Steady state analysis of unsaturated flow above a shallow water-table aquifer drained by ditches     

C. Kao  S. Bouarfa  D. Zimmer 《Journal of Hydrology》2001,250(1-4):122-133

The one-dimensional pressure head profile above a fixed water-table was studied for different steady infiltration rates. As shown in previous studies, when the infiltration rate (q_in) is less than the soil saturated hydraulic conductivity (Ks), this profile can be divided into two parts: (1) from the water-table surface (z₀) to an elevation z_γ, the pressure head varies from 0 to a value h_γ such as K(h_γ)=−q_in; (2) above the elevation z_γ the pressure head is constant and equal to h_γ. Above the water-table the zone where the pressure head is variable has been called ‘transition zone’. Its height is shown to be highly variable and to depend on soil properties as well as on the infiltration rate. This transition zone is not the ‘capillary fringe’ as defined by Gillham (Gillham R.W., 1984. The capillary fringe and its effect on water-table response. J. Hydrol. 67, 307–324). Numerical experiments performed with HYDRUS-2D^® for the case of a water-table drained by parallel ditches have shown that the height of the transition zone is similar in the one-dimensional profile and in the two-dimensional system as long as the local slope of the water-table is small. This result is important since in a two-dimensional system, the transition zone is the place where all the horizontal component of the unsaturated flow occurs. The ratio of the horizontal component of the unsaturated flow vs the total horizontal flow in both the unsaturated and saturated zones has been computed. For a given soil, this ratio decreases as the infiltration rate increases; for a given infiltration rate, the soil with the thinnest transition zone transfers the largest amount of water above the water-table.  相似文献   

On the large-scale atmospheric turbulence     

S. -K. Kao 《Pure and Applied Geophysics》1971,88(1):186-209

Summary The dynamical equations of the velocity correlation and spectrum functions for three-dimensional anisotropic turbulence in a stratified, rotating atmosphere are derived and discussed. The characteristics of the horizontal two-dimensional isotropic turbulence are analyzed.National Center for Atmospheric Research, sponsored by the National Science Foundation. On leave from the University of Utah, Salt LakeCity, Utah.  相似文献   

A preliminary study of crustal structure in Taiwan region using receiver function analysis   总被引：2，自引：0，他引：2  

Kwang-Hee Kim  Jer-Ming Chiu  Honn Kao  Qiyuan Liu  Yih-Hsiung Yeh 《Geophysical Journal International》2004,159(1):146-164

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Local thickening of the Cascadia forearc crust and the origin of seismic reflectors in the uppermost mantle     

Andrew J. Calvert  Kumar Ramachandran  Honn Kao  Michael A. Fisher 《Tectonophysics》2006,420(1-2):175

Seismic reflection profiles from three different surveys of the Cascadia forearc are interpreted using P wave velocities and relocated hypocentres, which were both derived from the first arrival travel time inversion of wide-angle seismic data and local earthquakes. The subduction decollement, which is characterized beneath the continental shelf by a reflection of 0.5 s duration, can be traced landward into a large duplex structure in the lower forearc crust near southern Vancouver Island. Beneath Vancouver Island, the roof thrust of the duplex is revealed by a 5–12 km thick zone, identified previously as the E reflectors, and the floor thrust is defined by a short duration reflection from a < 2-km-thick interface at the top of the subducting plate. We show that another zone of reflectors exists east of Vancouver Island that is approximately 8 km thick, and identified as the D reflectors. These overlie the E reflectors; together the two zones define the landward part of the duplex. The combined zones reach depths as great as 50 km. The duplex structure extends for more than 120 km perpendicular to the margin, has an along-strike extent of 80 km, and at depths between 30 km and 50 km the duplex structure correlates with a region of anomalously deep seismicity, where velocities are less than 7000 m s^− 1. We suggest that these relatively low velocities indicate the presence of either crustal rocks from the oceanic plate that have been underplated to the continent or crustal rocks from the forearc that have been transported downward by subduction erosion. The absence of seismicity from within the E reflectors implies that they are significantly weaker than the overlying crust, and the reflectors may be a zone of active ductile shear. In contrast, seismicity in parts of the D reflectors can be interpreted to mean that ductile shearing no longer occurs in the landward part of the duplex. Merging of the D and E reflectors at 42–46 km depth creates reflectivity in the uppermost mantle with a vertical thickness of at least 15 km. We suggest that pervasive reflectivity in the upper mantle elsewhere beneath Puget Sound and the Strait of Georgia arises from similar shear zones.  相似文献   

