Anomalous Midsummer Rainfall in Yangtze River-Huaihe River Valleys and Its Association with the East Asia Westerly Jet

In this study, the interannual and interdecadal relationship between midsummer Yangtze River-Huaihe River valley （YHRV） rainfall and the position of the East Asia westerly jet （EAWJ） were investigated. The midsummer YHRV rainfall was found to significantly increase after the 1980s. Moreover, the location of the EAWJ was found abnormally south of the climatic mean during 1980–2008 （ID2） compared to 1951–1979 （ID1）. During ID2, associated with the southward movement of the EAWJ, an anomalous upper-level conver-gence occurred over middle-high latitudes （35° –55° N） and divergence occurred over lower latitudes （～30°N） of East Asia. Correspondingly, anomalous descending and ascending motion was observed in middle-high and lower latitudes along 90°–130° E, respectively, favoring more precipitation over YHRV. On an interan-nual time scale, the EAWJ and YHRV rainfall exhibited similar relationships during the two periods. When the EAWJ was centered abnormally southward, rainfall over YHRV tended to increase. However, EAWJ-related circulations were significantly different during the two periods. During ID1, the circulation of the southward-moving EAWJ exhibited alternating positive–negative–positive distributions from low to middle– high latitudes along the East Asian coast; the most significant anomaly appeared west of the Okhotsk Sea. However, during ID2 the EAWJ was more closely correlated with the tropical and subtropical circulations. Significant differences between ID1 and ID2 were also recorded sea surface temperatures （SSTs）. During ID1, the EAWJ was influenced by the extratropical SST over the northern Pacific; however, the EAWJ was more significantly affected by the SST of the tropical western Pacific during ID2.

A New Precipitation Index for the Spatiotemporal Distribution of Drought and Flooding in the Reaches of the Yangtze and Huaihe Rivers and Related Characteristics of Atmospheric Circulation

Characteristics of the spatiotemporal distributions of precipitation anomalies in the reaches of the Yangtze River and Huaihe River （YHR） were studied using EOF method. Four main precipitation pat-terns for the YHR in summer identified by the first two modes： a region-wide flood over the entire YHR （RWF）; a region-wide drought over the entire YHR （RWD）; a flood in the south with a drought in the northern region of the Yangtze River （FS-DN）; and a drought in the south with a flood in the northern region of the Yangtze River （DS-FN）. Based on the first two modes and the actual precipitation departure percentage, a new precipitation index is defined in this paper. The typical flood/drought years associated with the various rainfall patterns defined by this precipitation index are more representative and closer to reality compared to some existing precipitation indexes which just use the area-mean precipitation or the EOF time components individually. The characteristics of atmospheric circulation in summer corresponding to the four main precipitation patterns over the YHR in summer show the features of atmospheric circulation differ in different precipitation pattern years. Although the different patterns share a common main influential circulation system, such as the blocking high over northeastern Asia, the low trough of westerly flows in the mid latitudes, the West Pacific Subtropical High （WPSH）, and the high ridge over the Tibet Plateau, the difference in location and intensity of these systems can lead to different distributions of precipitation anomalies.

Possible connection between anomalous activity of Scandinavian Atmospheric Teleconnection Pattern and winter snowfall in the Yangtze-Huaihe River Basin of China

The temporal and spatial characteristics of winter snowfall in the Yangtze–Huaihe River Basin (YHRB) of China and its possible connection with Scandinavian Atmospheric Teleconnection Pattern (SCAND) anomalies are explored based on daily meteorological data contained in the Daily Surface Climate Dataset for China (V3.0) during the period 1960–2012. Results show that winter snowfall in the YHRB exhibits consistent anomalies over the whole region for the interannual variation during 1960–2012. Further analysis suggests that winter snowfall anomalies in the YHRB are closely linked to the anomalous wintertime SCAND activity. When there is more winter snowfall in the YHRB, SCAND is usually in a positive phase, accompanied by a strengthened Urals blocking high and East Asian trough, which is conducive to strengthened cold-air activity, intensified vertical motions, and more water vapor transport in the YHRB. In contrast, less winter snowfall in the YHRB usually happens in the negative phase of SCAND. Our results provide useful information to better understand the relevant mechanism responsible for anomalous winter snowfall in this area.

