Geostatistical analysis of spatial variability of rainfall and optimal design of a rain gauge network

Kriging is a geostatistical estimation technique for regionalized variables that exhibit an autocorrelation structure. Such a structure can be described by a semivariogram of the observed data. The punctual-kriging estimate at any point is a weighted average of the data, where the weights are determined by using the semivariogram and an assumed drift, or lack of drift, in the data. The kriging algorithm, based on unbiased and minimum-variance estimates, involves a linear system of equations to calculate the weights. Kriging is applied in an attempt to describe the spatial variability of rainfall data over a geographical region in northern Greece. Monthly rainfall data of January and June 1987 have been taken from 20 measurement stations throughout the above area. The rainfall data are used to compute semivariograms for each month. The resulting semivariograms are anisotropic and fitted by linear and spherical models. Kriging estimates of rainfall and standard deviation were made at 90 locations covering the study area in a rectangular grid and the results used to plot contour maps of rainfall and contour maps of kriging standard deviation. Verification of the kriging estimates of rainfall are made by removing known data points and kriging an estimate at the same location. This verification is known as the jacknifing technique. Kriging errors, a by-product of the calculations, can then be used to give confidence intervals of the resulting estimates. The acceptable results of the verification procedure demonstrated that geostatistics can be used to describe the spatial variability of rainfall. Finally, it is shown how the property of kriging variance depends on the structure and the geometric configuration of the data points and the point to be estimated can also be used for the optimal design of the rain gauge network in an area.     

新安江流域降雨量空间插值方法和参数筛选

选取新安江流域48个雨量站点2000-2010年的降雨量数据以及地理地形资料,利用反距离权重(IDW)、径向基函数(RBF)、普通克里金(OK)和残差克里金(RK)方法进行插值,根据交叉验证结果筛选最佳的方法和参数.结果表明:年尺度上,考虑高程、纬度等地形因子影响的RK方法插值精度最高,然后是IDW,OK和RBF;邻近站点的搜索策略对IDW插值精度影响较大;考虑各向异性的OK法插值精度较高,模型之间的差别不大.月尺度上,IDW法对降雨量丰富的月份插值精度较高;RBF对降雨较少且分布均匀的月份插值效果好;数据越符合正态分布,OK法的插值精度越高;RK方法则适用于降雨与地理因素相关性好的月份.     

雨量站网分布对雨量插值算法及径流响应的影响

为比较雨量站网密度及分布对不同空间插值算法的影响,选取6种雨量站密度的不同分布,采用4种空间插值算法对研究区2006—2014年的日降雨进行插值,并将面均雨量作为新安江模型的输入,分析和比较其降雨径流响应。结果表明:①雨量站网空间分布越均匀,降雨插值误差越小,其径流模拟的精度也越高;②在雨量站网均匀布置的情况下,各空间插值算法的插值结果差异较小;雨量站网布置不均匀时,站点数目越少各空间插值算法插值结果差异越大;③计算点雨量时,考虑空间变量的克里金法能更准确地计算日降雨的结果;计算面雨量时,不同插值算法间差异较小,建议选用计算简便的插值算法,比如泰森多边形、反距离权重法。     

Regionalization of the Modified Bartlett–Lewis rectangular pulse stochastic rainfall model across the Korean Peninsula

The six parameters of the Modified Bartlett–Lewis Rectangular Pulse (MBLRP) model were regionalized across the Korean Peninsula for all 12 calendar months. The parameters of the MBLRP model were estimated at each of the 59 rain gauges and they were spatially interpolated using the Ordinary Kriging method in order to produce maps. The parameter search space used in the parameter estimation process was repetitively narrowed through cross-validation in order to remove the impact of the multi-modality of the MBLRP model. The synthetic rainfall time series generated based on the parameter maps successfully reproduced the various statistical properties of the observed rainfall, such as mean, variance, lag-1 autocorrelation, and probability of zero rainfall at a wide range of time accumulation levels (e.g. hourly through daily). The maps representing the general rainfall characteristics, such as the average rainfall depth per rain storm, the average rain storm duration, the average number of rain cells per rain storm, and the average rain cell duration were also produced based on the estimated parameters. Lastly, some helpful tips in regionalizing the parameters of the Poisson cluster rainfall models are discussed.     

