形对到达角的影响。还发现冲出物受地形限制而改变冲出方向时可能增加冲出角。考虑上述两种地形约束作用的冲出距离预测值将小于传统的预测方法。     

地质力学模型相似材料配比的正交试验研究

选择正确的相似材料是进行地质力学模型试验的前提,然而,选择合适的材料配比是成功模拟原型工程的关键。经过对大量的相似材料研究现状的调研,在借鉴前人经验的基础上,选择以铁矿粉、重晶石粉、石英砂为骨料,松香酒精溶液为胶结剂,石膏为调节剂的铁晶砂胶结剂作为模型试验的相似材料。采用正交试验法进行配比试验,选择了4因素3水平的正交试验表设置,一共9组配比试验方案,制作小模型试块。通过对小模型试块的物理力学性质试验,获得了相似材料密度、抗压/拉强度、弹性模量、泊松比、黏聚力、内摩擦角等参数指标,运用极差分析法分析了各个因素对相似材料参数指标影响的主次关系以及影响的规律特性。试验发现,胶结剂浓度对相似材料的主要参数指标影响显著。     

动力相似预报的策略和方法研究

为了在现有模式和资料条件下有效提高数值预报水平, 深入开展了动力相似预报(DAP)的策略和方法研究. 提出“利用历史相似信息对模式预报误差进行预报”的新思路, 从而将动力预报问题转化为预报误差的估计问题, 并发展了一种基于相似误差订正的预测新方法(FACE). 进一步将FACE应用于业务海气耦合模式的跨季度预测试验, 夏季平均环流和降水的预测结果表 明, FACE能在一定程度上减小预报误差、恢复预报方差、提高预报技巧. 此外, 敏感性试验显示, 相似的个数、选取变量和度量标准都对FACE预报有显著影响.     

Mein-Larson入渗模型的改进研究

降雨入渗模型对于降雨型滑坡稳定性的评价是相当重要的,目前常用的降雨入渗模型是Mein-Larson入渗模型,但该模型假定了土体初始含水率沿深度方向为一定值,而实际上土体初始含水率沿深度方向为非线性分布的.考虑到实际的土体初始含水率分布情况,提出了描述土体初始含水率的分布的反比例函数,对Mein-Larson入渗模型进行...     

氧化锰对金(Ⅰ)和金(Ⅲ)络和物的吸附

对 pH 2～ 1 1 .6和 0 .0 1 mol/L或 0 .1mol/LNaNO3 溶液中 ,δ MnO2 对Au Cl4-,AuCl2 -和Au(S2 O3 ) 2 3 -表现出不同程度的吸附 .在pH 4和两种电解质条件下δ MnO2 吸附AuCl4-和Au(S2 O3 ) 2 3 -后表面金的最大吸附密度分别为 0 .1 8～ 0 .2 1和 0 .2 8μmol/m2 ,金的表面覆盖率约等于或低于 1 % . 3种金络合物的吸附均表现为随pH上升而减少 ,符合阴离子的吸附规律 ;其吸附大小次序为 :Au(S2 O3 ) 2 3 ->AuCl4->AuCl2 -;3种金的本征平衡常数logKint为 1 .1 7～ 2 .71 ,均大大地高于铜和镉的本征吸附常数 ;δ MnO2 优先吸附AuCl4-的水解混合配体络合物 ,并形成内圈表面络合物 .     

地震动随机函数模型研究(Ⅰ)——模型建立

基于随机过程的随机函数解释,发展了一种随机地震动模型.模型包括两个部分,分别是基于理论物理关系的Fourier幅值谱模型和基于经验关系的Fourier相位谱模型.基于拟加速度谱概念建立的幅值谱模型能够反映强震记录的幅值特性,而Fourier相位谱模型则利用累积相位谱的单值连续特性,以线性多项式与三角级数组合的形式给出.模拟记录与实测记录对比结果显示两者不仅在波形结构上相似性良好,而且反应谱层次亦吻合良好.     

