Análises da evapotranspiração de referência e do índice de aridez para o Nordeste do Brasil

O Nordeste do Brasil (NEB) possui elevados valores de Evapotranspiração de Referência (ET0) e déficits de chuvas, que culminam num aspecto de semiaridez predominante. O objetivo neste trabalho foi analisar a ET0 com as respectivas repercussões para o Índice de Aridez (IA) no NEB. De posse dos dados mensais (1980 a 2013) da ET0 e também de precipitação para o cômputo do IA preconizado por Thornthwaite (1948), calculou-se a climatologia e determinou-se as sub-regiões da ET0 por meio da Análise de Cluster. O IA foi analisado para identificar relações com a ET0. Em seguida determinaram-se as periodicidades através da análise de Wavelet, com 5% de significância estatística. Os resultados demonstraram que o NEB apresenta 5 sub-regiões para a ET0 e a Sub-região 3 (S3) obtém os maiores valores médios mensais (174,8 mm, em média) e anuais (2098,0 mm), seguida da S2, S4, S1 e S5 com respectivos valores médios anuais de 1736,9 mm, 1643,5 mm, 1489,3 mm, e 1362,8 mm. Na primavera, o IA é predominantemente maior, sobre o NEB, e a ET0 supera a precipitação. As periodicidades permitiram determinar que a variável dominante para o IA é a precipitação, e que no período seco (periodicidade entre 4 a 8 meses), a ET0 não apresenta correlações altas com o IA

Characterization of Rainfall Patterns in the Semiarid Brazil

The Semiarid Brazil (SAB) is the wettest semiarid region of the world, and its economy is strongly based on family farming, predominantly in non-irrigated conditions. Dryland farming in this region is influenced by climate variability, which increases the risk of crop losses during periods of drought. Thus, the objective of this study is to identify rainfall and number of rainy days patterns in the period from 1979 to 2014, using data provided by the Global Precipitation Climatology Project (GPCP). Cluster analysis was used in order to define homogeneous groups in terms of precipitation and number of rainy days within each month. The statistical technique of discriminant analysis was used to verify the classification of homogeneous groups as defined by the cluster analysis. Four precipitation groups were created in the SAB, namely SAB I, SAB II, SAB III and SAB IV, where SAB I is the wettest one. It comprises the southern and eastern portions of the SAB and has an average annual accumulated rainfall of about 1,000 mm. The SAB IV is the second wettest group and extends throughout the east of Alagoas, Pernambuco, Paraíba and Rio Grande do Norte states, Ceará and western Piauí, with an average annual total of 820 mm. SAB II and SAB III are the driest groups, with 748 and 570 mm respectively. The accuracy of the classification of precipitation groups was 94%. Regarding the number of rainy days, the east and the north of the SAB present the largest number of rainy days, in JFMA, with a total of 310 mm distributed in 81 days. In the western and southern portions of the SAB the same rainfall and number of rainy days behavior patterns were observed. The highest means were registered in NDJ, with a total of 451 mm in 64 days and 55 days, respectively. As for the dry months, July and August registered rainfall means of 8 mm in 11 and 9 days, respectively. The accuracy of the classification of groups by number of rainy days was 95%

Eventos extremos de precipitação nas mesorregiões da Paraíba e suas relações com a TSM dos oceanos tropicais

