Spatial patterns in thunderstorm rainfall events and their coupling with watershed hydrological response   总被引：1，自引：0，他引：1  

Efrat Morin  David C. Goodrich  Robert A. Maddox  Xiaogang Gao  Hoshin V. Gupta  Soroosh Sorooshian 《Advances in water resources》2006

Weather radar systems provide detailed information on spatial rainfall patterns known to play a significant role in runoff generation processes. In the current study, we present an innovative approach to exploit spatial rainfall information of air mass thunderstorms and link it with a watershed hydrological model. Observed radar data are decomposed into sets of rain cells conceptualized as circular Gaussian elements and the associated rain cell parameters, namely, location, maximal intensity and decay factor, are input into a hydrological model. Rain cells were retrieved from radar data for several thunderstorms over southern Arizona. Spatial characteristics of the resulting rain fields were evaluated using data from a dense rain gauge network. For an extreme case study in a semi-arid watershed, rain cells were derived and fed as input into a hydrological model to compute runoff response. A major factor in this event was found to be a single intense rain cell (out of the five cells decomposed from the storm). The path of this cell near watershed tributaries and toward the outlet enhanced generation of high flow. Furthermore, sensitivity analysis to cell characteristics indicated that peak discharge could be a factor of two higher if the cell was initiated just a few kilometers aside.  相似文献   

Calculation of the cosmogenic nuclide production topographic shielding scaling factor for large areas using DEMs     

Alexandru T. Codilean 《地球表面变化过程与地形》2006,31(6):785-794

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A Hertz contact model with non‐linear damping for pounding simulation     

Susendar Muthukumar  Reginald DesRoches 《地震工程与结构动力学》2006,35(7):811-828

This paper investigates the cogency of various impact models in capturing the seismic pounding response of adjacent structures. The analytical models considered include the contact force‐based linear spring, Kelvin and Hertz models, and the restitution‐based stereomechanical approach. In addition, a contact model based on the Hertz law and using a non‐linear hysteresis damper (Hertzdamp model) is also introduced for pounding simulation. Simple analytical approaches are presented to determine the impact stiffness parameters of the various contact models. Parameter studies are performed using two degree‐of‐freedom linear oscillators to determine the effects of impact modelling strategy, system period ratio, peak ground acceleration (PGA) and energy loss during impact on the system responses. A suite of 27 ground motion records from 13 different earthquakes is used in the analysis. The results indicate that the system displacements from the stereomechanical, Kelvin and Hertzdamp models are similar for a given coefficient of restitution, despite using different impact methodologies. Pounding increases the responses of the stiffer system, especially for highly out‐of‐phase systems. Energy loss during impact is more significant at higher levels of PGA. Based on the findings, the Hertz model provides adequate results at low PGA levels, and the Hertzdamp model is recommended at moderate and high PGA levels. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

滇黔桂湘地区中生代复合大陆动力成矿系统特征   总被引：9，自引：0，他引：9  

方维萱  胡瑞忠  苏文超  王国芝 《大地构造与成矿学》2006,30(4):470-480

通过大陆构造地质研究和分析认为在印支期SW→NE挤压构造应力场的驱动下,本区沉积盆地内可能形成自SW→NE向的盆地流体大规模流动(滇东南→桂西北)。在燕山早期,环太平洋板块自SE→NW挤压构造应力场驱动下,本区可能形成自SE→NW向的盆地流体大规模流动(桂东南→黔西北→滇东北),且可能被限定在康滇断块隆升区西边界的以东地区。在燕山晚期,伴随大陆构造进入伸展-走滑体制和山间断陷盆地的形成,幔源热物质侵位形成盆地流体的垂向热(流)应力驱动源,这种张剪性构造为流体成矿提供了良好的构造背景。古潜山、褶皱-断裂带、逆冲断裂-褶皱带和脆韧性剪切带可能是本区主要流体圈闭构造和矿床定位构造,成矿系列可划分为改造型拉分盆地中古潜山控制的F-Fe-S-Sb-Au成矿系列、褶皱-断裂带热水再造成因的Sb-As-Hg-Au成矿系列、改造型盆地边部逆冲断裂-褶皱带中热流体成因的Ge-Ag-Pb-Zn成矿系列和脆韧性剪切带中W-Sb-Au成矿系列。  相似文献   

全球变化与中国东北样带(NECT)   总被引：24，自引：0，他引：24  

周广胜  王玉辉  蒋延玲 《地学前缘》2002,9(1):198-216

全球变化陆地样带是从机理上理解陆地生态系统对全球变化的响应 ,预测全球变化对陆地生态系统的可能影响 ,实现预警、调节和减小全球变化不良影响 ,科学地规划和管理陆地生态系统的有效研究平台。在介绍国际全球变化陆地样带提出的背景与选定标准、中国东北样带的位置与特征的基础上 ,较系统地总结了近年来中国东北样带的研究进展 :建立了用于模型发展和比较的不同时间和空间尺度的中国东北样带数据集 ,从机理上初步探讨了全球变化对于森林、草甸草原和典型草原的可能影响 ,发展了用于古植被气候重建的植物种与表土花粉类型的定量关系模型、多尺度耦合的羊草草原生态系统动态模型和基于林窗原理的森林生态系统动态模型 ,并对全球变化对中国东北样带的影响进行了初步评估 ,进而针对我国作为发展中国家 ,财力有限的特点 ,提出未来中国东北样带研究拟充分利用我国特殊的生态环境与区域特色 ,围绕“生态过程与生态安全及其对全球变化的响应与反馈”这一关键科学问题 ,做出一些在国际上既有显示度 ,又服务于我国社会经济可持续发展的研究成果。  相似文献   