基于多植物生长模式的SWAT模型的修正与有效性初探

以农林系统的非点源污染模拟为目标,通过研究建立变化密度及多种类混杂的森林生长模型,修正了SWAT模型采用平均森林植被密度和单一植物生长模式估算生物累积量的问题,并建立了与之相适应的森林优势组份丰度遥感反演模型、叶面积指数和消光系数遥感反演模型以获取森林生长模型的相关参数.同时,根据间作套种下的辐射能利用Keating方程,引入间作套种指数变量,修正SWAT原有的单一生物量日积累模型,探讨了作物复种指数、间作套种指数遥感反演方法和以此为基础的作物间作套种生长模型.以亚热带季风湿润区红壤背景下的鄱阳湖流域子流域梅江流域为试验区,以野外实测数据为基础,探讨修正SWAT模型的有效性.结果表明:修正后的SWAT模型与原始SWAT模型相比,在模拟流量和营养盐负荷方面,得到了较好的改善.在模拟流量方面,有效性提高了7.8%,流量峰值的模拟也得到了改善,能更好地反映地表蓄流方面的实际情况;在模拟营养盐负荷方面,有效性提高了6.4%(总磷)和6.1%(总氮).     

模型扩展和地形平化起伏地形处理方案在地震走时层析成像中的对比研究

中国大陆中西部普遍具有强烈的地形起伏,起伏地形会对地震资料的处理分析产生严重干扰.精细处理起伏地形成为高精度地震成像的必然要求.传统方法通过填充低速介质将不规则模型扩展为规则模型来处理起伏地形.近年来,借助坐标变换将物理空间不规则模型转换为计算空间规则模型的地形平化方法,为解决起伏地形问题提供了新思路.本文基于经典的模型扩展和新发展的地形平化方法分别处理起伏地形,从走时正演、射线追踪和反演成像三个方面,全面细致地评判了两种地形处理方法在起伏地形层析成像中的适用性和有效性.结果表明,模型扩展中阶梯状近似和填充介质速度参与计算,会造成起伏地形走时计算精度损失,出现虚假射线路径和错误出射角,导致反演分辨率降低,成像结果模糊甚至失真;地形平化中采用贴体网格参数化,能够保证离散模型完全匹配起伏地形,并且保持起伏地形在物理空间和计算空间中均为自由表面.在此基础上发展的层析成像技术具有高度的保真性,有效地处理了地形起伏效应,为起伏地形区域精细速度成像提供了有力的技术保障.

     

Modification of water masses in the Barents Sea and its coupling to ice dynamics: a model study

The physical and biological environment of the Barents Sea is characterised by large variability on a wide range of scales. Results from a numerical ocean model, SINMOD, are presented showing that the physical variability is partly forced by changes in annual net ice import. The mean contribution from ice import in the simulation period (1979–2007) is about 40% of the total amount of ice melted each year. The annual ice import into the Barents Sea varies between 143 and 1,236 km³, and this causes a substantial variability in the amount of annual ice melt in the Barents Sea. This in turn impacts the freshwater content. The simulated freshwater contribution from ice is 0.02 Sv on average and 0.04 Sv at maximum. When mixed into a mean net Atlantic Water (AW) inflow of 1.1 Sv with a salinity of 35.1, this freshwater addition decreases the salinity of the modified AW to 34.4 and 33.9 for the mean and maximum freshwater fluxes, respectively. Ice import may thus be important for the Barents Sea production of Arctic Ocean halocline water which has salinity of about 34.5. The changes in the ice melt the following summer due to ice import also affect the formation of dense water in the Barents Sea by changing stratification, altering the vertical mixing rates and affecting heat loss from the warm AW. The model results thus indicate that ice import from the Arctic has a great impact on water mass modification in the Barents Sea which in turn impacts the ventilation of the Arctic Ocean.     

Turbulent transport of angular momentum in magnetized fluids and torsional oscillations of the sun

Abstract

Fluxes of angular momentum produced by turbulence in rotating fluids are derived with the effects of a magnetic field included. It is assumed that the rotation is slow but that the magnetic field is of arbitrary strength. A mean magnetic field is shown to produce qualitative changes of the sources of the differential rotation rather than the quenching of differential rotation usually expected. A new equatorward flux of angular momentum arises through the influence of the toroidal magnetic field. The possibility of interpreting the torsional oscillations of the Sun as a consequence of the magnetic perturbations of the turbulent angular momentum fluxes is discussed.     

