城市暴雨强度公式复核 −以杭州主城区为例

在气候变化与快速城镇化共同影响下,很多城市暴雨特性发生变化,现行的暴雨强度计算公式可能不再适用,需要复核和更新。以杭州市主城区为例,根据钱塘江江畔闸口站1982—2022年降雨极值资料,分别选用皮尔逊Ⅲ型分布和耿贝尔分布曲线进行线型拟合,采用粒子群优化算法推求暴雨强度公式参数,与现行规范给出的暴雨强度公式进行复核分析。结果表明：在重现期为2~20 a时,根据皮尔逊Ⅲ型分布和耿贝尔分布推求得到暴雨强度新公式的平均绝对均方差均小于0.05mm/min,平均相对均方差均小于5%,符合精度要求;仅当降雨历时为10min时,2个新公式的暴雨强度要小于现行公式的暴雨强度,其他历时下2个新公式的暴雨强度都明显大于现行公式的暴雨强度;经合理性分析,本研究根据最新暴雨资料推求的暴雨强度公式可为杭州市主城区排水防涝工程设计和相关设施建设提供参考。     

A rationale for using local and regional point rainfall data for design and analysis of urban storm drainage systems

The Danish measuring network for high-resolution rainfall data consists of approximately 70 tipping bucket rain gauges of which 41 have been operated for more than 10 years. The gauges are separated by one to 300 km and cover an area of 43,000 km2. Significant geographical variations of extreme rainfall characteristics have been observed. Part of these variations can be explained by correlation with the mean annual rainfall and the existence of a metropolitan effect in the Greater Copenhagen area. The remaining variation may be attributed to sampling errors and small-scale spatial variations close to the gauges. Engineering methodologies all require rain data of some kind, ranging from design storms based on idf-curves for use in simple calculations to high-resolution time series for use in detailed simulation studies. A comprehensive regional analysis was carried out to account for the geographical variation and to improve estimation for large return periods exceeding the actual length of the measured time series. Ideally, rainfall data used as input to urban drainage calculations should always be based on regional rain information. Regional design storms can be made readily available based on theory developed in this study. However, a satisfactory framework for generating synthetic rain series from regional rain information is not yet available. Thus, there will still be a need for using historical rain series in the near future. To improve the basis for choosing representative historical rain series all the Danish gauges have been classified according to their deviations from the regional distribution.     

Significant climate change of extreme rainfall in Denmark.

During recent years, practitioners of urban drainage have complained that they felt that surcharging occurred more frequently. Therefore, a study was initiated focussing on the variations in extreme rainfall during the last two decades. In Denmark, a total of 41 rain gauges with a high resolution in time and volume have an observation period close to 20 years. The rainfall observed at these gauges was selected for this study. Three variables were analysed for statistically significant trends during the observation period: Maximum average 10 min intensity, maximum average 6h intensity and the total volume of individual rain events. For the 10 min maximum intensity there is a statistically significant trend towards more extreme and more frequently occurring rain storms. The trend is pronounced in the eastern part of the country and below statistically significant levels in the western part of the country. For the 6 h maximum intensity and total volume of events the trends are less pronounced. The findings are confirmed by comparison to physically based climate models and studies based on large regions.     

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.     

海口市极端降雨事件演变趋势分析

城市暴雨内涝与极端降雨事件息息相关。为揭示城市暴雨内涝成因,利用海口站1953-2012年日降雨量资料,采用线性倾向估计法、Mann-Kendall趋势检验法、Mann-Kendall突变检验法和小波分析法等探讨了海口市极端降雨事件演变规律。结果表明:近60年来海口市极端降雨指标均呈现出上升趋势,但极端降雨日数上升趋势较弱,短历时暴雨强度增加,对城市内涝带来较大压力;极端降雨事件的突变年份在2007年附近,暗示海口市在2007年附近对土地的开发利用是一个节点;海口市降雨周期性不是很显著。     

Non-Stationary Rainfall Intensity-Duration-Frequency Relationship: a Comparison between Annual Maximum and Partial Duration Series

