Vicente de Paulo Rodrigues da Silva

Programa computacional para a estimativa da temperatura do ar para a região Nordeste do Brasil

The objective of this research was to establish a model to estimate air temperature (Estima_T) as a function of geographical coordinates and Sea Surface Temperature Anomalies (SSTA). The mean monthly time series of air temperatures (daily mean, minimum and maximum) of 69 weather stations and SSTA of the Tropical Atlantic were analyzed. The model Estima_T showed good agreement between real and estimated air temperature data of Northeast Brazil. The results showed statistically significant correlation at 1% level between observed air temperatures and those estimated by model in the whole area of study.

Mapeamento do saldo de radiação com imagens Landsat 5 e modelo de elevação digital

Net radiation is an important component of the surface energy balance in studies of evapotranspiration of irrigated crops and in evaporation of hydrological basins. The objective of this research was to determine the surface radiation balance, by using multispectral imagery of the Thematic Mapper (Landsat 5 satellite). In this study the SEBAL (Surface Energy Balance Algorithm for Land) and DEM (Digital Elevation Model) were used in order to correct the albedo and vegetation indices under the influence of the slope aspects were used for each study area. TM (Thematic Mapper) imageries were used for two different dates (December 4, 2000 and October 4, 2001). The calculations were accomplished with and without use of the DEM. The land surface temperature and albedo values with DEM were larger than without DEM in both years, for two selected areas. Results also show that for obtaining net radiation based on imagery of the TM - Landsat 5 the topographical effects of the study area must be considered.

Study of some climate scenarios for the northeastern region of Brazil.

The main objective of this study is to assess the current climatic conditions in northeastern region of Brazil and to obtain some climatic scenarios for the years 2050 and 2100. Time series of mean air temperature and rainfall from 1961 to 2007 period and 89 stations in the study region were used. The non-parametric test of Mann-Kendall was used to assess the statistical significance level of the analyzed time series. Also, the software SEVAP was used to determine potential evapotranspiration, humidity index, aridity index and water index. Results showed an increasing trend in the time series of air temperature, which were statistically significant by the Mann-Kendall test, for the current period and for the 2050 and 2100 scenarios. Mean air temperature has its highest rate for the current period and for the 2050 scenarios and a reduced increase between the 2050 and 2100 scenarios. The aridity and water indexes indicated an increase while the humidity index showed a reduction for two analyzed scenarios in northeastern region of Brazil, principally in the semiarid area.

Evapotranspiração de referência nos perímetros irrigados do estado de Sergipe

The knowledge of reference evapotranspiration (ETo) is essential for the irrigation scheduling of crops throughout the world. This work used daily meteorological data of Class A pan evaporation, maximum and minimum air temperatures, insolation, wind speed at 2 m above surface and relative humidity from 1989 to 1993 for four irrigated perimeters of Sergipe. These data were used for estimating ETo based on the following methods: Class A pan evaporation, Solar Radiation, Hargreaves & Samani, Linacre and Penman-Monteith (FAO/56). The daily values of ETo were compared to those obtained by FAO Penman-Monteith method in order to choose the best method of estimating ETo for the region. The best performance was obtained for those models which used the solar radiation as the data input. The Class A pan evaporation method did not show favorable performance in any irrigated perimeter.

Fluxos de energia e desenvolvimento da cultura do abacaxizeiro

The canopy of the pineapple crop changes considerably during the growing season, from a leafless stage to a fully closed canopy at the end of the productive cycle. In order to evaluate the effects of the energy balance components on the developmental stage of the pineapple crop, a field experiment was carried out from March, 2001 to July, 2002 with pineapple crop, cv. Perola, cultivated under supplemental irrigation conditions in the State of Paraiba, Brazil. The method of energy balance based on the Bowen ratio was used to obtain energy balance components during the experimental period. The energy balance components were strongly affected by leaf area index and plant height during all developmental stages of the canopy, especially the sensible heat flux. Results showed that the dry matter weight is totally independent of the energy partitioning. The sensible heat flux varied in function of the volume of water applied in irrigation during the experimental period.

Análises da precipitação pluvial no Estado da Paraíba com base na teoria da entropia

The objective of this study was the evaluation of the rainfall variability in Paraiba state. Daily rainfall observed from a network of 58 rain gauges in Paraiba State and mean daily temperature observed at Campina Grande weather station were analyzed using entropy theory. The results showed that rainfall entropy is high in localities and periods with high rainfall values and is low in localities and periods with low rainfall values. Maximum values of rainfall entropy occurred in the rainy period and minimum values occurred in the dry period. However, the entropy of the temperature time serie was constant, with maximum value of 8.53 bits. This study shows that for any time series the entropy decreases exponentially with increase of standard deviation.

