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1.
G Nageswara Rao 《Journal of Earth System Science》2001,110(1):87-94
It is well known that heavy rainfall occurs in the southwestern sector of the monsoon depressions due to strong convergence
in that sector. By examining the rainfall distribution associated with the monsoon disturbances (lows and depressions) in
one of the central Indian river basins, ‘Godavari’, the author found that when the disturbance-centre is away from the basin,
heavy rainfall may also occur in the basin area close to the confluence line and cause severe floods in the river. The confluence
line is the zone of convergence between the northeasterlies to the west of the disturbance centre and the monsoon westerlies.
This study further reveals the importance of the position and movement of the confluence line with respect to the basin, on
which the intensity and the raising period of the resulting flood depend. 相似文献
2.
古亚洲与特提斯交汇带盆地群油气资源潜力 总被引：6，自引：1，他引：6
古亚洲与特提斯构造交汇带盆地群发育石炭系、侏罗系(中下统)、白垩系(下统)等多套烃源岩,具有厚度大、分布广、有机质丰度高的特点.石炭系烃源岩有机质进入成熟-过成熟热演化阶段,侏罗系烃源岩有机质已进入大量生油阶段,白垩系烃源岩也处于生油高峰,具有良好的油气成藏的物质基础;区内储集岩发育,石炭-二叠系储集层以低孔隙度、低渗透率为特征,石炭系储集层主要为潮坪-泻湖相沉积的碎屑岩,二叠系储集层为一套河流相粗碎屑岩;侏罗-白垩系储集层物性相对较好,以中孔、中渗,或中孔、高渗为特征,为以河流-三角洲沉积砂体;在石炭-二叠系、中新生代地层中均见到了不同级别的油气显示或获工业油流.存在3种不同的生储盖组合,即①自生自储式组合.②下生上储的间隔式组合.③潜山型组合.预测油气资源量36.85亿t,目前已发现的油气储量仅为1亿t,具较大的勘探潜力. 相似文献
3.
针对天然河流交汇区域复杂的地形条件及水流运动特性,采用水气两相流三维数值模型,对长江与嘉陵江交汇区水流运动进行深入研究,分析了交汇区域分离区、剪切层、流速场及螺旋度的变化特性。研究结果表明:长江与嘉陵江交汇的水流分离区形状受地形影响明显,随着水位的增加向右岸移动,剪切层整体呈一个扭曲的曲面;干支流原有的环流在交汇之后重新汇合,左岸未出现明显的环流,右岸逆时针的环流有减弱趋势,交汇区域纵向流速呈现高速与低速带分布特征。此外,长江和嘉陵江在交汇口下游螺旋度呈现左侧为负、右侧为正的对称分布,水流结构表现出逐渐形成双螺旋流的趋势,其中左侧的螺旋流逆时针运动,右侧的螺旋流顺时针运动。 相似文献
4.
为了提高传统径流汇流模拟的时效性,提出了一种基于通用计算的径流汇流模型。模型采用纳维-斯托克斯作为基础方程。首先,文章探讨了利用通用计算进行径流汇流模拟的实现方法并设计了模拟计算流程。然后,以涪江流域中段为研究区域,将流域内25个常规站和区域站的实况降水数据为数据源,分别利用本文径流汇流模型和FloodArea模型对流域进行径流模拟,并将两种模型模拟结果与水文站实测数据进行对比分析。结果发现,基于通用计算的径流汇流模型不仅在模拟效率上相对于FloodArea模型有很大程度的提高,而且模拟结果具有更小的水位变化误差,与水文站实测水文数据具有更好拟合效果。模拟时效性和结果准确性的同时提升表明本文的径流汇流模型对暴雨洪涝预警预报具有重要的意义。 相似文献
5.
本文介绍了CYS300型全液压地热水井钻机的性能参数、关键机械部件结构及液压系统的设计。钻机选用齿轮泵作为液压系统动力元件,配合液压多路阀实现对动力头双液压马达和给进油缸等执行元件液压油的合流,通过液控二速阀实现动力头双液压马达的串并联工作,输出4种转速和扭矩,在满足钻机性能参数设计要求的同时,简化液压系统的设计,减少液压系统能量损耗,降低维护和使用成本。钻机采用油缸三链条倍速机构实现动力头的给进提升,具有结构简单、性能可靠、抗冲击能力强、提升平稳等优点。现场工程施工应用表明：CYS300型全液压地热水井钻机性能稳定可靠,工艺和复杂地层适用能力强,操作安全舒适,钻进效率高。 相似文献
6.
