水文干旱与气象干旱临界转变条件的判定及响应关系

水文干旱与气象干旱的响应关系对于建立健全干旱监测预报系统具有重要意义。基于区域水文干旱指数(SHI)与标准化降水指数(SPI),结合游程理论和非线性关系模型分析喀什河流域水文干旱与气象干旱的特征、响应关系及驱动因素。结果表明:水文干旱的年平均干旱历时和干旱烈度大于气象干旱,且随着SPI和SHI时间尺度的增加,识别出的干旱历时和干旱烈度也有所增加。基于三参数(log 3 P1)对数函数(Logarithm)模型可以更好地表征两者的响应关系。在3个月尺度下,气象干旱历时至少为1. 10个月且干旱的烈度至少为0. 83时,将诱发水文干旱;在6个月尺度下,气象干旱历时至少为1. 60个月且干旱的烈度至少为0. 91时,易发生水文干旱。     

Utilization of Time-Based Meteorological Droughts to Investigate Occurrence of Streamflow Droughts

Complexities of streamflow drought analyses motivate utilization of simple, alternative methods, which can provide timely information for effective water resources management. For this purpose time-based meteorological drought characteristics, identified by SPI _{3 − month} , SPI _{6 − month} and SPI _Anuual are investigated. A boxplot approach is used to exclude non-rainy months from the analysis. Streamflow drought characteristics are described by drought intensities, and are calculated by the threshold level method. The non-parametric Wilcoxon–Mann–Whitney test is used to investigate relations between streamflow drought intensities and SPI _{3 − month} , SPI _{6 − month} and SPI _Anuual . The study area is the Doroodzan Watershed and Reservoir in southwestern Iran, with four rain gauge and two hydrometric stations. According to the results, most of time-based SPI values show significant relations (at 5% level of significance) with streamflow drought intensities. However, the most significant relation is between SPI _Anuual of Jamalbeik rain gauge station (centrally located in the study area) and drought intensities of Chamriz hydrometric station (located at the reservoir inlet). Comparison of study results with available records of documented droughts, confirms applicability of the proposed procedures. The SPI _Anuual is based on one-year-ahead moving average rainfalls. Then, SPI _Anuual of Jamalbeik station can be used to investigate occurrence of streamflow drought in Chamriz hydrometric station.     

不同干旱指数在新疆哈巴河地区旱情评价中的应用研究

利用新疆哈巴河地区1962-2014年间的气象资料,比较分析多时间尺度的标准化降水指数(SPI)和标准化降水蒸发指数(SPEI)在该地区的适用性,并基于两种干旱指数计算结果分析哈巴河地区53a间的干旱演变特征。结果表明:各时间尺度(年、季、月)下的SPI指数与SPEI指数呈现显著性相关;单月小尺度下,SPEI指数评价干旱事件等级较实际情况要严重,SPI指数在实际使用中更具优势;12月长时间尺度下,SPI指数和SPEI指数均体现出巴河地区干旱逐步减轻的趋势,在气候变暖大背景下考虑气温变化的SPEI指数较SPI指数更符合当地实际;各季节尺度下,SPI和SPEI指数发生各干旱等级事件的比例相差不大,实际使用中建议春冬季使用SPI指数,夏秋季使用SPEI指数或修正过的SPI指数,同时需要重点关注夏秋季干旱。     

基于SPI和SPEI的淮河中上游流域气象干旱时空分布特征对比研究

基于淮河流域1960-2017年逐月降水、气温资料,采用SPI、SPEI等干旱指数和线性趋势法、Mann-Kendall、小波分析等数学统计方法对年和四季气象干旱的趋势性、周期性及干旱频次进行时空分布特征的对比研究。结果表明:流域年、夏冬两季两种干旱指数呈微弱增加趋势,SPEI较SPI上升幅度略大,春秋两季均呈微弱减少趋势,SPEI较SPI下降幅度略大;研究时段内同一区域的两种干旱指数反映的干湿变化周期性基本一致;年尺度淮河以北SPEI显示中旱频次较多而SPI显示轻旱频次较多,其他时间尺度南北区域接近一致;两种干旱指数的空间变化趋势除夏季较为一致外,年、春秋两季在同一区域上SPEI显示的干旱化趋势较SPI略强,冬季SPI显示绝大部分区域呈湿润化趋势而SPEI呈干旱化趋势;两种指数在空间分布上存在一定程度的差异性,四季SPEI显示的干旱频次普遍比SPI统计的干旱频次高。研究结果对于干旱客观性评估和水旱灾害防治管理具有重要参考价值。     

