The Relation between Atmospheric Intraseasonal Oscillation and Summer Severe Flood and Drought in the Changjiang-Huaihe River Basin

The intraseasonal oscillation (ISO) is studied during the severe flood and drought years of the Changjiang-Huaihe River Basin with the NCEP/NCAR reanalysis data and the precipitation data in China. The results show that the upper-level (200 hPa) ISO pattern for severe flood (drought) is characterized by an anticyclonic (cyclonic) circulation over the southern Tibetan Plateau and a cyclonic (anti-cyclonic) circulation over the northern Tibetan Plateau. The lower-level (850 hPa) ISO pattern is characterized by an anticyclonic (cyclonic) circulation over the area south of the Changjiang River, the South China Sea, and the Western Pacific, and a cyclonic (anticyclonic) circulation from the area north of the Changjiang River to Japan. These low-level ISO circulation patterns are the first modes of the ISO wind field according to the vector EOF expansion with stronger amplitude of the EOF1 time coefficient in severe flood years than in severe drought years. The analyses also reveal that at 500 hPa and 200 hPa, the atmospheric ISO activity over the Changjiang-Huaihe River basin, North China, and the middle-high latitudes north of China is stronger for severe flood than for severe drought. The ISO meridional wind over the middle-high latitude regions can propagate southwards and meet with the northward propagating ISO meridional wind from lower latitude regions over the Changjiang-Huaihe River Basin during severe flood years, but not during severe drought years.

A Multi-scale Perspective on Drought Monitoring and Assessment for the Pearl River Basin

It is accepted that climate change has a great impact on water cycle and regional water balance,and thus it would change the formation and evolution conditions of drought in some degree. By using data at 42 meteorological stations of the Pearl River Basin,the Standardized Precipitation Evapotranspiration Index（ SPEI） at different time scales was calculated. Based on the SPEIs of 1- 12 months,a newly proposed index for drought--Joint Drought Index（ JDI） was established under the multi-scale perspective through the copula function. Since short-term SPEIs are essential for the identification of emerging droughts and long-term SPEIs are useful for prolonged droughts,the JDI,which integrates all the usefull informations of drought and can thus form an overall judgement,is superior than the single SPEI in drought monitoring. By the forcast evaluation system and comparison to the actual drought,the accuracy and effectiveness of JDI in drought monitoring were verified. In general,JDI can be used as a new ideal index for future drought monitoring and assessment. Additionly,we analyzed the spatio-temperal characteristics of drought across the Pearl River Basin using the JDI. The results indicate that mild drought was the most frequent drought occurred in the Pearl River Basin over the past half century,and moderate drought followed. Severe drought and extreme drought would appear occasionally while exceptional drought could hardly be found. A dry-wet-dry interdecadal variation pattern had been found from the 1960 s to the 2000 s. Since the 21 stcentury,an obvious trend toward drought can be observed in the whole basin,especially in the Xijiang subbasin,which,consequently,poses an increasing challenge for the water resource planning and management.

数字孪生驱动的长江流域干旱防御平台设计与开发

在全球气候变化的背景下,长江流域发生了多次严重的高温干旱灾害,流域抗旱管理面临着旱情监测告警效率较低、旱灾预报预警精度不高、抗旱预案推演能力不足等瓶颈,迫切需要开展数字化转型。从长江流域抗旱减灾业务管理和“四预”应用需求出发,基于智慧水利和数字孪生建设的总体要求,综合运用WebGL、GIS等技术,建立了干旱防御数字孪生平台,研发了遥感干旱监测评估、干旱专业模型动态加载、旱警水位超限预警、抗旱预案可视化等关键技术,初步实现了“预报-预警-预演-预案”全链条贯通业务应用,切实提升了长江流域抗旱管理智能化、精细化水平,为流域干旱防灾减灾提供了技术支撑。

Drought monitoring and reliability evaluation of the latest TMPA precipitation data in the Weihe River Basin, Northwest China

