scholarly journals Dependency of Evaporation and Class A Pan Coefficient on Meteorological Parameters

Author(s):  
Antensay Mekoya
2002 ◽  
Vol 59 (3) ◽  
pp. 417-420 ◽  
Author(s):  
Marco Antônio Fonseca Conceição

Estimating reference evapotranspiration (ETo) based on Class A pan evaporation (ECA) is very usual in irrigated areas. For this purpose the ECA values are multiplied by a pan coefficient (Kp) to obtain ETo. Kp values can be estimated in different ways being, however, important to know which method would estimate the best value for a given locality. In the present work estimated values of ETo based on Class A pan evaporation, using Kp values determined by different methods, were compared to Penman-Monteith-FAO (EToPM) values for the northwest region of the São Paulo State, Brazil. The annual average Kp, determined dividing EToPM by ECA, was 0.74. For the rainy months (December to March) the average Kp value was 0.80 and for the dry months (April to November) 0.70. The reference evapotranspiration estimated using Kp determined by the Snyder equation presented the best regression coefficients when compared to EToPM.


Irriga ◽  
2018 ◽  
Vol 21 (1) ◽  
pp. 119 ◽  
Author(s):  
ALAN DELON ANDRADE ◽  
WEZER LISMAR MIRANDA ◽  
LUIZ GONSAGA de CARVALHO ◽  
PAULO HENRIQUE FERNANDES FIGUEIREDO ◽  
THALINE BIGHI SILVEIRA da SILVA

DESEMPENHO DE MÉTODOS DE CÁLCULO DO COEFICIENTE DE TANQUE PARA ESTIMATIVA DA EVAPOTRANSPIRAÇÃO DE REFERÊNCIA ALAN DELON ANDRADE1, WEZER LISMAR MIRANDA2, LUIZ GONSAGA DE CARVALHO3, PAULO HENRIQUE FERNANDES FIGUEIREDO1, THALINE BIGHI SILVEIRA DA SILVA4 1Graduando em Engenharia Agrícola, Departamento de Engenharia, Universidade Federal de Lavras – Lavras, MG. Fone: (35)8834-3582. E-mail: [email protected]; [email protected] Agrícola, Doutorando em Recursos Hídricos em Sistemas Agrícolas, Departamento de Engenharia, Universidade Federal de Lavras – Lavras, MG. E-mail: [email protected] Agrícola, Prof. Doutor, Departamento de Engenharia, Universidade Federal de Lavras – Lavras, MG. E-mail: [email protected] em Engenharia Florestal, Departamento de Ciências Florestais, Universidade Federal de Lavras – Lavras, MG. E-mail: [email protected] 1 RESUMO Há diferentes processos aplicáveis ao adequado manejo da irrigação e dentre esses os que utilizam a estimativa da evapotranspiração de referência (ETo) como parâmetro. Assim, com este trabalho objetivou-se avaliar diferentes métodos de determinação do coeficiente de tanque (Kp) utilizado na estimativa da ETo com base em dados de evaporação do Tanque Classe “A” (TCA). Os dados meteorológicos foram coletados diariamente entre 1/1/2004 e 31/12/2013. A estimativa de ETo padrão foi realizada pelo método de Penman-Monteith-FAO (PM-FAO). Os métodos utilizados para a obtenção do Kp foram: Allen et al. (1998), Cuenca (1989), Snyder (1992), Pereira et al. (1995) e Doorenbos e Pruitt (1977). O desempenho dessas metodologias foi avaliado pela comparação entre a estimativa de ETo obtida pelo método do TCA com os diferentes valores de Kp em relação à ETo estimada pelo método de PM-FAO. Na escala mensal todas as metodologias avaliadas apresentaram um desempenho satisfatório. Para a avaliação em escala diária o melhor desempenho foi da metodologia proposta por Pereira et al. (1995).Palavras-chave: coeficiente de tanque, manejo de irrigação, agrometeorologia, Penman-Monteith-FAO ANDRADE, A. D.; MIRANDA, W. L.; CARVALHO, L. G. DE; FIGUEIREDO, P. H. F.; SILVA, T. B. S. DAPERFORMANCE OF METHODS FOR CALCULATING THE PAN COEFFICIENT FOR ESTIMATING REFERENCE EVAPOTRANSPIRATION 2 ABSTRACT There are different processes applicable to the suitable irrigation management, and among them there are those which use the reference evapotranspiration (ETo) estimation as a parameter. This research aimed to evaluate different methods for determining pan coefficient (Kp), used to estimate ETo, based on evaporation data of Class "A" pan (TCA). Daily meteorological data were collected at Principal Climatological Station, which is located at the Federal University of Lavras. The period of time analyzed was from 01/01/2004 to 12/31/2013. The standard ETo estimation was performed using Penman-Monteith-FAO (FAO-PM) method. The methods utilized to obtain Kp were: Allen et al. (1998), Cuenca (1989), Snyder (1992), Pereira et al. (1995), and Doorenbos & Pruitt (1977). The performance of these methods was evaluated by comparing the estimated ETo obtained by the PM-FAO method with ETo estimated by the TCA method with different Kp values. In the monthly scale all tested methodologies showed satisfactory performance. For the evaluation in daily scale, the best performance was the methodology proposed by Pereira et al. (1995).Keywords: pan coefficient, irrigation management, agrometeorology, Penman-Monteith-FAO