Quantifying the Uncertainty Interaction Between the Model Input and Structure on Hydrological Processes

Input error is one of the main sources of uncertainty in hydrological models. It mainly comes from the uncertainty of precipitation data, which is caused by inaccurate measurement at the point scale and imperfect representation at the regional scale. The structural error of the hydrological model is dependent on the input, and the uncertainty interaction between the model input and structural will increase the cumulative error of the hydrological process. Therefore, the objective of this study is to investigate the impacts of the uncertainties of rain gauge station input levels and hydrological models on flows with different magnitudes by setting nine input levels of rain gauge stations using three hydrological models (i.e., HyMod, XAJ and HBV). The variance decomposition method based on subsampling was used to dynamically quantify the contribution rates of rain gauge station input levels, hydrological models, and their interaction to the runoff simulation uncertainty. The results show that different rain gauge station input levels and hydrological models dynamically affected the hydrological simulation due to an uneven spatiotemporal distribution of precipitation. Moreover, the simulation accuracy was poor at low flow but better at high flow. Increasing the number of rainfall stations input under a certain threshold could significantly improve the hydrological simulation accuracy. In addition, the contributions of the uncertainties of the rain gauge station input levels and its interaction with the hydrological model to runoff were significantly enhanced in the flood season, but the contribution of the hydrological model uncertainty was still dominant. The results of this study can provide a decision-making basis and scientific guidance for the management and planning of water resources within basins under the influence of a changing environment.

     

基于雨量测站应急机制的洪水预报方法

为提高洪水预报方案的容错能力,改善雨量资料缺测或粗差情况下的预报效果,提出了基于雨量测站应急机制的洪水预报方法。通过构建测站降雨相似度矩阵(SRSM),量化表示测站间实测降雨的相似性。在此基础上,采用有限测站相似度加权法及时合理替换问题雨量资料,然后将处理后的雨量信息代入系统进行计算,从而保证洪水预报的及时性,同时改善预报效果,降低了预报方案对资料的敏感性。将该方法应用于上犹江流域,结果显示:对于典型洪水(洪号20010611),一般预报方法的洪峰、洪量预报误差分别为-24.8%、-6.3%。采用应急预报方法后,洪峰、洪量预报误差减小到-10.6%、1.3%。在雨量资料缺测情况下,对于流域的10场历史洪水,洪峰、洪量平均预报误差从18.3%、18.2%降为6.0%、6.7%,合格率从40%上升为100%。结果表明,基于雨量测站应急机制的洪水预报方法模拟效果明显优于一般预报方法,能够考虑实际应用中的突发情况,有效提高了洪水预报精度,保证了预报的及时性,改善了预报方案的容错能力,值得进一步研究与推广。     

JDZ05-1型雨量数据采集器在降雨观测中的应用

简要介绍JDZ05-1型雨量数据采集器的工作性能,对JDZ05-1型雨量数据采集器与20 cm口径的(普通雨量器和自记雨量计)对比观测的雨量资料进行了回归分析,得出了各雨量站JDZ05-1型雨量数据采集器与普通雨量器、自记雨量计收集的雨量资料之间的相关性,从而揭示相关性的换算变化规律。     

优化Z—R关系及其在北京地区面雨量估测中的应用

运用最优化方法,选取北京市新一代天气雷达2007年5场降雨的基数据资料与对应的地面雨量计资料进行Z—R关系研究,对比由雨量计观测值和雷达估测值插值得到的面雨量分布情况。结果表明：采用缺省的Z—R关系估算出的区域面雨量普遍偏小很多,优化后雷达估测的雨强分布与雨量站点测量的雨强分布更接近,且雷达定量估测区域面雨量的精度有了...     

陕西省月平均气温空间插值方法研究

为弥补陕西省气象站点数量有限、空间分布不均等问题,对常用空间插值方法进行比较研究,探寻适宜陕西省气温空间插值方法。根据陕西省内外110个气象站点1981-2010年的月平均温度,选用反距离权重法、普通克里金法与多元线性回归法进行空插值,利用实际验证法进行精度评估。结果表明,考虑了经度、纬度和高程的多元线性回归法的插值精度最高,普通克里金法次之,反距离权重法精度最低;多元线性回归分析法对陕西省气温插值最为适宜。     

Precipitation Trends and Variability in River Basins in Urban Expansion Areas

River basins are important territorial units for geographical analysis, and are crucial for environmental planning, especially in metropolitan settings. The aim of this article was to evaluate rainfall trends and variability in the Guapimirim-Macacu basin, located in an urban development area in the Rio de Janeiro Metropolitan Region. Annual, monthly and daily records were collected from twenty rain gauge stations, for the period of 1967 to 2015. Analyses conducted using the RClimDex software revealed an increase in rainfall volume and number of wet days. The remaining indicators and patterns observed across stations also suggested that changes in precipitation trends occurred mostly on the day scale, and were likely attributable to global climate change. After controlling for seasonality and normalizing the series, a linear tendency between the mean monthly precipitation in the Guapimirim-Macau basin and sea surface temperature (SST), obtained from the National Centers for Environmental Prediction, revealed that rainfall in the region is strongly correlated with Pacific and Atlantic SST, revealing the importance of the South Atlantic Convergence Zone for rainfall variability in the area of study, especially in summer. These data are important for development planning and the management of water resources and supply in the Rio de Janeiro Metropolitan Region.

