Goodness-of-fit tests for multi-dimensional copulas:Expanding application to historical drought data

The question of how to choose a copula model that best fits a given dataset is a predominant limitation of the copula approach, and the present study aims to investigate the techniques of goodness-of-fit tests for multi-dimensional copulas. A goodness-of-fit test based on Rosenblatt＇s transformation was mathematically expanded from two dimensions to three dimensions and procedures of a bootstrap version of the test were provided. Through stochastic copula simulation, an empirical application of historical drought data at the Lintong Gauge Station shows that the goodness-of-fit tests perform well, revealing that both trivariate Gaussian and Student t copulas are acceptable for modeling the dependence structures of the observed drought duration, severity, and peak. The goodness-of-fit tests for multi-dimensional copulas can provide further support and help a lot in the potential applications of a wider range of copulas to describe the associations of correlated hydrological variables. However, for the application of copulas with the number of dimensions larger than three, more complicated computational efforts as well as exploration and parameterization of corresponding copulas are required.

Photosynthesis of Digitaria ciliaris during repeated soil drought and rewatering

The ability of psammophyte photosynthesis to withstand and recover from severe droughts is crucial for vegetation sta- bility in semi-arid sandy lands. The responses of gas exchange and chlorophyll fluorescence of an annual grass, Digitaria ciliaris, were measured through three soil drought and rewatering cycles. Results showed that the net photosynthesis rate （P,） decreased by 92%, 95%, and 63% at end of the three drought periods, respectively, water use efficiency （WUE） decreased by 67%, 54%, and 48%, while the constant intercellular CO2 concentration （Ci） increased by 1.08, 0.88, and 0.45 times. During those three cycles, the trapping probability with no dark adaptation （Fv＇/Fm＇） decreased by 55%, 51%, and 9%, the electron transport per cross section （ET0＇/CS0＇） decreased by 63%0, 42%, and 18%, and the dissipation per cross section （DI0＇/CS0＇） increased by 97%, 96%, and 21%. These results indicated that D. ciliaris was subjected to photoinhi- bition and some non-stomatal limitation of photosynthesis under drought. However, after four days of rewatering, its photosynthetic characteristics were restored to control values. This capability to recover from drought may contribute to making the plant＇s use of water as efficient as possible. Furthermore, the photosynthesis decreased more slowly in the subsequent drought cycles than in the first cycle, allowing D. ciliaris to enhance its future drought tolerance after drought hardening. Thus, it acclimatizes itself to repeated soil drought.

Dust Events in the Western Parts of Iran and the Relationship with Drought Expansion over the Dust-Source Areas in Iraq and Syria

The most famous deserts exist in subtropical regions which is the direct outcome of insufficient precipitation and high temperatures. The Middle East deserts are subjected often to dust, which reduces horizontal visibility to 5 km, and sometimes even to less than 100 m. The severe and prolong drought recently afflicting the west Asia region has been suggested to be instrumental in producing an increased output of dust into the atmosphere from the region. Regarding the increasing of dust events over the west of Iran with the external origin in the recent decade (from 2000 to present), so the main dust-source areas over Iraq and Syria have been detected using the dust-source map of the southwest of Asia, satellite images and soil type maps. We considered the relationship between the increasing of dust events in the western of Iran and drought expansion over the main dust-production areas during the recent decade. Dust frequency data series, and drought variables which include the VHI (vegetation health index), precipitation and temperature data series in long-term and monthly scales have been monitored and compared. And then we used the correlation analysis that indicated the significant proximity between the dust events and droughts/dryness in a yearly scale and also during the warm season (May to Aug). Meantime the derived results from the T-student test for the aforementioned data series confirm the fact that the droughts are parallel to the increasing of dust events from 1996 to 2011 (especially in the recent decade). We found that the recent droughts in the external dust source areas had the remarkable potential to increase the dust events in the west of Iran.

Screening Test of Maize Varieties in Mountainous Arid Areas

Drought and water shortage are the biggest limiting factors of dry farming,and variety plays an important role in an increase in the yield of dryland maize.Screening high-yield maize varieties is helpful to the continuous increase and stable yield of dryland grain.In this experiment,the growth period,characters and yield of 12 maize varieties were analyzed.The results show that the yield of Ganyu series was low,while the yield of Lianda 169 was the highest(8 080.93 kg/ha),which was 31.40% higher than Jinsui 4.The yield of Dunyu 16 was6 621.06 kg/ha,7.64% higher than Jinsui 4.The two varieties had good comprehensive characters,so they could be popularized and planted in dry farming areas of Lanzhou City.