The high resolution satellite precipitation products bear great potential for large-scale drought monitoring, especially for those regions with sparsely or even without gauge coverage. This study focuses on utilizing the latest Version-7 TRMM Multi-satellite Precipitation Analysis （TMPA 3B42V7） data for drought condition monitoring in the Weihe River Basin （0.135×10^6 km2）. The accuracy of the monthly TMPA 3B42V7 satellite precipitation data was firstly evaluated against the ground rain gauge observations. The statistical characteristics between a short period data series （1998-2013） and a long period data series （1961-2013） were then compared. The TMPA 3B42V7-based SPI （Standardized Precipitation Index） sequences were finally validated and analyzed at various temporal scales for assessing the drought conditions. The results indicate that the monthly TMPA 3B42V7 precipitation is in a high agreement with the rain gauge observations and can accurately capture the temporal and spatial characteristics of rainfall within the Weihe River Basin. The short period data can present the characteristics of long period record, and it is thus acceptable to use the short period data series to estimate the cumulative probability function in the SPI calculation. The TMPA 3B42V7-based SPI matches well with that based on the rain gauge observations at multiple time scales （i.e., 1-, 3-, 6-, 9-, and 12-month） and can give an acceptable temporal distribution of drought conditions. It suggests that the TMPA 3B42V7 precipitation data can be used for monitoring the occurrence of drought in the Weihe River Basin.

Evaluation of Drought Hazard Area of GharehAghaj Basin in Iran, Using GIS

In GharehAghaj basin drought has the most profound effect on the way of living and regional economy. Drought Hazard by nature is a result of interrelated parameters concerned. The objective of this paper presents a model to assess hazard of drought using the Geographical Information System (GIS). The data analyzed have been gathered from the records, reports and maps published by the governmental offices of Iran. Various drought hazard indicators have different severity classification in different models. The drought hazard indicator maps take into account the meteorological, hydrological, physical and socioeconomic characteristics that related to drought hazard. Each of the hazard indicator maps and also final hazard map are classified into 4 hazard classes of drought: mild, moderate, severe and very severe. The final hazard classes were defined on the basis of hazard scores arrived at by assigning the appropriate attributes to the indicators and the final hazard map was prepared by overlaying different hazard indicator maps in the GIS, deploying the new model. The final Hazard Map shows that moderate hazard areas (89.87% of the basin) are much widespread than areas under severe hazard (10.13% of the basin) which are observed in the Southeast of the region.

近53 a辽河流域旱涝灾害的时空特征

针对气候变化背景下辽河流域旱涝事件的频繁发生,以国家气象中心提供的地面降水日值数据集V3.0为基础数据,采用Z指数法表征旱涝事件,并应用集合经验模态分解法(EEMD)分析了辽河流域1968—2020年逐年、逐生长季的旱涝事件分布特征及其周期性规律,结果表明:(1)辽河流域近53 a中发生旱涝事件的灾害年份约占总时间序列的2/3以上,集中发生于上世纪80、90年代中后期及本世纪00年代.(2)近53 a中,重度干旱或洪涝事件均以流域东南部的河流下游及入海口区域最为严重,流域东南部的旱涝程度反差最为强烈.(3)对于辽河流域范围的旱涝事件来说,周期特征以短时高频振荡为主,年代际尺度的波动对于周期规律的贡献率相对较低.

海河“23·7”流域性特大洪水防御启示与对策——以永定河为例

在极端天气常态化的背景下,流域应具有承受、化解和抵御洪涝和干旱灾害的韧性。分析了海河“23·7”流域性特大洪水的特点,在此基础上,阐述了此次洪水过程中永定河流域综合治理各项措施发挥的作用、存在的问题,按照建设韧性流域的要求,对提升永定河流域防洪能力提出建议。

Detection of Spatial, Temporal and Trend of Meteorological Drought Using Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) in the Upper Tana River Basin, Kenya

