基于DEM的宁明县地形因子分析

以ASTER GDEM 30 m分辨率的DEM为基础数据,ArcGIS为软件平台,提取宁明县坡度、坡向、地形起伏度、地表粗糙度、地表切割深度等地形特征要素,并对地形特征进行定量分析.结果表明,县域内坡度在0°～81 °范围内均有分布,但相对集中于5°～ 35°之间;南坡、北坡坡向面积相差较小,分布相对均衡;西北部、南部地形起伏较大,最大处可达702 m;地表粗糙度处于0.15～1之间;地表切割深度最深处达到340.67 m.     

池养条件下军曹鱼仔鱼的消化道内容物

采用光镜解剖观察的方法对池塘培育的1~20日龄军曹鱼仔鱼消化道内容物的种类、数量和大小进行研究。结果显示:军曹鱼仔鱼于2日龄开口,主要摄食桡足类无节幼体和桡足幼体及枝角类;在2~20日龄阶段,桡足类在军曹鱼仔鱼食谱中占据主要成分;从13日龄开始摄食虾、蟹类幼体等大型浮游动物,两个阶段的食物选择性指数存在显著差异。     

通海台垂直摆受建筑载荷影响的数值模拟研究

针对通海台垂直摆NS和EW测项自2019-04出现同步趋势转折变化,计算2017~2020年NS和EW测项M₂波潮汐因子。结合监测井等地下介质结构资料,构建通海台沿垂向分层的三维有限元物理模型,定量分析不同岩石参数模型下建筑载荷对通海台NS向及EW向位移影响的差异特征。结果表明：1）2019-04后NS测项N倾变化量达到约2 750 ms,而EW测项E倾变化量达到约580 ms,NS测项趋势变化量显著大于EW测项;2）2017~2020年NS和EW测项M₂波潮汐因子较为稳定,NS测项M₂波潮汐因子在0.7左右波动,EW测项M₂波潮汐因子在0.52左右波动,数据的转折变化未能在潮汐频段引起同步变化;3）位于通海台东北部的医院建筑物载荷在通海台附近产生N向和E向位移加载,与垂直摆NS和EW测项在2019-04后出现的N倾和E倾趋势转折变化较为一致,模拟得到的N向位移量约为E向位移量的3倍。     

Comparison of interception,forest floor evaporation and transpiration in Pinus radiata and Eucalyptus globulus plantations

Studies of evapotranspiration (ET) processes in forests often only measure one component of total ET, most commonly interception. This study examined all three components of annual ET (interception, evaporation from the forest floor and transpiration) and the correlations between them at 18 plantation forest sites in two species. All plantations had closed canopies, and sparse or no understorey. Single‐sided leaf area index averaged 3.5 (standard deviation ±0.5) in Eucalyptus globulus Labill. and 6.1 (±0.8) in Pinus radiata D.Don. Measurements included annual totals of rainfall in the open and under the canopy, stem flow (four sites only), evaporation from the forest floor and transpiration by the overstorey. Interception (I) averaged 19% (±4.9) of annual rainfall in E. globulus compared with 31% (±11.1) in P. radiata. However, higher annual interception in P. radiata did not result in higher total ET because annual evaporation from the forest floor (E) averaged 29% (±4.9) of rainfall in E. globulus but only 15% (±3.5) in P. radiata. Hence, the relative contribution of annual I plus E to ET did not differ significantly between the two species, averaging 48% (±7.3) of annual rainfall in E. globulus compared with 46% (±11.8) in P. radiata. As reported previously, transpiration did not differ significantly between the two species either, but was strongly related to depth‐to‐groundwater. In closed canopy plantations, mean annual ET did not differ between the two species. We conclude that when grown in plantations under similar soil and climatic conditions, conifer and broad‐leaved tree species can have similar annual ET, once the canopy of the plantation has closed. Lower average annual interception in broad‐leaved trees was offset by higher soil evaporation. These results highlight the importance of measuring all components of ET in studies of vegetation water use. Copyright © 2014 John Wiley & Sons, Ltd.     

Low‐cost monitoring of snow height and thermal properties with inexpensive temperature sensors

Small, self‐recording temperature sensors were installed at several heights along a metal rod at five locations in a case study catchment. For each sensor, the presence or absence of snow cover was determined on the basis of its insulating effect and the resulting reduction of the diurnal temperature oscillations. Sensor coverage was then converted into a time series of snow height for each location. Additionally, cold content was calculated. Snow height and cold content provide valuable information for spring flood prediction. Good agreement of estimated snow heights with reference measurements was achieved and increased discharge in the study catchment coincided with low cold content of the snow cover. The results of the proposed distributed assessment of snow cover and snow state show great potential for (i) flood warning, (ii) assimilation of snow state data and (iii) modelling snowmelt process. Copyright © 2010 John Wiley & Sons, Ltd.     

