Differences in oxygen-18 and deuterium content of throughfall and rainfall during different flood events in a small headwater watershed

Inter-storm stable isotopic values of rainfall and throughfall for three flooding events were measured during the period of July to August 2011 to estimate their differences in a first-order chestnut watershed, Meilin, within the Taihu Lake basin. Comparison of δ²H and δ¹⁸O was conducted from four aspects: (1) sampling methods, (2) calculation methods, (3) stable isotopes and (4) flood events. Arithmetic and weighted incremental values of throughfall were generally lighter than those of rainfall. Isotopic composition of both incremental rainfall and throughfall exhibits marked temporal variation, particularly during large storm events; the former shows a higher variation than the latter. Differences of averaged precipitation and throughfall between storms were small, but individual storm variations were larger. Isotopic differences using different calculation methods are not significant; however, the differences resulting from sampling methods are of greater importance.     

几种模拟逐日降水的分布函数比较分析

在模拟逐日降水方面,将马尔科夫链和某种分布函数相结合建立随机模型的方法在国外很多地区被证明是有效的,但该方法在我国的适用性研究并不多见.本文应用哈尔滨48年的实测降水资料,基于一阶马尔科夫两状态转移概率,分别采用皮尔逊Ⅲ型分布、伽玛分布和偏正态分布函数模拟了哈尔滨的1000年逐日降水过程.对比分析结果表明,伽玛分布更适合模拟哈尔滨的逐日降水过程,基于伽玛分布函数模拟的月份降水量和降水天数与实测降水数据符合较好.     

Cell-Site Diversity Performance of LMDS Systems Operating in Heavy Rain Climatic Regions

In this paper, the potential performance advantages of ce ll-site diversity in millimeter-wave fixed cellular systems located in heavy rain climatic regions are examined. Cell-site diversity is considered an efficient technique to mitigate the aggravating effects of atmospheric propagation of radiowaves at millimeter frequency bands and, particularly, to combat rain attenuation. The paper is focused on the analytical estimation of the performance improvement of LMDS systems due to diversity reception. A physical prediction model for rain attenuation, properly modified to take into account the behaviour of the rainfall medium in tropical and subtropical areas, is the basis of the analysis. Implementations of the proposed model are presented along with an investigation of its various aspects. This work was mainly stimulated by the recent strong interest to provide technically and economically feasible solutions for broadband wireless access to the developing countries.     

Predicting extreme rainfall over eastern Asia by using complex networks

A climate network of extreme rainfall over eastern Asia is constructed for the period of 1971-2000, employing the tools of complex networks and a measure of nonlinear correlation called event synchronization （ES）. Using this network, we predict the extreme rainfall for several cases without delay and with n-day delay （1 ≤ n ≤ 10）. The prediction accuracy can reach 58% without delay, 21% with 1-day delay, and 12% with n-day delay （2 ≤ n ≤ 10）. The results reveal that the prediction accuracy is low in years of a weak east Asia summer monsoon （EASM） or 1 year later and high in years of a strong EASM or 1 year later. Furthermore, the prediction accuracy is higher due to the many more links that represent correlations between different grid points and a higher extreme rainfall rate during strong EASM years.     

基于HP-ENN-MC模型降雨量预测

综合HP滤波、Elman神经网络、马尔科夫链的优点建立HP-ENN-MC模型对某地区10年内降雨量进行预测.以某地区1990-2015年植物生育期(6-10月)的降雨量数据作为实验训练样本,以2010-2015年(6-10月)的降雨量数据为实验的测试样本,证明HP-ENN-MC模型的实用性.由最后实验结果得到,预测平均相对误差为3.83%.所建模型能够对降雨量准确预测,与Elman、ENN-MC模型相比,HP-ENN-MC模型对降雨量预测更有效.     

基于GDEM–GAVA的白羊城沟泥石流成灾风险数值分析

降雨型泥石流是一个降雨–洪水–泥沙输运–推移质运动的多过程耦合过程。本文借助颗粒碎屑流仿真系统（GDEM–GAVA）,对白羊城沟泥石流的成灾风险进行了分析。首先通过历史灾情数据反分析出了沟道物源的力学参数,而后基于该参数分析了不同降雨强度下该泥石流的成灾临界降雨时长。计算结果表明,白羊城沟泥石流物源的饱和黏聚力为0.5～1 kPa,饱和内摩擦角为5°～10°;降雨强度为65 mm/h时,沟道形成泥石流的时间为3.6 h;降雨强度为78 mm/h时,沟道形成泥石流的时间为2.8 h;降雨强度为88 mm/h时,沟道形成泥石流的时间为2.3 h。上述泥石流成灾风险的分析结果可为白羊城沟泥石流的科学预警提供必要的依据。

     

雷达定量测量降水的检验“真值”求取方法研究

利用湖南省2013年汛期(4—9月)的高密度区域自动站的雨量数据,引入Cressman逐步订正法求取0.01?×0.01?精细网格的区域降水量,并与距离平方倒数法、距离指数法和距离平方指数法计算的区域降水量进行比较.结果表明,Cressman逐步订正法计算的区域降水量与距离平方倒数法和距离指数法的结果相当,但其空间结构更为精细和准确,更好地反映了雨量站数据的分布特征.交叉验证表明Cressman逐步订正法与原始区域自动站值最为接近,误差绝对值小于0.5 mm的雨量站占总站数的98.71%,误差标准差为0.24 mm.对于0.01?×0.01?精细的空间分辨率而言,Cressman逐步订正法利用高密度的区域自动站数据求得的区域降水量可以用于检验雷达定量估测降水.     

我国东部持续性暴雨水汽输送特征的比较分析

运用基于拉格朗日方法的气流轨迹模式（HYSPLIT）,并结合欧拉方法,分析了江淮、江南和华南3个不同区域多个PHR过程期间的水汽通道和水汽输送特征以及通道建立和维持的天气学条件.不同区域PHR过程发生时,水汽通道及其贡献率、异常环流特征等都不同,且这些差异主要集中在南海和西太平洋地区.从水汽收支来看,华南与另外2个区域的差异较大.从水汽通道和异常环流的角度上看,江南与另外2个区域的差异较大.     

Large Scale Experiment on Transport of Trichloroethylene in a Controlled Aquifer

Pollution by dense non-aqueous phase liquids (DNAPLs) represents a major threat to groundwater resources. In a real case of site contamination, the efficiency of remediation techniques is often limited by a lack of knowledge of both the extent of the pollution and the behavior of the different phases of the pollutant in the subsurface. An experiment simulating pollution of an aquifer by a chlorinated solvent (Trichloroethylene: TCE) was conducted on a large controlled experimental site called SCERES. The experiment consisted of an injection of 8.9 liters of TCE under controlled conditions at 35cm below the soil surface with an appropriate set up. The goal was to study the behavior of the three phases of the pollutant (trapped TCE phase forming the impregnation body, vapors in the vadose zone, and dissolved traces in the aquifer) in order to better comprehend the mechanisms which govern the propagation and the transfer of this type of pollution underground. The SCERES experimental data indicate that mass transfer from the saturated zone to the vadose zone is important, affecting the repartition of the vapor plume and causing a significant decrease of dissolved TCE concentrations in the groundwater. Furthermore, vertical leaching of TCE vapors due to rainfall strongly influences the degree of groundwater pollution and its lateral extent. The transient mass balance of the experiment is very satisfactory and shows that the main part of the spilled quantity is lost to the atmosphere.