流域可持续性理想域和现实状态测度

可持续发展是当今世界各国公认的发展准则,但其概念的模糊性与测度方法的单一性阻碍了这一理念的有效应用。在水生态阈值、经济增长底限值和社会发展警戒值等共同约束下,水生态保护目标、经济增长目标与社会发展目标等多目标相互博弈而存在区间范围的基础上,提出了流域可持续性及其理想域的概念以及时间、空间、认知、子系统效益博弈关系、可行区间等决定要素。基于优化方法建立流域可持续性理想域测度模型,并以此为基准,提出了考虑流域系统内外相互作用现实状态的改进离差法测度模型。结果表明:流域可持续性理想域和现实状态测度模型更加符合实际情况,且能够反映流域内外的交互作用对可持续性的影响,为今后流域可持续发展评估提供了一种新思路和方法。     

Estimating palaeo-water depth from the physical rock record

Palaeo-water depth and its change with time is a key factor in environmental analysis and in sedimentology in general. The literature published on this topic and on related subjects, however, is substantial albeit scattered within and between different communities (geologists, oceanographers, engineers, physicists etc.). Here I focus on proxies for palaeo-bathymetry as obtained from the physical rock record. Floral, faunal and chemical evidence for palaeo-water depth, being equally important, must be dealt with elsewhere. An assessment of the main depth-related parameters in actualistic settings is presented and their applicability to the fossil sedimentary record discussed. The outcome reveals the full complexity of this topic. There is, for example, no such thing as an average wave-base depth applicable to a wide range of fossil case settings. This because wave and current climates in general, and particularly so in neritic and coastal settings, are intriguingly complex. Furthermore, observations from modern oceans are not a priori applicable to fossil ones. Acknowledging these problems and limitations, critically evaluated quantitative proposals for depth indicative facies and features in the sedimentary record are presented and error bars discussed.     

基于小波方法的非线性回归模型研究

介绍小波方法和非线性回归估计的基本理论,研究利用小波变换得到非线性回归估计函数的方法,且将该方法的结果与仅用回归估计的结果进行对比研究,发现对监测数据列进行小波分解并对小波系数作用于阈值,然后通过对小波系数估计能得到回归参数。研究结果表明基于小波方法的非线性回归模型更接近变形体变形规律,是一种能够更好地进行预测的方法,该模型切实可行。     

阿拉山口1957—2007年气候变化特征

根据塔中气象站1996－2008年的气象数据分析、野外观测试验及理论计算,对塔克拉玛干沙漠腹地塔中地区近10a来的风沙环境特征进行了初步分析,结果表明：塔中地区地表沙源平均粒径约为2.88φ（136μm）,属于细砂、极细砂;年平均风速均在2.5m·s-1以下,近10a来呈整体下降趋势,风速的月变化呈单峰分布,最大值出现在6—7月,风向与起沙风向以偏东风为主;2m高度的起沙风速约为4.1 m·s-1;年浮尘、扬沙日数呈波动式上升趋势,年沙尘暴日数呈缓慢下降趋势;年风蚀气候因子平均为28.3。     

Trends of Temperature Extremes in China and its Relationship with Global temperature anomalies Relationship with Global Temperature Anomalies

Changes of temperature extremes over China were evaluated using daily maximum and minimum temperature data from 591 stations for the period 1961--2002. A set of indices of warm extremes, cold extremes and daily temperature range (DTR) extremes was studied with a focus on trends. The results showed that the frequency of warm extremes (F_WE) increased obviously in most parts of China, and the intensity of warm extremes (I_WE) increased significantly in northern China. The opposite distribution was found in the frequency and intensity of cold extremes. The frequency of high DTR extremes was relatively uniform with that of intensity: an obvious increasing trend was located over western China and the east coast, while significant decreases occurred in central, southeastern and northeastern China; the opposite distribution was found for low DTR extreme days. Seasonal trends illustrated that both F_WE and I_WE showed significant increasing trends, especially over northeastern China and along the Yangtze Valley basin in spring and winter. A correlation technique was used to link extreme temperature anomalies over China with global temperature anomalies. Three key regions were identified, as follows: northeastern China and its coastal areas, the high-latitude regions above 40^oN, and southwestern China and the equatorial eastern Pacific.     

