scholarly journals CALIBRATION OF THE HARGREAVES-SAMANI EQUATION FOR SPECIFIC PERIODS OF THE YEAR IN THE MUNICIPALITY OF JAÍBA-MG, BRAZIL

2017 ◽  
Vol 25 (5) ◽  
pp. 445-453
Author(s):  
Anunciene Barbosa Duarte ◽  
Lucas Borges Ferreira ◽  
Edson Fagne Dos Santos
Keyword(s):  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Climatic Conditions ◽  
Crop Water ◽  
Climatic Effects ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Crop Water Demand ◽  
Limited Application ◽  
Monteith Equation

Reference evapotranspiration (ET0) explains the climatic effects on crop water demand. The Food and Agriculture Organization (FAO) recommends the Penman Monteith equation as a standard method for estimating ET0. However, because this equation requires a large amount of meteorological data, it has limited application. An alternative is the Hargreaves-Samani (HS) equation, which only requires air temperature data, and can be calibrated to specifc locations and periods. The present study aimed to calibrate the empirical parameters (coeffcients and exponent) of the HS equation for specifc periods of the year, as well as evaluate the behavior and calibration of this equation throughout the year in the municipality of Jaíba-MG, Brazil. The daily meteorological data from 1996 to 2011 were gathered from a weather station located in the municipality of Jaíba-MG. A general calibration was performed per semester, per season, per month, and during periods with similar climatic conditions. The calibration of the HS equation, in all of the forms studied, promoted better ET0estimations. The calibrations for specifc periods of the year only promoted slight increases in performance in relation to the general calibration, therefore they, in general, presented equal performance to each other.

scholarly journals Optimal Selection of Empirical Reference Evapotranspiration Method in 36 Different Agricultural Zones of China

Agronomy ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 31
Author(s):  
Yong Yang ◽  
Rensheng Chen ◽  
Chuntan Han ◽  
Zhangwen Liu ◽  
Xiqiang Wang
Keyword(s):  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Aridity Index ◽  
Empirical Method ◽  
Climatic Conditions ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Temperature Method ◽  
The Relationship ◽  
Selection Of

The Food and Agriculture Organization has proposed the current version of the Penman–Monteith method (FAO56-PM) as the standard for calculating reference evapotranspiration (ET0); however, high meteorological data requirements limit its application in many areas. There is thus an urgent need to identify the best alternative empirical method to accurately calculate ET0 in regions that lack sufficient meteorological data. In this study, three temperature-based methods and five radiation-based methods were evaluated using ET0 values generated using the FAO56-PM method in 36 agricultural zones in China based on meteorological data from 823 stations, measured between 2011 and 2020. The results showed that the optimal temperature-based method and radiation-based method differed for different agricultural zones, and no one temperature method or radiation method could be suitable for all agricultural zones. The eight empirical methods were regionally calibrated to improve the ET0 calculation accuracy in the different zones. The relationship between the optimal methods and climatic conditions showed that the most reliable empirical method could be selected according to the local annual mean temperature and aridity index. The results provide useful guidance for the selection of reliable empirical ET0 methods in agricultural zones outside China.

scholarly journals Comparison of meteorological data, related to reference evapotranspiration, from conventional and automatic stations in the Sertão and Agreste regions of Pernambuco, Brazil

DYNA ◽  
2021 ◽  
Vol 88 (216) ◽  
pp. 176-183
Author(s):  
Iug Lopes ◽  
Miguel Julio Machado Guimarães ◽  
Juliana Maria Medrado de Melo ◽  
Ceres Duarte Guedes Cabral de Almeida ◽  
Breno Lopes ◽  
...  
Keyword(s):  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Global Solar Radiation ◽  
Concordance Index ◽  
Good Relationship ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Daily Scale ◽  
Weather Stations ◽  
Meteorological Elements

The objective was to perform a comparative study of the meteorological elements data that most cause changes in the reference Evapotranspiration (ETo, mm) and its own value, of automatic weather stations AWS and conventional weather stations CWS of the Sertão and Agreste regions of Pernambuco State. The ETo was calculated on a daily scale using the standard method proposed by the Food and Agriculture Organization (FAO), Penman-Monteith (FAO-56). The ETo information obtained from AWS data can be used to update the weather database of stations, since there is a good relationship between the ETo data obtained from CWS and AWS, statistically determined by the Willmott's concordance index (d > 0.7). The observed variations in the weather elements: air temperature, relative humidity, wind speed, and global solar radiation have not caused significant changes in the ETo calculation.

scholarly journals Combination of satellite imagery with meteorological data for estimating reference evapotranspiration

2018 ◽  
pp. 75
Author(s):  
D. Montero ◽  
F. Echeverry ◽  
F. Hernández
Keyword(s):  
Land Surface Temperature ◽  
Land Surface ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Meteorological Station ◽  
Significant Relation ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Digital Elevation ◽  
Weather Stations

