THE RELATIONSHIP BETWEEN THE ATMOSPHERIC HEATING SOURCE/SINK ANOMALIES OF ASIAN MONSOON AND FLOOD/DROUGHT IN THE YANGTZE RIVER BASIN IN THE MEIYU PERIOD

NCEP/NCAR reanalysis data and a 30-year precipitation dataset of observed daily rainfall from 109 gauge stations are utilized in this paper.Using the REOF we analyzed the spatial distribution of precipitation in the 109 stations in the Yangtze River Basin in Meiyu periods from 1978 to 2007.The result showed that the spatial distribution of precipitation in the Yangtze River Basin can be divided into the south and north part.As a result,relationships between an atmospheric heating source(hereafter called <Q_1>) over the Asian region and the precipitation on the south and north side of Yangtze River in Meiyu periods were separately studied in this paper.The results are shown as follows.The flood/drought to the north of Yangtze River(NYR) was mainly related to the <Q_1> over the East Asia summer monsoon region:when the <Q_1> over the Philippines through Western Pacific and the south China was weakened(strengthened),it would probably result in the flood(drought) in NYR;and the precipitation on the south side of Yangtze River(SYR)was related to the <Q_1> over the east Asia and Indian summer monsoon region:when the <Q_1> over the areas from south China to the northern East China Sea and Yellow Sea and south-eastern Japan was strengthened(weakened),and the <Q_1> over the areas from the Bay of Bengal to south-eastern Tibetan Plateau was weakened(strengthened),it will lead to flood(drought) in SYR.

Water vapor transport over China and its relationship with drought and flood in Yangtze River Basin

The characteristics of water vapor transport(WVT) over China and its relationship with precipitation anomalies in the Yangtze River Basin(YRB) are analyzed by using the upper-air station data in China and ECMWF reanalysis data in summer from 1981 to 2002.The results indicate that the first mode of the vertically integrated WVT is significant whose spatial distribution presents water vapor convergence or divergence in the YRB.When the Western Pacific Subtropical High(WPSH) is strong and shifts southward and westward, the Indian Monsoon Low Pressure(IMLP) is weak, and the northern part of China stands behind the middle and high latitude trough, a large amount of water vapor from the Bay of Bengal(BOB), the South China Sea(SCS) and the western Pacific forms a strong and steady southwest WVT band and meets the strong cold water vapor from northern China in the YRB, thus it is likely to cause flood in the YRB.When WPSH is weak and shifts northward and eastward, IMLP is strong, and there is nearly straight west wind over the middle and high latitude, it is unfavorable for oceanic vapor extending to China and no steady and strong southwest WVT exists in the region south of the YRB.Meanwhile, the cold air from northern China is weak and can hardly be transported to the YRB.This brings on no obvious water vapor convergence, and then less precipitation in the YRB.

Comparative research on integrated development of large river basins:a case study of the Yangtze and the Rhone

Since 2001, the French and Chinese researchers have done a cooperative research on the comparison of integrated development of large fiver basins. The Yangtze River was chosen as a crux of this research and linked with other older river experiments like the Rhone, the Nile and the Mississippi. This research includes not only the environmental issues but also economic and social issues. One special issue journal has been published in French for our research results. Other two collective and comparative books in French and Chinese will be finished at the end of this year. In the future, the comparison should be widened to Italy （the Po）, Egypt （the Nile development planning） and the United States （the Mississippi Basin） and we would like to enlarge our research group and want to link up different teams and research projects, in order to get a global understanding of large fiver regions phenomenon.

Analysis of Causes and Seasonal Prediction of the Severe Floods in Yangtze／Huaihe Basins during Summer 1991

The present paper shows that a seasonal prediction for the large scale flooding and waterlogging of the mid-lower Yangtze/ Huaihe River basins in the summer of 1991 made successfully in early April 1991.The seasonal forecasting method and some predictors are also introduced and analyzed herein. Because the extra extent of the abnormally early onset of the plum rain period in 1991 was unexpected,great efforts have been made to find out the causes of this abnormality. These causes are mainly associated with the large scale warming of SST surrounding the south and east part of Asia during the preceding winter,while the ENSO-like pattern of SSTA occurred in the North Pacific.In addition,the possible influence of strong solar proton events is analyzed.In order to improve the seasonal pre4iction the usage of the predicted SOl in following spring/summer is also introduced.The author believes thatthe regional climate anomaly can be correctly predicted for one season ahead only on the basis of physical understanding of the interactions of many preceding factors.

