Modelling the effect of low soil temperatures on transpiration by Scots pine     

Per‐Erik Mellander  Manfred Sthli  David Gustafsson  Kevin Bishop 《水文研究》2006,20(9):1929-1944

For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring‐early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70‐year‐old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high‐latitude stands. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Some statistical aspects of estimating the local red clump absolute magnitude     

Chris Koen  Fred Lombard 《Monthly notices of the Royal Astronomical Society》2003,343(1):241-248

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Identification of a 12–17 d time-scale in X-ray observations of GRS 1915+105     

J. Greenhough  S. C. Chapman  S. Chaty  †  R. O. Dendy  G. Rowlands 《Monthly notices of the Royal Astronomical Society》2003,340(3):851-855

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A Bayesian approach to discrete object detection in astronomical data sets     

M. P. Hobson  C. McLachlan 《Monthly notices of the Royal Astronomical Society》2003,338(3):765-784

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Shear and objective stress rates in hypoplasticity     

D. Kolymbas  I. Herle 《国际地质力学数值与分析法杂志》2003,27(9):733-744

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WEKU – a GIS-Supported stochastic model of groundwater residence times in upper aquifers for the supraregional groundwater management     

R. Kunkel  F. Wendland 《Environmental Geology》1997,30(1-2):1-9

 The supraregional GIS-supported stochastical model, WEKU, for the determination of groundwater residence times in the upper aquifers of large groundwater provinces is presented. Using a two-dimensional analytical model of groundwater flow, groundwater residence times are determined within two extreme cases. In the first case, maximal groundwater residence times are calculated, representing the part of groundwater, that is drained by the main surface water of a groundwater catchment area. In the second case, minimal groundwater residence times for drainage into the nearest surface water are determined. Using explicit distribution functions of the input parameters, mean values as well as potential ranges of variations of the groundwater residence times are derived. The WEKU model has been used for the determination of groundwater residence times throughout Germany. The model results – mean values and deviations of the groundwater velocity and the maximal and minimal groundwater residence times in the upper aquifers – are presented by general maps and discussed in detail. It is shown that the groundwater residence times in the upper aquifer vary regionally, differentiated between less than 1 year and more than 2000 years. Using this information, the time scales can be specified, until measures to remediate polluted groundwater resources may lead to a substantial groundwater quality improvement in the different groundwater provinces of Germany. With respect to its supraregional scale of application, the WEKU model may serve as a useful tool for the supraregional groundwater management on a state, federal or international level. Received: 15 August 1995 · Accepted: 15 October 1995  相似文献   

Models for the magnitude‐distribution of brightest cluster galaxies     

J. P. Bernstein †  Suketu P. Bhavsar ‡ 《Monthly notices of the Royal Astronomical Society》2001,322(3):625-630

The brightest, or first-ranked, galaxies (BCGs) in rich clusters show a very small dispersion in luminosity, making them excellent standard candles. This small dispersion raises questions about the nature of BCGs. Are they simply the extremes of normal galaxies formed via a stochastic process, or do they belong to a special class of atypical objects? If they do, are all BCGs special, or do normal galaxies compete for the first rank? To answer these questions, we undertake a statistical study of BCG magnitudes using results from extreme value theory. Two-population models do better than one-population models. A simple scenario where a random boost in the magnitude of a fraction of bright normal galaxies forms a class of atypical galaxies best describes the observed distribution of BCG magnitudes.  相似文献   

RELAXING ASSUMPTIONS OF PERFECT INFORMATION IN PARK VISITATION MODELS*     

Daniel J. Stynes  Daniel M. Spotts  John R. Strunk 《The Professional geographer》1985,37(1):21-28

Variables related to urban park awareness are identified and methods for relaxing assumptions of perfect information in park use models are discussed. Park awareness is related to park characteristics (age and degree of development of the park), population characteristics (race, age, length of residence, recreation participation), and distance. Park attributes are stronger predictors of both park awareness and use than is distance. These findings parallel similar research on the cognitive aspects of shopping decisions.  相似文献   

REVIEWS OF GEOGRAPHIC SOFTWARE     

《The Professional geographer》1987,39(1):85-94

Reviews of geographic software in this article: DEMO-GRAPHICS: WORLD POPULATIONS AND PROJECTIONS. ESP GAUSS. CEMODEL S. Damus LIMDEP. William H. Greene MICROSTAT 4.1 OTIS PCIPS. (Personal Computer Image Processing System) . H.J. Meyers and R. Bernstein. REGRESSION ANALYSIS OF TIME SERIES (RATS) SPSS/PC+ URBAN DATA MANAGEMENT SOFTWARE (UDMS)  相似文献   

    

Guocheng Pan  D. P. Harris 《Mathematical Geology》1991,23(6):861-886

A new multidimensional scaling (MS) technique, referred to as the Pijk model, is formulated on the basis of associations among triple objects (samples or variables), instead of pairs of objects as used in the usual MS methods, such as factor analysis. The computational scheme provided for this method is the reduction of an original problem to a standard eigenvalue-eigenvector problem. The major goal of the technique is simplification and reduction of data structures and the rescaling of original objects into a new and reduced space, so that patterns and relations of the original objects can be conventiently examined in two-dimensional factor plots. The Pïjk method is illustrated and tested by using a set of geochemical data related to the epithermal gold and silver vein deposits in the Walker Lake quadrangle of Nevada and California. The characteristics of element associations suggested in the Pijk analysis are consistent with field observations. A preliminary comparison between the new method and the ordinary factor analysis also is made on the basis of the same data set. Results are encouraging in that analysis by the Pijk model captures triple-object associations that might be missed by the ordinary factor analysis which considers only pair-variable correlations  相似文献