Simulation of urban expansion based on cellular automata and maximum entropy model

Urban expansion is a hot topic in land use/land cover change(LUCC) researches. In this paper, maximum entropy model and cellular automata(CA) model are coupled into a new CA model(Maxent-CA) for urban expansion. This model can help to obtain transition rules from single-period dataset. Moreover, it can be constructed and calibrated easily with several steps.Firstly, Maxent-CA model was built by using remote sensing data of China in 2000(basic data) and spatial variables(such as population density and Euclidean distance to cities). Secondly, the proposed model was calibrated by analyzing training samples,neighborhood structure and spatial scale. Finally, this model was verified by comparing logistic regression CA model and their simulation results. Experiments showed that suitable sampling ratio(sampling ratio equals the proportion of urban land in the whole region) and von Neumann neighborhood structure will help to yield better results. Spatial structure of simulation results becomes simple as spatial resolution decreases. Besides, simulation accuracy is significantly affected by spatial resolution.Compared to simulation results of logistic regression CA model, Maxent-CA model can avoid clusters phenomenon and obtain better results matching actual situation. It is found that the proposed model performs well in simulating urban expansion of China. It will be helpful for simulating even larger study area in the background of global environment changes.     

A hillslope-based hydrological model using catchment area and width functions

Abstract

A flow-interval hillslope discretization scheme is proposed for catchment hydrological modelling. By this scheme, a two-dimensional catchment is simplified into a one-dimensional cascade of flow intervals linked by the main stream. Each flow interval comprises a set of parallel hillslopes. The hillslope is the fundamental computational unit in the hydrological model providing lateral inflow to the main stream. The size of hillslope is determined by the catchment area and width functions. Catchment runoff is the total of hillslope responses through the river routing. Tests in four Japanese catchments showed that the model performed well on simulating the overall water balance, general flow pattern, and daily and hourly hydrographs of a whole catchment, as well as simultaneous simulation in different subcatchments. Characteristics of catchment hydrological responses and model applicability are discussed.     

Modification and discussion of the Green-Ampt model for an evolving wetting profile

ABSTRACT

The Green-Ampt (GA) model has been widely used to evaluate soil water infiltration. While a simple piston profile is commonly used, the wetting profile of a soil changes during infiltration and a quarter-ellipse has been found to better describe its evolution. This study aims to improve the GA model and discuss the model parameters when the quarter-ellipse profile is utilized. The soil column is divided into three zones: saturated, transient and dry. The variable γ is introduced to express the ratio of the saturated zone depth to the wetting front depth. A modified GA model is derived via mathematical methods, but an exact solution is difficult to obtain. Therefore, a simplified (SGA) model is developed via a segmented method. Compared with the measured results, the SGA model is more accurate than the traditional model. Finally, the model parameters are discussed and a value of γ = 0.5 is recommended.     

A coupled sediment routing and lateral migration model for gravel‐bed rivers

We describe additions made to a multi‐size sediment routing model enabling it to simulate width adjustment simultaneously alongside bed aggradation/incision and fining/coarsening. The model is intended for use in single thread gravel‐bed rivers over annual to decadal timescales and for reach lengths of 1–10 km. It uses a split‐channel approach with separate calculations of flow and sediment transport in the left and right sides of the channel. Bank erosion is treated as a function of excess shear stress with bank accretion occurring when shear stress falls below a second, low, threshold. A curvature function redistributes shear stress to either side of the channel. We illustrate the model through applications to a 5·6‐km reach of the upper River Wharfe in northern England. The sediment routing component with default parameter values gives excellent agreement with field data on downstream fining and down‐reach reduction in bedload flux, and the width‐adjustment components with approximate calibration to match maximum observed rates of bank shifting give plausible patterns of local change. The approach may be useful for exploring interactions between sediment delivery, river management and channel change in upland settings. Copyright © 2011 John Wiley & Sons, Ltd.