Gustavo Bastos Lyra

Regiões homogêneas e funções de distribuição de probabilidade da precipitação pluvial no Estado de Táchira, Venezuela

The objective of this work was to determine regions of monthly pluvial precipitation based on the seasonal and the probability distribution that best fit to precipitation of those areas in the State of Tachira, Venezuela. Long-term series of 24 throughout 62 years of monthly precipitation data of 25 climatological stations were used. The Wards clustering methods of analyses was used to group the months with similar monthly pluvial precipitation and also the climatological locations with similar precipitation (homogeneous regions). The adjust of the probability density functions exponential, Gamma, Gumbel, normal, log-normal were evaluated with three parameters as well as Weibull distributions in order to observe monthly precipitation data. The precipitation seasonal variation at the State of Tachira presents three periods statistically defined as: dry, transition, and wet. For the dry and wet periods, four homogeneous regions of locations with similar monthly precipitation could be identified and, in the transition period, three regions. In the dry period, the recommended probability distribution is the exponential, except for the homogeneous regions with the largest rainfall values during that period, when Gamma distribution is better. In the wet period, in all regions, normal distribution prevails, except for August, when Gamma prevails. As far as transition periods are concerned, Gamma distributions are better in April and normal distribution, in November.

Crescimento e fotossíntese de cana-de-açúcar em função de variáveis biométricas e meteorológicas

Sugarcane growth can be obtained by biophysical models in which gross photosynthesis (GP) is obtained as a function of solar radiation. This work aims to evaluate sugarcane varieties under irrigation in relation to intercepted photosynthetic active radiation (PARint) and the estimated accumulative GP. To achieve that, a study was conducted at the Federal University of Alagoas during 2008 and 2009, with RB sugarcane varieties. Biometric measurements, production variables and meteorological elements were made. The intercepted photosynthetic irradiance (PAR) was obtained by the difference between PAR and transmitted PAR (PART), which was determined by Beers Law. The daily GP was estimated numerically by the trapezoidal approach. The production variables had correlations with accumulated PARint and accumulated GP during the crop cycle. The average global solar radiation in the region for rainy season (May-August) was 14.9 MJ m-2. The variety RB92579 had the highest production variables as well as higher intercepted PAR and accumulated GP in the cycle due to its greater capacity for regrowth and energy conversion in photoassimilate.

Modelagem do crescimento de cultivares de cana-de-açúcar no período de formação da cultura

The objective of the present study was to adjust growth models to the above-ground accumulated sugarcane dry matter, during the crop formation period, for cultivars RB92579, RB867515, RB928064 and RB855453. Dry matter data were obtained during the execution of experiment under field conditions from October 26, 2011 to May 18, 2012. Experimental data were collected from 45 days after planting, in one or two week time intervals, totalizing 17 sampling dates. The obtained values were subjected to nonlinear regression analysis in order to determine the parameters of the expolinear, logistic and Gompertz models. All evaluated models were capable of adequately simulating the dry matter accumulation by the cultivars during the studied period, with values of the adjusted determination coefficient above 0.9245. Based on the expolinear growth model, it was observed, at the end of the experimental period, that the accumulated dry mass was stightly superior for the cultivar RB855453 as compared to the RB867515, which outperformed the cultivars RB928064 and RB92579.

Componentes da radiação solar em cultivo de tomate sob condições de ambiente protegido

ABSTRACT The objective of this paper was to evaluate of net radiation, photosynthetic and solar irradiation ingreenhouse conditions cultivated with tomato crop and its relationship with the global solar irradiationof the external environment. The tomato was cultivated in greenhouse (not acclimatized), with coveringof polyethylene 0.12 mm of thickness. The global solar irradiation (Rgi), the net radiation (Rni) and theflux density of photosynthetic photons were obtained by radiometers connected to a datalogger installedinto the protected environment. The external data (global solar irradiation, Rg) were collected in theAgrometeorological Station of the Agricultural Science Center of Federal University of Alagoas. Theprotecting environment promoted reduction in the solar irradiation, expressed as the transmittance of thepolyethylene in 62%. The relationships between the components of radiation from internal and externalenvironment were expressed satisfactorily by linear regressions, with coefficients of determination (R

Manning roughness coefficient for Paracatu river, Brazil

Pela teoria do escoamento em canais abertos, o coeficiente de rugosidade de Manning e um dos principais parâmetros para descricao da vazao sobre uma superficie. Uma das dificuldades da aplicacao da equacao de Manning e a definicao do seu coeficiente de rugosidade em rios e canais, razao pela qual o presente estudo tem como objetivo, estimar o coeficiente de rugosidade de Manning para os periodos de vazao minima e maxima media mensal, em alguns trechos do rio Paracatu, e propor um modelo baseado em redes neurais artificiais para estimar o coeficiente de rugosidade. O coeficiente foi determinado em funcao das caracteristicas geometricas do canal (area molhada, raio hidraulico e declividade do canal) e das series de vazao de seis postos fluviometricos do rio Paracatu. Utilizaram-se series de vazao de 21 anos (1976-1996). O coeficiente de rugosidade nao apresenta tendencia (maior ou menor) em funcao apenas do periodo seco ou de cheia. As caracteristicas da margem e do leito do rio influenciam diretamente nos valores de coeficiente de rugosidade. O modelo baseado em rede neural apresentou desempenho satisfatorio, o que possibilita estimar o coeficiente de rugosidade em funcao da cota, vazao, declividade e do raio hidraulico do rio.