The aim of this study was to identify trends in extreme precipitation indices on the Paraíba State, and to correlate them with the Sea Surface Temperature (SST) anomalies in the Atlantic and Pacific Oceans. The daily precipitation data for the period 1935-2004, were from 23 rain gauges belonging to Instituto Nacional de Meteorologia (INMET). To calculate the extreme rainfall indexes the RClimdex software was used. Then, the statistical least squares method and the non-parametric Mann-Kendall test were applied to identify trends and their statistical significance. The correlation between the extreme precipitation indices and the SST were then calculated. It was found a higher number of sites with positive trends in the period 1935 to 1969, and the highest correlations were with the Atlantic. The Sertão and Agreste Mesoregions of Paraiba state were well related to SST anomalies in the Atlantic, Pacific and Atlantic Multidecadal Oscillation (AMO), Borborema with the AMO and the Atlantic and the Litoral with AtlanticO objetivo desse estudo foi identificar tendências de índices extremos de precipitação sobre a Paraíba, e correlacioná-los com as anomalias de Temperatura da Superfície do Mar (TSM) dos Oceanos Atlântico e Pacífico. Os dados de precipitação diária, no período de 1935 a 2004, foram oriundos de 23 postos pluviométricos pertencentes ao Instituto Nacional de Meteorologia (INMET). Utilizou-se o programa RClimdex para calcular os índices extremos de precipitação, e aplicou-se o método dos mínimos quadrados e o teste não paramétrico de Mann-Kendall para identificar as tendências e suas respectivas significâncias estatísticas. Em seguida, foram calculadas as correlações entre os índices extremos de precipitação e a TSM. Foi encontrado maior número de localidades com tendências positivas no período de 1935 e 1969, e as maiores correlações foram com o Atlântico. As Mesorregiões do Sertão e Agreste do estado da Paraíba tiveram relação com as anomalias de TSM do Atlântico, Pacifico e Oscilação Multidecadal do Atlântico (OMA), a Borborema com as do Atlântico e OMA e, o Litoral com o Atlântico

Evaluation of water use efficiency in cotton irrigated in the Apodi plateau according to SWAP model.

O algodão foi durante o século XX o principal produto agrícola do Semiárido brasileiro. Porém, no início da década de oitenta a cotonicultura entrou em decadência. Essa decadência se deveu principalmente ao barateamento do produto no mercado interno em conseqüência dos preços subsidiados do mercado internacional. O restabelecimento da cotonicultura é de fundamental importância para o desenvolvimento do Semiárido brasileiro. No entanto, esse restabelecimento está condicionado a adoção de novas tecnologias ao sistema de produção, principalmente relacionados ao uso da água, visto que o cultivo do algodoeiro irrigado minimiza os riscos e maximiza o seu potencial produtivo. Diante desse contexto, esta pesquisa tem como objetivo avaliar a eficiência de uso da água do algodoeiro irrigado em uma área do Semiárido brasileiro. O estudo foi realizado mediante a aplicação do modelo SWAP para simular o efeito de diferentes tratamentos de irrigação baseados no déficit de irrigação (DI), na evapotranspiração (ETc) e na produtividade. A eficiência da irrigação foi avaliada através do indicador Eficiência de Uso da Água (EUAET) com base na evapotranspiração. O SWAP é um modelo de simulação integrada de base física para o transporte de água, calor e de solutos na zona saturada/insaturada baseada na