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1.
Stable oxygen isotope analysis and measurement of several dissolved cations and anions of bulk meltwater samples have provided information about the hydrochemical environment of the glacial hydrological system at Imersuaq Glacier, an outlet tongue from the Greenland ice‐sheet, West Greenland. The samples were collected at frequent intervals during the period 20–28 July 2000 in a small (<20 L s?1) englacial meltwater outlet at the glacier margin. The results document the following findings: (i) a marked diurnal variation of δ18O is related to the composition of oxygen isotope provenances, mainly near‐marginal local superimposed ice and basal up‐sheared ice further up‐glacier; (ii) a relationship is seen between all base cations (Na+, K+, Ca2+, Mg2+), SO42? and δ18O, indicating that solute acquisition is provided by solid–solution contact with the up‐sheared ice—as the relationship with Cl? is weak the influence of seasalt‐derived solutes is small in the area; (iii) when the melt rate is high, two diurnal maxima of δ18O values and solute concentrations are measured, and it is suggested that a snow meltwater component is responsible for the second maximum of δ18O—a short residence time leads to a delayed decrease in ion concentrations. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
Information systems developed for different applications within the environmental domain have common characteristics, which can potentially be abstracted for sharing and reuse of design and software modules. This article presents an approach to designing for reuse by abstracting commonalities in the design of a Marine Information System (MIS), facilitating data management in a prototype operational monitoring, forecasting, and management system for the North Atlantic and the Nordic Seas. A detailed study of the requirements and data analysis was carried out, and Object-Oriented Technology (OOT) is employed to encapsulate abstractions and to promote reuse of code and design. This article identifies the Object-Oriented Frameworks (OOFW) required to build the MIS. It also provides guidelines to environmental scientists for restructuring legacy software and employing modern programming techniques. 相似文献
3.
Given incident logarithmic profiles of wind and pollutant concentration above a rough, absorbing surface, the three-dimensional distribution of pollutant concentration over a hill of gentle slope is determined from a linearized model. The model is applied in neutrally stratified flow, without chemistry, and is integrated using spectral methods in the horizontal and a finite-difference scheme in the vertical. This approach allows for flexibility in choosing a closure scheme and a variety of surface boundary conditions. This was not possible in the analytic approach of Padro (1987) who added pollutant concentration and flux to the MS3DJH/1 model of Walmsley et al. (1980). The present model requires as input the turbulent kinetic energy, E, dissipation, , and the perturbation vertical velocity, w, from the three-dimensional boundary-layer flow model of Beljaars et al. (1987), hereinafter referred to as MSFD, The latter model also supplies wind velocity perturbations at the upper boundary, as input to upper boundary conditions on the pollutant flux perturbations.The present study describes applications of the model to idealized terrain features: isolated two- and three-dimensional hills and ridges and an infinite series of ridges. (Application to real terrain, however, presents no difficulties.) Comparisons were made with different (though uniform) surface roughnesses. Tests were performed to examine the effect of upstream terrain features in the periodic domain and to illustrate the importance of the vertical resolution of the output for interpreting results from the sinusoidal terrain case. 相似文献
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6.
Jacob Fosso Jean-Jacques Ménard Jacques-Marie Bardintzeff Pierre Wandji Félix M. Tchoua Hervé Bellon 《Comptes Rendus Geoscience》2005,337(3):315-325
Mount Bangou, an Eocene volcano (40K–40Ar ages between 44.7 and 43.1 ± 1 Ma) is the oldest dated volcano of the Cameroon Line. In this region, two magmatic series, evolving by fractional crystallization, show transitional affinities that are exceptionally known in this sector. Mineral compositions of basaltic rocks (scarce modal olivine and occurrence of normative hypersthene) as well as geochemical characteristics (low Ba, La, Ta contents and high Y/Nb ratios) are in agreement with this trend. The succession of magmas evolving in time from transitional to more typical alkaline compositions is evidenced in a continental setting. To cite this article: J. Fosso et al., C. R. Geoscience 337 (2005). 相似文献
7.
