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Guimares F.V.A.,Fundacao Cearense de Meteorologia e Recursos Hidricos | de Lacerda C.F.,Federal University of Ceara | Marques E.C.,Federal University of Ceara | de Abreu C.E.B.,Federal University of Ceara | And 3 more authors.
Brazilian Journal of Plant Physiology | Year: 2012

The growth and nutrient assimilation was evaluated in CaCl2- and CaSO4-supplemented cowpea plants subjected to salt stress (75 mM NaCl). The salinity significantly reduced the cowpea vegetative growth. The addition of CaCl2 in the growth medium did not significantly affect plant growth, while for the CaSO4, the beneficial effects of Ca2+ were moderate. Salinity increased the Na+, K+, Cl-, N and P content in the plants, however it decreased the content of Ca2+ and Mg2+. Increases in Ca2+ concentration in the nutrient solution caused decreases in the Na+ and Mg2+ contents and increases in Ca2+, K+, P, and Cl- contents. The supplemental Ca2+ may alleviate the Na+ toxicity and may improve nutritional and ionic balance in cowpea, but it cannot overcome the osmotic effects associated with the increased total salt concentration. Source

Geraldo-Ferreira A.,Fundacao Cearense de Meteorologia e Recursos Hidricos | Geraldo-Ferreira A.,University of Valencia | Soria-Olivas E.,University of Valencia | Gomez-Sanchis J.,University of Valencia | And 3 more authors.
Expert Systems with Applications | Year: 2011

The knowledge of net radiation at the surface is of fundamental importance because it defines the total amount of energy available for the physical and biological processes such as evapotranspiration, air and soil warming. It is measured with net radiometers, but, the radiometers are expensive sensors, difficult to handle, that require constant care and also involve periodic calibration. This paper presents a methodology based on neural networks in order to replace the use of net radiometers (expensive tools) by modeling the relationships between the net radiation and meteorological variables measured in meteorological stations. Two different data sets (acquired at different locations) have been used in order to train and validate the developed artificial neural model. The statistical results (low root mean square errors and mean absolute error) show that the proposed methodology is suitable to estimate net radiation at surface from common meteorological variables, therefore, can be used as a substitute for net radiometers. © 2011 Elsevier Ltd. All rights reserved. Source

Cohen J.C.P.,Federal University of Para | Fitzjarrald D.R.,Albany State University | D'Oliveira F.A.F.,Federal University of Para | Saraiva I.,Centro Regional Of Manaus | And 3 more authors.
Revista Brasileira de Meteorologia | Year: 2014

Standard Amazonian rainfall climatologies rely on stations preferentially located near river margins. River breeze circulations that tend to suppress afternoon rainfall near the river and enhance it inland are not typically considered when reporting results. Previous studies found surprising nocturnal rainfall maxima near the rivers in some locations. We examine spatial and temporal rainfall variability in the Santarém region of the Tapajós-Amazon confluence, seeking to describe the importance of breeze effects on afternoon precipitation and defining the areal extent of nocturnal rainfall maxima.We used three years of mean S band radar reflectivity from Santarém airport with a Z-R relationship appropriate for tropical convective conditions. These data were complemented by TRMM satellite rainfall estimates. Nocturnal rainfall was enhanced along the Amazon River, consistent with the hypothesis that these are associated with the passage of instability lines, perhaps enhanced by local channeling and by land breeze convergence. In the daytime, two rainfall bands appear in mean results, along the east bank of the Tapajós River and to the south of the Amazon River, respectively. © 2014, Sociedade Brasileira de Meteorologia. All rights reserved. Source

Guimaraes F.V.A.,Fundacao Cearense de Meteorologia e Recursos Hidricos | de Lacerda C.F.,Federal University of Ceara | Marques E.C.,Federal University of Ceara | de Miranda M.R.A.,Federal University of Ceara | And 3 more authors.
Plant Growth Regulation | Year: 2011

The effects of supplemental Ca2+ on membrane integrity and lipid composition of cowpea plants submitted to salt stress (75 mM NaCl) were evaluated. The experimental design was factorial (2 × 6+1) corresponding to six saline treatments supplemented with CaCl2 and six saline treatments supplemented with CaSO4, both at 0.5, 1.25, 2.5, 5.0, 7.5 and 10.0 mM, plus control treatment (plants grown in half-strength Hoagland's nutrient solution without supplemental calcium addition). Samples of leaves and root tips were analyzed for total lipid, glycolipid and fatty acid contents and membrane damage symptoms. Salt stress greatly reduced total lipid content in leaves and roots and caused great damage to membrane structures. In leaves, the glycolipid content was differently influenced by calcium treatments. Moreover, salinity increased the saturated/unsaturated fatty acid ratio in leaves and an increase in the concentration of calcium intensified this response. In roots, only saturated fatty acids were detected and their content was strongly influenced by salinity and very little by calcium treatments. Supplemental Ca2+ was unable to ameliorate the negative effects of salinity on the structural integrity and fluidity of plant membranes in cowpea. © 2011 Springer Science+Business Media B.V. Source

da Silva R.R.,Federal University of Santa Catarina | Gandu A.W.,Fundacao Cearense de Meteorologia e Recursos Hidricos | Cohen J.C.,Federal University of Para | Kuhn P.,Federal University of Amazonas | Mota M.A.,Federal University of Para
Revista Brasileira de Meteorologia | Year: 2014

The OLAM model has as its characteristics the advantage to represent simultaneously the global and regional meteorological phenomena using the application of a grid refinement scheme. During the REMAM project the model was applied for a few case studies to evaluate its performance on numerical weather prediction for the eastern Amazon region. Case studies were performed for the twelve months of the year of 2009. The model results for those numerical experiments were compared with the observed data for the region of study. Precipitation data analysis showed that OLAM is able to represent the average mean accumulated precipitation and the seasonal features of the events occurrence, but can’t predict the local total amount of precipitation. However, individual evaluation for a few cases had shown that OLAM was able to represent the dynamics and forecast a few days in advance the development of coastal meteorological systems such as the squall lines that are one of the most important precipitating systems of the Amazon. © 2014, Sociedade Brasileira de Meteorologia. All rights reserved. Source

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