The rainfall Intensity-Duration-Frequency (IDF) relationship is the primary input for storm water management and other engineering design applications across the world and it is developed by fitting an appropriate theoretical probability distribution to annual maximum (AM) series or partial duration series (PDS) of rainfall. The existing IDF relationship developing methods consider the extreme rainfall series as a stationary series. There exist few studies that compared AM and PDS datasets for developing rainfall IDF relationship in a stationary condition. However, during the last few decades, the intensity and frequency of extreme rainfall events are increasing due to global climate change and creating a non-stationary component in the extreme rainfall series. Therefore, the rainfall IDF relationship developed with the stationary assumption is no longer tenable in a changing climate. Hence, it is inevitable to develop non-stationary rainfall IDF relationship and to understand the differences in non-stationary rainfall IDF relationships derived using AM and PDS datasets. Consequently, the objectives of this study are: (1) to develop non-stationary rainfall IDF relationships using both AM and PDS datasets; (2) to compare them in terms of return level estimation. In particular, the non-linear trend in different durations’ PDS and AM datasets of Hyderabad city (India) rainfall is modeled using Multi-objective Genetic Algorithm (MGA) generated Time based covariate. In this study, the PDS datasets are modeled by the Generalized Pareto Distribution (GPD) while the AM datasets are modeled by the Generalized Extreme Value Distribution (GEVD). The time-varying component is introduced in the scale parameter of the GPD and the location parameter of the GEVD by linking the MGA generated covariate. In addition, the complexity of each non-stationary model is identified using the corrected Akaike Information Criteria (AICc) and the statistical significance of trend parameter in the non-stationary models is estimated using the Likelihood Ratio (LR) test. Upon detecting significant superiority of non-stationary models, the return levels of extreme rainfall event for 2-, 5-, 10- and 25-year return periods are calculated using non-stationary models. From the results, it is observed that the non-stationary return levels estimated with PDS datasets are higher than those estimated with AM datasets for short durations and smaller return periods while the non-stationary return levels estimated with AM datasets are higher than those estimated with PDS datasets for long durations and higher return periods.     

1951- 2015 年广西极端降雨时空演变特征

基于两种高时空分辨率的 1951- 2015 年日降雨序列数据, 选择 11 个极端降雨指数, 采用 Mann-Kendall( M- K) 检验法和极点对称模态分解法, 分析了广西极端降雨事件的多尺度非线性时空演变特征。结果表明: 1951 - 2015 年广西 11 个极端降雨指数除连续湿润日 CWD、中雨日数 R10总体呈现下降趋势外, 其余 9 个指数均呈现较显著的增强趋势; 广西连续干日指数 CDD 高值区位于桂东和桂西, 其余指数均呈现出从桂东北及南部向桂西南、桂西北递减的空间分布特征; 各极端降雨指数显示, 广西极端降雨演变多在 2008- 2010 年发生显著的突变; 广西极端降雨演变存在 2. 85~ 3. 34 a 和 5. 34~ 9. 19 a 的年际准周期, 存在 10. 09~ 17. 11 a 和 22. 35~ 35. 62 a 的年代际准周期, 其多重周期的波动振荡主要以极端降雨的年际变化贡献为主。     

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。     

郑州市雨岛效应多方法集成评估及量化研究

为研究城市化发展带来的雨岛效应问题,选用郑州市1978—2018年社会经济资料和1960—2020年逐日降雨资料,在利用六阶段论和“S”形曲线法分析郑州城市化发展水平的基础上,多方法并举构建雨岛效应评估方法体系;基于年降水量、年汛期降水量对郑州市雨岛效应进行趋势和周期变化分析,并引入标准化距离法量化评估雨岛效应。结果表明：郑州市中心城区雨岛效应在1997年和2004年有明显突变增强趋势;年降水量、年汛期降水量雨岛效应增强趋势分别持续4 a和10 a,且分别具有8～10 a、15～20 a的第一主周期和17～20 a、6～10 a的第二主周期;标准化距离法计算的年降水量、汛期降水量增雨系数标准化显化值分别为0.261和0.643,说明郑州市雨岛效应集中于汛期。     