Magnitude,Scale,and Dynamics of the 2020 Mei-yu Rains and Floods over China

Large parts of East and South Asia were affected by heavy precipitation and flooding during early summer 2020.This study provides both a statistical and dynamical characterization of rains and floods affecting the Yangtze River Basin(YRB).By aggregating daily and monthly precipitation over river basins across Asia,it is shown that the YRB is one of the areas that was particularly affected.June and July 2020 rainfall was higher than in the previous 20 years,and the YRB experienced anomalously high rainfall across most of its sub-basins.YRB discharge also attained levels not seen since 1998/1999.An automated method detecting the daily position of the East Asian Summer Monsoon Front(EASMF)is applied to show that the anomalously high YRB precipitation was associated with a halted northward progression of the EASMF and prolonged mei-yu conditions over the YRB lasting more than one month.Two 5-day heavy-precipitation episodes(12−16 June and 4−8 July 2020)are selected from this period for dynamical characterization,including Lagrangian trajectory analysis.Particular attention is devoted to the dynamics of the airstreams converging at the EASMF.Both episodes display heavy precipitation and convergence of monsoonal and subtropical air masses.However,clear differences are identified in the upper-level flow pattern,substantially affecting the balance of airmass advection towards the EASMF.This study contextualizes heavy precipitation in Asia in summer 2020 and showcases several analysis tools developed by the authors for the study of such events.

A comparative study of the atmospheric circulations associated with rainy-season floods between the Yangtze and Huaihe River Basins

Here we present the results from the composite analyses of the atmospheric circulations and physical quantity fields associated with rainy-season for the selected floods cases over the Yangtze and Huaihe River basins for the 21 years(1990–2010),using the daily rain gauge measurements taken in the 756 stations throughout China and the NCEP/reanalysis data for the rainyseasons(June–July)from 1990 to 2010.The major differences in the atmospheric circulations and physical quantity fields between the Yangtze and Huaihe River basins are as follows:for flooding years of the Yangtze River Basin,the South Asia high center is located further east than normal,the blocking high over the Urals and the Sea of Okhotsk maintains,and the Meiyu front is situated near 30°N whereas for flooding years of the Huaihe River Basin,the South Asia high center is further west than normal,the atmospheric circulations over the mid and high latitudes in the Northern Hemisphere are of meridional distribution,and the Meiyu front is situated near 33°N.In addition,there are distinct differences in water vapor sources and associated transports between the Yangtze and Huaihe River basins.The water vapor is transported by southwesterly flows from the Bay of Bengal and monsoon flows over the South China Sea for flooding years of the Yangtze River Basin whereas by southeast monsoons from the eastern and southern seas off China and monsoon flows over the South China Sea for flooding years of the Huaihe River Basin.

Large-scale atmospheric singularities and summer long-cycle droughts-floods abrupt alternation in the middle and lower reaches of the Yangtze River