     

超大量程雨量计在泄洪雾化测量中的应用

结合国家发明专利和一项实用新型专利,介绍一种用于测量泄洪雾化超高强度降雨的超大量程雨量计,其基本特征是承雨口面积小于储水容器水平截面面积.利用垂向雨量计和水平雨量计分别测量两个方向的降雨强度,达到测量最大斜向降雨的目的,并能准确获取降雨角度.该雨量计在两个工程应用中的实测成果充分证明,新型雨量计克服了传统雨量计难以测量...     

Sensitivity of Simulating Hydrologic Processes to Gauge and Radar Rainfall Data in Subtropical Coastal Catchments

This research evaluated the impact of three rainfall datasets on hydrologic process simulations in two coastal catchments located in Alabama. In this study, rain gauge time series recorded by the U.S. National Oceanic and Atmospheric Administration (NOAA) and Geological Survey (USGS) along with radar precipitation data derived from NOAA National Weather Service (NWS) were input into the Hydrological Simulation Program??FORTRAN (HSPF). Automatic parameter calibration was performed using daily streamflow data recorded at USGS Fish and Magnolia River gauge stations from 07/01/2002 to 12/31/2008. HSPF parameters were optimized using the Model-Independent Parameter Estimation (PEST) program. Model parameter ranges were refined by incorporating physical characteristic of the study areas and after analyzing observed streamflow time series. This approach, in turn, helped PEST optimization tool to find the most physically-related set of parameters that can be transferred to any watershed with similar characteristics and minimum parameter calibration. On average, annual USGS and radar rainfall values were around 480?mm and 250?mm, respectively lower than NOAA precipitation records. Overall, it is found that the NOAA precipitation input data resulted in better daily flow simulations than results from radar and USGS rainfall time series. Streamflows derived from USGS rainfall time series showed the worst model performance at both catchment outlets because of missing data, low amounts, and temporal delay of peaks. This study found that annual actual evapotranspiration values were closed among rainfall time series and varied from 900 to 958?mm. Deep percolation values for Magnolia and Fish River, regardless of rainfall source, ranged from 66 to 192?mm/year. Major discrepancies were found at storm runoff values. Gauge rainfall time series yielded the closest streamflow values compared to observed flow time series at both watershed outlets. Rainfall derived from radar yielded consistent and acceptable runoff results in Fish and Magnolia River models. In both case studies, the high spatial variability of rainfall storm events was not adequately captured by any of the rainfall datasets and yielded high uncertainty in model results.     

西南地区降水量插值方法比较——以丽江市为例

我国西南地区由于地形复杂,海拔落差大,且雨量站分布不均,资料代表性差,针对这一区域的降雨预报效果不尽如人意,每年因局地强降水造成的损失巨大。旨在探讨适合山区等海拔落差较大地区的降水插值方法的一般思路,提高该地区降水估测精度。丽江市最大海拔落差达4 516 m,是西南地区典型的山地型城市。以丽江市40个雨量站40 a的月降雨数据为基础,选择6个站为检验站,运用反距离权重法、普通克里金法、样条函数法、趋势面法进行了最优插值方法的探讨。插值误差分析的结果表明:反距离权重法在该研究区域效果较好,幂指数增加到8以上时,相对误差基本稳定在7.8%;克里金法对降雨量的插值效果也较好,生成的插值图平滑;样条函数法插值效果最差。研究成果可为我国西南地区及其他山地地区降雨预报提供参考。     

Regionalization of Rainfall Intensity-Duration-Frequency using a Simple Scaling Model

Design storm is one of the most important tools to design hydraulic structures, hydrologic system and watershed management, mostly extracted by intensity- duration - frequency (IDF) curves for a given specific duration and return period. As for conventional methods to calculate IDF curves, the precipitation should be recorded for different durations so that foregoing curves can be extracted. Such data can be collected from rain gauge stations. In many areas, just daily precipitation data are available by which IDF curves cannot be extracted as per conventional methods. The aim of this research is to make IDF curves for short-term durations according to time scaling model as well as daily rainfalls. The relationships of this method are characterized with three variables including mean (μ ₂₄) and standard deviation (σ ₂₄) of daily rainfall intensity, and scaling exponent (H) by which all IDF curves might be drawn. The method used in present paper entails for less computational steps than conventional methods and by far has low parameters considerably than others in turn increases reliability. Scaling method is used to extract the IDF curves in rain-gauge stations in Khuzestan province located in southwest Iran and results proved the efficiency and robustness of the scaling method. Also ability of scaling concept method was examined in constructing of regional IDF.     

