Subseasonal Change in the Seesaw Pattern of Precipitation between the Yangtze River Basin and the TropicalWestern North Pacific during Summer

There is a well-known seesaw pattern of precipitation between the tropical western North Pacific(WNP) and the Yangtze River basin(YRB) during summer. This study identified that this out-of-phase relationship experiences a subseasonal change;that is, the relationship is strong during early summer but much weaker during mid-summer. We investigated the large-scale circulation anomalies responsible for the YRB rainfall anomalies on the subseasonal timescale. It was found that the YRB rainfall is mainly affected by the tropical circulation anomalies during early summer, i.e., the anticyclonic or cyclonic anomaly over the subtropical WNP associated with the precipitation anomalies over the tropical WNP. During mid-summer, the YRB rainfall is mainly affected by the extratropical circulation anomalies in both the lower and upper troposphere. In the lower troposphere, the northeasterly anomaly north of the YRB favors heavier rainfall over the YRB by intensifying the meridional gradient of the equivalent potential temperature over the YRB. In the upper troposphere, the meridional displacement of the Asian westerly jet and the zonally oriented teleconnection pattern along the jet also affect the YRB rainfall. The subseasonal change in the WNP–YRB precipitation relationship illustrated by this study has important implications for the subseasonalto-seasonal forecasting of the YRB rainfall.

Decadal Change in the Influence of the Western North Pacific Subtropical High on Summer Rainfall over the Yangtze River Basin in the Late 1970s

It is well known that on the interannual timescale,the westward extension of the western North Pacific subtropical high(WNPSH)results in enhanced rainfall over the Yangtze River basin(YRB)in summer,and vice versa.This study identifies that this correspondence experiences a decadal change in the late 1970s.That is,the WNPSH significantly affects YRB precipitation(YRBP)after the late 1970s(P2)but not before the late 1970s(P1).It is found that enhanced interannual variability of the WNPSH favors its effect on YRB rainfall in P2.On the other hand,after removing the strong WNPSH cases in P2 and making the WNPSH variability equivalent to that in P1,the WNPSH can still significantly affect YRB rainfall,suggesting that the WNPSH variability is not the only factor that affects the WNPSH-YRBP relationship.Further results indicate that the change in basic state of thermal conditions in the tropical WNP provides a favorable background for the enhanced WNPSH-YRBP relationship.In P2,the lower-tropospheric atmosphere in the tropical WNP gets warmer and wetter,and thus the meridional gradient of climatological equivalent potential temperature over the YRB is enhanced.As a result,the WNPSH-related circulation anomalies can more effectively induce YRB rainfall anomalies through affecting the meridional gradient of equivalent potential temperature over the YRB.

An Analysis of Natural Factors Affecting the Dispersal and Establishment of Iron Age III (800-550 B.C)Settlements in the Western Zayandeh- Rud River Basin (West and Northwest of Isfahan)

Humans are always effect to their surroundings,which makes it possible to create habitable environments and create habitat patterns that fit the surrounding environment.The interaction between human being and environment either in the form of human effect on the environment or the environment effect on the human,cannot be considered out of the environment.According to this approach in archaeology,environmental factors have an important role in assessing settlements in each period.In addition to the recognition of the degree of environmental impact,this approach makes the degree of adaptation of the habitats with the dominant environmental conditions possible.As geospatial tools become more powerful,GIS archaeology has evolved as well,making it possible to visualize ancient settlements and analyze changes in the use of space over time.By incorporating historic map data,physical details of an area’s landscape and known information about past inhabitants,archaeologists can accurately predict the positions of sites with cultural,historical relevance.In this research Iron Age III(800-550 B.C)sites in the west and northwest of Isfahan were studied via GIS.The area studied is one of the most important but unknown areas of archaeological research due to its location in the center of the Iranian plateau and a link between the north-west and the south-west of the country.The environmental characteristics of the studied area have attracted the attention of humans since ancient times.Therefore,it was considered necessary to conduct archaeological excavations.To achieve this goal,the area was first studied archaeologically.As a result of this survey,approximately 50 ancient sites were identified which included the statistical population used for analysis.The effect of environmental variables including altitude,slope(percentage and direction),climate,geological structure,distances and proximity to water resources,land use and proximity to communication paths on the distribution of settlements in the study area was investigated.Through analytical-descriptive method,the factors affecting the formation and distribution of the establishment patterns of the period in question were examind.After analyzing the information and maps,the results indicated that among all the factors,three environmental factors were the most important in the formation of ancient settlements of the Iron Age III era in the west and northwest of Isfahan:factors relating to water resources,proximity to communication paths,and slope percentage and direction.