陕西宽坪岩群变基性熔岩锆石U-Pb年龄   总被引：6，自引：0，他引：6  

李靠社 《陕西地质》2002,20(1):72-78

宽坪岩群广东坪岩组绿片岩岩石学、岩石化学、稀土、微量元素、副矿物等研究表明其原岩为基性火山岩。对商州市板桥地区基性熔岩变质而成的绿片岩区域地质、地球化学特点、锆石特征进行了详细研究和单颗粒锆石U-Pb同位素年龄测定。放射性成因铅丢失最少的岩浆成因锆石的206Pb/238U表面年龄为1154Ma,变质成因锆石的206Pb/238U表面年龄为444Ma。5个锆石颗粒构成的不一致线上交点年龄为1827±11Ma,代表基性熔岩形成年龄;下交点年龄为418±8Ma,代表加里东期变质年龄。综合认为宽坪岩群形成时代为早元古代。  相似文献   

TOPEX/POSEIDON-derived space–time variations of the Kuroshio Current: applications of a gravimetric geoid and wavelet analysis     

Cheinway Hwang  Ricky Kao 《Geophysical Journal International》2002,151(3):835-847

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The Source-Scanning Algorithm: mapping the distribution of seismic sources in time and space   总被引：10，自引：0，他引：10  

Honn Kao  Shao-Ju Shan 《Geophysical Journal International》2004,157(2):589-594

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Assessment of Cryosat-2 and SARAL/AltiKa altimetry for measuring inland water and coastal sea level variations: A case study on Tibetan Plateau lake and Taiwan Coast     

Huan-Chin Kao  Kuo-Hsin Tseng  C.K. Shum  Tzu-Pang Tseng  Yuan-Yuan Jia 《Marine Geodesy》2019,42(4):327-343

Satellite altimetry has been proven as an effective technology to accurately measure water level, ice elevation, and flat land surface changes since the 1990s. To overcome limitations of pulse-limited altimetry, new altimetric missions such as Cryosat-2 and Satellite with ARgos and AltiKa (SARAL/AltiKa), have been designed to have higher along-track spatial resolution to measure more accurately inland water levels for small water bodies, and coastal sea level changes. In this study, we evaluate the performance of Cryosat-2 low-resolution (LRM) and SARin modes and SARAL/AltiKa Ka-band data on two connected lakes in central Tibetan Plateau, and in the coastal region of Taiwan. Results are compared with in situ tide gauge data in Taiwan and altimetric lake level time series from the CNES Hydroweb database. Our results show that water level change trends observed by Cryosat-2 20-Hz retracked observations, the SARAL/AltiKa 40-Hz Ice-1 retracked data, and the Hydroweb measurements are consistent with the estimated water level trend of ～0.30?m/y, during 2011–2017, and 2013–2015, for the Tibetan Migriggyangzham Co and Dorsoidong Co, respectively. For the coastal region, the performance of SARAL/AltiKa is better than that of Cryosat-2 LRM data in Taiwan. This finding demonstrates the superiority of the Ka-band over Ku-band radar altimetry.  相似文献   

CFL 03型风廓线雷达自动标校方法研究     

任京伟  梁华  孙健  孙祥  杨彬  曹烤  王德伦  高雪峰 《气象科技》2014,42(4):563-569

风廓线雷达已经广泛应用于国民经济的许多领域,现在对于其应用已不仅仅局限于风场资料,对回波强度、信噪比、速度谱宽等信息的使用也越来越多。因此,对其开展标校工作就显得非常重要。以CFL-03型风廓线雷达为例,介绍了一种风廓线雷达的自动标校技术,从技术方案设计到信号流程、系统硬件组成,以及对其实现方法进行了研究,并用机外仪器对设备进行了测试,将测试结果和自动标校结果进行了对比,对比结果证明该自动标校系统的精度达到了设计目的,能够满足雷达业务运行要求。  相似文献   

Spatial and temporal variations in rainfall characteristics in mountainous and lowland areas in Taiwan     

Shih‐Chun Kao  Tomonori Kume  Hikaru Komatsu  Wei‐Li Liang 《水文研究》2013,27(18):2651-2658

Although changes in rainfall characteristics have been noted across the world, few studies have reported those in mountainous areas. This study was undertaken to clarify spatial and temporal variations in rainfall characteristics such as annual rainfall amount (Pr), mean daily rainfall intensity (η), and ratio of rain days (λ) in mountainous and lowland areas in Taiwan. To this aim, we examined spatial and year‐to‐year variations and marginal long‐term trends in Pr, η, and λ, based on rainfall data from 120 stations during the period 1978–2008. The period mean rainfall () at the lowland stations had strong relationships with the period mean daily rainfall intensity () and the period mean ratio of rain days () during those 31 years. Meanwhile, was only strongly related to at mountainous stations, indicating that influences on spatial variations in were different between lowland and mountainous stations. Year‐to‐year variations in Pr at each station were primarily determined from the variation in η at most stations for both lowland and mountainous stations. Long‐term trend analysis showed that Pr and η increased significantly at 10% and 31% of the total 120 stations, respectively, and λ decreased significantly at 6% of the total. The increases in Pr were mostly accompanied by increases in η. Although stations with significant η increases were slightly biased toward the western lowland area, increases or decreases in Pr and λ were not common. These results contribute to understanding the impacts of possible climate changes on terrestrial hydrological cycles. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献