Estimation of Evapotranspiration by Various Net Radiation Estimation Formulae for Non-Irrigated Grass in Brazil

Antonio Ribeiro da Cunha^1*, Edgar Ricardo Schöffel², Clovis Alberto Volpe¹

¹School of Agronomic Sciences, Sao Paulo State University (UNESP), Botucatu, Brazil.
²Eliseu Maciel School of Agronomy, Federal University of Pelotas, Pelotas, Brazil.

DOI: 10.4236/jwarp.2014.615131                

Abstract

The objective of this study was to assess the accuracy of estimating evapotranspiration (ET) using the FAO-56 Penman-Monteith (FAO-56-PM) model, with measured and estimated net radiation (Rn_measured and Rn_estimated, respectively), the latter obtained via five different models. We used meteorological data collected between August 2005 and June 2008, on a daily basis and on a seasonal basis (wet vs. dry seasons). The following data were collected: temperature; relative humidity; global global solar radiation (Rs); wind speed and soil heat flux. The atmospheric pressure was determined by aneroid barograph, and sunshine duration was quantified with a Campbell-Stokes recorder. In addition to the sensor readings (Rn_measured), five different models were used in order to obtain the Rn_estimated. Four of those models consider the effects of cloud cover: the original Brunt model; the FAO-24 model for wet climates; the FAO-24 model for dry climates, and the FAO-56 model. The fifth was a linear regression model based on Rs. In estimating the daily ET0 with the FAO-56-PM model, Rn_measured can be replaced by Rn_estimated, in accordance with the FAO-24 model for dry climates, with a relative error of 2.9%, or with the FAO-56 model, with an error of 4.9%, when Rs is measured, regardless of the season. The Rn_estimated obtained with the fifth model has a relatively high error. The original Brunt model and FAO-24 model for wet climates performed more poorly than did the other models in estimating the Rn and ET0. In overcast conditions, the original Brunt model, the FAO-24 model for wet climates, the FAO-24 model for dry climates, the FAO-56 model and the model of linear regression with Rs as the predictor variable tended to overestimate Rn and ET, those estimates becoming progressively more accurate as the cloud cover diminished.

Keywords

Evapotranspiration, Net Radiation, Solar Radiation, Cloud Cover, Empirical Models