对流层折射对超视距雷达信号定位的影响

超视距雷达信号的精确定位对于提高超视距探测能力有十分重要的意义。但由于对流层中的折射效应，定位系统所测目标的仰角、距离等参量均存在一定的折射误差。主要分析对流层的折射效应对超视距雷达信号定位的影响，并且给出相应的折射误差图（仰角误差和距离误差）；此外，还针对3种不同的大气折射指数模型进行比较，得出折射误差对比图。     

The influence of water retention curve hysteresis on the stability of unsaturated soil slopes

Hysteresis is a common feature exhibited in hydraulic properties of an unsaturated soil. The movement of wetting front and the hysteresis effect are important factors which impact the shear strength of the unsaturated soil and the mechanics of shallow landslides. These failures are mainly triggered by the deepening of the wetting front accompanied by a decrease in matric suction induced by infiltration. This research establishes a method for determining a stability analysis of unsaturated infinite soil slopes, integrating the influence of infiltration and the water retention curve hysteresis. Furthermore, the present stability analysis method including the infiltration model and the advanced Mohr–Coulomb failure criterion calculates the variations of the safety factor (FS) in accordance with different slope angle, depth and hydrological processes. The experimentally measured data on the effect of hysteresis are also carried out for comparison. Numerical analyses, employing both wetting and drying hydraulic behaviour of unsaturated soil, are performed to study the difference in soil‐water content as observed in the experiments. The simulating approximations also fully responded to the experimental data of sand box. The results suggest that the hysteresis behaviour affect the distribution of soil‐water content within the slope indeed. The hysteresis made the FS values a remarkable recovery during the period of non‐rainfall in a rainfall event. The appropriate hydraulic properties of soil (i.e. wetting or drying) should be used in accordance with the processes that unsaturated soil actually experience. This method will enable us to acquire more accurate matric suction head and the unsaturated soil‐shear strength as it changes with the hysteretic flow, in order to calculate into the stability analysis of shallow landslides. An advanced understanding of the process mechanism afforded by this method is critical to realizing a reliable and appropriate design for slope stabilization. It also offers some immediate reference information to the disaster reduction department of the government. Copyright © 2011 John Wiley & Sons, Ltd.     

On the hydraulic intake shape factor for a circular opening located at an impervious boundary: Influence of inclined stratification

In this paper, we develop an exact closed form solution for a circular entry point located at the interface between an impermeable material and a stratified porous medium, where the principal plane of hydraulic isotropy is inclined to the interface. Copyright © 2010 John Wiley & Sons, Ltd.     

A modified global model for predicting the tritium distribution in precipitation, 1960–2005

A modified global model for predicting the tritium concentration in precipitation has been developed using the dataset of International Atomic Energy Agency/the World Meteorological Organization (IAEA/WMO) over the period from 1960 to 2005. The tritium concentration in precipitation and its history can be estimated at any location using the model. The modified global model of tritium in precipitation (MGMTP) here presented has higher accuracy than the global model of tritium in precipitation (GMTP) developed by Doney et al. ( 1992 ). The new model is not only more appropriate for a particular station but also applicable for the un‐normalized observations directly. Another advantage of MGMTP is that it can estimate a longer history (from 1960 to 2005) of tritium content in precipitation than GMTP (from 1960 to 1986). The seasonal cycle of tritium in precipitation has also been modelled in the form of a simple cosine function with five parameters. Copyright © 2011 John Wiley & Sons, Ltd.     

Seasonal rainfall–runoff relationships in a lowland forested watershed in the southeastern USA

Hydrological processes of lowland watersheds of the southern USA are not well understood compared to a hilly landscape due to their unique topography, soil compositions, and climate. This study describes the seasonal relationships between rainfall patterns and runoff (sum of storm flow and base flow) using 13 years (1964–1976) of rainfall and stream flow data for a low‐gradient, third‐order forested watershed. It was hypothesized that runoff–rainfall ratios (R/P) are smaller during the dry periods (summer and fall) and greater during the wet periods (winter and spring). We found a large seasonal variability in event R/P potentially due to differences in forest evapotranspiration that affected seasonal soil moisture conditions. Linear regression analysis results revealed a significant relationship between rainfall and runoff for wet (r² = 0·68; p < 0·01) and dry (r² = 0·19; p = 0·02) periods. Rainfall‐runoff relationships based on a 5‐day antecedent precipitation index (API) showed significant (r² = 0·39; p < 0·01) correspondence for wet but not (r² = 0·02; p = 0·56) for dry conditions. The same was true for rainfall‐runoff relationships based on 30‐day API (r² = 0·39; p < 0·01 for wet and r² = 0·00; p = 0·79 for dry). Stepwise regression analyses suggested that runoff was controlled mainly by rainfall amount and initial soil moisture conditions as represented by the initial flow rate of a storm event. Mean event R/P were higher for the wet period (R/P = 0·33), and the wet antecedent soil moisture condition based on 5‐day (R/P = 0·25) and 30‐day (R/P = 0·26) prior API than those for the dry period conditions. This study suggests that soil water status, i.e. antecedent soil moisture and groundwater table level, is important besides the rainfall to seasonal runoff generation in the coastal plain region with shallow soil argillic horizons. Copyright © 2011 John Wiley & Sons, Ltd.