Drought events across the world are increasingly becoming a critical problem owing to its negative effects on water resources. There is need to understand on-site drought characteristics for the purpose of planning mitigation measures. In this paper, meteorological drought episodes on spatial, temporal and trend domains were detected using Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) in the upper Tana River basin. 41 years (1980-2016) monthly precipitation data from eight meteorological stations were used in the study. The SPI and EDI were used for reconstruction of the drought events and used to characterize the spatial, temporal and trend distribution of drought occurrence. Drought frequency was estimated as the ratio of a defined severity to its total number of events. The change in drought events was detected using a non-parametric man-Kendall trend test. The main drought conditions detected by SPI and EDI are severe drought, moderate drought, near normal, moderate wet, very wet and extremely wet conditions. From the results the average drought frequency between 1970 and 2010 for the south-eastern and north-western areas ranged from 12.16 to 14.93 and 3.82 to 6.63 percent respectively. The Mann-Kendall trend test show that drought trend increased in the south-eastern parts of the basin at 90% and 95% significant levels. However, there was no significant trend that was detected in the North-western areas. This is an indication that the south-eastern parts are more drought-prone areas compared to the North-western areas of the upper Tana River basin. Both the SPI and the EDI were effective in detecting the on-set of drought, description of the temporal variability, severity and spatial extent across the basin. It is recommended that the findings be adopted for decision making for drought-early warning systems in the river basin.

基于蒸散发干旱指数的子牙河流域干旱时空变化特征分析

为探究子牙河流域干旱时空分布特征,基于2001—2021年逐月降水和遥感蒸散栅格数据,采用标准化降水蒸散指数(SPEI)和标准化蒸散发亏缺指数(SEDI)表征流域干旱情况,运用Sen斜率估计和Mann-Kendall检验法分析了流域2001—2021年季尺度干旱时空分布及变化趋势,统计了干旱面积、干旱次数、干旱历时和干旱烈度等特征变量。结果表明:SPEI对子牙河流域旱情发生时间、程度和范围识别的准确率更高,2001—2021年流域SPEI呈上升趋势,表现出湿润化态势,冬季SPEI呈下降趋势,表现为干旱化态势,忻州、阳泉市等地存在显著干旱化的区域;流域各季节干旱面积占比呈现波动变化,部分年份出现大范围季节性干旱,夏旱和秋旱干旱面积占比最高,超过90%;忻州和阳泉市部分区域、石家庄市西部区域和衡水市北部区域呈现干旱次数少、历时长、烈度大的特点,邯郸和邢台市部分区域、衡水市南部区域、石家庄市东部区域表现为干旱次数多、历时短、烈度小的特征。

Regional Drought Severity Assessment at a Basin Scale in the Limpopo Drainage System

A spatial analysis of drought characteristics in the Limpopo basin is undertaken to evaluate its regional implications to water management challenges. In this study, drought duration, frequency and severity are investigated. In addition drought Severity-Area-Frequency (SAF) curves were constructed. The entire Limpopo River Basin is subdivided into four homogeneous regions based on topographic and climate variations in the basin, which was constructed with the K-Means Clustering algorithm. Using the medium range time series of the Standardized Precipitation Index (SPI) as an indicator of drought for each homogeneous region, monthly and annual SAF curves and maps of probability of drought occurrence were produced. The results indicated localized severe droughts in higher frequencies compared to moderate to severe low frequency droughts spread over wider areas in the basin. The approach can be used to develop improved drought indicators to assess the relationship between drought hazard and vulnerability and to enhance the performance of methods currently used for drought forecasting. In general, this preliminary investigation reveals that the western part of the basin will face a higher risk of drought when compared to other regions of the Limpopo Basin in terms of the medium-term drought patterns. The Limpopo Basin is water stressed and livelihood challenges remain high, thus impacts of droughts and related resilience options should be taken into account in the formulation of regional sustainable water resources development strategies.

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。

近50年滇池流域汛期降水时空演变特征分析

以滇池流域1970—2020年汛期(5—10月)降水量资料为依据,利用地理信息技术,采用Mann-Kendall检验法、小波分析等方法,分析近50年来滇池流域汛期降水年际变化的趋势性、周期性以及集中度、集中期、降水中心和旱涝发生频率等演变特征。结果表明:(1)近50年来,滇池流域汛期降水总体呈减少趋势,中部地区降水呈增加趋势,盘龙江上游的松华坝水库以上区域及南部地区降水呈减少趋势;(2)汛期降水年际变化存在31 a的主周期,中部主城区降水集中度高于南部地区;(3)汛期降水的中心整体呈现向东部、南部方向偏移的态势,且移动趋势显著;(4)滇池流域旱涝频发,尤其盘龙江中段昆明主城区为旱涝多发区。该成果对滇池流域水旱灾害防御及水资源管理具有参考意义。