Unraveling the mechanisms underlying lake expansion from 2001 to 2020 and its impact on the ecological environment in a typical alpine basin on the Tibetan Plateau

Yanhu Lake basin(YHB)is a typical alpine lake on the northeastern Tibetan Plateau(TP).Its continuous expansion in recent years poses serious threats to downstream major projects.As a result,studies of the mechanisms underlying lake expansion are urgently needed.The elasticity method within the Budyko framework was used to calculate the water balance in the Yanhu Lake basin(YHB)and the neighboring Tuotuo River basin(TRB).Results show intensification of hydrological cycles and positive trends in the lake area,river runoff,precipitation,and potential evapotranspiration.Lake expansion was significant between 2001 and 2020 and accelerated between 2015 and 2020.Precipitation increase was the key factor underlying the hydrological changes,followed by glacier meltwater and groundwater.The overflow of Yanhu Lake was inevitable because it was connected to three other lakes and the water balance of all four lakes was positive.The high salinity lake water diverted downstream will greatly impact the water quality of the source area of the Yangtze River and the stability of the permafrost base of the traffic corridor.

Contrasts of Atmospheric Circulation and Associated Tropical Convection between Huaihe River Valley and Yangtze River Valley Mei-yu Flooding

The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu （i.e., the East Asian rainy season in June） and the related tropical convection were investigated. During the both flooding cases, although the geopotential height anomalies always exhibit equivalent barotropic structures in middle to high latitudes at middle and upper troposphere, the phase of the Rossby wave train is different over Eurasian continent. During flooding in the Huaihe River valley, only one single blocking anticyclone is located over Baikal Lake. In contrast, during flooding in the Yangtze River valley, there are two blocking anticyclones. One is over the Ural Mountains and the other is over Northeast Asia. In the lower troposphere a positive geopotential height anomaly is located at the western ridge of subtropical anticyclone over Western Pacific （SAWP） in both flooding cases, but the location of the height anomaly is much farther north and west during the Huaihe River mei-yu flooding. Fhrthermore, abnormal rainfall in the Huaihe River valley and the regions north of it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian peninsula. However, the rainfall in the Yangtze River valley and the regions to its south in China is strongly related to the convection over the western tropical Pacific. Numerical experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River valley extending to Japan Sea with enhanced precipitation; and vapor divergence over the Yangtze River valley and the regions to its south with deficient precipitation. While the weakened convection in the tropical West Pacific results in moisture converging over the Yangtze River and the region to its south, along with abundant rainfall.

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.

Variations of Meiyu Indicators in the Yangtze-Huaihe River Basin during 1954-2003

To better understand climate variations of Meiyu, some new indicators for theonset and retreat dates, duration, and Meiyu precipitation in the Yangtze-Huaihe River valley areobjectively developed by using observed daily precipitation data from 230 stations in eastern Chinaduring 1954-2003. The rainy season onset and retreat dates in each station can be denned in terms ofthresholds for rainfall intensity and persistence. Then, the onset and retreat dates of the Meiyufor the Yangtze-Huaihe River basin have been determined when more than 40% of stations reach thefirst rainy season thresholds in the study region. Based on the indicators of Meiyu in theYangtze-Huaihe River basin, variations of Meiyu rainfall during 1954-2003 are analyzed. The resultssuggest that Meiyu rainfall in the Yangtze-Huaihe River basin has increased in recent 50 years. Inaddition, interannual and interdecadal variability of Meiyu is also obvious. All the indicatorsdisplay a predominant period of about 3 years.

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.

Interannual variability of the Meiyu onset over Yangtze-Huaihe River Valley and analyses of its previous strong influence signal

Meiyu onset (MO) over Yangtze-Huaihe River Valley (YHRV) possesses obvious characteristics of interannual variations. Based on NCEP/NCAR reanalysis data sets, NOAA OLR and ERSST data, the in-terannual variability of MO(IVMO) and its previous strong influence signal (PSIS) are investigated. The possible mechanisms that the PSIS affecting IVMO are also discussed. The results show that the pre-vious CP-ENSO (Central Pacific El Nio/Southern Oscillation) event is the PSIS affecting IVMO and it has a better accuracy rate of short-term climate prediction and practicality. The MO is most likely to be late (early) with the warm (cold) phase of CP-ENSO in previous boreal February and spring. CP-ENSO affects MO mainly by means of EAP (East Asian-Pacific) or JP (Japanese-Pacific) teleconnection, in which the tropical western North Pacific anticyclone plays an important role. In the years of CP-ENSO warm phase, the tropical warm wet water vapor transportation to YHRV is late. The anomalous positive sea surface temperature near the equatorial central Pacific results in late northward jump of the western Pacific subtropical high and late establishment of Indian southwest monsoon via air-sea interaction, which leads to late seasonal transition of the atmospheric circulations over East Asia from boreal spring to summer. Late seasonal transition of the atmospheric circulations and late tropical warm wet water vapor transport to YHRV are the primary reasons that cause the late MO. The situations are directly opposite in the years of CP-ENSO cold phase.