equação de Richard. O crescimento e desenvolvimento da cultura foram simulados através do módulo detalhado baseado no WOFOST. O modelo foi calibrado com dados oriundos de duas campanhas experimentais, nas quais foi determinada a ETc por meio da técnica de razão de Bowen. Foram coletadas ainda medidas do teor de água no solo, índice de área foliar e fitomassa. Foram analisados sete tratamentos de água. Os resultados mostraram que o incremento de água na lâmina de irrigação provocou incrementos na ETc. Por outro lado, a produtividade apresentou incrementos quando submetida a tratamentos baseados no DI e redução de seus valores se a irrigação é abundante. Devido a esse comportamento houve significante relação polinomial quadrática entre a produtividade e a lâmina de irrigação. Por sua vez, a EUAET apresentou comportamento similar à produtividade e também apresentou significante relação quadrática com a irrigação aplicada. O tratamento que apresentou o melhor desempenho foi o T3-75%, cuja lâmina de irrigação corresponde a 75% da irrigação total. O referido tratamento apresentou EUAET igual a 0,54 kg m-3. A faixa de variação da EUAET dos sete tratamentos estudados variou de 0,39 a 0,54 kg m-3.Cotton was in the twentieth century the main agricultural product of the Brazilian Semiarid. However, in the early eighties the cotton industry went into decline. This decline was mainly due to the cheapening of the product in the domestic market at subsidized prices as a result of the international market. The revival of cotton production is crucial for the development of the semiarid lands of Brazil However, this restoration depends on the adoption of new technologies in the production system, mainly related to water use, since the irrigation minimizes risk and maximizes the productive potential of cotton crop. Given this context, this research aims to evaluate the water use efficiency of irrigated cotton crop in semiarid lands of Brazil. The study was conducted by applying the SWAP model to simulate the effect of different irrigation treatments based on deficit irrigation (DI), in the evapotranspiration (ETc) and Yield (Y) crop. The irrigation efficiency was assessed by the Water Use Efficiency (WUEET) performance indicator based on evapotranspiration. The Soil, Water, Atmosphere and Plant (SWAP) model is a physically based, detailed agro-hydrological model that simulates vertical transport of water, solutes and heat in unsaturated/ saturated soils. The crop growth and development was simulated by the detailed module based on WOFOST. The model was calibrated with data from two experimental campaigns, in which the cotton ETc was determined by Bowen ratio technique. Measurements of soil water content, leaf area index and biomass were also collected in such campaigns. Seven water treatments were considered. The results showed that the water increase in irrigation water supply to increases in ETc. On the other hand, showed increases Y when subjected to treatments based on the DI to drop and if irrigation is abundant. Because of this behavior there was a significant quadratic relationship between Y and irrigation water supply. In turn, the WUEET had similar behavior to Y and also showed a significant relationship with the irrigation water supply. The treatment that showed the best performance was the T3-75%, whose irrigation accounts for 75% of the full irrigation. This treatment has WUEET equal to 0.54 kg m-3. The WUEET the seven experimental treatments ranged from 0.39 to 0.54 kg m-3.CNP