<p>The Food and Agriculture Organization of the United Nations (FAO) in its publication No. 56 of the Irrigation and Drainage Series presents the FAO Penman-Monteith procedure for the estimation of reference evapotranspiration from meteorological data, however, its calculation may be complicated in areas where there are no weather stations. This paper presents an evaluation of the potential of the Land Surface Temperature and Digital Elevation Models products derived from the MODIS and ASTER sensors, both on board the Terra EOS AM-1 satellite, for the estimation of reference evapotranspiration using the Penman-Monteith FAO-56, Hargreaves, Thornthwaite and Blaney-Criddle models. The four models were compared with the method proposed by FAO calculated with the observed data of a ground based meteorological station, finding a significant relation with the models Penman-Monteith FAO-56 and Hargreaves.</p>

scholarly journals Evapotranspiration and crop coefficient for potato in organic farming

2013 ◽  
Vol 33 (1) ◽  
pp. 201-211 ◽  
Author(s):  
Daniel F. de Carvalho ◽  
Dione G. da Silva ◽  
Hermes S. da Rocha ◽  
Wilk S. de Almeida ◽  
Eraldo da S. Sousa
Keyword(s):  
Water Consumption ◽  
Solanum Tuberosum L ◽  
Meteorological Data ◽  
Crop Coefficient ◽  
Climatic Conditions ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Historical Series ◽  
The One ◽  
Crop Coefficients

The aim of this study was to quantify the water consumption and the crop coefficients (Kc) for the potato (Solanum tuberosum L.), in Seropédica, Rio de Janeiro (RJ), Brazil, under organic management, and to simulate the crop evapotranspiration (ETc) using the Kc obtained in the field and the ones recommended by the Food and Agriculture Organization (FAO). The water consumption was obtained through soil water balance, using TDR probes installed at 0.15m and 0.30m deep. At the different stages of development, the Kc was determined by the ratio of ETc and reference evapotranspiration, obtained by Penman-Monteith FAO 56. The crop coefficients obtained were 0.35, 0.45, 1.29 and 0.63. The accumulated ETc obtained in the field was 109.6 mm, while the ETc accumulated from FAO's Kc were 142.2 and 138mm, respectively, considering the classical values and the values adjusted to the local climatic conditions. The simulation of water consumption based on meteorological data of historical series from 1961 to 2007 provided higher value of ETc when compared with the one obtained in the field. From the meteorological data of historical series, it was observed that the use of Kc recommended by FAO may overestimate the amount of irrigation water by 9%, over the same growing season.

scholarly journals Performance evaluation of artificial neural networks in estimating reference evapotranspiration with minimal meteorological data

2013 ◽  
Vol 13 (1) ◽  
pp. 18-27
Keyword(s):  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Learning Rule ◽  
Food And Agriculture ◽  
Air Temperatures ◽  
Food And Agriculture Organization ◽  
Cascade Correlation ◽  
Ann Models ◽  
Artificial Neural ◽  
Artificial Neural Network Ann

Detailed meteorological data required for the equation of FAO-56 Penman-Monteith (P-M) method that was adopted by Food and Agriculture Organization (FAO) as a standard method in estimating reference evapotranspiration (ETo) are not often available, especially in developing countries. The Hargreaves equation (HG) has been successfully used in some locations to estimate ETo where sufficient data were not available to use the P-M method. This paper investigates the potential of two Artificial Neural Network (ANN) architectures, the multilayer perceptron architecture, in which a backpropagation algorithm (BPANN) is used, and the cascade correlation architecture (CCANN), in which Kalman’s learning rule is embedded in modeling the daily ETo with minimal meteorological data. An overview of the features of ANNs and traditional methods such as P-M and HG is presented, and the advantages and limitations of each method are discussed. Daily meteorological data from three automatic weather stations located in Greece were used to optimize and test the different models. The exponent value of the HG equation was locally optimized, and an adjusted HGadj equation was used. The comparisons were based on error statistical techniques using P-M daily ETo values as reference. According to the results obtained, it was found that taking into account only the mean, maximum and minimum air temperatures, the selected ANN models markedly improved the daily ETo estimates and provided unbiased predictions and systematically better accuracy compared with the HGadj equation. The results also show that the CCANN model performed better than the BPANN model at all stations.