Spatial Rainfall Variability and an Increasing Threat of Drought, According to Climate Change in Uttaradit Province, Thailand

This study presents the work commenced in northern Thailand on spatial and temporal variability of rainfall. Thirty years (1988-2017) rainfall data of eight meteorological stations were used for assessing temporal variability and trend analysis. The results showed decreasing trend in rainfall from its first half of the observed study period (1988-2002) to last half of the time period (2003-2017) in total average annual as well as monsoonal average rainfall by 14.92% and 15.50% respectively. It was predicted from linear regression results that by 2030 the average annual and monsoonal rainfall will drop by 35% and 34.10% respectively. All stations showed negative trend except Fakara met-station in annual rainfall. In the seasonal trend analysis, the results showed decreasing trend almost in all met-stations. Mann-Kendall trend test was applied to assess the trend. All met-stations show significant negative trend. To assess drought in the study area, Standardized Precipitation Index (SPI) was applied to 12-month temporal time period. The results predicted meteorological drought in the near future. The spatial distribution of rainfall presented changing phenomena in average annual, monsoonal, winter, and summer seasons in both analyzed periods.

Upstream-Downstream Relationships in Terms of Annual Streamflow Discharges and Drought Events in Nebraska

Upstream-downstream relationships of annual streamflow discharges and severity and frequency of stream-flow drought events are critical in understanding how streamflow droughts propagate over time and space. Such information can be used to resolve water disputes, trigger mitigation strategies, and understand how streamflow changes due to changes in the environment. During drought years, such information is even more critical as water resources are contested. The objective of this research is to study the upstream-downstream relationships of streamflow in Nebraska along four major river systems with diverse hydrologic characteris-tics and human activities: North Platte, Big Blue, Republican, and Niobrara. The relationships among the upstream and downstream stations along the four rivers are investigated by comparing several statistics de-rived from the annual flow discharge and on drought events. Trend analysis and coefficient of variation are applied to annual flow discharge values, and a host of drought-related parameters (e.g., annual maximum drought duration, annual accumulated drought duration, number of drought events) are also computed with respect to five different levels of streamflow drought events: water shortage, mild drought, moderate drought, significant drought, and extreme drought. The paired-t test and ANOVA with MIXED procedure are subse-quently applied to the statistics to observe whether there is a significant difference between upstream and downstream stations along a river. The analysis allows us to characterize the upstream-downstream relation-ships of the four river systems, laying the groundwork for further investigations to identify the reasons for some of the trends and observations. These findings will be essential in water resources management during or prior to hydrological droughts.

新安江流域气象干旱和水文干旱特征及两者之间的关系研究

新安江流域是传统丰水区,对该区域进行干旱演变规律以及气象-水文干旱传播特征及其响应关系的研究,对于流域水资源的调度和管理具有重要科学意义。基于新安江流域近63 a的降水和径流数据,利用标准化降水指数(Standardized Precipitation Index,SPI)和标准化径流指数(Standardized Runoff Index,SRI),研究不同时间尺度的新安江气象干旱和水文干旱的演变规律,并分析流域水文干旱对气象干旱的时滞效应。结果表明:(1)1960—2022年新安江流域的气象干旱和水文干旱主要发生在20世纪60年代、70年代末到80年代中期以及21世纪初,2010年至今新安江整体处于水资源丰盈状态,其余时段则干旱与湿润交替发生。(2)近63 a的数据显示,新安江流域总体呈现变湿趋势,干旱事件有所减少。其中冬季和夏季变湿最为明显,且水文角度变湿趋势比气象角度更为明显。(3)新安江流域的水文干旱与气象干旱显著相关,通常在气象干旱发生后1~3个月出现。水文干旱对气象干旱在汛期的相关性和响应速度均高于非汛期。因此,应更加关注汛期的流域干旱并采取针对性措施。

基于CMIP6耦合WRF的黄河上游复合干旱热浪事件演变规律

复合干旱热浪事件较传统极端气候事件破坏性更强,近年来在全球范围内发展迅速,黄河上游作为气候敏感区受其影响尤其突出,刻画其特征并分析未来可能气候条件下的演变趋势对事件防控有重要意义。本文提出了一种基于第六次国际耦合模式比较计划CMIP6耦合天气预报研究模式WRF的未来气象数据动力降尺度方法。识别了黄河上游不同情景下的复合干旱热浪事件及其特征,揭示了复合事件与单一事件的区别,分析了复合干旱热浪事件的未来演变规律。结果表明:(1)历史期、SSP245和SSP585情景下复合干旱热浪事件较单一事件的温度升高3.8%、13.1%、13.5%,干旱指数降低5.8%、2.6%、2.6%,极端特征更加显著。(2)SSP245情景下复合干旱热浪事件特征呈西南高、东北低的空间分布形式,而在SSP585情景下以北部、东部区域分布最高。(3)未来各情景下区域整体复合干旱热浪事件特征呈显著上升趋势,其中SSP585的上升趋势高于SSP245。

