Using a regional frequency analysis approach for calculating the Standardized Precipitation Index: an operational approach based on the two-parameter gamma distribution     

dos Santos Junior  Edimar Pereira  Xavier  Ana Carolina Freitas  Martins  Letícia Lopes  da Rocha Sobierajski  Graciela  Blain  Gabriel Constantino 《Theoretical and Applied Climatology》2022,148(3-4):1199-1216

Theoretical and Applied Climatology - The Standardized Precipitation Index (SPI) is a worldwide used probability-based drought index. Considering that the two-parameter gamma distribution (gam) is...  相似文献   

Two apparatuses for sampling benthic fauna in surf zones     

P.C. Fleischack  A.J. de Freitas  R.B. Jackson 《Estuarine, Coastal and Shelf Science》1985,21(2):287-293

A suction corer which has been used in the turbulent surf zone is described as well as a scoop dredge which proved effective in shallow water and on dry beaches. The former is also effective under calm conditions in water ranging from a few centimetres to depths in excess of 20 m. These apparatuses both allow the rapid collection of consistent quantitative samples which is of prime importance in the surf zone.  相似文献   

Arsenic Speciation in Transplanted Lichens and Tree Bark in the Framework of a Biomonitoring Scenario     

A Machado  Z Šlejkovec  J. T. Van Elteren  M. C. Freitas  M. S. Baptista 《Journal of Atmospheric Chemistry》2006,53(3):237-249

Arsenic and its chemical species were determined in transplanted lichens (Parmelia caperata) and tree bark (Platanus hybrida), in order to get a better understanding of their atmospheric cycling and the suitability of these materials for biomonitoring purposes. Various strategies were used (discontinuous and cumulative exposure of transplants) to biomonitor two locations in Portugal, viz. the northern Lisbon area and Sines, both highly industrialised areas.Analytical techniques comprised instrumental nuclear activation analysis (INAA), inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography-hydride generation atomic fluorescence spectrometry (HPLC-HGAFS) for determination of total arsenic in solid materials, total arsenic in extracts of solid materials and arsenic species in extracts of solid materials, respectively.Only a fraction (up to 50%) of the extracted arsenic species could be identified and quantified in the transplanted lichens, being mainly inorganic arsenic and some methylated arsenic species. Since in a previous study these methylated arsenic species were not found in aerosols collected in the same area, it is probable that the lichen transplants studied (Parmelia caperata) do not behave as genuine passive biomonitors but are able to actively methylate inorganic arsenic to methylated arsenic species. Furthermore, this lichen-induced methylation occurs with some delay, possibly as a reaction to the transplantation of the lichen itself, and therefore transplanted lichens are only suitable for long-term biomonitoring studies. For tree bark only total arsenic concentration data could be generated since speciation analysis failed due to too low an initial total arsenic concentrations.  相似文献   

Lichen-Transplant Biomonitoring in the Assessment of Dispersion of Atmospheric Trace-Element Pollutants: Effects of Orientation Towards the Wind Direction     

A. P. Marques  M. C. Freitas  M. A. Reis  H. Th. Wolterbeek  T. Verburg  J. J. M. De Goeij 《Journal of Atmospheric Chemistry》2004,49(1-3):211-222

Transplants of the epiphytic lichen Parmelia sulcata were suspended in nylon bags in a special device allowing a fixed orientation of the lichen towards the wind direction, viz. facing the wind (F orientation) or shielded from the wind by its substrate (T orientation). The F- and T-orientation data were mutually compared and also with reference values (= time zero values of the transplants). The data were analysed via Monte Carlo added target transformation factor analysis (MCATTFA) to get information on possible emission-source profiles and their contributions to total-element levels in transplants, in F- and T-orientations. Both orientations did not differ for Na, Mg, P, Cl, K, Fe, Co, Ni, Ga, Se, Br, Sr, Ba, La, Nd, Sm, Lu and Ta, but showed some time-related differences for Cr and Zn. For the remaining elements the data presents a high variability. Under the conditions of the experiment, F- and T-oriented transplants generally did not result in differences in source profiles reflected, nor in differences in source contributions to element levels in the transplants.  相似文献   