On the Relationship between the Winter Eurasian Teleconnection Pattern and the Following Summer Precipitation over China

The Eurasian teleconnection pattern （EU） is an important low-frequency pattern with well-known impacts on climate anomalies in Eurasia. The difference of low-level v-winds in several regions in the Eurasian mid-high latitudes is defined as the EU index （EUIv）. In this study, the relationship between the winter EUIv and precipitation in the following summer over China is investigated. Results show that there is a significant positive （negative） correlation between the winter EUIv and the following summer precipitation over North China （the Yangtze River-Huaihe River basins）. Meanwhile, an interdecadal variability exists in the interannual relationship, and the correlation has become significantly enhanced since the early 1980s. Thus, the proposed EUIv may have implications for the prediction of summer precipitation anomalies over China. In positive winter EUIv years, three cyclonic circulation anomalies are observed--over the Ural Mountains, the Okhotsk Sea, and the subtropical western North Pacific. That is, the Ural blocking and Okhotsk blocking are inactive, zonal circulation prevails in the mid-high latitudes, and the western Pacific subtropical high tends to be weaker and locates to the north of its normal position in the following summer. This leads to above-normal moisture penetrating into the northern part of East China, and significant positive （negative） precipitation anomalies over North China （the Yangtze River-Huaihe River basins）, and vice versa. Further examination shows that the SST anomalies over the Northwest Pacific and subtropical central North Pacific may both contribute to the formation of EUIv-related circulation anomalies over the western North Pacific.

The Relationship of Land-Ocean Thermal Anomaly Difference with Mei-yu and South China Sea Summer Monsoon

Based on the NCEP/NCAR reanalysis data for the period of 1948-2004 and the monthly rainfall data at 160 stations in China from 1951 to 2004, the relationships among the land-ocean temperature anomaly difference in the mid-lower troposphere in spring （April-May）, the mei-yu rainfall in the Yangtze River- Huaihe River basin, and the activities of the South China Sea summer monsoon （SCSSM） are analyzed by using correlation and composite analyses. Results show that a significant positive correlation exists between mei-yu rainfall and air temperature in the middle latitudes above the western Pacific, while a significant negative correlation is located to the southwest of the Baikal Lake. When the land-ocean thermal anomaly difference is stronger in spring, the western Pacific subtropical high （WPSH） will be weaker and retreat eastward in summer （June-July）, and the SCSSM will be stronger and advance further north, resulting in deficient moisture along the mei-yu front and below-normal precipitation in the mid and lower reaches of the Yangtze River, and vice versa for the weaker difference case. The effects and relative importance of the land and ocean anomalous heating on monsoon variability is also compared. It is found that the land and ocean thermal anomalies are both closely related to the summer circulation and mei-yu rainfall and SCSSM intensity, whereas the land heating anomaly is more important than ocean heating in changing the land-ocean thermal contrast and hence the summer monsoon intensity.

Energy Budgets on the Interactions between the Mean and Eddy Flows during a Persistent Heavy Rainfall Event over the Yangtze River Valley in Summer 2010

In this study,a persistent heavy rainfall event（PHRE） that lasted for around 9 days（from 0000 UTC 17 to0000 UTC 26 June 2010） and caused accumulated precipitation above 600 mm over the Yangtze River valley,was reasonably reproduced by the advanced research WRF model.Based on the simulation,a set of energy budget equations that divided the real meteorological field into the mean and eddy flows were calculated so as to understand the interactions between the precipitation-related eddy flows and their background circulations（BCs）.The results indicated that the precipitation-related eddy flows interacted with their BCs intensely during the PHRE.At different layers,the energy cycles showed distinct characteristics.In the upper troposphere,downscaled energy cascade processes appeared,which favored the maintenance of upper-level eddy flows;whereas,a baroclinic energy conversion,which reduced the upper-level jet,also occurred.In the middle troposphere,significant upscaled energy cascade processes,which reflect the eddy flows＇ reactionary effects on their BCs,appeared.These effects cannot be ignored with respect to the BCs＇ evolution,and the reactionary effects were stronger in the dynamical field than in the thermodynamical field.In the lower troposphere,a long-lived quasi-stationary lower-level shear line was the direct trigger for the PHRE.The corresponding eddy flows were sustained mainly through the baroclinic energy conversion associated with convection activities.Alongside this,the downscaled energy cascade processes of kinetic energy,which reflect the direct influences of BCs on the precipitation-related eddy flows,were also favorable.A downscaled energy cascade of exergy also appeared in the lower troposphere,which favored the precipitation-related eddy flow indirectly via the baroclinic energy conversion.