Evaluating Models Of The Neutral, Barotropic Planetary Boundary Layer Using Integral Measures: Part Ii. Modelling Observed Conditions     

G. D. Hess  J. R. Garratt 《Boundary-Layer Meteorology》2002,104(3):359-369

The steady-state, horizontally homogeneous, neutral, barotropiccase forms the foundation of our theoretical understanding of the planetary boundary layer (PBL).While simple analytical models and first-order closure models simulate atmospheric observationsof this case well, more sophisticated models, in general, do not. In this paperwe examine how well three higher-order closure models, E - - l, E - l, and LRR - l,which have been especially modified for PBL applications, perform in predicting the behaviour of thecross-isobaric angle ₀, the geostrophic drag coefficient C_g, and the integral of the dissipationrate over the boundary layer, as a function of the surface Rossby number Ro. For comparison we alsoexamine the performance of three first-order closure mixing-length models, two proposed byA. K. Blackadar and one by H. H. Lettau, and the performance of the standard model forsecond-order closure and a modification of it designed to reduce the overprediction of turbulence inthe upper part of the boundary layer.  相似文献   

二十世纪九十年代区域气候模拟研究进展   总被引：44，自引：9，他引：35  

赵宗慈  罗勇 《气象学报》1998,56(2):225-241

由于区域气候异常与社会经济及人类发展有紧密联系,因而长期以来受到各国气候学家的极大重视,与此密切相关的对区域气候的模拟研究也有了较大发展。进入２０世纪９０年代以来,区域气候模拟研究的进展更加明显。文中将着重分析全球气候模式对区域气候模拟的可靠性与不确定性;国内外对区域气候的模拟研究进展;以及对区域气候变化模拟研究的展望。  相似文献   

我国地球空间数据框架的设计思想与技术路线   总被引：1，自引：0，他引：1  

李德仁  龚健雅  朱欣焰  梁宜希 《武汉大学学报(信息科学版)》1998,(4)

根据当前我国基础地理信息系统的发展态势,较为详尽地讨论了１∶１万至１∶５万基础地理信息系统的设计思路,提出了地球空间数据框架（ＤＧＤＦ）的概念,即基于数字正射影像和ＤＥＭ及与若干层矢量框架数据（如大地控制、交通图、水系、境界、行政边界、注记等）的整体集成的栅格－矢量一体化空间数据库,目的在于尽快建立起有活力的和可更新的国家和省级基础地理信息系统。还详尽讨论了建立基础地理信息系统的主要技术路线和数据采集与数据处理的工艺流程。  相似文献   

Estimation of dynamic ocean topography in the Gulf Stream area using the Hotine formula and altimetry data   总被引：3，自引：2，他引：1  

Changyou Zhang 《Journal of Geodesy》1998,72(9):499-510

Two modifications of the Hotine formula using the truncation theory and marine gravity disturbances with altimetry data are developed and used to compute a marine gravimetric geoid in the Gulf Stream area. The purpose of the geoid computation from marine gravity information is to derive the absolute dynamic ocean topography based on the best estimate of the mean surface height from recent altimetry missions such as Geosat, ERS-1, and Topex. This paper also tries to overcome difficulties of using Fast Fourier Transformation (FFT) techniques to the geoid computation when the Hotine kernel is modified according to the truncation theory. The derived absolute dynamic ocean topography is compared with that from global circulation models such as POCM4B and POP96. The RMS difference between altimetry-derived and global circulation model dynamic ocean topography is at the level of 25cm. The corresponding mean difference for POCM4B and POP96 is only a few centimeters. This study also shows that the POP96 model is in slightly better agreement with the results derived from the Hotine formula and altimetry data than POCM4B in the Gulf Stream area. In addition, Hotine formula with modification (II) gives the better agreement with the results from the two global circulation models than the other techniques discussed in this paper. Received: 10 October 1996 / Accepted: 16 January 1998  相似文献   

A comparison of drainage networks derived from digital elevation models at two scales   总被引：2，自引：0，他引：2  

Xinhao Wang  Zhi-Yong Yin 《Journal of Hydrology》1998,210(1-4):221-241

Automated generation of drainage networks has become increasingly popular with powerful analytical functions in geographic information systems (GIS) and with the increased availability of digital elevation models (DEMs). This paper compares drainage networks derived from DEMs at two scales, 1:250 000 (250K) and 1:24 000 (24K), using various drainage parameters common in hydrology and geomorphology. The comparison of parameters derived from the 250K DEMs with those from the 24K DEMs in 20 basins ranging from 150 to 1000 km² in West Virginia shows that the goodness-of-fit between parameter estimates based on the DEMs varies. Results clearly show that superior estimations are produced from the 24K DEMs. Better estimates can be obtained from the 250K DEMs for stream length and frequency parameters than for gradient parameters. However, the estimation of the mean gradient parameters based on the 250K DEMs seems to improve with increasing terrain complexity. Finally, basin size does not strongly affect the accuracy of parameter estimates based on the 250K DEMs.  相似文献