基于Copula函数的新型综合干旱指数构建与应用

干旱指数是研究干旱的重要工具,构建综合干旱指数是目前干旱监测、风险评估的前沿和趋势。本文基于阿基米德Copula函数,联合降雨(气象)、径流(水文)两种要素,构建了一种能够综合表征气象干旱和水文干旱的新型综合干旱指数MSDI_p,并用其表征渭河流域的干旱演变特征,且进一步对其背后的驱动力进行了探究。结果表明:(1)MSDI_p指数既能像标准化降水指数(SPI)一样敏锐地捕捉干旱的发生,也能像标准化径流指数(SRI)一样很好地刻画干旱的持续时间和结束,同时具备气象和水文两种干旱指数表征不同类型干旱的优势,能综合表征干旱演变特征;(2)受气候变化和人类活动影响,渭河流域过去50余年综合干旱呈显著增强趋势;(3)渭河流域综合干旱指数序列存在变异点(1994年),且未来流域干旱情势有加剧趋势;(4)太阳黑子和大气环流异常因子等对渭河流域综合干旱的发生有较大影响,其中太阳黑子活动的影响最强。且除直接影响外,太阳黑子还能通过影响大气环流异常因子进而对综合干旱的发生造成间接影响。     

Drought variability and its connection with large-scale atmospheric circulations in Haihe River Basin

Drought is one of the most widespread and devastating extreme climate events when water availability is significantly below normal levels for a long period. In recent years, the Haihe River Basin has been threatened by intensified droughts. Therefore, characterization of droughts in the basin is of great importance for sustainable water resources management. In this study, two multi-scalar drought indices, the standardized precipitation evapotranspiration index(SPEI) with potential evapotranspiration calculated by the Penmane Monteith equation and the standardized precipitation index(SPI), were used to evaluate the spatiotemporal variations of drought characteristics from 1961 to 2017 in the Haihe River Basin. In addition, the large-scale atmospheric circulation patterns were used to further explore the potential links between drought trends and climatic anomalies. An increasing tendency in drought duration was detected over the Haihe River Basin with frequent drought events occurring in the period from 1997 to 2003. The results derived from both SPEI and SPI demonstrated that summer droughts were significantly intensified. The analysis of large-scale atmospheric circulation patterns indicated that the intensified summer droughts could be attributed to the positive geopotential height anomalies in Asian mid-high latitudes and the insufficient water vapor fluxes transported from the south.     

A New Method for Joint Frequency Analysis of Modified Precipitation Anomaly Percentage and Streamflow Drought Index Based on the Conditional Density of Copula Functions

In this study, a new method was proposed to model the occurrence of related variables based on the conditional density of copula functions. The proposed method was adopted to investigate the dynamics of meteorological and hydrological droughts in the Zarinehroud basin, southeast of Lake Urmia, during the period 1994–2015. For this purpose, the modified precipitation anomaly percentage and streamflow drought indices were extracted. Finally, the joint frequency analysis of duration-duration and severity-severity characteristics of meteorological and hydrological droughts was analyzed. Analysis of 7 different copulas used to create the joint distribution in the Zarinehroud basin indicated that the Frank copula had the best performance in describing the relationship between the meteorological and hydrological drought severities and durations. By examining the results of the bivariate analysis of duration-duration of meteorological and hydrological droughts at different stations, the expected meteorological and hydrological drought durations were estimated in the years ahead. For example, at Chalkhmaz station, 4- to 7-month duration for the hydrological drought and 9- to 12-month duration for the meteorological drought is expected in the years ahead. The joint frequency analysis of drought characteristics allows to determine the meteorological and hydrological drought characteristics at a single station at the same time using joint probabilities. Also, the results indicated that by knowing the conditional density, the hydrological drought characteristics can be easily estimated for the given meteorological drought characteristics. This could provide users and researchers useful information about the probabilistic behavior of drought characteristics for optimal operation of surface water.

