A Matrix Approach Coupled with Monte Carlo Techniques for Solving the Net Radiative Balance of the Urban Block   总被引：2，自引：0，他引：2  

Marta J. N. Oliveira Panão  Helder J. P. Gonçalves  Paulo M. C. Ferrão 《Boundary-Layer Meteorology》2007,122(1):217-241

A new method is developed for solving the shortwave and longwave net radiative balance of a three-dimensional urban structure, represented by parallelepiped blocks uniformly distributed in each direction. The method is based on a novel approach to determine the shape factors among surfaces, which are estimated by Monte Carlo techniques due to the complex geometry associated with the three-dimensional urban structure. Then, a set of linear equations is solved to quantify the radiative balance, in order to obtain their exact solution, considering all the inter-reflections among surfaces. The comparison between the new and the ray-tracing tracking methods resulted in a Pearson correlation coefficient of 0.996. However, by integrating the linear equations’ exact solution with Monte Carlo techniques, the new method reduces by a factor of 36 the central processing unit (CPU) time used to perform the calculations of the ray-tracing tracking method. The use of the model for a sensitivity study allows us to verify the effective absorptance and emittance increases with the canyon aspect ratio of the urban layout. An urban structure formed by square cross-sectional blocks absorbs more solar radiation than an urban structure formed by rectangular cross-sectional blocks. The approximation of a specific geometry for an equivalent bi-dimensional infinite street can be applied for rectangular cross-sectional blocks, where the width is 11 times or more greater than the depth dimension.  相似文献   

On the individual calibration of hailpads     

Covadonga Palencia  Claude Berthet  Marta Massot  Amaya Castro  Jean Dessens  Roberto Fraile   《Atmospheric Research》2007,83(2-4):493-504

This paper is a comparative study between the two most common hailpad calibration systems: one annual calibration of a whole consignment of material, and the individual calibration of each plate after a hailfall. Individual calibration attempts to minimize errors due to differences in sensitivity to the impact of hailstones between plates from the same consignment, or due to differences in the inking process before the actual measurement.The comparison was carried out using calibration data from the past few years in the hailpad network in south-western France, and data from an individual calibration process on material provided by the hailpad network in Lleida (Spain). The same type of material was used in the two cases.The results confirm that the error in measuring hailstone sizes is smaller in the case of an individual calibration of hailpads than when one single calibration process was carried out for a whole consignment. The former is approximately 80% of the latter. However, this error could have been higher if it had not been the same person carrying out the single calibration process and the measuring of the dents: it has been found that differences in the inking process may account for up to 20% of the error in the case of small hailstones. Calibration errors affecting other variables, e.g. energy or parameter λ of the exponential size distribution are generally higher (5% and 18%, respectively) than errors due to the spatial variability of the hailstones. However, the calibration method does not influence the maximum size, since the relative error attributed to the spatial variability is about 8 times the calibration error.In conclusion, if errors in determining energy or parameter λ are to be reduced to a minimum, it is highly advisable to be consistent in applying the measuring procedure (if possible with the same person carrying out the measurements all the time), and even to use individual calibration on each plate, always bearing in mind that technicians have to be trained appropriately in order to achieve the highest possible degree of uniformity.  相似文献   

Spatial variation in pore water geochemistry in a mangrove system (Pai Matos island, Cananeia-Brazil)     

X.L. Otero  T.O. Ferreira  P. Vidal-Torrado  F. Macías 《Applied Geochemistry》2006,21(12):2171-2186

Spatial variation in salinity, pH, redox potential, and in the concentrations of dissolved Mn, Fe²⁺ and sulphides in pore water were investigated in a mangrove system in the state of São Paulo (Brazil). Total organic C (TOC), S, Fe and Mn were analyzed in the solid phase, along with acid volatile sulphide (AVS), density of roots and percentage of sand. Five zones, situated along the length of a 180 m transect were considered in the study. Four of these were colonized by different species of vascular plants (Spartina, Laguncularia, Avicennia and Rhizophora) and were denominated soils; the other was not colonized by vegetation, and was denominated sediment. The results indicated important differences between the physicochemical conditions of the pore water in the vegetated zones and the sediment. In the former, two geochemical environments were identified, based on soil depths. The upper 20 cm contained the largest quantity of roots, and the conditions were oxic (Eh > 350 mV) or suboxic (Eh: 100–350 mV), acidic, and with high concentrations of Fe and Mn in the pore water. Below this depth, the soil became anoxic, the concentration of sulphides (HS⁻) increased significantly and the concentrations of dissolved Fe and Mn decreased significantly. The total S and the AVS fraction increased with depth, while TOC concentrations decreased, indicating that the decreases in Fe and Mn were due to the precipitation of metal sulphides. However, clear differences among the vegetated zones were not observed. The sediment was always anoxic, but with low concentrations of sulphide in the interstitial water, and was neutral or slightly alkaline. As in the soils, the concentrations of sulphides and total S increased significantly with depth, indicating that the conditions favoured the synthesis and stability of metal sulphides.  相似文献   

Areal versus linear evaluation of relationship between drainage basin lithology and geochemistry of stream and overbank sediments in low-order mountainous drainage basins     

Zoran Peh  Slobodan Miko  Marta Mileusnic 《Environmental Geology》2006,49(8):1102-1115