A comprehensive model inter-comparison study investigating the water budget during the BALTEX-PIDCAP period 总被引:2,自引:0,他引:2
D. Jacob B. J. J. M. Van den Hurk U. Andræ G. Elgered C. Fortelius L. P. Graham S. D. Jackson U. Karstens Chr. Köpken R. Lindau R. Podzun B. Rockel F. Rubel B. H. Sass R. N. B. Smith X. Yang 《Meteorology and Atmospheric Physics》2001,77(1-4):19-43
Summary A comparison of 8 regional atmospheric model systems was carried out for a three-month late summer/early autumn period in
1995 over the Baltic Sea and its catchment area. All models were configured on a common grid using similar surface and lateral
boundary conditions, and ran in either data assimilation mode (short term forecasts plus data assimilation), forecast mode
(short term forecasts initialised daily with analyses) or climate mode (no re-initialisation of model interior during entire
simulation period). Model results presented in this paper were generally post processed as daily averaged quantities, separate
for land and sea areas when relevant. Post processed output was compared against available analyses or observations of cloud
cover, precipitation, vertically integrated atmospheric specific humidity, runoff, surface radiation and near surface synoptic
observations.
The definition of a common grid and lateral forcing resulted in a high degree of agreement among the participating model results
for most cases. Models operated in climate mode generally displayed slightly larger deviations from the observations than
the data assimilation or forecast mode integration, but in all cases synoptic events were well captured. Correspondence to
near surface synoptic quantities was good. Significant disagreement between model results was shown in particular for cloud
cover and the radiative properties, average precipitation and runoff. Problems with choosing appropriate initial soil moisture
conditions from a common initial soil moisture field resulted in a wide range of evaporation and sensible heat flux values
during the first few weeks of the simulations, but better agreement was shown at later times.
Received September 8, 2000 Revised April 3, 2001 相似文献
8.
A. F. Carril C. G. Menéndez A. R. C. Remedio F. Robledo A. S?rensson B. Tencer J.-P. Boulanger M. de Castro D. Jacob H. Le Treut L. Z. X. Li O. Penalba S. Pfeifer M. Rusticucci P. Salio P. Samuelsson E. Sanchez P. Zaninelli 《Climate Dynamics》2012,39(12):2747-2768
The ability of four regional climate models to reproduce the present-day South American climate is examined with emphasis on La Plata Basin. Models were integrated for the period 1991–2000 with initial and lateral boundary conditions from ERA-40 Reanalysis. The ensemble sea level pressure, maximum and minimum temperatures and precipitation are evaluated in terms of seasonal means and extreme indices based on a percentile approach. Dispersion among the individual models and uncertainties when comparing the ensemble mean with different climatologies are also discussed. The ensemble mean is warmer than the observations in South Eastern South America (SESA), especially for minimum winter temperatures with errors increasing in magnitude towards the tails of the distributions. The ensemble mean reproduces the broad spatial pattern of precipitation, but overestimates the convective precipitation in the tropics and the orographic precipitation along the Andes and over the Brazilian Highlands, and underestimates the precipitation near the monsoon core region. The models overestimate the number of wet days and underestimate the daily intensity of rainfall for both seasons suggesting a premature triggering of convection. The skill of models to simulate the intensity of convective precipitation in summer in SESA and the variability associated with heavy precipitation events (the upper quartile daily precipitation) is far from satisfactory. Owing to the sparseness of the observing network, ensemble and observations uncertainties in seasonal means are comparable for some regions and seasons. 相似文献
9.
Naomi Mazzilli Hervé Jourde Thomas Jacob Vincent Guinot Nicolas Le Moigne Marie Boucher Konstantinos Chalikakis Hélène Guyard Anatoly Legtchenko 《Environmental Earth Sciences》2013,68(6):1631-1646
This work examines the relevance of the inclusion of ground-based gravity data in the calibration process of a global rainfall-discharge reservoir model. The analysis is performed for the Durzon karst system (Larzac, France). The first part of the study focuses on the hydrological interpretation of the ground-based gravity measurements. The second part of the study investigates further the information content of the gravity data with respect to water storage dynamics modelling. The gravity-derived information is found unable to either reduce equifinality of the single-objective, discharge-based model calibration process or enhance model performance through assimilation. 相似文献