     

Factors Influencing Markov Chains Predictability Characteristics, Utilizing SPI, RDI, EDI and SPEI Drought Indices in Different Climatic Zones

Comparability analyses were carried out to investigate behavioural aspects of effective drought index (EDI), standardized precipitation index (SPI), reconnaissance drought index (RDI) and standardized precipitation evapotranspiration index (SPEI), considering 3-month, 6-month and annual time periods. Investigations included parametric/non-parametric correlation analysis among indices, climatic zone influence, record length impacts and evapotranspiration role (RDI and SPEI) on Markov chains predictability characteristics. Except for the EDI, all indices/cases (all climatic zones) showed significant correlation. In arid/semi-arid climates, the 3-month and 6-month maximum drought severities were detected by the RDI and annual maximum drought severities were detected by the SPEI, emphasizing the evapotranspiration influence. In all climatic zones, the EDI values for wet (dry) periods were higher (lower), compared to other indices. First order dependency was detected for the EDI (all cases) and the SPI (most cases), over entire period (1951–2011) and sub-periods [(1951–1981), (1982–2011)]. The largest number of second order dependency was detected by the SPEI, followed by a relatively large number of such cases by the RDI (3-month time period), for the 61-year data period. This research showed that several factors influence Markov chains predictability characteristics in drought studies, particularly the impact of record length and evapotranspiration (RDI and SPEI) were confirmed.     

滇中引水工程主要受水区水汽输送时空变化

基于ERA-Interim再分析资料,以滇中引水工程主要受水区为研究对象,计算了受水区上空21 a水汽输送通量及水汽输送通量散度,并对其水汽输送、水汽辐合与水汽辐散等特征进行分析,研究其水汽输送时空变化特征。结果表明:研究区年平均水汽输送由西北至东南方向逐渐增加,并以纬向输送为主;水汽来源随季节移动,研究区夏季受西南风控制,水汽输送强度明显小于其他3个季节;5—7月份,研究区水汽输送强度逐渐衰减,7月份,研究区850 hPa气压层南部地区存在水汽辐合中心,450 hPa气压层西南部为水汽辐散带,在西南部易于形成降水。     

不同季节气象干旱向水文干旱的传播及其动态变化

研究变化环境下气象干旱向水文干旱的传播与影响机制,有利于揭示水文干旱的形成过程与机理,从而建立基于气象干旱的水文干旱预警.为揭示不同季节气象干旱向水文干旱的传播动态变化及其驱动因素,本研究以无定河、窟野河和沁河流域为研究区域,采用标准化降水指数(SPI)和标准化径流指数(SRI)分别表征气象干旱和水文干旱,分析气象、水...     

黄河流域气象干旱与水文干旱时空特征及其传递关系EI北大核心CSCD

基于标准化降水蒸散指数(SPEI)和标准化径流指数(SRI),比较了黄河流域气象干旱和水文干旱的时空分布差异,分析了二者时间尺度上的关联性,并选取典型干旱事件进一步探讨了两种干旱类型的传递关系。结果表明:两种干旱类型空间上有相似的趋势和频次,但在黄河源区和黄河中南部(渭河流域)差异显著,其干旱历时均有随年代延长的趋势,水文干旱历时增长尤为明显;在时间尺度上,SPEI与SRI在大部分区域基本一致,但在黄河源区和渭河流域差异较大,尤其是短时间尺度上差异更显著;气象干旱与水文干旱并非一一对应,多场短历时间断气象干旱受时滞效应、异常气象波动等影响,可能引发一场长历时连续水文干旱或多场短历时间断水文干旱,一场长历时连续气象干旱强度衰减可能引发多场短历时间断水文干旱。     

1962-2017年典型半干旱草原区不同时间尺度干旱特征分析

干旱是我国北方地区主要的自然灾害之一,对干旱指标的监测分析可为地区旱情评估、预警以及为制订抗旱减灾对策提供科学依据。以内蒙古高原半干旱草原区1962-2017年0.5°×0.5°降水格点数据为基础,分别计算不同时间尺度(年、季)的标准化降水指数(SPI),通过分析其干旱频次、频率以及站次比的变化,对研究区1962-2017年的干旱时空特征进行了分析。结果表明:近年来,研究区干旱程度有所加剧,且中南部地区为各类干旱事件的频发区。此外,轻旱多发生于秋季,且主要分布于研究区中部及南部,而特旱事件常在夏季发生,其高频区位于研究区西部。20世纪90年代各季均出现了大范围轻旱,夏季分别于2001和2010年出现全域性中旱及全域性特旱。     