The comparison of two multiple regression models is based on the assumption that geochemical composition of the drainage basin alluvial sediments is derived primarily from the underlying bedrock lithology. The parent material is integrated with both stream sediment and overbank sediment geochemistry via the two essentially different approaches as regards the drainage basin geomorphological data: (1) as the relative area of influence representing a portion of the catchment basin occupied by a specific rock type and (2) as the relative “line” of influence representing a narrow zone of the underlying bedrock traversed by the perennial streams which form the active stream network. The model comparison is established on the goodness-of-fit test for both experimental designs and for the same set of data. Both experiments converge on the linear approach as the more appropriate model in evaluating the lithologic influence on the analysed sample media in small mountainous watersheds.  相似文献   

Determination of the apparent copper complexing capacity of seawater by anodic stripping voltammetry     

Marta Plavšić  Damir Krznarić  Marko Branica 《Marine Chemistry》1982,11(1):17-31

A new experimental technique using differential pulse anodic stripping voltammetry with a thin-film mercury electrode and efficient mixing of the electrolyte for the apparent copper complexing capacity of seawater is proposed. The effects of some factors such as type of electrode and cell, pH of the solution, potential of deposition, time of equilibration, and influence of a non-ionic surface active agent on the measurements are examined. Experimental results for the apparent copper complexing capacity of seawater are calculated presuming 1:1 inert complex formation. By using EDTA as a model ligand, it is shown that the proposed procedure with efficient mixing of the solution excludes any appreciable kinetic influence upon the electroanalytical results.  相似文献   

Diffuse Component Spectra of Solar Active Regions at Submillimeter Wavelengths     

Adriana?V.?R.?SilvaEmail author  Tatiana?F.?Laganá  C.?Guillermo?Gimenez?De?Castro  Pierre?Kaufmann  Joaquim?E.?R.?Costa  Hugo?Levato  Marta?Rovira 《Solar physics》2005,227(2):265-281

Solar maps at 212 and 405 GHz obtained by the Solar Submillimetric Telescope (SST) show regions of enhanced brightness temperature, which coincide with the location of active regions. A statistical study of the radio emission from these active regions was performed for the first time at such high frequencies during 23 days on June and July 2002, when the atmospheric opacity was low. The brightest regions on the maps were chosen for this study, where the brightness excess observed varies from 3 to 20% above quiet Sun levels (i.e., 200–1000 K) at both wavelengths. Sizes of the regions of enhanced emission calculated at half the maximum value were estimated to be between 2′ and 7′. These sizes agree with observed sizes of active regions at other wavelengths such as Hα and ultraviolet. An important result is that the flux density spectra of all sources increase toward submillimeter frequencies, yielding flux density spectral index with an average value of 2.0. The flux density of the active region sources were complemented with that from maps at 17 and 34 GHz from the Nobeyama Radio Heliograph. The resulting spectra at all four frequencies were fit considering the flux density to be due to thermal bremsstrahlung from the active region. In the calculations, the source radius was assumed to be the mean of the measured values at 212 and 405 K. The effective temperatures of the radio emitting source, assumed homogeneous, obtained from this fit were 0.6–2.9 × 10⁴ K, for source diameters of 2′–7′.  相似文献   

Later Holocene vegetation history of the Isles of Scilly,UK: coastal influence and human land use in a small island context          下载免费PDF全文

Marta Perez  Ralph M. Fyfe  Dan J. Charman  W. Roland Gehrels 《第四纪科学杂志》2015,30(8):764-778

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‘Non‐European’ palaeomagnetic directions from the Carpathian Foredeep at the southern margin of the European plate     

Emő Márton  Antek K. Tokarski  Oldřich Krejčí  Marta Rauch  Barbara Olszewska  Pavla Tomanová Petrová  Antoni Wójcik 《地学学报》2011,23(2):134-144

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Water flow and solute transport model of potentially toxic elements through unsaturated zone at regional wellfield Kosnica          下载免费PDF全文

Stanko Ružičić  Marta Mileusnić  Kristijan Posavec  Zoran Nakić  Goran Durn  Vilim Filipović 《水文研究》2016,30(22):4113-4124

The objective of this work was to build a prognostic water flow model and potentially toxic elements (lead, cadmium, zinc) transport model in the unsaturated zone. Research was conducted in the catchment area of Kosnica regional wellfield, where the unsaturated zone is characterised by Fluvisol. Lower sorption capacities were determined in the first horizons for all three potentially toxic elements. Correlation coefficient of the measured and simulated values of tracer concentration is 0.58 for the AC horizon and 0.84 for the 2C/C1 horizon. Based on calibrated water flow and transport parameters, a prognostic water flow model and potentially toxic elements (lead, cadmium, zinc) transport model in the unsaturated zone was built. In case of an accidental spill of potentially toxic elements with concentrations of 1000 mg/l, the risk of contamination of the aquifer is present. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Climate variability and Alpine glaciers evolution in Northwestern Italy from the Little Ice Age to the 2010s     

Guido Nigrelli  Stefania Lucchesi  Stefania Bertotto  Gianfranco Fioraso  Marta Chiarle 《Theoretical and Applied Climatology》2015,122(3-4):595-608

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