The Impact of Atmospheric Heat Sources over the Eastern Tibetan Plateau and the Tropical Western Pacific on the Summer Rainfall over the Yangtze-River Basin

The variability of the summer rainfall over China is analyzed using the EOF procedure with a new parameter （namely, mode station variance percentage） based on 1951-2000 summer rainfall data from 160 stations in China. Compared with mode variance friction, the mode station variance percentage not only reveals more localized characteristics of the variability of the summer rainfall, but also helps to distinguish the regions with a high degree of dominant EOF modes representing the analyzed observational variable. The atmospheric circulation diagnostic studies with the NCEP/NCAR reanalysis daily data from 1966 to 2000 show that in summer, abundant （scarce） rainfall in the belt-area from the upper-middle reaches of the Yangtze River northeastward to the Huaihe River basin is linked to strong （weak） heat sources over the eastern Tibetan Plateau, while the abundant （scarce） rainfall in the area to the south of the middle-lower reaches of the Yangtze River is closely linked to the weak （strong） heat sources over the tropical western Pacific.

Assessment of soil erosion in a tropical mountain river basin of the southern Western Ghats,India using RUSLE and GIS

Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km^2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha^(-1) yr^(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha^(-1) yr^(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(<5 t ha^(-1) yr^(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.

Sensitivity of digital elevation models:The scenario from two tropical mountain river basins of the Western Ghats,India

The paper evaluates sensitivity of various spaceborne digital elevation models （DEMs）, viz., Advanced Spaceborne Thermal Emission and Reflection Radiometer （ASTER）, Shuttle Radar Topography Mapping Mission （SRTM） and Global Multi-resolution Terrain Elevation Data 2010 （GMTED）, in comparison with the DEM （TOPO） derived from contour data of 20 m interval of Survey of India topographic sheets of 1 ： 50,000 scale. Several topographic attributes, such as elevation （above mean sea level）, relative relief, slope, aspect, curvature, slope-length and -steepness （LS） factor, terrain ruggedness index （TRI）, topo- graphic wetness index （TWI）, hypsometric integral （lhyp） and drainage network attributes （stream number and stream length） of two tropical mountain river basins, viz. Muthirapuzha River Basin and Pambar River Basin are compared to evaluate the variations. Though the basins are comparable in extent, they differ in respect of terrain characteristics and climate. The result.,; suggest that ASTER and SRTM provide equally reliable representation of topography portrayed by TOP（） and the topographic attributes extracted from the spaceborne DEMs are in agreement with those derived from TOPO. Despite the coarser resolution, SRTM shows relatively higher vertical accuracy （RMSE -- 23 and 20 m respectively in MRB and PRB） compared to ASTER （RMSE - 33 and 24 m） and GMTED （RMSE - 59 and 48 m）. Vertical accuracy of all the spaceborne DEMs is influenced by relief of the terrain as well as type of vegetation. Further, GMTED shows significant deviation for most of the attributes, indicating its inability for mountain-river-basin-scale studies.