标准—检测—认证体系支撑防汛抗旱产品行业高质量发展的思考

标准、检验检测和认证作为国家质量基础设施的重要组成,对产业升级、技术创新和质量提升有重要作用,已经在我国消防和环保等诸多行业发挥了重要作用。但是防汛抗旱产品领域尚未建立起成熟的标准—检测—认证体系。我国防汛抗旱产品具有种类多、类型杂、涉及行业广的特点,为规范防汛抗旱产品市场,促进防汛抗旱产品行业高质量发展,在简要分析国内外防汛抗旱领域标准—检测—认证制度基础上,针对我国防汛抗旱产品行业发展现状,提出了在防汛抗旱产品领域建设标准—检测—认证体系的相关建议。

基于SPEI指数分析1980-2019年漓江流域干旱特征

分析漓江流域1980-2019年的多时空尺度干旱特征变化,为漓江流域气象预警以及科学减灾等提供理论依据。基于漓江流域6个气象站点1980-2019年逐月降水与气温资料,计算不同时间尺度下的标准化降水蒸散指数,并结合Mann-Kendall检验法、Pettitt突变检验进一步研究干旱突变、干旱频率以及干旱的持续时间。结果表明:漓江流域干旱事件以轻旱和中旱为主,空间上灵川的干旱频率较高,时间上2015年是漓江流域干旱情况的一个突变点。不同时间尺度上,春秋两季逐渐干旱化,而夏季则相对湿润,冬季无明显变化趋势;月与年尺度的SPEI值变化较为平稳。剖析成因,春秋两季的降雨量逐年减少而均温逐年提升造成流域内趋于干旱化,但结合夏季气象资料,年尺度上的降雨与均温均是增长趋势,导致流域内总体上并无干旱趋势且以微弱的速率湿润化。

1960—2020年珠江流域跨季节尺度干旱时空变化

全球气候变化背景下,珠江流域干旱事件尤其是跨季节干旱事件频发,研究珠江流域不同时间尺度下的干旱时空特征对于流域水资源配置和农业结构调整至关重要。为了了解珠江流域跨季节干旱时间时空变化特征,研究基于1960—2020年珠江流域44个气象站逐日气象观测数据,计算不同时间尺度下的标准化降水蒸散指数(standardized precipitation evapotranspiration index,SPEI),结合线性倾向估计法、Mann-Kendall突变检验以及Morlet小波分析,分析了近60 a来珠江流域跨季节干旱时空变化特征。结果表明:1)1960—2020年间珠江流域跨季节干旱事件中,秋冬及秋冬春连旱化趋势显著,呈弱干旱化趋势,且干旱化频率有所上升,连旱强度以中旱和轻旱为主,连旱影响范围以局域性为主,其次为全域性,秋冬春季节连旱在1962年和1997年分布出现由干转湿和由湿转干的突变。2)珠江流域秋冬及秋冬春季节连旱普遍存在9~14 a变化周期,相关分析表明珠江流域干湿变化与同期厄尔尼诺现象显著相关。3)珠江流域秋冬及秋冬春季节连旱尺度下大致呈东西干而中间湿的空间分布格局,红水河至左江及郁江流域连旱化趋势减弱,但连旱化频率仍较高,东江流域秋冬季节连旱化频率高且呈弱连旱化趋势,湿润化速率自西南向东北递减,未来发生季节连旱风险高。研究结果可为珠江流域干旱监测与防灾减灾措施提供指导和建议。

变暖环境下华北地区农业气象灾害风险评估Ⅰ:基于综合指标体系法农业干旱风险评估及适应对策建议

随着全球气候变化,干旱发生频率及强度持续增加,农业干旱灾害风险评估是当前防灾减灾的重要方法之一。基于自然灾害风险形成机理,构建华北农业干旱风险评估指标体系模型,利用内部检验法对模型进行稳健性检验,根据华北34个市农业干旱风险形成特点聚类分类,并提出相应的风险防范建议。结果表明:调整风险评估模型中的指标和方法时,华北地区34个市农业干旱风险排名变化幅度多为1~2.5位,模型稳健性较好;除防灾减灾能力较高的北京、天津外,华北中部和北部农业干旱风险最高,与危险性和脆弱性指标较高有关,河南北部以及山东南部农业干旱风险较低,主要得益于该地区各市危险性较低;华北34个市可分为6个农业干旱风险集群,集群分布在空间上无分散、跨市分布,城市聚集性较好,其中北部山区集群4干旱风险最高,与其极高的环境脆弱性和低防灾减灾能力有关,应在农业种植结构上适当降低农业种植面积并加大农业投入;位于中部和南部的集群2、5和6具有较高的粮食种植面积且粮食因干旱减产率较高,可通过增加农业投入、提高灌溉保证率等进一步降低农业干旱风险。

