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181.
D. Labat C. T. Hoang J. Masbou A. Mangin I. Tchiguirinskaia S. Lovejoy D. Schertzer 《水文研究》2013,27(25):3708-3717
Karstic watersheds are highly complex hydrogeological systems that are characterized by a multiscale behaviour corresponding to the different pathways of water in these systems. The main issue of karstic spring discharge fluctuations consists in the presence and the identification of characteristic time scales in the discharge time series. To identify and characterize these dynamics, we acquired, for many years at the outlet of two karstic watersheds in South of France, discharge data at 3‐mn, 30‐mn and daily sampling rate. These hydrological records constitute to our knowledge the longest uninterrupted discharge time series available at these sampling rates. The analysis of the hydrological records at different levels of detail leads to a natural scale analysis of these time series in a multifractal framework. From a universal class of multifractal models based on cascade multiplicative processes, the time series first highlights two cut‐off scales around 1 and 16 h that correspond to distinct responses of the aquifer drainage system. Then we provide estimates of the multifractal parameters α and C1 and the moment of divergence qD corresponding to the behaviour of karstic systems. These results constitute the first estimates of the multifractal characteristics of karstic spingflows based on 10 years of high‐resolution discharge time series and should lead to several improvements in rainfall‐karstic springflow simulation models. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
182.
There are various factors governing the spatial and temporal variability of soil water storage including soil properties, topography and vegetation. Some factors act locally, whereas others act nonlocally, which means that a factor measured at one location has effect on soil water storage at another location. The objective of this study was to examine the effects of local and nonlocal controls of soil water storage in a hummocky landscape using cyclical correlation analysis. Soil water storage, soil properties and terrain indices were measured along a 128‐point transect of 576 m long from the semiarid, hummocky, prairie pothole region of North America. There are large coefficients of determination (r2) between soil water storage and sand content (r2 = 0.32–0.53), organic carbon content (r2 = 0.22–0.56), depth to carbonate layer (r2 = 0.13–0.63), wetness index (r2 = 0.25–0.45) and other variables at the measurement scale at different times, indicating strong local effects from these variables. The correlation coefficients were also calculated by physically shifting the spatial series of soil water storage with respect to that of controlling factors. The shifting improves the correlation between the spatial series, and the length of shifting indicated the difference in the response of soil water to its controlling factors. For example, the value of r2 increased more than eightfold (r2 = 0.47–0.64) after shifting the spatial series of soil water storage by 54 m, almost equal to the average length of existing slope, compared with the very weak correlation (r2 = 0.02–0.08) at the measurement scale. This indicated the nonlocal effect from the relative elevation. The identification of nonlocal effects from factors improves the prediction of soil water storage. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
183.
Abstract Ecohydrology is the science that studies the mutual interaction between the hydrological cycle and ecosystems. Such an interaction is especially intense in water-controlled ecosystems, where water may be a limiting factor, not only because of its scarcity, but also because of its intermittent and unpredictable appearance. Soil moisture is the key variable modulating the complex dynamics of the climate-soil-vegetation system and controlling the spatial and temporal patterns of vegetation. In this note the authors' perspective to the field is discussed and some open questions are outlined. 相似文献
184.
Falling sphere observations of anisotropic gravity wave motions in the upper stratosphere over Australia 总被引:1,自引:0,他引:1
A study of inertial scale gravity wave motions in the region of the atmosphere between 30 and 60 km has been undertaken, using wind and temperature data derived from rocket-borne falling sphere density experiments performed over Woomera, Australia between 1962 nad 1976. The gross features of the wave field compare favorably with those found in similar northern hemispheric studies. Wave propagation is found to be both vertically and horizontally anisotropic. A rotary spectral analysis indicates predominately upgoing wave energy, suggesting that the majority of sources of these waves lie below 30 km. A detailed statistical investigation of the waves, made using the Stokes parameters technique, reveals that phase progression is also highly directional in the horizontal, with a significant zonal component in summer, but with a strong meridional component in winter. Propagation towards the southeast is inferred in summer, with the waves possibly emanating from tropospheric sources in equatorial regions to the north of Australia. The technique also shows that, on average, the waves appear to have mean ellipse eccentricities (=f/) around 0.4–0.45. Indirect estimates of a number of important wave parameters are made. In particular,v andw flux estimates are made over several height intervals. The vertical gradient of density weighted flux implies wave-induced mean flow accelerations of the order 0.1–1 ms–1day–1. This suggests that dissipating gravity waves are a significant source of the momentum residuals that are encountered in studies of satellite data from this region. 相似文献
185.
186.
梅雨锋次天气尺度涡旋旋转风和辐散风动能收支 总被引:2,自引:3,他引:2
本文选取1991年7月5日20:00-6日20:00梅雨锋上移动性次天气尺度涡旋引起的长江中下游特大暴雨为实例。采用准拉格朗日球坐标系的旋转风和辐散风动能方程,计算得到次天气尺度涡旋发展和成熟两个阶段对流层各层旋转风动能和辐散风动能的收支特征为:在对流层高层(100-400hPa)两个阶段的旋转风动能源汇相同,辐散风动能源汇有异,即水平动能通量项和“摩擦”项符号相反;在中层(400-700hPa) 相似文献
187.
主要论述了国内外目前对弥散率尺度效应以及渗透系数等夺数的空间变异性研究的现状和今后的研究趋势。文中提出了含水层水力参数的尺度效应问题,并指出庄重视地下水驱动力场变化对参数的影响研究。 相似文献
188.
Gregory J. Carbone 《The Professional geographer》1995,47(1):30-40
The accuracy of impact estimates relating climate change to regional-scale agricultural production is constrained by the temporal and spatial resolution of climate change projections. Several techniques have been used to compensate for these limitations in order to provide reasonable estimates of the impact of climate change on crop yield. One approach assumes that variability over time can substitute for spatial variability, thereby reducing the need to estimate the impacts at a spatially dense network of stations—an assumption that has not been generally tested. This study evaluates this assumption using methods similar to those employed in the climate impact literature. The findings suggest that current practices are generally defensible if the goal is to provide a range of possible crop responses to climate change. However, the results also show that the assumption is highly sensitive to specific interactions at the soil-plant-atmosphere interface and, consequently, does not hold under certain circumstances. 相似文献
189.
王桥 《武汉大学学报(信息科学版)》1993,(4)
本文提出了一种新的实用地图数据检索方法——“放大镜”式地图数据检索,建立了相应的软件系统,并讨论了该方法的数学基础、软件的特点,还给出了应用实例。 相似文献
190.
Damage caused by the earthquake of 7 December 1986 (M = 5.7) and its aftershocks in low-storey residential buildings in the town of Strazhitza, Bulgaria, situated in the epicentral zone are systematized. A scale of damages is compiled for two types of buildings which is coordinated with the MSK-64 scale. The territorial distribution of the seismic intensity is compared with the results of the detailed engineering-geological study. A correlation between the Quarternary deposit thickness and the observed seismic intensity is obtained.Paper presented at the 21st general assembly of the European Seismological Commission held in Sofia, 1988. 相似文献