长江流域干旱评估指标、时空特征及成因研究进展

在梳理长江流域干旱相关研究成果的基础上,从气象干旱、水文干旱、农业干旱3个角度评述了当前长江流域干旱评估指标的研究现状,阐述了长江流域干旱的时空特征及成因。指出当前研究在区域干旱的精准识别和多因素交互作用方面仍面临严峻挑战,未来长江流域干旱的主要研究方向包括提高多源数据综合利用水平,增强干旱监测的时效性与准确性;完善干旱监测及预报体系,提高干旱预测的科学性与可靠性;深化人类活动对干旱的响应研究,揭示人类活动与自然因素在干旱事件中的相互作用机制。

洞庭湖水文对流域干旱情势的响应及归因分析

【目的】极端气候变化加剧了通江湖泊水文情势的波动性,亟需从流域视角探究流域干旱情势对通江湖泊水文环境的影响。【方法】以我国典型通江湖泊洞庭湖及洞庭湖流域为研究对象,选取2010—2020年及2022年极端干旱情景下洞庭湖流域5个代表性气象水文站的降水量、温度、水位等数据,结合水文趋势分析、标准化降水指数(SPI)和回归分析等方法,对洞庭湖流域和湖泊的气象水文演变特征、干旱情势以及湖泊水位与流域干旱情势的响应关系进行了全面分析。【结果】结果表明,研究期间洞庭湖流域降水量呈小幅上升趋势,流域温度变化趋势不显著,但澧水流域温度总体较低,变化范围16.07~17.41℃。洞庭湖水位总体呈波动上升趋势,变化在23.63~25.81 m。洞庭湖流域SPI指数变化在-0.86~0.31,正常和轻旱年份占比分别为91%和9%。流域年内干旱情势总体呈先升后降变化趋势,正常和湿润等级频率分别变化在0.18%~0.64%和0.18%~0.36%。洞庭湖水位与流域降水和径流量呈显著正相关,与温度呈显著负相关。2022年洞庭湖水位呈先升后降变化趋势,6月达到年内水位最高值(30.45 m)后骤降。2022年1—6月洞庭湖流域干旱情势总体处于湿润和正常等级,后降至中旱和重旱等级。【结论】洞庭湖流域年际干旱情况多为正常年份,其余为轻旱年份。与多年月均水位相比,2022年极端干旱情景下洞庭湖水位峰值由往年7月提前至6月,随后水位骤降。此外,4月、5月、7月洞庭湖水位与流域SPI指数显著相关,反映了当前月份湖泊水位对流域干旱情势的深度响应,刻画了流域降水异常引起的洞庭湖“夏旱”特征。以上结果可为水文及农业部门应对气象灾害、实施农业生产保护措施等提供科学参考。

鄱阳湖流域气象干旱的区域性特征及干旱过程演变

基于1960—2020年鄱阳湖流域及周边29个国家气象站的连续观测资料,通过计算标准化降水蒸发指数(SPEI)并结合游程理论,研究分析了气象干旱的区域性特征及干旱过程演变。结果表明:①鄱阳湖流域月尺度气象干旱的发生频率为31.7%~34.8%,不同等级干旱发生频率的空间格局差异明显;②春、秋季节流域尺度SPEI呈现微弱下降趋势,干旱影响范围呈不显著的增加趋势,夏、冬季节情况与此相反;③就干旱区域性特征而言,鄱阳湖流域季节性气象干旱以全流域性干旱和局域性干旱为主(发生频率分别为29.5%和23.4%),区域性干旱和部分区域性干旱的发生频率(分别为10.7%和5.7%)相对较低;④游程理论揭示在过去的61 a间共发生50次流域尺度气象干旱事件,干旱事件的发生频次随干旱历时的增加显著减少,其中干旱历时最长的可达49个月;⑤流域尺度气象干旱事件的历时、峰值烈度以及总烈度的演变呈现较强的年代际波动特征;⑥干旱历时与总烈度之间存在显著的线性关系,与峰值烈度之间存在显著的幂函数关系,与平均烈度之间的相关关系不明显。这些研究结果明晰了鄱阳湖流域气象干旱的区域性特征与干旱过程演变,为合理开展流域气象干旱影响评估和制定防范策略提供科学依据。