抗旱保水剂在辽西玉米上的应用效果研究

辽西地区干旱少雨、土壤保水能力差、水分利用效率低,这些一直是制约当地玉米增产的关键因素。通过对比试验的方法,研究抗旱保水剂和肥料混合施用与常规施肥两种条件下,对玉米生育性状及产量的影响。试验结果表明,应用抗旱保水剂的玉米生育性状好于常规施肥,株高增加6~16.4 cm、茎粗增加0.28~1.3 cm、穗粒数增加42~54个、百粒质量增加1.05~1.7 g,增产87.8~121.55 kg/667 m^(2)、增产率为10.2%~17.29%。

沙生生境环境下河道生态修复施工技术

滹沱河没有进行过系统整治,未形成标准的防洪体系,很多堤段存在土质岸坡未护砌和堤身不稳定以及堤脚的冲刷隐患,保护区防洪能力不足10年一遇标准,现状河道萎缩严重,行洪能力逐步降低,弃渣和泥沙淤积侵占河道,河道的自然河川生态功能减弱,生物栖息地遭破坏,河道自净能力降低,同时,流域内天然植被稀少,水土流失严重,自然生态景观效果差。基于此背景,本文依托滹沱河生态修复三期工程(鹿泉区)主河槽治理工程施工,以理论研究为指导,通过河道生态修复与绿化施工相结合的施工工艺进行改良并应用于实际施工中,颇具工程借鉴意义。

南水北调中线工程水源区和受水区的降水时空变化特征及丰枯遭遇

[目的]基于1950—2022年时间序列ERA5再分析降水数据,探究南水北调中线工程水源区和受水区降水量时空变化特征,旨在保障跨流域调水的可行性和持续性,为南水北调中线工程水资源调度和运行管理提供科学参考。[方法]采用Mann-Kendall检验、小波分析、云模型以及Copula函数等方法,分析水源区和受水区降水变化趋势以及丰枯遭遇特征。[结果]①1950—2022年南水北调工程水源区和受水区分别按照年降水量34.75和39.35mm/(10a)幅度减少,水源区年降水量存在43a的主周期,受水区年降水量存在55a的主周期。②云模型隶属云图夏季降水量分布不均且离散程度较高,而冬季分布均匀且较集中。③调水不利的组合汛期和非汛期遭遇频率分别为23.15%和25.92%。[结论]水源区和受水区年降水量均呈现明显减少趋势,水源区丰枯交替变化显著;南北丰枯异步概率大于丰枯同步,同枯频率不高,有利于调水工程的安全性和可靠性。研究结果可为制定南水北调中线工程相关政策和技术指导提供理论依据,有助于工程的规划和管理,提高水资源利用效率和可持续性。

基于SPEI的中国干旱多尺度时空特征分析

干旱作为影响社会经济发展的自然灾害之一,探究中国干旱时空变化特征,对干旱预防和策略制定具有重要意义。以1979-2020年中国7个区域的标准降水蒸散指数(SPEI)网格数据作为基础,应用干旱频率和强度指标,结合改进的Mann-Kendall检验(MMK)方法和滑动时间窗口法,分析不同时间尺度(1个月、3个月、6个月、12个月)下的中国干旱时空特征。结果表明:在空间上,青藏高原、内蒙草原地区、西北荒漠地区、东北湿润半湿润温带地区的干旱程度更为突出;干旱频率随SPEI时间尺度增大而减小,随干旱等级(SPEI-3、SPEI-6以及SPEI-12尺度)的增加而减少;中国空间趋势变化为西北荒漠地区、青藏高原、内蒙草原地区、华中华南湿润亚热带地区北部、华北湿润半湿润暖温带地区南部、东北湿润半湿润温带地区具有显著干旱化趋势,青藏高原和东北湿润半湿润温带地区均具有明显的干湿差异。在时间上,西北荒漠地区的SPEI-1~SPEI-12尺度、青藏高原的SPEI-1~SPEI-12尺度、内蒙草原地区的SPEI-1~SPEI-12尺度、东北湿润半湿润温带地区的SPEI-6和SPEI-12尺度、华中华南湿润亚热带地区SPEI-1、SPEI-3和SPEI-12尺度的干旱较为突出。研究结果可为中国干旱预防和影响评估提供一定参考依据。