基于SPEI的贵州省气象干旱时空演变特征及双变量区域频率分析

为深入探究贵州省干旱事件发展规律及区域重现期特征,采用贵州省1960—2017年逐月气象资料计算标准化降水蒸散指数（SPEI）,采用三阈值法游程理论、小波理论、Copula函数等方法对干旱时空演变特征、周期特征以及区域重现期特征进行分析。结果表明：1960—2017年贵州省干旱整体上呈严重化趋势,各分区存在差异,其中黔西南地区的干旱化趋势最为明显,SPEI线性倾向率为-0.003/10a;干旱强度由高到底的分区排序依次为黔东、黔北、黔西南、黔中、黔西北、黔南,且黔中地区的干旱发生频率最高;贵州省四季干旱的主周期分别为18、15、30和8 a,空间上南北分布差异显著,周期较长的区域范围呈现先增加后减少的趋势;贵州省黔北地区的干旱重现期最小,表明此区域发生极端干旱事件的概率较大,遭受干旱灾害的可能性较大。研究结果可为贵州省水资源管理及干旱风险防治提供科学依据。     

A Non-Stationary Reconnaissance Drought Index (NRDI) for Drought Monitoring in a Changing Climate

Traditionally, drought indices are calculated under stationary condition, the assumption that is not true in a changing environment. Under non-stationary conditions, it is assumed the probability distribution parameters vary linearly/non-linearly with time or other covariates. In this study, using the GAMLSS algorithm, a time-varying location parameter of lognormal distribution fitted to the initial values (α₀) of the traditional Reconnaissance Drought Index (RDI) was developed to establish a new index called the Non-Stationary RDI (NRDI), simplifying drought monitoring under non-stationarity. The fifteen meteorological stations having the longest records (1951–2014) in Iran were chose to evaluate the NRDI performances for drought monitoring. Trend analysis of the α₀ series at multiple time windows was tested by using the Mann-Kendall statistics. Although all stations detected decreasing trend in the α₀ series, eight of them were significant at the 5% probability level. The results showed that the time-dependent relationship is adequate to model the location parameter at the stations with the significant temporal trend. There were remarkable differences between the NRDI and the RDI, especially for the time windows larger than 6 months, implying monitoring droughts using the NRDI under non-stationarity. The study suggests using the NRDI where the significant time trend appears in the initial values of RDI due to changing climate.     

Assessing Socioeconomic Drought Based on a Standardized Supply and Demand Water Index

Socioeconomic drought occurs when a water shortage is caused by an imbalance between the supply and demand of water resources in natural and human socioeconomic systems. Compared with meteorological drought, hydrological drought, and agricultural drought, socioeconomic drought has received relatively little attention. Hence, this study aims to construct a universal and relatively simple socioeconomic drought assessment index, the Standardized Supply and Demand Water Index (SSDWI). Taking the Jianjiang River Basin (JJRB) in Guangdong Province, China, as an example, we analyzed the socioeconomic drought characteristics and trends from 1985 to 2019. The return periods of different levels of drought were calculated. The relationships among socioeconomic, meteorological, and hydrological droughts and their potential drivers were discussed. Results showed that: (1) SSDWI can assess the socioeconomic drought conditions well at the basin scale. Based on the SSWDI, during the 35-year study period, 29 socioeconomic droughts occurred in the basin, with an average duration of 6.16 months and average severity of 5.82. Socioeconomic droughts mainly occurred in autumn and winter, which also had more severe droughts than other seasons. (2) In the JJRB, the joint return periods of “∪” and “∩” for moderate drought, severe drought, and extreme drought were 8.81a and 10.81a, 16.49a and 26.44a, and 41.68a and 91.13a, respectively. (3) Because of the increasing outflow from Gaozhou Reservoir, the occurrence probability of socioeconomic drought and hydrological drought in the JJRB has declined significantly since 2008. Reservoir scheduling helps alleviate hydrological and socioeconomic drought in the basin.