1960-2016年三峡库区极端降水事件时空变化特征

利用三峡库区20个气象站1960-2016年的逐日降水资料,应用线性倾向估计、Mann-Kendall 突变分析法、小波分析法和克里金插值法,分析库区极端降水事件的时空变化特征。结果表明：1960-2016年,三峡库区极端降水事件总体上呈现减少的趋势,其中Rx5day、CWD减少趋势显著,而SDII、Rx1day、R99p等指数表现为不显著增加趋势,这可能是由于PRCPTOT减少速率小于CWD而造成了雨量再分配;极端降水指数突变多发生于1990年前后;PRCPTOT、R10、R95p的气候倾向率在三峡库区中部地区均表现为明显下降趋势,而CWD则在东北和西南部呈增加趋势,表明三峡库区极端降水存在均化的趋势;三峡库区极端降水指数的变化主周期相似,大多数为4~6 a的短周期,仅R10与R25存在12~16 a的中周期,表明三峡库区极端降水事件正在向强度大、周期短的方向演化;气候因子均对极端降水指数有较大影响,太阳黑子相对数与极端降水指数呈正相关关系,其他则为负相关,在时序性上,表现为PRCPTOT滞后于大多数气候因子。该研究可为三峡库区极端气候变化的模拟预测及防灾减灾提供参考。     

昆明地区降水、气温及极端天气的长期变化趋势

利用昆明气象站1951年-2013年逐日气温和降水资料,采用线性趋势、Sen斜率估计、Mann-Kendall等方法分析昆明降水、气温和极端天气的变化特征与趋势,结果表明:1951年-2013年间,1994是年平均气温突变点;年平均气温和四季气温均呈升温趋势;年降水量和夏、秋两季降水量呈下降趋势,春、冬两季降水呈上升趋势,但趋势并不显著;在极端降水指数中,持续湿期呈下降趋势,持续干期和一日最大降水量呈上升趋势,趋势并不显著;在极端温度指数中,热日持续指数、暖夜指数及暖昼指数均呈显著上升趋势,冷日持续指数、冷夜指数及冷日指数均呈显著下降趋势。     

Analysis of rainfall time series with regard to temporal disaggregation for the use in urban hydrology

The temporal resolution of rain data recorded by national weather services is often lower (10-min resolution) than the data needed for rainfall-runoff simulations (1–5 min resolution). However, the time series are sufficiently long for statistical analysis. The goal of the project presented here is to develop a procedure that disaggregates the 10-min rainfall data of the Swiss Meteorological Institute (SMI) to 1-min time resolution. The aim is to implement the procedure in a computer program which can be used by practitioners for generating high resolution rainfall time series at a specific location. In a first step the 1-min data and the 10-min data of two rainfall time series in Switzerland (Heiden, Lucerne) were compared to find characteristic patterns and correlations. The position of 1-min peak within the 10-min interval, the ratio of 1-min peak to 10-min intensity as well as the distribution of the 1-min values within the 10-min interval were investigated. The analysis showed that the positions of the 1-min peaks within a 10-min interval were not uniformly distributed. The distribution depended on the temporal trend of the 10-min values. The ratio of 1-min peak to 10-min intensity seemed to tend towards a constant ratio for high intensities. The results for the two series (Heiden and Lucerne) were not significantly different. These first findings are encouraging with regard to developing a disaggregation to 1-min values which satisfy the accuracy needed in urban hydrology.     

Regional sub-hourly extreme rainfall estimates in Sicily under a scale invariance framework

Design of urban drainage systems or flood risk assessment in small catchments often requires knowledge of very short-duration rainfall events (less than 1 h). Unfortunately, data for these events are often unavailable or too scarce for a reliable statistical inference. However, regularities in the temporal pattern exhibited by storm records, known as scaling properties of rainfall, could help in characterizing extreme storms at partially gauged sites better than the application of traditional statistical techniques. In this work, a scaling approach for estimating the distribution of sub-hourly extreme rainfall in Sicily (Italy) is presented based on data from high-resolution rain gauges with a short functioning period and from low-resolution rain gauges with longer samples. First, simple scaling assumption was tested for annual maxima rainfall (AMR) data from 10 min to 24 h duration, revealing that the simple scaling regime holds from 20 to 60 min for most of the stations. Then, scaling homogeneous regions were classified based on the values of the scaling exponent. In each region, this parameter was regionalized through power-law relationships with the median of 1 h AMR data. After that, regional Depth Duration Frequency (DDF) curves were developed by combining the scale-invariant framework with the generalized extreme value (GEV) probability distribution and used to estimate T-year sub-hourly extreme rainfalls at sites where only rainfall data for longer durations (≥ 1 h) were available. The regional GEV simple scaling model was validated against sub-hourly historical observations at ten rain gauges, generally yielding, in relation to the scaling exponent value, to similar or better sub-hourly estimates than empirical approach.