An Ecologically Oriented Operation Strategy for a Multi-Reservoir System： A Case Study of the Middle and Lower Han River Basin, China

水库群的建设和调度改变了河流的自然流态,对河流生态系统造成了不利影响。本文提出了一种面向生态的水库群调度策略,将河流内不同生态功能所需的生态流量整合到水库群联合调度中,以实现生态流量需求和人类用水需求之间的均衡。该策略耦合了常规优化调度方案和一系列实时生态调度方案。在人类用水需求与生态流量需求冲突较小的时段,水库群调度在保障河流最小流量的前提下采用常规优化调度方案,最大限度地提高人类用水效益。在水库引发的水文改变对河流关键生态功能产生严重影响的时期,水库群调度采用实时生态调度方案,调整下泄流量,从而满足河流生态流量需求。该策略被应用于位于中国汉江中下游流域的一个大型水库群中。模拟调度结果表明,实时生态调度方案保证了河流关键生态功能的生态流量需求,其对人类用水效益的不利影响可通过常规优化调度方案得到部分补偿。本文提出的面向生态的水库群调度策略丰富了考虑生态流量需求的水库群联合调度的理论应用。

Estimation of soil erosion in a rain shadow river basin in the southern Western Ghats, India using RUSLE and transport limited sediment delivery function

Soil erosion and deposition in a tropical mountainous river basin, viz., Pambar River Basin (PRB), in a rain shadow region of the southern Western Ghats (India) were modelled using Revised Universal Soil Loss Equation (RUSLE) and transport limited sediment delivery (TLSD) function in GIS. Mean gross soil erosion in the basin is 11.70 t ha-1 yr-1, and is comparable with the results of previous soil erosion studies from the region. However, mean net soil erosion from the basin is 2.92 t ha-1 yr-1 only, which is roughly 25%of the gross soil erosion. Although natural vegetation belts show relatively higher gross- and net-soil erosion rates (mainly due to high LS and C factors), their sediment transport efficiency is remarkably less, compared to the land use/ land cover types with anthropogenic signatures (i.e., plantations and crop-lands). Despite the lesser amount of annual rainfall, the high rates of soil loss from the semi-arid areas of the basin might be the result of the poor protective vegetation cover as well as isolated high intensity rainfall events. The study highlights the significance of climate-specific plans for soil erosion manage-ment and conservation of the soil resources of the basins developed in rain shadow regions.

汉江流域粮食生产碳排放与经济发展的脱钩关系研究

汉江流域水资源丰富,是我国重要的粮食主产区,研究汉江流域粮食生产碳排放对促进农业绿色高质量可持续发展具有重要意义。采用排放系数法测算汉江流域2008—2021年时空尺度下的粮食生产碳排放总量和结构,并通过Tapio脱钩模型分析其与经济发展之间的脱钩关系。研究发现,2008—2021年碳排放总量年际间虽存在一定波动,但总体呈现上升趋势;农业生产要素中土地翻耕和化肥使用所产生的碳排放量比重较大;汉江流域整体呈现弱脱钩状态,上游以强脱钩状态为主,下游为弱脱钩状态;汉江流域各县区的经济发展与粮食生产碳排放脱钩状态存在时空差异,2014—2017年多地呈负脱钩状态。汉江流域粮食生产碳减排效果显著,粮食生产能力有效提升,农业经济发展也取得一定成效。

珠江口盆地文昌A凹陷西部新生代断裂体系特征及演化过程

断裂体系发育是珠江口盆地文昌A凹陷西部地区新生代构造演化的重要表现形式。利用最新的三维地震资料,在精细刻画断裂体系静态特征的基础上,结合断层活动速率计算恢复断裂体系的动态演化过程,明确了文昌A凹陷西部地区新生代断裂体系发育的时空差异;并结合区域应力背景分析,探讨了断裂体系演化的成因机制,认为新生代以来三大板块间俯冲、碰撞及古南海俯冲消亡、新南海扩张共同造成的南海北缘区域伸展应力场顺时针旋转控制了断裂体系演化的时空差异。研究表明,文昌A凹陷西部地区断裂体系的发育演化经历了裂陷、拗陷与构造活化三个阶段,分别发育了NE(NEE)向、近EW向以及NW(NWW)向三组优势方向断裂,揭示了区域应力场伸展方向由NW—SE向到近SN向再到NNE—SSW向顺时针转变的过程;依据断裂的组合及沿承关系可将其划分为早期发育的NE向与后期发育的NW向两组交叠断裂带,NE向断裂带活动强度大、具有强烈伸展性质,NW向断裂带与基底先存断裂密切相关,活动强度弱、叠加一定走滑性质。文昌A凹陷西部新生代断裂体系演化的时空差异是对南海北缘区域应力场顺时针旋转的响应。