Média diária do déficit de pressão de saturação do vapor d'água do ar e sua influência na vapotranspiração de referência pelo modelo de penman-monteith (FAO 56) em Piracicaba - SP

The results of the evapotranspiration obtained with the Dair_avg proceeding from 14 methods were evaluated, by using the lysimetric measures of a sward. These comparisons allowed to separate the Dar_avg calculating methods into three groups: a group always resulted into an overestimate ETo; in other one always tended to underestimating the ETo; and in the last tended to overestimating the low values (<4.5 mm day-1), while underestimating the high values of ETo. No significant statistical differences were observed (t test; p <0.05) in ETo as a function of the Dair_avg methods, when using the hourly average of the temperature and/or the air relative humidity in relation to those determined with the average of the maximum and minimum values of these elements. Among the methods proposed by paper FAO56, just the one using the average relative humidity to calculate the actual pressure (ea) showed a satisfactory estimate. The best estimates of ETo were obtained with the Dair_avg methods using the average of the air temperature in the determination of the saturation pressure (es) and the average of the relative humidity for the actual pressure (ea). The use of saturation-vapor-pressure deficit of the air at a single time (from 9 or 10 a.m. local) as a representative of Dair_avg showed to be a satisfactory alternative in estimating the ETo under the climatic conditions of Piracicaba, SP, Brazil.

Eficiência do uso da radiação em cultivos de milho em Alagoas

Maize was cultivated under three management systems: i) mulching (grass cover); ii) plastic cover in the inter rows and iii) traditional cultivation (bare soil). The components of the incident and transmitted solar radiation in a maize canopy were measured in order to determine the radiation use efficiency (RUE). The photosynthetic irradiation (HF) was considered as 44% of the solar global irradiation. The transmitted HF (HFT) was estimated using Beers law applied to a plant canopy (HFT = HF exp (-k LAI)), with the light extinction coefficient (k) by fitting an exponential function, which related the fraction of HFT (HFT/HF) and leaf area index (LAI). The intercepted HF (HFI) was calculated by the difference (HFI = HF - HFT). The RUE was estimated using a linear regression (forced to pass through the origin) between the dry matter accumulation (DM) and HFI. The k was 0.628 with the determination coefficient of 0.88. The plants RUE in plots covered with plastic was 3.85 g DM MJ-1 of HFI, showing a higher efficiency compared to other treatments (bare soil 3.31 g MJ-1 and grass 3.58 g MJ -1). However, this promoted lower LAI and therefore had less accumulated HFI, resulting in lower production of DM.

ÍNDICE ULTRAVIOLETA EM MACEIÓ, AL: ANÁLISE PRELIMINAR

The goal of this work was to evaluate the UV index daily variationin Maceio, Alagoas. Sensors were used in the solar ultraviolet radiationspectrum with spectral range of 290-390nm and overall (300-1100nm)installed at 2m above the surface. Measurements were taken on days 11to 15 of July, 2009. The highest values were observed in the IUV timenext to midday, and high to very high. Until 9 a.m. and after 15 p. m.localtime, the index was between low to moderate. The duration in hours ofIUV considered high by the World Health Organization wasapproximately 4 hours.

Water vapour and carbon dioxide fluxes in sugarcane grown in megathermal humid climate in Northeastern Brazil

The understanding about biophysical processes taking place between the crop and the atmosphere is essential to define the appropriate management practices in order to increase crop yield. The aim of the present study is to analyze water vapour and carbon dioxide (CO2) fluxes in sugarcane crop between the development and the mid-season as an environmental variables function, as well as to assess the correction effects on fluxes. Latent heat flux (lambdaE) and net ecosystem CO2 exchange (NEE) micrometeorological measurements were performed through the eddy covariance technique (EC), between June7th and November 17th, 2013 in a sugarcane crop grown in Northeastern Brazil. Days were characterized according to cloudiness conditions through the clearness index (Kt). The lambdaE and NEE, set through the EC technique, needed correction due to heat and water vapour transfer, because CO2 and lambdaE raw fluxes tend to overestimate and underestimate the values, respectively. Both lambdaE and NEE followed the daily photosynthetic solar irradiance course, but maximum values were not recorded at the same time. Apparent quantum yield and water use efficiency were higher under partly cloudy skies; both variables can be applied to simulation models in order to improve management practices and increase yield.

Observed and modelled solar radiation components in sugarcane crop grown under tropical conditions

Abstract The net radiation over vegetated surfaces is one of the major input variables in many models of soil evaporation, evapotranspiration as well as leaf wetness duration. In the literature there are relatively few studies on net radiation over sugarcane crop in tropical climates. The main objective of the present study was to assess the solar radiation components measured and modelled for two crop stages of a sugarcane crop in the region of Rio Largo, Alagoas, North-eastern Brazil. The measurements of the radiation components were made with a net radiometer during the dry and rainy seasons and two models were used to estimate net radiation: the Ortega-Farias model and the Monteith and Unsworth model. The highest values of net radiation were observed at the crop development stage, due mainly to the high indices of incoming solar radiation. The daily average albedos of sugarcane at the crop development and mid-season stages were 0.16 and 0.20, respectively. Both models showed a better fit for the crop development stage than for the mid-season stage. When they were inter-compared, Monteith and Unsworth model was more efficient than Ortega-Farias model, despite the dispersion of their simulated radiation components which was similar.