Analysis of eviromenmentol parameters in Gilbués - Pi Using Satellite Imagens

ABSTRACT: This paper aims to analyze the desertification process in the Gilbués region, southwestern portion of Piauí state, through remote sensing techniques with a perspective of verify whether there is a relationship of environmental parameters (surface albedo, NDVI, surface temperature, radiation and energy balances, as well as nonevaporative fraction) with the desertification process presented in this study area. We used images from the satellite Landsat 5-TM of August 19, 1994 and August 15, 2010 and applied the SEBAL and S-SEBI algorithms for obtaining environmental parameters analyzed. It was diagnosed cover removal of native vegetation, which may indicate areas undergoing to desertification and/or environmental degradation. Similarly, there was a reduction of surface net radiation, increased soil heat fluxes, reduction of energy used for evaporation and increases in the energy used for heating the soil and air, causing the temperature increase, and a systematic increase of the soil moisture deficit in the studied region

Evapotranspiração real obtida através da relação entre o coeficiente dual de cultura da FAO-56 e o NDVI Real actual evapotranspiration obtained through the relationship between the FAO-56 crop dual coefficient and NDVI

Um requisito fundamental para adoção de manejo da irrigação é a determinação diária da evapotranspiração (ET) das culturas. Em caráter operacional o método do coeficiente de cultura proposto pela Food Agriculture Organization (FAO), através do seu relatório 56 (Irrigation and Drainage Paper), é largamente utilizado na determinação da ET, e tem apresentado precisões que o tornam mundialmente aceito. A ET com base no coeficiente de cultura (Kc), obtido a partir de índices de vegetação, particularmente o NDVI, tem sido calculada em vários estudos e para diversas culturas alcançando muita precisão, quando comparado com observações de campo. Diante do exposto, este trabalho teve por objetivo calcular a ET diária e sazonal da cultura do algodoeiro utilizando o método do Kc dual obtido em função do Índice de Vegetação por Diferença Normalizada - NDVI, obtido a partir de imagens TM - Landsat 5 livre da presença de nuvens. Os resultados revelaram precisões bastante confiáveis, pois foram verificadas diferenças menores que 10%, quando comparados com valores da ET obtidos pela técnica da Bowen, corroborando com o desempenho alcançado pelo método em outras pesquisas realizadas em outras regiões do planeta. Dessa forma, pode-se concluir que o método apresenta bastante confiabilidade e simplicidade.A fundamental requirement for adoption of irrigation management is to determine the crop daily evapotranspiration (ET). On an operational basis the crop coefficient method proposed by the Food and Agriculture Organization (FAO) through its report 56 (Irrigation and Drainage Paper) is widely used in the determination of ET and due to its accurate estimative, it has been globally accepted. The ET-based crop coefficient (Kc) obtained from vegetation indices, particularly the Vegetation Index Normalized Difference (NDVI) has been measured in several studies and various crops showing great accuracy when compared to field observations. The objective of this study was to calculate the daily and seasonal ET of cotton crop using the method of dual Kc obtained as a function of the NDVI obtained from TM - Landsat 5 images clouds free. The obtained results are reliable, because less than 10% differences were found when comparing to the Bowen ratio technique observations, corroborating to the method performance achieved in other experiments conducted in other regions of the Earth. Thus, one can conclude that the method both simple and reliable

Caatinga Albedo Preserved and Replaced by Pasture in Northeast Brazil

The caatinga is considered South America’s largest seasonally dry tropical forest (SDTF) and one of the most vulnerable endemic biomes in relation to climate change. The surface albedo in caatinga is relevant to understanding the role of this biome in the climate of the Northeast region of Brazil. Thus, a comparative analysis was conducted between the albedos of preserved and anthropized caatinga (pasture). Data were collected using CNR4-type net radiometers during the dry and rainy seasons. The mean albedo values were higher in the Pasture both in the dry and rainy season, with values of 0.181 and 0.177, respectively. In the caatinga, the mean albedo values were 0.137 in the dry season and 0.146 in the rainy season. The hourly average values for albedo, taken between 6:30 a.m. and 4 p.m., with intervals of 30 min, were also higher in the pasture. For convenience, this study uses local standard time (LST), which is 3 h behind from coordinated universal time (UTC). The greatest dispersions in the frequencies of the mean hourly albedo values occurred in the early morning and late afternoon. Some of the consequences of this study is the confirmation that there is an increase in albedo in caatinga replaced by pasture and this causes a reduction in the net radiation and also the finding that a region where there is adequate pasture management also enables albedo management and from solar radiation. And that further studies can indicate the impacts on temperature and precipitation, especially in warmer periods during the dry season

Estimativa da necessidade hídrica do algodoeiro irrigado usando imagens de satélite

Remote sensing data in the thermal infrared part of the spectrum provides indirect estimates of water stress for vegetated surfaces that is defined as a function of the ratio between actual and potential evapotranspiration rates. Methods to estimate the actual evapotranspiration (ETr) from satellite images with thermal bands are very useful, because they can provide an accurate estimate for large areas. In this context, in 2008 an experiment was carried out in Apodi, RN, in order to estimate the ETr for irrigated cotton. It was used the Bowen ratio obtained with field data to validate data obtained by satellite images through the SEBAL (Surface Energy Balance Algorithm for Land methodology) algorithm. The cotton was seeded in 3.6 ha with 0.9 m between rows. The crop actual evapotranspiration was estimated using three images from Landsat 5, obtained at the 34DAE, 50DAE and 82DAE. The Bowen ratio and reference evapotranspiration (ET0) were determined using meteorological data and also from equipments installed in the experimental area. After the estimation of ET obtained under field conditions and the estimation of ETr by satellite, results were analyzed to evaluate the comparative error. It was observed that the ETr estimated from the algorithm SEBAL shows similar results to those obtained by Bowen ratio and can be used to assess the water requirement of cotton.Pages: 653-65