汉江流域植被生长与水热的时滞累积效应

目的在全球气候变暖的背景下,研究汉江流域植被生长与气温和降水的时滞累积效应,对流域生态环境建设具有重要的意义。方法基于2001-2020年MODIS NDVI月数据和月均温、月降水数据,通过相关和时滞累积效应分析不同生态分区及植被的生长季NDVI(归一化植被指数)变化差异及其对气温和降水的响应。结果与结论(1)汉江流域生长季NDVI呈波动上升趋势,均值为0.7,与气温和降水的相关系数均值分别为0.263和0.223,正相关区域多分布于生态功能保护区和山地丘陵的植被茂密地带,负相关区域多分布于平原和盆地的栽培植被种植地带及各市人类生产生活区。(2)汉江流域生长季NDVI与气温和降水存在明显的时滞累积效应,受累积1个月滞后0个月-累积3个月滞后3个月影响的植被面积均超过了50%,气温的时滞累积效应由中间向东西两侧递减,降水则自西向东明显增加,气温的时滞累积效应对植被覆盖的促进效果大于抑制效果,降水则相反。(3)6类植被对气温和降水时滞累积的负相关性均减弱。除针叶林和阔叶林外,气温在累积6个月滞后3个月的情况下对其他类型植被覆盖的影响最大,响应程度最高的是低覆盖植被;降水在累积3个月滞后2个月的情况下对6类植被覆盖的影响最大,降水对6类植被的平均最值相关系数大小为草丛>草甸>灌丛>栽培植被>针叶林>阔叶林。

西安至十堰高速铁路环保选线研究

西安至十堰高速铁路西安至商洛段穿越秦岭高中山区,郧西至十堰段跨越汉江,具有沿线地形起伏大、地质条件复杂、环境敏感区域密集、生物多样性丰富、水环境保护要求严格等特点,保护秦岭及汉江流域的生态环境成为西十高铁建设中需要考虑的重要因素。通过采取GIS+BIM的技术手段,制作区域环境敏感区图层,搭建多维度区域生态保护目标空间分布及管控范围的环保选线平台,结合工程技术条件开展各方案的环境可行性及环境影响程度的综合比选,从而得出对环境影响最小的线路方案,为设计选线及控制工程方案决策提供有力支撑。研究结果表明,通过先期开展敏感区路段环境影响专题论证,可进一步优化工程选线及工程形式,保障项目依法合规。

珠江口盆地西部潜山油气成藏条件与勘探实践

潜山是油气勘探中重要的圈闭类型,近年渤海湾盆地潜山获丰富油气发现(邓运华,2015;叶涛等,2021),潜山成为中国近海油气勘探储量增长点。珠江口盆地位于南海北部海域,为新生代陆缘拉张型断陷盆地。珠江口盆地西部文昌凹陷是主要生烃凹陷(陈林等,2021),凹陷周缘发育琼海凸起、神狐隆起、阳江低凸起等多个大型正向构造单元.

汉江流域襄阳段地表水总磷浓度的变化特征

为助力长江保护修复攻坚战地方精准施策,基于2016—2022年汉江流域襄阳段12个地表水国控监测断面的总磷浓度及区域降雨量开展了水环境形势分析、磷污染来源解析,并对区域总磷浓度变化特征进行了研究。结果显示,研究期内汉江流域襄阳段12个国控断面总磷年均浓度总体达标情况较好,但大部分断面总磷月均浓度无法长期稳定达标,其中唐白河张湾、蛮河岛口和清河王湾村3个国控断面超标较严重,蛮河、唐白河和清河的总磷浓度较高、污染较严重。汉江流域襄阳段流域的总磷浓度整体呈现下降趋势,受汉江支流总磷浓度影响较大,且与月均降雨量呈显著正相关关系,可为流域内总磷污染防治的重点区域、重点领域提供参考。

Drought analysis using multi-scale standardized precipitation index in the Han River Basin,China