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Allen, R.G., Pereira, L.S., Raes, D. and Smith, M. (1998) Crop Evapotranspiration-Guidelines for Computing Crop Water Requirements. FAO Irrigation and Drainage Paper 56. http://www.fao.org/docrep/X0490E/X0490E00.htm
[2]	Doorenbos, J. and Pruitt, W.O. (1977) Crop Water Requirements. FAO Irrigation and Drainage Paper 24, FAO, Rome, 144 p.
[3]	Batchelor, C.H. (1984) The Accuracy of Evapotranspiration Estimated with the FAO Modified Penman Equation. Irrigation Science, 5, 223-233. http://dx.doi.org/10.1007/BF00258176
[4]	Llasat, M.C. and Snyder, R.L. (1998) Data Error Effects on Net Radiation and Evapotranspiration Estimation. Agricultural and Forest Meteorology, 91, 209-221. http://dx.doi.org/10.1016/S0168-1923(98)00070-7
[5]	Brotzge, J.A. and Crawford, K.C. (2003) Examination of the Surface Energy Budget: A Comparison of Eddy Correlation an Bowen Ratio Measurement Systems. Journal of Hydrometeorology, 4, 160-178. http://dx.doi.org/10.1175/1525-7541(2003)4<160:EOTSEB>2.0.CO;2
[6]	Santiago, A.V., Pereira, A.R., Folegatti, M.V. and Maggiotto, S.R. (2002) Reference Evapotranspiration Measured with a Weighing Lysimeter and Estimated by Penman-Monteith (FAO-56) on a Monthly and Ten-Days Time Scales. Revista Brasileira de Agrometeorologia, 10, 57-66.
[7]	Pereira, A.R., Sentelhas, P.C. and Folegatti, M.V. (2002) Substantiation of the Daily FAO-56 Reference Evapotranspiration with Data from Automatic and Conventional Weather Stations. Revista Brasileira de Agrometeorologia, 10, 251-257.
[8]	Gavilan, P., Berengena, J. and Allen, R.G. (2007) Measuring versus Estimating Net Radiation and Soil Heat Flux: Impact on Penman-Monteith Reference ET Estimates in Semiarid Regions. Agricultural Water Management, 89, 275-286. http://dx.doi.org/10.1016/j.agwat.2007.01.014
[9]	Oliveira, A.D. and Volpe, C.A. (2003) Comparison of Methods for Estimating Reference Evapotranspiration Using Data of Conventional and Automatic Weather Stations. Revista Brasileira de Agrometeorologia, 11, 253-260.
[10]	Carvalho, D.F., Silva, L.D.B., Guerra, J.G.M., Cruz, F.A. and Souza, A.P. (2007) Installation, Calibration and Operation of a Weighing Lysimeter. Agricultural Engineering, 27, 363-372.
[11]	Zanetti, S.S., Sousa, E.F., Carvalho, D.F. and Bernardo, S. (2008) Reference Evapotranspiration Estimate in Rio de Janeiro State Using Artificial Neural Networks. Revista Brasileira de Engenharia Agricola e Ambiental, 12, 174-180. http://dx.doi.org/10.1590/S1415-43662008000200010
[12]	Iziomon, M.G., Mayer, H. and Matzarakis, A. (2000) Empirical Models for Estimating Net Radiative Flux: A Case Study for Three Mid-Latitude Sites with Orographic Variability. Astrophysics and Space Science, 273, 313-330. http://dx.doi.org/10.1023/A:1002787922933
[13]	Linacre, E. (1992) Climate Data and Resources: A Reference and Guide. Routledge, London.
[14]	Snyder, R.L., Duce, P., Spano, D. and Eching, S. (1998) Hourly Estimation of Net Radiation over Grass. Proceedings of the 23rd Conference on Agriculture and Forest Meteorology, Albuquerque, 2-6 November 1998, 139-140.
[15]	Turco, J.E.P., Faria, M.T. and Fernandes, E.J. (2005) Influence of Net Radiation Obtention Method Compared to the Reference Evapotranspiration Estimate Methods. Irriga, 10, 215-228.
[16]	Silva, L.D.B., Folegatti, M.V., Vila Nova, N.A. and Carvalho, D.F. (2007) Relationship of Net Radiation Measurements over Bahia Grass and Guinea Grass with Incoming Global Solar Radiation in Piracicaba, Sao Paulo State, Brazil. Revista Brasileira de Agrometeorologia, 15, 250-256.
[17]	Azevedo, P.V., Leitao, M.M.V.B.R., Sousa, I.F. and Maciel, G.F. (1990) Radiation Balance of Irrigated Crops in the Semiarid Region of Northeastern Brazil. Revista Brasileira de Meteorologia, 5, 403-410.
[18]	Teixeira, A.H.C. (2001) Evaluation of Components of Energy Balance in Banana Crop during the First Year. Revista Brasileira de Engenharia Agricola e Ambiental, 5, 28-32. http://dx.doi.org/10.1590/S1415-43662001000100006
[19]	Pezzopane, J.R.M., Pedro Junior, M.J. and Gallo, P.B. (2005) Solar and Net Radiation in a Coffee Crop Grown Unshaded and Shaded by “Prata Ana” Banana Plants. Bragantia, 64, 485-497. http://dx.doi.org/10.1590/S0006-87052005000300020
[20]	Neves, L.O., Costa, J.M.N., Andrade, V.M., Lola, A.C., Pezzopane, J.R.M. and Pedro Junior, M.J. (2003) Energy Balance on “Niagara Rosada” Vineyard. Bragantia, 62, 155-161. http://dx.doi.org/10.1590/S0006-87052003000100019
[21]	Heldwein, A.B., Maldaner, I.C., Radons, S.Z., Loose, L.H., Lucas, D.D.P. and Hinnah, F.D. (2012) Estimation of Net Radiation in Sunflower as a Function of Global Solar Radiation. Revista Brasileira de Engenharia Agricola e Ambiental, 16, 194-199. http://dx.doi.org/10.1590/S1415-43662012000200010
[22]	Azevedo, P.V., Teixeira, A.H.C., Silva, B.B., Soares, J.M. and Saraiva, F.A.M. (1997) Evaluation of the Reflectance and Net Radiation over a European Wine Grape Vineyard. Revista Brasileira de Agrometeorologia, 5, 1-7.
[23]	Pezzopane, J.R.M. and Pedro Junior, M.J. (2003) Energy Balance on “Niagara Rosada” Vineyard. Bragantia, 62, 155-161. http://dx.doi.org/10.1590/S0006-87052003000100019