     

Drought Concepts and Characterization

Abstract

A better knowledge of droughts is required to improve water management in water scarce areas. To appropriately cope with droughts, there is the need to adopt adequate concepts relative to droughts and water scarcity, to properly use drought indices that help characterize them, including ones relative to their severity, and to develop prediction tools that may be useful for early warning and that may reduce the respective lead time needed for appropriate response. In this paper, concepts relative to drought and other water scarcity regimes are discussed aiming both to distinguish droughts from other water scarcity regimes and to base a common understanding of the general characteristics of droughts as hazards and disasters. Three main drought indices are described aiming at appropriate characterization of droughts: the theory of runs, the Palmer Drought Severity Index (PDSI), and the Standardized Precipitation Index (SPI). Their application to local and regional droughts in the region of Alentejo, Portugal is presented focusing on the respective comparison and possible adequateness for drought monitoring. Results indicate some difficulties in using the theory of runs, particularly because it requires a subjective definition of thresholds in precipitation and does not provide a standardized classification of severity. Results show that draught characterization with the PDSI and the SPI produce coherent information, but the PDSI is limited relative to the SPI because it requires more data to perform a soil water balance while the SPI needs only precipitation data, which are more easily available in numerous locations. It is concluded that adopting the SPI is appropriate, but there is advantage in combining different indices to characterize droughts.     

辽西北地区干旱时空变化特征分析

利用辽西北地区14个气象站与水文站1971年-2010年的基础数据,得到降水量距平值、连续无雨日数、河道来水量距平值和相对湿润度,并以这四项指标为基础,利用可变模糊评价法得到辽西北地区综合干旱级别特征值,再结合线性倾向估计法、Mann-Kendall趋势检验与反距离权重法对辽西北地区的气象、水文综合干旱时空分布特征进行分析。结果表明:辽西北整体旱情呈显著加重趋势,1971年-1980年以轻度干旱为主,旱情较严重的时期为20世纪80年代后,1981年-1990年干旱程度最为严重,1980年-2010年是重度干旱高发期,但特大干旱少有发生;辽西北东北部和西南部地区旱情较为严重,且随时间变化呈现出加重趋势,而中部地区干旱较轻,因此抗旱减灾的重点应集中在该区的东北部和西南部地区。     

云南2009—2014年持续性气象水文干旱特征及成因分析

基于戴-帕尔默干旱强度指数(Dai Palmer drought severity index,Dai-PDSI)和径流干旱指数(streamflow drought index,SDI),分析云南地区2009—2014年持续性气象干旱与水文干旱时空演变特征,并利用NCAR/NCEP再分析资料,从西太平洋副热带高压、青藏高压、南支槽、对流层垂直运动及水汽垂直分布等视角,分析2009—2014年云南持续性干旱的原因。结果表明:(1)2009—2014年是云南地区自1961年以来最严重的一次持续性极端干旱过程,2009年10月—2010年9月是最干旱的时段;夏季与冬季是干旱最严重的两个季节。(2)在空间上,云南中东部旱情最重,东南部稍轻。(3)水文干旱伴随气象干旱而生,金沙江和南盘江出现重度水文干旱,澜沧江出现中等水文干旱,从强度上讲,水文干旱弱于气象干旱。(4)夏季西太平洋副热带高压偏西偏强,青藏高压持续偏强、中心偏西,云南上空的大气持续受它们控制,盛行下沉气流;冬季南支槽偏弱,不利于引导孟加拉湾水汽北上;在其他季节,大气多以下沉运动为主,对流层水汽严重不足。     

Comparison of soil moisture at different depths for drought monitoring based on improved soil moisture anomaly percentage index

To better understand the characteristics and mechanisms of droughts at different drought stages, this study selected the Xiangjiang River Basin in China as the study area, and evaluated soil moisture (SM) at different depths for drought monitoring, through SM data simulated with the variable infiltration capacity (VIC) model. To solve the problem of unreasonable drought/wetness classifications based on the soil moisture anomaly percentage index (SMAPI), an improved soil moisture anomaly percentage index (ISMAPI) was developed by introducing the Box–Cox transformation. The drought/wetness frequency generated by ISMAPI demonstrated preferable spatial comparability in comparison with those from SMAPI. The lag time of ISMAPI relative to the standardized precipitation evapotranspiration index was closely related to soil depth, and was characterized by a fast response in shallow soil layers and a relatively slow response in deep soil layers. SM in shallow soil layers provided a measure for monitoring short-term droughts, whereas SM in deep soil layers provided a better measure for long-term persistent drought events. Furthermore, the occurrence and mitigation time of drought events identified by SM in deep soil layers usually lagged behind that identified by SM in shallow soil layers. Compared with deep SM, SM in shallow soil layers responded faster to meteorological anomalies, thereby resulting in shorter periods of SM persistence in shallow soil layers than in deep soil layers. This can explain the differences of SM at different depths in drought monitoring.