Experiment on Dust Flux During Duststorm Periods over Desert Area

The present study investigates the characteristics of turbulent transfer and the conditions for dust emission and transport using the dust concentration and micrometeorological data obtained during dust events occurring in the spring of 2004 over the Hunshandake desert area. The turbulent exchange coefficients and turbulent fluxes of momentum and heat are calculated. The relationships between dust flux, friction velocity, and wind speed are also explored. The results show that thermal turbulence is dominant during daytime of non-dusty days. The dynamic turbulence increases obviously and the sensible heat flux reduces by different degrees during dust events. There is an efficient downward transfer of momentum before duststorm occurrence, and both the dynamic turbulence and the thermal turbulence are important in the surface layer. The dynamic turbulence even exceeds the thermal turbulence during severe duststorm events. The values of dust flux vary in the range of -5 5, -30 30, and -200-300 μg m^-2 s^-1 during non-dusty days, blowing dust, and duststorm events, respectively. A slight upward transport of dust is observed during non-dusty days. The dust flux gradually varies from positive to negative during duststorm periods, which indicates the time evolution of dust events from dust rising to stably suspending and then deposition. The dust flux is found to be proportional to u＊^3. The threshold values of wind speed and friction velocity are about 6 and 0.4 m s^-1, respectively.     

GHM类正交多小波变换及其在地震资料去噪中的应用

多小波是对小波理论的一个新发展,它可以同时满足正交性、对称性、短支撑等良好的特性要求。文中介绍了多小波基本理论、多小波变换具体过程及预处理方法,提出了基于GHM类多小波变换的地震资料软阈值去噪方法,通过对合成数据和实际资料进行处理分析,表明多小波变换在有效压制随机噪声的同时,能较好地保留原信号的特征信息,是一种行之有效的去噪方法     

Is groundwater response timing in a pre‐alpine catchment controlled more by topography or by rainfall?

Groundwater levels in steep headwater catchments typically respond quickly to rainfall, but the timing of the response may vary spatially across the catchment. In this study, we investigated the topographic controls and the effects of rainfall and antecedent conditions on the groundwater response timing for 51 groundwater monitoring sites in a 20‐ha pre‐alpine catchment with low permeability soils. The median time to rise and median duration of recession for the 133 rainfall events were highly correlated to the topographic characteristics of the site and its upslope contributing area. The median time to rise depended more on the topographic characteristics than on the rainfall characteristics or antecedent soil wetness conditions. The median time to rise decreased with Topographic Wetness Index (TWI) for sites with TWI < 6 and was almost constant for sites with a higher TWI. The slope of this relation was a function of rainfall intensity. The rainfall threshold for groundwater initiation was also a function of TWI and allowed extrapolation of point measurements to the catchment scale. The median lag time between the rainfall centroid and the groundwater peak was 75 min. The groundwater level peaked before peak streamflow at the catchment outlet for half of the groundwater monitoring sites, but only by 15 to 25 min. The stronger correlations between topographic indices and groundwater response timing in this study compared to previous studies suggest that surface topography affects the groundwater response timing in catchments with low permeability soils more than in catchments with more transmissive soils. Copyright © 2015 John Wiley & Sons, Ltd.     

铁路挡风墙挡风效果和积沙情况分析

对我国"百里风区"铁路沿线的已有挡风墙在受强侧风作用时避免行进列车倾覆方面的有效性以及挡风墙沿线所存在的积沙问题进行了定量分析,在此基础上,给出了列车车速和挡风墙高度对导致运行列车的某一节车厢倾覆的临界倾覆风速影响的规律以及对沙粒沉积的影响.结果表明.列车运行速度和挡风墙高度对车厢的临界倾覆风速有明显影响,目前在"百里...