[24]	CEPAGRI (2012) Centre for Meteorological and Climate Research Applied to Agriculture. Climate of Counties. http://www.cpa.unicamp.br/outras-informacoes/clima_muni_279.html
[25]	UNESP-DCE (2012) Department of Exact Sciences—Agrometeorological Station of the Superior School of Agrarian and Veterinary Sciences. http://www.fcav.unesp.br
[26]	Brunt, D. (1932) Notes in Radiation in the Atmosphere. Quarterly Journal of the Royal Meteorological Society, 58, 389-420. http://dx.doi.org/10.1002/qj.49705824704
[27]	André, R.G.B. and Volpe, C.A. (1988) Estimation of Net Radiation in Jaboticabal (SP). Revista de Geografia, 7, 1-8.
[28]	Escobedo, J.F., Gomes, E.N., Oliveira, A.P. and Soares, J. (2009) Modeling Hourly and Daily Fractions of UV, PAR and NIR to Global Solar Radiation under Various Sky Conditions at Botucatu, Brazil. Applied Energy, 86, 299-309. http://dx.doi.org/10.1016/j.apenergy.2008.04.013
[29]	Willmott, C.J., Ackleson, S.G., Davis, R.E., Feddema, J.J., Klink, K.M., Legates, D.R., O’donnell, J. and Rowe, C.M. (1985) Statistics for the Evaluation and Comparison of Models. Journal of Geophysical Research, 10, 8995-9005. http://dx.doi.org/10.1029/JC090iC05p08995
[30]	Galvao, J.A.C. and Fisch, G. (2000) Radiation Balance in Pasture in the Amazon. Revista Brasileira de Agrometeorologia, 8, 1-10.
[31]	Von Randow, R.C.S. and Alvala, R.C.S. (2006) Estimation of Long-Wave Atmospheric Radiation over Pantanal Sul Mato Grossense during the Dry Seasons of 1999 and 2000. Revista Brasileira de Meteorologia, 21, 398-412.
[32]	Fontana, D.C., Berlato, M.A. and Bergamaschi, H. (1991) Energy Balance in Irrigated and Non-Irrigated Soybeans. Pesquisa Agropecuaria Brasileira, 26, 411-418.
[33]	Cunha, A.R., Volpe, C.A. and Escobedo, J.F. (2008) Estimating Reference Evapotranspiration by Penman-Monteith Method (FAO-56) with Measured Net Radiation for Different Sensors. Agronomia Tropical, 58, 81-84.
[34]	Kipp, Z. (2000) CNR1 Net Radiometer Instruction Manual. Kipp & Zonen, Delft, 42 p.
[35]	Cobos, D.R. and Baker, J.M. (2003) Evaluation and Modification of a Domeless Net Radiometer. Agronomy Journal, 95, 177-183. http://dx.doi.org/10.2134/agronj2003.0177
[36]	Tagliaferre, C., Silva, R.A.J., Rocha, F.A., Santos, L.C. and Silva, C.S. (2010) Comparative Study of Different Methodologies for Determining Reference Evapotranspiration in Eunapolis-BA. Revista Caatinga, 23, 103-111.
[37]	Oliveira, L.M.M., Montenegro, S.M.G.L., Azevedo, J.R.G. and Santos, F.X. (2008) Reference Evapotranspiration in the Experimental Basin of Gameleira, PE, Using Lysimeter and Indirect Methods. Revista Brasileira de Ciencias Agrarias, 3, 58-67.
[38]	Alencar, L.P., Delgado, R.C., Almeida, T.S. and Wanderley, H.S. (2011) Comparison of Different Methods for Daily Estimating Reference Evapotranspiration for the Region of Uberaba. Revista Brasileira de Ciencias Agrarias, 6, 337-343.
[39]	Reis, E.F., Braganca, R., Garcia, G.O., Pezzopane, J.E.M. and Tagliaferre, C. (2007) Comparative Study of the Estimate of the Evaporate Transpiration Regarding the Three Locality State of Espirito Santo during the Dry Period. Idesia, 25, 75-84.
[40]	Pereira, D.R., Yanagi, S.N.M., Mello, C.R., Silva, A.M. and Silva, L.A. (2009) Performance of the Reference Evapotranspiration Estimating Methods for the Mantiqueira Range Region, MG, Brazil. Ciencia Rural, 39, 2488-2493. http://dx.doi.org/10.1590/S0103-84782009000900016
[41]	Souza, A.P., Carvalho, D.F., Silva, L.B.D., Almeida, F.T. and Rocha, H.S. (2011) Reference Evapotranspiration Estimates in Different Cloudiness Conditions. Pesquisa Agropecuaria Brasileira, 46, 219-228.
[42]	Pilau, F.G., Battisti, R., Somavilla, L. and Righi, E.Z. (2012) Performance of Methods for Estimating Reference Evapotranspiration in the Municipalities of Frederico Westphalen and Palmeira das Missoes, State of Rio Grande do Sul, Brazil. Ciencia Rural, 42, 283-290.
[43]	Oliveira, R.Z., Oliveira, L.F.C., Wehr, T.R., Borges, L.B. and Bonono, R. (2005) Comparative Study of Estimative Models for Reference Evapotranspiration for the Region of Goiania, GO. Journal of Biosciences, 21, 19-27.
[44]	Oliveira, L.F.C., Carvalho, D.F., Romao, P.A. and Cortes, F.C. (2001) Comparative Study of Estimative Models for Reference Evapotranspiration for Selected Sites in Goias and Distrito Federal. Pesquisa Agropecuaria Tropical, 31, 121-126.
[45]	Oliveira, G.M. and Leitao, M.M.V.B.R. (2000) Evapotranspiration Estimates and Consequences Due to Errors in the Determination of the Net Radiation and Advective Effects. Revista Brasileira de Engenharia Agricola e Ambiental, 4, 343-347. http://dx.doi.org/10.1590/S1415-43662000000300007
[46]	Fietz, C.R. and Fisch, G.F. (2009) Evaluation of Models to Estimate Net Radiation and the Priestley-Taylor Method in the Region of Dourados, MS, Brazil. Revista Brasileira de Engenharia Agricola e Ambiental, 13, 449-453.
[47]	Nielsen, L.B., Prahm, L.P., Berkowicz, R. and Conradsen, K. (1981) Net Incoming Radiation Estimated from Hourly Global Radiation and/or Cloud Observations. Journal of Climatology, 1, 255-272. http://dx.doi.org/10.1002/joc.3370010305