1995 ◽  
Vol 76 (2) ◽  
pp. 75-82 ◽  
Author(s):  
Antonio Roberto Pereira ◽  
Nilson A. Villa Nova ◽  
Anderson Soares Pereira ◽  
Valter Barbieri
Keyword(s):  
Class A ◽  

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 531b-531
Author(s):  
Christopher L. Browne ◽  
Thomas W. Cook

Knowledge of the current irrigation requirement of well-watered grass provides the basis for efficient scheduling of turf and landscape irrigation. A portable, miniature pan evaporimeter has been developed to conveniently provide this information for localized micro-climates. The underlying equation for the instrument is: IRnet = (Kpan • Epan - Kpan • R) where IRnet is the net irrigation requirement of healthy, non-stressed grass; Kpan is the pan coefficient for the instrument; Epan is accumulative pan evaporation; Kpan • Epan is “reference evapotranspiration”; and Kpan • R is a measure of effective rainfall received. This equation was established using turfgrass sites located throughout the Pacific Northwest over a 3-year period. The sites were in proximity to U.S. Class “A” pan evaporimeters, and were automatically irrigated using moisture sensors. Tests of the miniature evaporimeter against automated meteorological stations have determined the factors that influence its pan coefficient, and therefore its ultimate design.


Irriga ◽  
2001 ◽  
Vol 6 (3) ◽  
pp. 120-127
Author(s):  
Reginaldo Ferreira Santos ◽  
Antonio Evaldo Klar

DISTRIBUIÇÃO DA EVAPORAÇÃO EM ESTUFA PLÁSTICA NA PRIMAVERA  Reginaldo Ferreira SantosCentro de Ciências Exatas e Tecnológica da UNIOESTE- CP 711CEP 858114-110, Cascavel, PR - Fone: 0XX45 2203155.  E-mail: [email protected] Evaldo KlarDepartamento de Engenharia Rural - Faculdade de Ciências Agronômica- UNESP - CEP 18603-970 - Botucatu, SP. CP: 237.  E-mail:  [email protected]  1  RESUMO O presente trabalho teve como objetivo avaliar a distribuição da evaporação no interior de uma estufa plástica, com uma cultura de pimentão, através da variabilidade espacial e comparar a evaporação dos microevaporímetros com os valores do Tanque classe "A". O experimento foi conduzido no Campus da Universidade Estadual Paulista - FCA/UNESP, no período de primavera, em estufa plástica de polietileno de baixa densidade (PEBD). Na distribuição da evaporação em estufa com orientação norte/sul, verificou-se que as maiores evaporações ocorreram nas extremidades sul e norte tendente ao lado oeste. Já as menores evaporações localizaram-se no centro. No período de primavera, a evaporação média nos microevaporímetros superestimou em 55% a evaporação determinada no Tanque classe "A". UNITERMOS: evaporação, geoestatística, estufa.  SANTOS, R.F, KLAR, A.E.  EVAPORATION DISTRIBUTION INSIDE A PLASTIC TUNNEL IN THE SPRING SEASON  2  ABSTRACT                 The main aim of this study was to verify the evaporation distribution inside a plastic tunnel, with pepper crop, oriented to north/south, through spatial variability and to compare Class A Pan evaporation to punctual evaporations of 40 equidistant microevaporimeters placed from 50cm the soil. The study was carried out at the College of Agricultural Sciences/UNESP, Botucatu – SP in the spring season.  The highest evaporation occurred next to north and to south sides of the tunnel, with tendency to west. Consequently, the lowest evaporations occurred at the center area. The microevaporimeter evaporations were 55% higher than those obtained from Class A Pan. KEYWORDS: evaporation distribution, microevaporimeter.


2021 ◽  
Vol 10 (8) ◽  
pp. 522
Author(s):  
Stavroula Dimitriadou ◽  
Konstantinos G. Nikolakopoulos

Actual evapotranspiration (ETa) has been insufficiently investigated in Greece. This study aimed to estimate annual ETa by empirical methods (Turc, modified Turc, and Coutagne) for the Peloponnese, Greece, a Mediterranean testbed, between 2016–2019, four of the warmest years since the preindustrial era, and compare them to MODIS ET. Furthermore, measurements of annual pan evaporation (Epan) were performed for two Class A pan stations in the Peloponnese with different reliefs and conditions. The empirical methods and statistical formulae (RMSD, MB, and NMB) were developed as models in ArcMap. The outcomes of the Turc method resembled MODIS ET ranges for all years, followed by those of Coutagne. The estimates by the modified Turc method were almost identical to MODIS ET. Therefore, the modified Turc method can be used as an alternative to MODIS ET (and vice versa) for the Peloponnese for 2016–2019. Moreover, the Epan at Patras University station (semiurban, low elevation) exhibited an upward trend resembling the trends of the empirical methods over the study years, whereas the Epan at Ladonas station (higher elevation, lakeside) required investigation on a monthly time scale. Additionally, the gradual decrease of pan-water icing at Ladonas in December (from 20 d in 2016 to 0 d in 2019) could imply an undergoing decrease in snowpack storage retention across the mountains of the Peloponnese.


2014 ◽  
Vol 61 (3) ◽  
pp. 277-288 ◽  
Author(s):  
A Sanchez-Lorenzo ◽  
SM Vicente-Serrano ◽  
M Wild ◽  
J Calbó ◽  
C Azorin-Molina ◽  
...  
Keyword(s):  
Class A ◽  

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