The daily precipitation data at 720 sta- tions over China for the 1957―2003 period during summer (May―August) are used to investigate the summer subseasonal long-cycle droughts-floods abrupt alternation (LDFA) phenomenon and a long-cycle droughts-floods abrupt alternation index (LDFAI) in the middle and lower reaches of the Yangtze River (MLYRV) is defined to quantify this phenomenon. The large-scale atmospheric circula- tion features in the anomalous LDFA years are ex- amined statistically. Results demonstrate that the summer droughts-to-floods (DTF) in the MLYRV usually accompany with the more southward western Pacific subtropical high (WPSH), negative vorticity, strong divergence, descending movements develop- ing and the weak moisture transport in the low level, the more southward position of the South Asia high (SAH) and the westerly jets in the high level during May―June, but during July―August it is in the other way, northward shift of the WPSH, positive vorticity, strong convergence, ascending movements and strong moisture transport in the low level, and the northward shift of the SAH and the westerly jets in the high level. While for the summer floods-to-droughts (FTD) in the MLYRV it often goes with the active coldair mass from the high latitude, positive vorticity, strong convergence, ascending movement develop- ing and the strong moisture transport in the low level, and the SAH over the Tibetan Plateau in the high level, but during July―August it is often connected with the negative vorticity, strong divergence, de- scending movements developing and the weak moisture transport in the low level, the remarkable northward shift of the WPSH, the SAH extending northeastward to North China and the easterly jets prevailing in the high level over the MLYRV. In addi- tion, the summer LDFA in the MLYRV is of significant relationship with the Southern Hemisphere annual mode and the Northern Hemisphere annual mode in the preceding February, which offers some predictive signals for the summer LDFA forecasting in the MLYRV.

The Diagnostic Study on the Drought and Flood Over the Yangtze River Basin With Weather Satellite Observations

The drought and flood over the Yangtze River basin are closely related to the anomaly of the general circulation. The impacts of the disasters resulting from it on the China national economy are of great importance. Attention is paid to them by meteorologists and forecasters in China. Most of the previous studies on it used the conventional data. Because the weather satellite observation has the advantages of continuity, homogeneous spatial and temporal resolution and global coverage, it greatly makes up the defect of the conventional measurements. The outgoing longwave radiation (OLR) observed from

An Integrated Flood Disaster Prevention System for the Sustainable Development of the Yangtze River Basin

Flood disasters have been a serious restraint to the sustainable development of the Yangtze River Basin (YRB). After analyzing the major causes to the flood disasters of YRB, the paper proposes an integrated flood disaster prevention system for the sustainable development of the YRB. The starting point of the system is to rationally coordinate the relationship of population, environment and economy.

海河“23·7”流域性特大洪水蓄滞洪区泥沙淤积分析

为探究海河“23·7”流域性特大洪水过程中蓄滞洪区泥沙淤积特征,评估受灾情况,基于实地淤积调查和高分遥感影像,计算淤积厚度空间分布,并结合DEM数据估算蓄滞洪量和蓄滞洪区利用率。结果表明:淤积厚度插值的均方根误差E_(RMS)为1.32,纳什系数E_(NS)为0.78,蓄滞洪量计算的E_(RMS)为0.75,E_(NS)为0.92,证明研究计算方法可行,计算结果可靠;8个蓄滞洪区共蓄洪24.63亿m^(3),蓄滞洪区利用率约为36.90%,平均淤积厚度为2.60 cm,总淤积量达7.67×10^(7) t;海河流域洪水含沙量约31.14 kg/m^(3),其中大清河系和永定河系的洪水含沙量达到过去20 a平均含沙量的20~40倍;此外,研究发现海河流域西部和北部山地的淤积情况更严重,较早启用的、位于上游的蓄滞洪区淤积量更大。

干旱区与湿润区旱涝急转演变特征对比研究

以长江、黄河和淮河流域为研究对象,基于标准化旱涝急转指数,利用趋势分析、变点检验、小波分析、随机森林等方法探究典型干旱区与湿润区旱涝急转演变特征及其驱动因子。结果表明:湿润和半湿润区是极端旱涝急转事件的高频发生区,干旱区是极端旱转涝事件的高频发生区;干旱区的突变发生在1998年,湿润区的突变在1978年,未来干旱区更易发生旱转涝事件,湿润区则相反;气象因子在湿润区对旱涝急转的贡献度更大,大气环流对干旱区的影响突出,旱涝急转与不同驱动因子间存在非线性关系。