长江泰州段引排水量时空分布特征分析

长江引排水是泰州市水资源的重要来源,本文选取长江泰州段的17个主要口门,统计了1959—2022年的引排水量并进行了对比分析。结果表明,受经济社会发展和水利基础设施建设的影响,引排水量年际变化较大,总体上呈现逐渐增大的趋势,但近年来呈现波动趋势;受区域降水、季节性农灌用水和长江潮位等因素影响,沿江口门引排水量年内分配不均;高港水利枢纽的建成对区域水资源的分配影响较大。研究成果可为长江大保护、优化口门调度方案、区域水资源开发利用及计划用水等管理工作提供数据参考。

引江济淮工程(河南段)水资源调配系统设计与开发

为强化引江济淮工程(河南段)水资源统一调配,基于Spring Boot和Vue前后端分离开发的模式,利用天地图API、WebGL、Echarts等技术设计研发引江济淮工程(河南段)水资源调配系统。从设计思路、功能界面、关键技术3个角度论述系统设计思路和实现过程,从而实现地理信息服务、供需水预测、水资源优化配置、水资源优化调度等功能,实现水量分配可视化、运行调度智能化和跨流域调水管控一体化。系统测试结果表明:引江济淮工程(河南段)水资源调配系统的建立提高了受水区水资源精细化管理的水平,解决了引江济淮工程(河南段)跨流域调水的配置难题,为受水区水资源高效利用提供有效的技术支撑。

CMIP5模式对江淮流域极端气候指数的模拟评估及预估

基于1976-2005年淮河流域260个区域站点观测资料及CMIP5中19个全球气候模式模拟的16个极端气候指数格点资料,利用空间相关系数、均方根误差方法对CMIP5各模式和多模式集合模拟的极端气候指数分别进行评估,并研究在RCP4.5情境下CMIP5优选模式的多模式集合预估2016-2045年和2071-2100年的江淮流域极端气候指数变化情况,结果表明:(1)CMIP5中有11个模式与站点观测的空间相关系数较高。其中,CCSM4、CMCC-CM模拟TXx的结果最好,ACCESS1-0、MPI-ESM-LR、MPI-ESM-MR和GFDL-ESM2M对于TNn具有较好的模拟能力,ACCESS1-0、CMCC-CM对Rx1day具有良好的模拟能力。(2)CMIP5多模式集合模拟结果能很好地再现1976-2005年R95p、R99p、CDD的空间分布特点,但是对GSL、CSDI及极端气候强度指数模拟的结果与站点资料偏差较大。(3)在RCP4.5情境下,CMIP5多模式集合模拟的江淮流域极端气候指数中,在2016-2045年的TXx普遍增加了1.0℃左右,TNn在安徽省北部和河南省东部增加了约1.8℃,Rx1day和Rx5day的高增长区集中在河南省北部;2071-2100年,TXx和TNn增长幅度大于2.1℃,Rx1day和Rx5day各站点增长幅度的差异减弱。