泾河柔远川与合水川流域降水强度趋势变化特征

开展降水强度趋势变化研究对提高防洪减灾和水资源管理水平具有重要意义。基于柔远川1980—2017年9个雨量站与合水川1981—2017年10个雨量站的日降水量和小时降水量实测资料,采用MK趋势检验法,分析了最大1 h降水强度(I h)、最大1 d降水强度(I d)及分级降水强度趋势变化特征。空间上,柔远川与合水川各站I h、I d空间分布差异均较大,I h的空间变差系数均大于I d,但合水川I h、I d的空间变差系数均大于柔远川;时间上,柔远川、合水川I d的空间变差系数分别呈显著增大与减小趋势(α=0.05),增大与减小幅度分别为0.018/10 a与0.039/10 a;柔远川I d极值呈显著性增大趋势,增大幅度为7.68 mm/(d·10 a);柔远川分级降水强度变化不显著,合水川中雨与大雨的降水强度呈显著增加趋势,增加幅度为0.61 mm/(d·10 a)和1.29 mm/(d·10 a)。     

Roman water law in rural Africa: the unfinished business of colonial dispossession

This study reviews combined rainfall observation using both radar and rain gauges. Sampling error theory is introduced and applied to an evaluation of the rain gauge network of the upstream region of the Imjin River Basin in North Korea. Under the assumption that the Ganghwa Radar is properly calibrated, an additional 13 rain gauges (including the eight that are currently in operation) is deemed sufficient to secure the quality of rainfall observation with 37 rain gauges without radar.     

利用测雨雷达信息计算区域降水量方法的研究

天气雷达覆盖面广、实时性强，对于观测区域内任意点都有回波与其对应。拟用测雨天气雷达信息来进行有关雨量的计算以弥补单纯依靠有限个雨量站点计算面雨量的不足。由于测雨雷达在探测过程中受各种因素制约，精度偏低，因此需要校正，采用了变分法和卡尔曼滤波相结合的雷达回波校正方法。     

Geostatistical mapping of precipitation: implications for rain gauge network design.

This study examined four univariate kriging techniques; simple kriging (SK), ordinary kriging (OK), multi-Gaussian kriging (MGC), and log-normal kriging (LNK); and two multivariate kriging algorithms; kriging with external drift (KED) using elevation and slope in two different models for the estimation of daily rainfall in a 250 m x 250 m grid over a 750 km2 area in the Canadian Boreal forest. Multivariate kriging did not enhance daily rainfall predictions. SK, OK, and LNK produced statistically comparative results with OK being slightly better. MGC was the worst univariate estimator, mainly due to the high percentage of data spikes. Sequential Gaussian simulation (SGS) was then implemented to produce 100 equiprobable maps of rainfall. A multi-objective approach; that is based on overlaying the map of the kriging variance, the DEM, and land use/land cover maps in a GIS framework to identify the areas of commonly favourable features; was proposed to identify potential future sampling locations.     

Identification of the SCS-CN Parameter Spatial Distribution Using Rainfall-Runoff Data in Heterogeneous Watersheds

The Soil Conservation Service Curve Number (SCS-CN) method is widely used for predicting direct runoff volume for a given rainfall event. However, previous results indicated that when the CN value is determined from measured rainfall-runoff data in a natural watershed it is not possible to attribute a single CN value to the watershed, but actually the calculated CN values vary systematically with the rainfall depth. In a previous study, the authors investigated the hypothesis that the observed correlation between the calculated CN value and the rainfall depth in a watershed reflects the effect of the inevitable presence of soil-cover complex spatial variability along watersheds. In this study, a method to determine SCS-CN parameter values from rainfall-runoff data in heterogeneous watersheds is proposed. This method exploits the observed correlation between the calculated CN values and the rainfall depths in order to identify the spatial distribution of CN values along the watershed taking in to account the specific characteristics of the watershed. The proposed method utilizes the available rainfall-runoff data, remote sensing data and GIS techniques in order to provide information on spatial watershed characteristics that drive hydrological behavior. Furthermore, it allows the estimation of CN values for specific soil-land cover complexes in more complex watersheds. The proposed method was tested in a small experimental watershed in Greece. The watershed is equipped with a dense hydro-meteorological network, which together with a detailed land cover and soil survey using remote sensing and GIS techniques provided the detailed data required for this analysis.     

粒子群算法优化BP在降雨空间插值中的应用

为更好地表达降雨量的空间分布,将粒子群算法(PSO)优化后的反向传输(BP)神经网络分别运用于三峡区间流域日、月和年降雨量的空间插值中,并与单纯BP神经网络和克里金的插值效果作对比。研究结果表明:在日和年的时间尺度上,PSO-BP插值性能较BP有明显改善,且优于克里金的插值效果;在月时间尺度上,PSO-BP插值效果与BP接近且优于克里金。因此,PSO-BP能较好地揭示降雨量在空间的分布规律,也具备在不同时间尺度上对降雨量进行空间插值的能力,是一种较优的降雨空间插值方法。