黄河流域植被总初级生产力对持续性干旱水分亏缺的响应

利用植被总初级生产力和高精度分层土壤含水量数据分析了2001—2020年黄河流域生长季总初级生产力时空分布和变化特征,量化了流域不同深度土壤湿度之间的相关关系,探究了不同植被类型在生长季的总初级生产力对土壤连续水分亏缺事件的响应关系。结果表明:黄河流域总初级生产力空间上呈东高西低、南高北低的分布特征,生长季耕地累积总初级生产力最大、林地次之、草地最小,研究期内流域总初级生产力整体呈上升趋势,耕地相对增速最大、草地次之、林地最小;流域土壤湿度在空间和时间上均有显著差异,表层土壤含水量波动对深层土壤含水量的影响随深度增加而减小,林地和耕地表层与深层土壤含水量的相关性远高于草地;流域草地和耕地总初级生产力对土壤水分的深度敏感区间为0~40 cm,林地的深度敏感区间为0~100 cm,在深度敏感区间内,随着土壤连续水分亏缺天数的增加,草地和耕地总初级生产力依次经历短暂平稳、加速下降、降速趋缓的变化过程,而林地总初级生产力则表现出短暂下挫、长时间平稳、加速下降的变化特征。

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。

2022年长江流域农业干旱发展过程及气象成因

2022年长江流域发生了大面积的干旱,此次干旱涉及范围广,持续时间长,对于农业、生态等方面都造成了较大影响。降水量相比同期减少,气温增加,导致土壤含水量降低,农业干旱同步发生。复演长江流域此次农业干旱的发展过程,探寻其气象成因,对于完善干旱发生机理的认识,实现干旱的有效应对具有重要意义。研究基于ERA5数据,对比2022年土壤含水量与多年同期均值,从时空维度揭示了2022年农业干旱的主要土壤含水量特征;采用标准化土壤湿度指数值,通过与往期干旱事件对比,阐明此次农业干旱的严重性;最后,从大气环流角度与外强迫场海温角度,分析了此次干旱的气象成因。分析表明,2022年,6-9月全流域的农业干旱程度分别为:无旱、极旱、极旱、极旱。流域遭受长达3个月的农业极端干旱,其中依据数值判断,8月干旱程度最深。就干旱气象成因而言,西太副高2022年6-9月较往年同期影响面积增大、强度增强,且西太副高位置异常偏西,近乎包括流域整个范围,导致流域整体处于单纯西太副高控制之下;同时,长江流域夏季降水与前一年秋冬季大西洋北部、太平洋北部的海温,以及同年春夏季太平洋东部、大西洋及印度洋海温关系较为密切,高相关性时段内的海温与往期均值存在差异性,引起相关干旱。

基于SPEI的洮河流域气象干旱时空特征分析

基于洮河流域1976—2020年逐月的气温和降水量资料,计算了季尺度和年尺度的标准化降水蒸散指数(SPEI),采用时间序列平稳性检验法和干旱频率法定量分析了季尺度和年尺度不同等级气象干旱频率的变化规律及空间分布特征,采用云模型分析了年尺度气象干旱时空分布的随机性与稳定性。结果表明:在季尺度上,四季的干旱频率都在30%左右,干旱主要发生在春冬两季;在年尺度上,流域以轻旱、中旱为主,轻旱、中旱发生频率高,重旱、特旱发生频率偏低,总体偏干旱;在空间分布上,干旱主要发生在流域的中下游区域;1976—2020年流域干旱化程度有所减弱,干旱化趋势稳定,干旱化程度波动较小。

东江流域控制性水工程联合调度策略与机制探讨

近年,东江流域旱涝事件并存,防洪与供水安全形势严峻,三大水库和干流梯级电站是东江流域水旱灾害防御中的重要水利工程。收集流域水工程多年运行经验、案例、数据,综述东江流域控制性水工程联合调度在管理体制、防洪调度、水量调度等方面的研究、实践现状,通过数学模型、统计等方法,对现状调度体制与机制中存在的问题进行分析。从管理、技术、研究等角度提出建议与对策。