Impact of global warming on the cowpea cultivation in the State of Paraíba.

No presente estudo se avaliam os impactos da mudanca do clima com base nos relatorios do Painel Intergovernamental em Mudancas do Clima (IPCC), no zoneamento agricola de riscos climaticos para a cultura do feijao-caupi (Vigna unguiculata L. Walp) cultivado em sistema de sequeiro, no Estado da Paraiba. Utilizou-se o modelo do balanco hidrico associado a tecnicas de geoprocessamento, e se objetivou a identificacao das regioes do Estado em que a cultura do feijao-caupi sofrera restricoes em face das mudancas climaticas. As variaveis consideradas no modelo foram precipitacao pluvial, coeficientes de cultura, evapotranspiracao potencial e duracao das fases fenologicas da cultura. Adotou-se, como limite para o indice de satisfacao da necessidade de agua para a cultura (ISNA), o valor de 0,50. A data foi considerada adequada para a semeadura quando a simulacao do balanco hidrico apresentou resultados de ISNA com frequencia minima de 80%, superior ao valor do criterio adotado. Tendo em vista um aumento de temperatura do ar de 3 e 6 oC, como sugerido pelo IPCC, o cultivo do feijao-caupi sofrera uma reducao significativa nas areas atualmente favoraveis ao seu cultivo no Estado da Paraiba.

Evapotranspiração e produtividade da mangueira sob diferentes tratamentos de irrigação

The objective of this study was to determine the evapotranspiration and yield as well, as the appropriate irrigation scheduling, for mango. The experimental design was in randomized blocks, with four treatments and four repetitions. The irrigation treatments were established based on the reference crop coefficient (Kcr), such as: treatment T1 (Kcr - 20%), treatment T2 (Kcr), treatment T3 (Kcr + 20%) and treatment T4 (control). The evapotranspiration of mango was obtained by the soil water balance method and the production components were also evaluated. Soil water pressure suction was measured based on twelve sets of mercury tensiometers positioned under the canopy of individual trees. Measurements were recorded three times per week at 08:00, 12:00 and 16:00 h. Throughout the mango fruiting cycle the mean daily evapotranspirations were 3.0, 3.2, 3.6 and 4.1 mm day-1 in the treatments T1, T2, T3 and T4, respectively. The maximum and minimum yields were 31.1 and 28.1 t ha-1 in the T3 and T4 treatments, respectively. The T3 treatment is more appropriate for the studied area.

Influência do calor armazenado no sistema solo-planta no balanço de energia em pomar de mangueiras

Neste estudo se objetivou a avaliacao da contribuicao do calor armazenado acima das placas de fluxo de calor no solo e no dossel vegetativo sobre os componentes do balanco de energia, no pomar de mangueiras. Os componentes do balanco de energia foram obtidos pelo metodo do balanco de energia com base na razao de Bowen. O teste t-Student foi usado para avaliar a existencia de diferenca significativa entre as medias dos componentes do balanco de energia, obtidas mediante as seguintes condicoes: (i) considerando-se o calor armazenado acima dos fluximetros e (ii) desconsiderando-se o calor armazenado acima dos fluximetros, cujos resultados indicaram que: 1) o efeito do calor armazenado no dossel vegetativo e irrelevante quando comparado com os outros componentes do balanco de energia em pomar de mangueiras; 2) o calor armazenado acima das placas de calor no solo nao interfere significativamente no calculo dos fluxos de calor sensivel e latente nem na evapotranspiracao da mangueira irrigada; 3) o fluxo de calor no solo, corrigido com o calor armazenado acima dos fluximetros, difere estatisticamente a nivel de 5% de probabilidade, daquele obtido sem a correcao do fluxo.

Shannon information entropy for assessing space-time variability of rainfall and streamflow in semiarid region.

The principle of maximum entropy can provide consistent basis to analyze water resources and geophysical processes in general. In this paper, we propose to assess the space-time variability of rainfall and streamflow in northeastern region of Brazil using the Shannon entropy. Mean values of marginal and relative entropies were computed for a 10-year period from 189 stations in the study area and entropy maps were then constructed for delineating annual and seasonal characteristics of rainfall and streamflow. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy as well as relative entropy for two sample stations. High degree of similarity was found between rainfall and streamflow, particularly during dry season. Both rainfall and streamflow variability can satisfactorily be obtained in terms of marginal entropy as a comprehensive measure of the regional uncertainty of these hydrological events. The Shannon entropy produced spatial patterns which led to a better understanding of rainfall and streamflow characteristics throughout the northeastern region of Brazil. The total relative entropy indicated that rainfall and streamflow carried the same information content at annual and rainy season time scales.