高海拔季节冻土区完全融化期土壤水分特征曲线适用性

以怒江源区那曲流域为例,基于4个试验场完全融化期(6—9月)的土壤体积含水量(0.15~0.51 cm^(3)/cm^(3))和土壤基质势数据(0~200 kPa)实测数据,选择Van Genuchten(VG)、Brooks-Corey(BC)和Campbell 3个模型进行拟合,以均方根误差ERMS和决定系数R2为评价指标,分析3个模型对高海拔季节冻土区不同土层和不同土壤质地的适用性。结果表明:从整体上看,VG模型(平均R2为0.992,平均ERMS为0.006 cm^(3)/cm^(3))的拟合效果优于BC模型(平均R2为0.972,平均ERMS为0.019 cm^(3)/cm/3)和Campbell模型(平均R2为0.984,平均ERMS为0.014 cm^(3)/cm^(3));但是在不同土层和不同土壤质地情况下模型的适用性有所区别,VG模型更适用于壤土和壤质砂土(平均R2为0.987,平均ERMS为0.008 cm^(3)/cm^(3))以及土壤深层(10~35 cm土层,平均R2为0.990,平均ERMS为0.007 cm^(3)/cm^(3)),Campbell模型更适用于砂质壤土(平均R2为0.985,平均ERMS为0.009 cm^(3)/cm^(3))以及土壤表层(5 cm土层,平均R2为0.993,平均ERMS为0.006 cm^(3)/cm^(3)),BC模型在不同条件下都不是最优模型;参数θr取值大小会显著影响土壤水分特征曲线的形状。本研究可为深入研究高海拔季节冻土区的土壤水分运动特性以及中华水塔区的水源涵养作用提供支持。

调水工程建设期安全-进度-投资系统风险分析——以引江济淮工程(河南段)为例

以引江济淮工程(河南段)为例,在确定安全-进度-投资系统风险评价指标体系的基础上,基于层次分析-模糊综合评价方法分析安全、进度、投资的单项风险;在考虑工程建设期安全、进度、投资的相互影响后,基于改进的综合风险评价方法分析安全-进度-投资系统风险。结果表明:当分析单项风险时,安全、进度和投资风险的评价结果均为一般风险;当分析系统风险时,得到安全风险>进度风险>投资风险;进一步分析指标体系中的准则层和指标层,安全风险的现场风险中施工技术方案风险排序第一,是后续风险管控的重点。本研究为提高工程建设期安全-进度-投资系统风险的可靠性、降低风险事件的发生提出了理论和技术参考。

引江济淮工程(河南段)多目标水量优化调度

引江济淮工程(河南段)涉及河道、闸泵、管道和调蓄水库,约束条件复杂,常规的优化调度算法难以搜索可行解,求解效率低。选用受水区缺水率平均值最小、泵站总抽水量最小和受水区缺水率标准差最小作为目标函数,从供水保障、供水成本和公平性角度构建多目标水量优化调度模型。基于可行搜索思路,结合逆序演算和顺序演算过程对约束条件进行处理,引入决策系数,通过映射关系使搜索空间保持在可行域中,结合多目标非支配排序遗传算法(non-dominated sorting genetic algorithms,NSGA-II)进行求解,得到Pareto最优解集,并采用熵权法进行方案优选。结果表明,基于可行搜索的NSGA-II算法能够有效求解复杂调度系统的多目标优化问题,综合考虑多个目标的最优方案相对单目标方案更加合理,结果可为引江济淮工程(河南段)运行管理提供决策支撑。

流域水网环境异质性及驱动力分析

【目的】水网结构和类型的产生与多种环境因素相关,对流域水网的环境异质性及驱动力方面的分析,是调整水系结构、合理恢复和保护水网的重要基础工作。【方法】以长江流域、黄河流域、淮河流域和海河流域为研究对象,基于典型水网类型,系统分析对比四大流域的环境异质性。进一步采用Pearson相关性分析、冗余分析、地理探测器分析方法,定量梳理各因子对于水网结构和类型的解释度。【结果】结果表明:网状和混合状水网流域内,坡度为0.0°~5.0°的比例大于55.05%,地形起伏度为0~70 m的比例大于67.98%,土地利用类型多为耕地和人造地表。矩形状、平行状、树枝状和扇状水网流域内,坡度为5.0°~35.0°的比例大于62.42%,地形起伏度为70~500 m的比例大于49.63%,土地利用类型多为耕地、林地和草地。土壤侵蚀强度、降水量、湿润指数、气温和水利设施数量也在不同水网类型中表现出异质性。气候因子与河流弯曲度显著正相关,地形因子、开发程度与水网的密度和流向最大频率均显著负相关。所选因子对四大流域水网结构特征的总解释率达53.47%。【结论】水网结构和类型受到多种因素的综合影响。坡度和湿润指数对水网结构有较大影响,解释率分别为21.40%和16.50%。降水量对水网类型的解释度最高,为16.61%。开发程度和气候因子的交互作用对水网类型的形成有重要影响,解释度接近50%。