Dynamics of urban boundary layer over São Paulo associated with mesoscale processes     

K. N. Nair  E. D. Freitas  O. R. Sánchez-Ccoyllo  M. A. F. Silva Dias  P. L. Silva Dias  M. F. Andrade  O. Massambani 《Meteorology and Atmospheric Physics》2004,86(1-2):87-98

Summary Examination of the Doppler SODAR data from Sao Paulo, Brazil, has given valuable information on the coupling between planetary boundary layer (PBL) and the free atmosphere above, which is reported here. In this communication a case study, on the dynamics of the urban boundary layer over the Metropolitan Area of Sao Paulo (MASP), Brazil, is examined for July 27, 1999 when a multiple gravity wave (GW), a low-level jet (LLJ) and a cold front (CF) all occurred in one single day in succession, making use of data from Doppler SODAR, surface meteorological instruments, satellite imageries and model derived values. The experimental findings are compared to provide validations of ground truth with the model-derived profiles based on the mesoscale analysis of Regional Atmospheric Modelling System (RAMS).It is seen that the multiple GW, the LLJ and the CF have different types of nonlinear coupling between the PBL and the free atmosphere. However, there is convincing matching between Doppler SODAR derived features, those of mesoscale analysis from RAMS and satellite view of cloud dynamics. The study provided valuable information on (i) the very nature of these events, (ii) the nonlinear hydrodynamical coupling between the PBL and the free atmosphere above, during such events, and (iii) the possible mechanism of CF influencing the formation of GW and LLJ.  相似文献   

Distribution and habitat partitioning of immature bull sharks (Carcharhinus leucas) in a Southwest Florida estuary     

Colin A. Simpfendorfer  Garin G. Freitas  Tonya R. Wiley  Michelle R. Heupel 《Estuaries and Coasts》2005,28(1):78-85

The distribution and salinity preference of immature bull sharks (Carcharhinus leucas) were examined based on the results of longline surveys in three adjacent estuarine habitats in southwest Florida: the Caloosahatchee River, San Carlos Bay, and Pine Island Sound. Mean sizes were significantly different between each of these areas indicating the occurrence of size-based habitat partitioning. Neonate and young-of-the-year animals occurred in the Caloosahatchee River and juveniles older than 1 year occurred in the adjacent embayments. Habitat partitioning may reduce intraspecific predation risk and increase survival of young animals. Classification tree analysis showed that both temperature and salinity were important factors in determining the occurrence and catch per unit effort (CPUE) of immatureC. leucas. The CPUE of <1 year oldC. leucas was highest at temperatures over 29°C and in areas with salinities between 7‰ and 17.5‰ Although they are able to osmoregulate in salinities from fresh to fully marine, youngC. leucas may have a salinity preference. Reasons for this preference are unknown, but need to be further investigated.  相似文献   

Relative Response of Biological and Non-Biological Monitors in a Coastal Environment     

A. Machado  M. C. Freitas  A. M. G. Pacheco 《Journal of Atmospheric Chemistry》2004,49(1-3):161-173

A field study was carried out in the spring and summer of 2003 (2 months each), to assess the efficiency of alternative exposure modes of biological monitors – lichen biomass and tree-bark biomass – together with prospective, non-biological monitors – cellulose acetate and Chelex-100 resin – versus conventional transplants of the same species. After exposure to the marine atmosphere of Sines (SW Portugal), saline elements (Cl, Na, K, Mg) contents were determined in all samples by instrumental neutron activation analysis (INAA). Manganese was used as the crustal reference for data normalisation. As a whole, the results pointed to a consistent elemental accumulation regardless of the season (spring, summer), and to some fair reproducibility of data. There were good correlations between Cl and Na in terms of both raw and normalised data, for either the biomonitors or the cellulose acetate. Elemental ratios generally agreed with the average relative composition of bulk seawater. The degree of association between Cl and Na appeared rather unaffected by the normalisation procedure, which suggests that (i) both elements most likely had an almost exclusive marine origin; and (ii) accounting for crustal inputs via Mn did not bias the results. Other sources than the sea-spray might contribute to the Mg levels, though, as only Mn-normalised data showed intrinsic (correlation) and extrinsic (ratio) consistency. The performance of the Chelex-100 resin was rather disappointing when compared to the other monitors.  相似文献   