     

佛冈县近5O年来降雨特征浅析

针对全球气温升高、气候变化导致降雨发生变化、极端事件频发问题,选用珠江流域中佛冈县作为研究区域,统计了1960--2009年佛冈县50年逐日降雨资料,发现佛冈县年总降雨近50年有所减小,尤其是5月和10月降雨量存在减少趋势,目最大降雨量也存在减小趋势,说明降雨减小的原因主要是暴雨量减小。由于降雨的减少主要是暴雨的减少所致,说明气候变化有可能降低佛冈县发生洪涝灾害的概率。     

1960—2013年昭通市极端降雨时空演变规律研究

气候变化引起的极端降雨量级和频次变化已经引起了广泛的关注,极端降雨演变规律的研究对于区域防洪减灾和水资源管理具有重要意义。基于昭通市及其周边的16个气象站点1960—2013年共54 a的降雨数据,选取世界气象组织推荐的6个极端降雨指数,采用线性趋势分析、Mann-Kendll法和滑动T检验等方法分析了昭通市的极端降雨时间演变规律,并基于ArcGIS10.2采用反距离插值法(IDW)分析了昭通市极端降雨指数的空间分布格局。结果表明:在趋势演变方面,昭通市的总降雨量PRCPTOT有下降趋势;而反映极端降雨量级的3项指数SDII,RX5day,R95p均呈上升趋势,其中RX5day上升趋势显著;而R10mm和CWD这2项反映极端降雨频率的指数均呈下降趋势,其中R10mm下降趋势显著。在空间分布方面,昭通市6项极端降雨指数具有较高的空间异质性,东北部降雨量级和频率较高,中部趋缓,而西南部总体上相对较低。相关分析的结果表明昭通地区极端降雨指数与高程呈现负相关关系,极端降雨主要发生在低海拔地区。研究成果有助于加深对该区域极端降雨发生规律的认识,为区域防洪减灾和水资源管理提供参考。     

Estimating Temporal Changes in Extreme Rainfall in Sicily Region (Italy)

An intensification of extreme rainfall events have characterized several areas of peninsular and insular Italy since the early 2000s, suggesting an upward ongoing trend likely driven by climate change. In the present study temporal changes in 1-, 3-, 6-, 12- and 24-h annual maxima rainfall series from more than 200 sites in Sicily region (Italy) are examined. A regional study is performed in order to reduce the uncertainty in change detection related to the limited length of the available records of extreme rainfall series. More specifically, annual maxima series are treated according to a regional flood index - type approach to frequency analysis, by assuming stationarity on a decadal time scale. First a cluster analysis using at-site characteristics is used to determine homogeneous rainfall regions. Then, potential changes in regional L-moment ratios are analyzed using a 10-year moving window. Furthermore, the shapes of regional growth curves, derived by splitting the records into separate decades, are compared. In addition, a jackknife procedure is used to assess uncertainty in the fitted growth curves and to identify significant trends in quantile estimates. Results reveal that L-moment ratios show a general decreasing trend and that growth curves for the last decade (2000–2009) usually do not stand above the others, with the only exception of the ones related to the outer western part of Sicily. On the other hand, rainfall quantile estimates for the same period are the highest values almost all over the region. An explanation can be found in the increase of subregional average medians, largely caused by recent severe local storms.     

中等排放情景下中国未来不同强度降雨变化及其对总降雨贡献的预估(2006—2100 年)

