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Doctoral Thesis
DOI
10.11606/T.11.2009.tde-04082009-111344
Document
Author
Full name
Greice Ximena Santos Oliveira
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 2009
Supervisor
Committee
Angelocci, Luiz Roberto (President)
Barbieri, Valter
Maniero, Miguel Angelo
Nova, Nilson Augusto Villa
Pereira, Francisco Adriano de Carvalho
Title in Portuguese
Relações entre medidas de evaporação de superfícies de água livre por evaporímetros e estimativas por métodos meteorológicos em duas regiões do Estado de São Paulo
Keywords in Portuguese
Agrometeorologia
Evaporação
Hidrologia
Lagos
Modelos matemáticos
Tanques
Vento.
Abstract in Portuguese
Este trabalho objetivou estabelecer relações entre evaporação de tanques Classe A e de 20 m2, em Piracicaba, SP e testar o desempenho de métodos meteorológicos de estimativa da evaporação de superfícies de água livre nessa localidade e em Jaboticabal, SP. Utilizou-se dados meteorológicos coletados em ambiente de um pequeno lago artificial em Piracicaba para cálculos dos métodos de balanço de energia-razão de Bowen, Penman, Priestley-Taylor e Penman simplificado. Dados meteorológicos observados sobre gramado foram usados para estimativa pelos métodos de Penman, Penman modificado, Dalton adaptado, Linacre e tanque Classe ASnyder. Os métodos foram avaliados utilizando índices de concordância e desempenho a partir de análise de regressão e de desvios por comparação com medidas do evaporímetro de 20 m2. Foram observadas relações lineares significativas entre os valores da evaporação dos tanques Classe A e de 20 m2 em todos os meses do ano em Piracicaba. A razão mensal entre as medidas dos evaporímetros apresentou variação ao longo do ano, com superestimativa pequena (até 3%) de fevereiro a junho e em novembro, e grande (10% a 15%) nos outros meses, em relação aos dados de Oliveira (1971) para a mesma localidade. A maior consistência estatística e representatividade da série de medidas, com 3 repetições de tanque Classe A, indicam que os fatores mensais de relações entre os dois evaporímetros podem substituir os obtidos por Oliveira (1971). Todos os métodos utilizados nos dois ambientes apresentaram boa concordância em termos médios com os observados no tanque de 20 m2, sempre com grande dispersão dos dados, diminuindo com o aumento do número de dias de contabilização da evaporação. O método de balanço de energia apresentou bom desempenho com cálculos realizados em períodos de 24 horas, mostrando desvios acentuados com contabilização no período diurno. O método de Penman mostrou bom desempenho quando utilizado para períodos de 24 horas, com subestimativas médias entre -6,0% e -10,5%, mas com superestimativas de +7,2 e +12,4% no período diurno. Os métodos de Priestley-Taylor (1972) e de Penman simplificado mostraram desvios médios pequenos (+2,7 e +5,7%), sendo considerados de bom desempenho. Para os métodos que usaram observações no posto meteorológico, o do tanque Classe ASnyder mostrou os menores desvios médios em Piracicaba (+3,9% a + 4,6%), mas apresentou maiores superestimativas (+14,0% a +14,4%) em Jaboticabal. Outra discrepância entre localidades foi observada para o método de Penmam modificado, com subestimativas entre 5,5 e 14,1% em Piracicaba, mas desvio de +1,0%, em Jaboticabal. O método original de Penman mostrou desvios similares em ambas localidades (-8,9% a 12,3%), enquanto o de Dalton adaptado apresentou desvios de +2,1% a 8,1%, mas com alta dispersão em todos dias de contabilização. Os métodos de Penman simplificado e o de Priestley-Taylor, no caso do lago, e o tanque Classe ASnyder, no caso do posto meteorológico, foram os que no geral apresentaram resultados mais comparáveis com os do tanque de 20 m2, sendo que par ao último deve-se atentar para o desvio sistemático em Jaboticabal.
Title in English
Relations between measurements of open-water surfaces evaporation by evaporimeters and estimates by meteorological methods in two regions of the State of Sao Paulo, Brazil
Keywords in English
Agrometeorology
Evaporation
Hydrology.
Lake
Mathematical models
Abstract in English
This study aimed to establish relations between evaporation Class A pan and 20 m2 tank, in Piracicaba region, State of Sao Paulo, Brazil and to test the performance of meteorological methods to estimate open-water surfaces evaporation in this same region and also in Jaboticabal, SP. Computation of daily evaporation was performed by using weather data, collected in the environment of a small artificial lake in Piracicaba, and the following methods: energy balance-Bowen ratio, Penman, Priestley-Taylor and Penman simplified. The methods of Penman, Penman adapted, Dalton adapted, Linacre and of Class A pan-Snyder were evaluated by using weather station data in both regions. The results of the methods were compared with the measurements of the 20 m2 tank evaporation, in a daily basis, and also for two, three or for the mean values for all days of measurements in every month, using indexes of agreement and performance from the regression analysis and deviations from the estimated and measured values. The linear relations between evaporation measured by the two evaporimeters were significative for all months in Piracicaba. The ratio of the two measurements showed variation throughout the year, with a small overestimation (about 3%) from February to June and November, and greater (10% to 15%) in the other months, compared to results of Oliveira (1971) for the same region. Due to the statistical consistency and representativeness of the series of 9 years and 3 repetitions of Class A pan, it is indicated that the factors of monthly relations between the two evaporímeters observed in this study can advantageously replace those obtained by Oliveira (1971). All methods used in the two environments showed good agreement, in average basis, with measurements by 20 m2 tank, with large dispersion of data, which decreased with the increase of the time step. The energy balance method showed good performance when the calculations were performed in 24-h periods, but large deviations compared to the tank with data integrated over the daylight period. The Penman method showed good performance when used for periods of 24 h, with an average underestimation between - 6.0 and -10.5% when integrated over the 24-h period, but with overestimation of +7.2 and +12.4% for the daylight period. The methods of Priestley-Taylor (1972) and Penman simplified showed small deviations between +2.7 and + 5.7%, being considered as having good performance compared to the evaporimeter. Among the methods that used weather station data, the class A- Snyder was the one that showed the lowest average deviation in Piracicaba (+3.9 to + 4.6%), but the greatest overestimation (+14.0% to 14.4%) in Jaboticabal. Another discrepancy between locations was observed for the Penman method modified, with underestimation between 5.5% and 14.1% in Piracicaba, but deviation of +1.0% in Jaboticabal. The original Penman method showed similar deviations in the two regions (-8.9% to 12.3%), while Dalton adapted method showed deviations of +2.1% to 8.1%. The methods of Penman simplified and Priestley-Taylor, used in the lake environment, and the Class A pan-Snyder method, with the use of wheater station data, were those that showed most comparable results with the 20 m2 tank evaporation, but in Jaboticabal, it is necessary to take to account the observed systematic mean deviation.
 
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Publishing Date
2009-08-11
 
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