Probing the relationship between surface waters and aquifers by <Superscript>18</Superscript>O measurements on the top of the Araripe Plateau/NE Brazil     

Luiz?Alberto?Ribeiro?Mendon?a  Horst?FrischkornEmail author  Maria?Marlúcia?Freitas?Santiago  Josué?Mendes Filho 《Environmental Geology》2004,46(2):295-302

The Araripe Plateau in northeastern Brazil has an area of about 8,000 km², confined by 39°05E and 40°55E, and 7°10S and 7°50S. Due to high permeability of soils, a surface drainage system is practically inexistent. Water is stored in excavations with clayey soil, the barreiros. Monthly samples were taken for ¹⁸O measurements, from September 1999 to August 2000, from four barreiros, three dug wells and five drilled wells. Results show that (1) groundwaters in the eastern part of the plateau are derived from present-day rainfall (¹⁸O–3.2), whereas groundwaters in the western portion are isotopically different (¹⁸O–5.0); (2) barreiros are strongly marked seasonally by elevated ¹⁸O during the dry period due to elevated evaporation; (3) a dug well at a distance of 30 m from a barreiro exhibits ¹⁸O similar to that of the reservoir, indicating a strong interaction between groundwater and surface water; and (4) a tubular well of 242-m depth, located in a fault, exhibits strong seasonal changes in ¹⁸O and electrical conductivity, revealing downward leakage between aquifers.  相似文献   

Relative effects of climate and source strength on atmospheric lead concentrations in Auckland,New Zealand     

H. C. Power  C. R. de Freitas  J. E. Hay 《Theoretical and Applied Climatology》1992,45(2):127-138

Summary Atmospheric lead levels were examined to assess the consequences of the 46 percent reduction in the lead content of premium grade petrol in New Zealand. Since this change was implemented in July 1986 observed levels of atmospheric lead decreased by 38 percent, but all or part of this reduction may have been due to factors other than fluctuations in lead emissions, notably variations in climate. Analysis of detailed atmospheric lead, meteorological and traffic data measured contemporaneously provided insight into the atmospheric processes influencing lead levels in Auckland and formed the basis of a statistical model capable of predicting monthly lead concentrations. The model was used to predict lead levels in Auckland for the period July 1986 through to July 1989 in the absence of any reduction in the lead content of petrol. Comparison with values observed for the same period showed that all of the reduction in atmospheric lead levels since July 1986 can be attributed to the reduction in the lead content of petrol. Policy planning implications of such a finding are considered.With 7 Figures  相似文献   

Efficient regionalization techniques for socio‐economic geographical units using minimum spanning trees     

R. M. AssunÇão  M. C. Neves  C. Da Costa Freitas 《International journal of geographical information science》2013,27(7):797-811

Regionalization is a classification procedure applied to spatial objects with an areal representation, which groups them into homogeneous contiguous regions. This paper presents an efficient method for regionalization. The first step creates a connectivity graph that captures the neighbourhood relationship between the spatial objects. The cost of each edge in the graph is inversely proportional to the similarity between the regions it joins. We summarize the neighbourhood structure by a minimum spanning tree (MST), which is a connected tree with no circuits. We partition the MST by successive removal of edges that link dissimilar regions. The result is the division of the spatial objects into connected regions that have maximum internal homogeneity. Since the MST partitioning problem is NP‐hard, we propose a heuristic to speed up the tree partitioning significantly. Our results show that our proposed method combines performance and quality, and it is a good alternative to other regionalization methods found in the literature.  相似文献