为探究中国整体和不同区域的不同强度降雨雨量及其对总降雨雨量贡献率的变化趋势,采用ＲCP6. 0 中等排放情景下 2006—2100 年 WＲF 30 km × 30 km 日值降水数据,根据中国气象局颁布的降水强度等级划分标准进行研究。结果表明: ( 1) 在降雨雨量上,中等排放情景下 2006—2100 年中国小雨减少,强降雨增加。在降雨雨量贡献率上,小雨和中雨对总降雨的贡献率呈减少趋势,其他五种强降雨对总降雨的贡献率在增加,说明强降雨增加,降雨朝着极端化方向发展。暴雨对总暴雨的贡献率呈增加趋势,而大暴雨和特大暴雨对总暴雨的贡献率呈减少趋势,总暴雨对总降雨贡献率的增加是由于暴雨的增加起了关键作用。( 2) 在不同分区上,北方、东北和西藏地区不同强度降雨均呈增加趋势; 东南和西南地区除小雨外均呈增加趋势; 西北东部地区仅小雨、大暴雨和特大暴雨呈增加趋势;西北西部地区仅小雨、中雨和总降雨呈增加趋势。在降雨雨量贡献率上,北方和西藏地区除小雨外均呈增加趋势; 东北、东南和西南地区除小雨和中雨外均呈增加趋势; 西北东部地区仅小雨呈增加趋势; 西北西部地区仅小雨和中雨呈增加趋势。( 3) 在不同强度暴雨对总暴雨贡献率上,七大分区中的特大暴雨对总暴雨的贡献率除西北西部变化趋势不显著外,其他分区均呈不同程度的增加趋势。所得成果为类似研究提供参考。     

人工降雨试验中风速对落地雨强空间分布的影响研究

气候变化和城镇化发展使得极端暴雨发生频率增加,实验室降雨试验可为极端暴雨灾害的研究提供数据支撑。通过开展不同情景下的实验室降雨试验与数值模拟,研究了风对落地雨强分布的影响,分析了风导致试验区域平均落地雨强减小的原因。结果表明：（1）风会使试验区域的实际平均落地雨强减小,主要原因是降雨中不同粒径雨滴在风场作用下漂移距离的不同,导致了地面受雨面积扩张。（2）受雨范围内落地雨强的均匀性受风速影响,落地雨强均匀性随风速增加而下降。为提高试验数据的准确性,在进行降雨模拟试验时需要考虑风速的影响,结合实验室实际条件合理确定试验范围。     

Semi-parametric Estimation Based on Second Order Parameter for Selecting Optimal Threshold of Extreme Rainfall Events

Analysis of extreme rainfall events can be performed using two main approaches; fitting Generalized Extreme Value distribution to the yearly peaks of events in the observation period or the annual maximum series, and fitting Generalized Pareto distribution to the peaks of events that exceed a given threshold or the partial duration series. Even though partial duration series are able to reduce sampling uncertainty and are useful for analyzing extreme values and tail asymmetries, the series require an optimal threshold. The objective of this study is to compare and determine the best method for selecting the optimal threshold of partial duration series using hourly, 12-hour and 24-hour data of rainfall time series in Peninsular Malaysia. Nine semi-parametric second order reduced-bias estimators are applied to estimate extreme value index and six estimators are used for the external estimation of the second order parameter. A semi-parametric bootstrap is used to estimate mean square error of the estimator at each threshold and the optimal threshold is then selected based on the smallest mean square error. Based on the plots of extreme value index and mean square error, several second order reduced-bias estimators behave reasonably well compared to Hill estimator, as indicated by their stable sample paths and flatter mean square errors.     

基于TIGGE多模式的6 h降雨预报精度对比分析

降雨数值预报是预防极端天气导致灾害事件的重要手段,其预报精度是预报产品是否被采用的依据。以跋山水库流域为研究对象,选取了TIGGE系统中的ECMWF、NCEP、CMA、JMA、UKMO共5个预报模式的控制预报与集合预报,分别从降雨分级预报检验和降雨量预报检验两个角度,利用Brier评分和Talagrand分布图,分析了2007—2019年5—9月控制预报和集合预报降雨数据的精度。结果表明:(1)就降雨分级预报而言,对于无雨、小雨和中雨量级,5个预报模式控制预报和集合平均预报效果相差不大;对于大雨量级,JMA和NCEP的控制预报效果最佳,JMA和UKMO的集合平均预报效果最佳;对于暴雨及以上量级,NCEP的控制预报和集合平均预报均效果最佳;(2)针对降雨量预报,UKMO控制预报和集合平均预报效果最佳;(3)无雨等级的Brier评分最高,且Brier评分随着降雨等级的提升而降低,表明大量级降雨时Brier评分较好;CMA的评分在无雨、小雨、中雨、大雨4个等级表现最好;(4)5个模式Talagrand分布形态均呈粗略的“U”字型,表明5个预报模式集合成员的分散不够。综合来看,UKMO和NCEP的预报效果最佳。据此研究可选出高精度的降雨预报产品。