洞庭湖四水流域水库群联合防洪优化调度

针对多防洪控制点的混联水库群联合防洪调度中防洪目标难以协调的问题,构建了以多流域协调条件下合成洪水洪峰流量最小为目标的水库群联合防洪调度模型,并采用逐步优化-逐次渐进算法(POA-SA)优化求解。在洞庭湖四水流域开展实例研究,基于防洪需求及各水库的特性,以四水流域下游尾闾控制站洪峰流量最小和四水汇流至洞庭湖的合成洪水洪峰流量最小为目标,提出典型年四水流域水库群联合防洪优化调度方案。结果表明:①针对1998年和2017年两场洪水,水库群联合优化调度后的四水合成汇入洞庭湖的洪峰削峰率比四水单独优化调度分别提高了9.4%和4.5%;②资水的柘溪水库和沅江的五强溪水库通过补偿调节,较好地实现了入湖洪水的错峰。对洞庭湖四水流域水库群联合调度可以保障四水流域自身防洪安全,并为洞庭湖防洪减压,研究成果可为流域水库群联合防洪调度提供参考。

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。

长江流域旱涝急转演变特征及其社会经济暴露度

旱涝急转是指干旱和洪水之间的快速转变,对农业生产和人类安全造成巨大威胁。本研究基于月尺度的旱涝急转量级指数,分析了长江流域历史和未来四种旱涝急转事件,并通过滑窗法构建了旱涝急转量级的时变函数,揭示了未来旱涝急转风险变化。同时,结合共享社会经济路径量化了人口和经济受旱涝急转风险变化影响的程度。结果显示,历史时期长江流域中下游旱涝急转事件频发,旱–涝和涝–旱事件每10年发生10~12次,而旱–涝–旱和涝–旱–涝事件每10年发生3~4次。未来旱–涝–旱和涝–旱–涝事件预计大幅增加,其中长江上游部分地区增长了约7倍。对于历史基准期50年一遇的旱涝急转事件,未来发生概率将增加5~10倍,给长江流域的人口和经济带来重大影响。

中国旱涝急转事件时空变化特征

【目的】旱涝急转事件造成的社会经济和生态环境影响严重,是我国发生频繁且广泛的一种复合型事件。明确我国旱涝急转事件发生的时空变化特征,可为地区制定防灾减灾措施提供科学依据。【方法】基于1961—2021年气象观测数据,使用Penman-Monteith模型计算潜在蒸散发,然后计算逐日的标准化降水蒸散指数(daily-SPEI),分流域对中国旱涝急转事件的频次、影响范围和趋势的变化特征进行分析。【结果】结果显示:(1)时间趋势上,1961—2021年中国受旱涝急转事件影响的范围以0.6%/10a的趋势增加,且平均每年有19.8%的范围发生旱涝急转事件。(2)空间分布上,旱涝急转事件主要分布在淮河流域、黄河流域、长江流域和松花江流域,事件发生频次在30次以上地区分别占流域总面积的63.1%、20.7%、15.0%、14.6%,事件频次最高达到53次。(3)中国旱涝急转事件存在明显的季节差异,主要发生在夏季事件发生频次在5次以上的空间范围占中国总面积的一半以上;其次是春季和秋季,事件发生频次在5次以上的空间范围占比均不足15%;冬季发生最少,事件发生频次在5次以下。【结论】结果表明:中国旱涝急转事件的影响范围整体呈增加趋势,中国中东部和东北部是旱涝急转事件发生频繁地区。研究结果可为旱涝急转事件的监测与应对提供科学基础。

长江流域防洪规划修编关键问题探讨

长江是中华民族的母亲河,是中华民族发展的重要支撑。进入21世纪以来,随着流域经济社会高速发展,流域蓄泄关系和防洪形势发生了新变化,加之全球气候变化背景下极端天气频发,给流域防洪带来了新挑战,治水思路和防灾减灾救灾理念发生深刻变化,迫切需要优化调整防洪目标和总体布局,科学制定防洪规划方案,擘画安澜长江新蓝图。针对新变化、新挑战和新要求,研究提出了新阶段长江防洪新方略、新目标和新举措,并重点探讨了城陵矶(莲花塘)站防洪控制水位调整、蓄滞洪区布局优化以及洲滩民垸防洪治理等重难点问题,为长江流域防洪规划修编提供支撑。