Regional drought analysis provides useful information for sustainable water resources management.In this paper,a standardized precipitation index(SPI) at multiple time scales was used to investigate the spatial patterns and trends of drought in the Han River Basin,one of the largest tributaries of Yangtze River,China.It was found that,in terms of drought severity,the upper basin of the Han River is the least,while the growing trend is the most conspicuous;a less conspicuous growing trend can be observed in the middle basin;and there is an insignificant decreasing trend in the lower basin.Meanwhile,the impact of drought on the Middle Route of the South-to-North Water Transfer Project was investigated,and it is suggested that water intake must be reduced in times of drought,particularly when successive or simultaneous droughts in the upper and middle basins of the Han River Basin occur.The results can provide substantial information for future water allocation schemes of the South-to-North Water Transfer Project.

基于黄河流域水资源均衡调配的南水北调西线一期工程水量配置

南水北调西线一期工程生效后黄河流域水量分配模式决定了黄河流域水资源配置格局重塑和南水北调西线工程供水效益评价,为国家水网构建提供重要技术支撑。考虑西线供水范围可覆盖黄河主要供水区的特点,西线调入水量应与黄河流域水资源统一配置,考虑生态优先、公平为主兼顾效率的原则,构建了流域用水分级配置方法,建立了基于流域水资源均衡调配的西线调入水量配置模式,开展了不同情景优化配置方案研究。结果表明:南水北调西线一期工程调水80亿m^(3),配置给黄河河流生态用水33.70亿m^(3),配置给流域河道外经济社会用水46.30亿m^(3),其中95%以上配置给黄河上中游地区,流域缺水率降低至7.0%~8.3%。优化配置方案体现了生态优先原则,保障了黄河河道内基本生态环境用水,均衡了河道外经济社会用水的公平和效率,有效缓解了流域缺水。

面向刚性约束的汉江流域水资源承载状况评价及管控建议

以汉江流域为研究对象,结合刚性约束要求,构建了适用于水资源管理考核和应用的评价指标体系和评价方法,以地市级行政区为评价单元开展水资源承载状况评价,划分水资源承载负荷等级,制定汉江流域水资源承载状况分区清单,并根据超载特征和超载成因研究提出对应的分区管控措施。结果表明:汉江流域内水资源承载状况为超载的地区有6个,为潜江市、南阳市、洛阳市、驻马店市、安康市、商洛市,水资源承载状况为临界状态的地区有1个,为汉中市,其余地级行政区均为“不超载”;汉江流域总体评价结果为临界超载状态。

踔厉西垂:早期秦文化资源保护利用的对策和建议——以西汉水上游考古发现为例

西汉水上游早期秦文化资源丰厚,具有独特的比较优势和鲜明的原初性特点。自20世纪90年代至今,该区域大量早期秦文化资源的发现和积累,开启了早秦文化遗存研究保护与利用的新纪元,取得了很多工作实绩,但同时也存在着很多问题。针对目前状况,必须采取务实性措施在宣传展示、品牌打造、学术研究等方面扎实推进,以提升早期秦文化作为陇南乃至甘肃历史文化名片形象和中华文明起源一分子的标志性地位,突出其厚重的文化品位和深刻内涵,踔厉奋进、守正创新,为文旅产业发展提供强大支持。

十九世纪珠江流域文化景观特征——基于西方文献的分析

自古以来,河流及其流域构成了一些最具活力和最复杂的景观。河流维系着人类社会,人类社会则以多种方式利用河流,从而产生璀璨的流域文明。广州作为西方人眼中的一座“神奇”城市,两千年来一直是中国最重要的海上门户,现如今,我们可以从外国商人、船长、旅行者、传教士等游记、报告或图像记录中获得大量关于珠江流域文化景观的详细描述。本文尝试将珠江流域的河流系统及其相关的文化景观作为人类经验的重要组成部分进行研究,透过西方人的视野,去分析其对珠江流域及其文化景观的所见所闻,并深入挖掘珠江流域文化景观的构成与特征,从而归纳出珠江流域文化景观中的人水共生关系,为珠江流域文化遗产保护研究提供了全新的视角与思路。

2010~2020年汉江中下游流域景观格局变化分析

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