新安江模型河网汇流参数Cs对洪峰模拟影响较大,目前Cs的确定需依赖于大量的历史数据,因此Cs的确定成为无资料地区和资料匮乏区水文模型应用中亟需解决的棘手问题.本文基于参数的物理意义,通过自相似河网结构的假定,构建Cs与河网形态、流域下垫面特征的相关联系,提出基于河链蓄量方程的Cs估算方法,对半干旱、半湿润和湿润地区等不同水文气象分区的11个流域的Cs值进行推算并代入新安江模型中进行模拟,经比较发现,11个流域子流域Cs计算均值与新安江模型率定结果相近,说明该Cs计算方法是合理的.选取陈河、屯溪两个典型流域研究单元流域属性对Cs的影响,由结果可以看出Cs与流域面积、河链数、河宽呈正相关,与单元流域距离出口的远近呈负相关,这表明流域分块后各单元流域Cs值不一致,而新安江模型中采用相同Cs值对不同单元进行调节必然会造成汇流计算的误差.为进一步提高该方法在无资料地区的应用效果,将新安江模型汇流模块修改为每个单元使用对应的Cs计算值进行滞后演算,以陈河和屯溪流域为例采用新安江模型Cs率定值、Cs计算均值以及修改后新安江模型3种不同方案进行模拟比较,从模拟结果可以得出,修改后的模型具有明显优势,将模型参数与下垫面条件建立了联系,模型物理机制提高且参数的独立性增强,对于新安江模型在无资料地区的应用具有重要的指导意义. 相似文献
7.
We examine the mesoscale structure of the atmospheric boundary layer (ABL), low-level circulation, and trade wind convection
over the sub-tropical island of Puerto Rico in mid-summer. Shallow afternoon thunderstorms are frequently seen over the western
plains of the island. Observational data include automatic weather station measurements, radiosonde profiles, infrared satellite
images, and mesoscale reanalysis data with a focus on the summer of 2006. Satellite microwave radar data (TRMM and CloudSat)
indicate that island clouds typically extend just above the −20°C level during afternoon hours with reflectivity values reaching
50 dBz. A singular value decomposition of 3-hourly high resolution satellite rainfall maps reveals an island mode. From this
a composite is constructed for a group of ten cases. With a Froude number ≈1 the trade winds pass over the mountains and standing
vortices and gravity waves are trapped in the meandering wake. The Weather and Research Forecasting (WRF) model at 1-km resolution
with 51 vertical layers is used to simulate the short-lived thunderstorms for two cases: 27 June and 20 July 2006. The model
correctly locates the convective cells that develop between 1400 and 1700 LST. The shallow afternoon thunderstorms are triggered
by surface heat fluxes, confluent sea breezes and a mountain wake. Recommendations for enhanced observations are given. 相似文献
8.
Many civil infrastructures are located near the confluence of two streams, where they may be subject to inundation by high flows from either stream or both. These infrastructures, such as highway bridges, are designed to meet specified performance objectives for floods of a specified return period (e.g. the 100 year flood). Because the flooding of structures on one stream can be affected by high flows on the other stream, it is important to know the relationship between the coincident exceedence probabilities on the confluent stream pair in many hydrological engineering practices. Currently, the National Flood Frequency Program (NFF), which was developed by the US Geological Survey (USGS) and based on regional analysis, is probably the most popular model for ungauged site flood estimation and could be employed to estimate flood probabilities at the confluence points. The need for improved infrastructure design at such sites has motivated a renewed interest in the development of more rigorous joint probability distributions of the coincident flows. To accomplish this, a practical procedure is needed to determine the crucial bivariate distributions of design flows at stream confluences. In the past, the copula method provided a way to construct multivariate distribution functions. This paper aims to develop the Copula‐based Flood Frequency (COFF) method at the confluence points with any type of marginal distributions via the use of Archimedean copulas and dependent parameters. The practical implementation was assessed and tested against the standard NFF approach by a case study in Iowa's Des Moines River. Monte Carlo simulations proved the success of the generalized copula‐based joint distribution algorithm. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
9.
在分析土力类泥石流的产流特征和规律，尤其是土源与水源关系的基础上，将水文学上常用的等流时线法的基本原理应用于小流域土力类粘性泥石流的汇流计算。在具体的计算中，以滇东北蒋家沟的一支沟－大凹子沟1994－06－16的泥石流为例进行泥石流汇流流量过程的试算。计算的结果应用观测的一些数值及现象和弯道超高的最大流量计算值检验，结果表明此计算大体可以定量地反映该流域流量的过程。通过此汇流计算还可以了解阵性泥石流与连续泥石流的产生关系和机理，也可以了解降雨时段与产流时段及汇流过程时段的差别。该研究的结果也存在主客观的局限性，这一局限性反映了进一步探讨流域的产流量规律、流域等流时区划分的规律、大流域汇流计算和泥石流的波坦化规律的必然性。 相似文献
10.
A field survey of thirty stream junctions from a small watershed, together with data collected by Miller (1958), allowed us to investigate morphometric adjustments occurring at confluences. The model proposed by Roy and Woldenberg (1986) was slightly modified and used as a tool for morphometric analysis. Two parameters are necessary in order to evaluate the rate of change in channel size at a confluence: the area ratio (channel capacity above the confluence: channel capacity below the confluence) and the discharge ratio (discharge of the minor tributary: discharge of the major tributary). Our data show that total channel capacity tends to decline below most confluences. A reduction in cross-sectional area implies an increase in average flow velocity. This interpretation is consistent with Lyell's observations and with results from recent flume experiments (Best and Reid, 1984). 相似文献