长江流域爬行动物物种多样性大尺度格局研究

本文研究了长江流域爬行动物物种多样性的大尺度格局。长江流域内共记录了爬行动物166种,隶属于3目18科68属,特有种和濒危物种分别有24种和54种。根据陆生爬行动物分布特点,依据山系和水系将长江流域分为19个区域,虽然物种数和G-F指数在各区域内变化不大(江源区较低),但特有种比例从上游到下游随海拔降低逐渐降低;利用Jaccard物种相似性系数对长江流域内19个区域进行聚类分析,可以将整个流域分成五部分:江源区,横断山区和云南高原区,四川盆地和秦巴山区,贵州高原、江南丘陵、两湖平原和长江三角洲,鄱阳湖平原、长江下游平原和淮阳山地(汉江—大别山),基本反映了流域内自然地理环境及我国大陆地势三级台阶变化的特点。

长江流域鱼类物种多样性大尺度格局研究

作者以长江流域鱼类编目数据库为基础数据,研究了长江流域鱼类物种多样性的大尺度格局。长江流域内共记录了鱼类378种(亚种),隶属于14目32科144属。其中淡水鱼338种(亚种),以鲤形目为主,达到269种(亚种),洄游鱼类11种,河口鱼类29种;流域内特有种和受威胁物种分别有162种(亚种)和69种(亚种)。根据鱼类分布特点,按水系将长江流域分为19个区域,除了江源区和金沙江中上游外,物种数和G-F多样性指数上游高于中下游,但各区域内差异不大,然而特有种比例从上游到下游随海拔降低而逐渐降低。利用Jaccard物种相似性系数对19个区域进行聚类分析,将整个流域分成三部分:(1)江源区和金沙江中上游,地理上属于青藏高原东南部波状平原部分和横断山区,(2)上游其他流域,地理上属于川西高原、云贵高原、四川盆地及秦巴山区,(3)中下游流域,地理上属于淮阳山地、江南丘陵和长江中下游平原,基本反映了流域内自然地理环境及我国大陆地势三级台阶变化的特点。

1999年夏季长江及以南地区洪涝的大尺度环流成因初探

通过对比分析 ,探讨了 1 999年夏季长江及以南地区洪涝灾害的环流成因。指出 1 999年处在LaNi na年 ,西太平洋副热带高压偏弱、偏北且异常偏东 ;南海夏季风前期偏强 ,后期偏弱 ;热带对流层上部南亚高压脊和洋中槽位置偏南 ;对流层下部长江下游至江南受气旋性异常环流影响 ,形成异常加强的水汽输送圈 ;夏季亚洲中纬度地区大陆高压维持 。

防洪工程信任对公众水灾风险认知的影响初探--基于长江流域部分地区问卷调查的分析

研究影响公众自然灾害风险认知的因素,有助于寻找风险因子,为加强风险沟通与理解、制定风险管理策略提供基础依据。防洪工程作为人类抵御水灾的重要手段,具备使公众对其产生信任动机的条件,成为影响公众水灾风险认知的重要因素之一。选择位于长江流域上游的重庆、中游的九江和岳阳、下游的上海和吴江等地区进行问卷调查,通过统计分析共885份有效问卷的数据,研究了公众对于防洪工程的信任程度,及其对水灾风险认知的影响。结果显示,防洪工程明显的御灾效果改变了大多数(3/4强)民众对水灾灾害属性的认识,由此建立了工程信任;信任使得多数(80%)公众对水灾风险的评估值很小,尤其是对个人受灾的风险估计出现乐观偏差;进而产生了消极与积极并存的防灾意愿倾向,并导致实际的防灾备灾行为不足。研究还发现,工程信任、风险评估是属于社会共构的心理特性,各地公众基本持一致的观点或态度,但存在一定的区域差异;相较而言,长江中游的民众对水灾的风险感知最强,其次是上游地区的民众,下游地区民众的风险感知最弱。由于对防洪工程的信赖而降低风险意识,是公众风险认知中存在的风险因子之一。