旱涝急转工况下土石坝上游粘土防渗体水力劈裂研究

近年来作为极端小概率事件的旱涝急转工况频繁出现,极易造成防渗体缺陷扩展,诱发工程失事。通过在模型试验与数值计算分析的基础上探讨了旱涝急转工况下土石坝粘土防渗体中的水力劈裂问题。结果表明,旱涝急转工况中的干旱过程促使土体基质渗透性降低,同时导致防渗体产生裂缝,具备了发生水力劈裂的必要条件。理论分析推导了沿裂缝所在平面产生水力劈裂破坏的渗透压力理论值,离心试验模型测得铺盖层孔压骤降的同时砂层孔压骤增,表明裂缝受高水压作用产生劈裂贯穿了防渗体,裂缝处测量孔隙水压力值与理论推导结果基本一致。旱涝急转过程中裂缝处土体内的压应力先是逐渐增大,随后不断减小最终转变为拉应力,从而导致水力劈裂。研究结果对旱涝急转工况下的土石坝安全运行具有指导作用。

基于SPEI的北疆1961—2020年气象干旱变化特征

基于北疆26个主要气象站点1961—2020年逐日气象数据,选取标准化降水蒸散指数(SPEI)为气象干旱指标,采用Mann-Kendall突变检验、小波分析等方法对北疆年及春、夏两季SPEI和不同等级气象干旱影响范围变化特征进行了探究。结果表明,北疆实际轻旱情况更适合以-1.0<SPEI≤0识别;与年尺度的湿润化趋势相反,北疆春、夏两季均呈不同程度的干旱化趋势,且夏季极端气象干旱(重旱、特旱)事件影响范围有显著扩大趋势;1961—2020年不同尺度SPEI有1~4年的主变化周期;北疆整体气候于20世纪80年代转变后在1993—2010年呈显著湿润化趋势,春、夏季气候分别于2014年及1997年出现了由湿转干的趋势信号;研究区夏季的干旱情况于1988年开始逐渐缓解,但在2008年再次突变后干旱情况又开始逐步加剧。

干旱地区植物根际促生菌鉴定及促生和耐旱特性研究

本试验以干旱区3种植物为材料,利用选择性培养基从植物根际分离筛选具有固氮、溶磷、分泌植物激素及耐旱的菌株,进行16S rRNA分子生物学鉴定,并通过纸上发芽试验验证菌株促生效果,以期为干旱地区专用微生物菌肥提供优良菌种资源。结果表明:从3种植物根际共分离出37株菌株,其中兼具溶磷、固氮促生特性的占35.1%,菌株固氮酶活性介于17.92~169.74 nmol C2H4/(h·mL),溶无机磷量为13.39~363.31μg/mL,溶有机磷量为58.69~99.37μg/mL。选择12株固氮、溶磷能力较好的菌株进行分泌植物激素及耐旱特性测定,发现12株菌株均能分泌吲哚乙酸且分泌量为2.86~27.60μg/mL;大部分菌株也均能分泌玉米素和脱落酸,分泌量分别为1.75~7.78μg/mL、1.98~4.61μg/mL。从中筛选出特性优良的菌株5株,经鉴定菌株YB6和HC7分别为枯草芽孢杆菌(Bacillus subtilis)和氧化微杆菌(Microbacterium oxydans),菌株HL7、HC9和HC3分别属于无色杆菌属(Achromobacter sp.)、苍白杆菌属(Ochrobactrum sp.)和叶杆菌属(Phyllobacterium sp.)。纸上发芽试验结果显示,5株植物根际促生菌既能促进种子的萌发,又能缓解干旱胁迫对种子生长的抑制作用,其中,菌株YB6和HC9对种子的萌发和生长效果较为突出,具有作为微生物肥料菌种资源在干旱区应用的潜力。

阜新市防汛抗旱工作存在的问题及对策研究

通过不断优化调整,阜新市基本形成了符合新时代防汛抗旱工作要求的新指挥体系,有效改善了技术支撑体系、应急抢险救援体系、监测预警体系、制度和责任体系等,经过2019年、2020年的实践检验,实现了防汛抗旱“少损失、少伤害、不死亡”的工作目标。基于此,全面探讨技术支撑、指挥决策、防汛措施、基层“防办”能力等方面存在的问题,并结合水旱灾害防御信息化特点提出下一步工作举措和对策。