Empirical Equations to Estimate Evapotranspiration in Mosul City

2020 ◽  
Vol 27 (4) ◽  
pp. 98-102
Author(s):  
Haqqi Yasin ◽  
Luma Abdullah
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Air Temperature ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Daily Data ◽  
Daily Sunshine ◽  
Measured Wind Speed

Average daily data of solar radiation, relative humidity, wind speed and air temperature from 1980 to 2008 are used to estimate the daily reference evapotranspiration in the Mosul City, North of Iraq. ETo calculator software with the Penman Monteith method standardized by the Food and Agriculture Organization is used for calculations. Further, a nonlinear regression approach using SPSS Statistics is utilized to drive the daily reference evapotranspiration relationships in which ETo is function to one or more of the average daily air temperature, actual daily sunshine duration, measured wind speed at 2m height and relative humidity

FRUIT AND BERRIES WORLD PRODUCTION AND INTERNATIONAL TRADE

2020 ◽  
Vol 10 (8) ◽  
pp. 1445-1464
Author(s):  
R.R. Mukhametzyanov ◽  
◽  
E.V. Britik ◽  
Keyword(s):  
International Trade ◽  
Large Scale ◽  
Import Substitution ◽  
World Market ◽  
Climatic Conditions ◽  
Global Rating ◽  
Production Volume ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
The World

Horticulture is an important branch of agriculture with particular importance in some countries of the world. The production of fruits, berries and nuts is an important part of forming a high-grade food supply for the population in many countries, including the developing ones. Basing on the statistical data from the Food and Agriculture Organization of the United Nations (UN), the authors examined the change in the production volume of these products in the world as a whole for 1961-2018, as well as for the period 1992-2018 in some countries - twenty largest producers in 2018; and a number of trends were identified. In particular, it was noted that in 2018 the global gross harvest of fruits and berries increased by 4.34 times compared to 1961, while that of nuts - by 7.04 times. A deeper analysis in the context of states, which are the main producers of fruits, berries and nuts, carried out for 1922-2018, indicates that there is a change in the positions of these countries in the corresponding world ranking. The quantitative and qualitative changes we observe inevitably have a significant impact both on the volume of the world market in terms of production, and, consequently, the supply of fruit and berry products, and on the parameters of international trade in fruits, berries and nuts. Due to the fact that the Russian Federation is not among the countries - largest producers of fruit and berry products (in 2018 it was the 31st in the global rating for fruits and berries, and the 52nd for nuts), it occupies a very significant position in the world on its imports, especially on some of them. In connection with the policy of import substitution, deployed in response to sanctions from a number of Western states, some positive changes are also observed in the Russian gardening industry. However, imports in the resources of fruits and berries still amounted to 53.6% in 2018. Naturally, many types of fruit and berry products are economically inexpedient to cultivate on an industrial scale in the natural and climatic conditions of our country, but it is necessary to carry out scientifically grounded and systematic work to increase the production of relatively traditional for Russia fruit and berry plants in the large-scale commodity sector.

scholarly journals Calibration of reference evapotranspiration models in Pará

2019 ◽  
Vol 42 ◽  
pp. e42475
Author(s):  
Vivian Dielly da Silva Farias ◽  
Deborah Luciany Pires Costa ◽  
Joao Vitor de Novoa Pinto ◽  
Paulo Jorge Oliveira Ponte de Souza ◽  
Everaldo Barreiro de Souza ◽  
...  
Keyword(s):  
Water Management ◽  
Linear Regression ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Climatic Conditions ◽  
Estimation Methods ◽  
Correction Factors ◽  
Regression Methods ◽  
Dry Seasons ◽  
Statistical Criteria

The use of empirical agrometeorological models that can be adjusted to the climatic conditions of different regions has become increasingly necessary to improve water management in grain-producing municipalities. The aim of this work is to examine the correlation between various reference evapotranspiration (ETo) estimation methods and the standard FAO 56 Penman-Monteith method, as well as to determine correction factors, when necessary, for crop-producing municipalities in the northeast of Pará, during both the rainy and dry seasons. We compared simpler methods of ETo estimation to the FAO 56 Penman-Monteith method. For this purpose, meteorological data from Tracuateua, Bragança, Capitão Poço and Castanhal, provided by the National Institute of Meteorology (INMET), were used. The calibration of equations was performed through linear regression. The accuracy of different estimation methods was examined. The Turc, FAO 24 Blaney-Criddle and regression methods presented the best results for all statistical criteria; the Priestley-Taylor, Makkink and FAO 24 Radiation methods presented excellent results after calibration. The methods of Camargo and Hargreaves-Samani produced the worst results for all the criteria.

International Wheat Council

1961 ◽  
Vol 15 (2) ◽  
pp. 339-340
Keyword(s):  
World War Ii ◽  
The United States ◽  
Climatic Conditions ◽  
Annual Review ◽  
Producer Price ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Price Supports ◽  
The Press ◽  
The World

The International Wheat Council held its 31st session in London from November 7 to 19, 1960, for the purpose of reviewing the world wheat situation in accordance with article 21 of the 1959 International Wheat Agreement. The meeting was attended by representatives of 29 member countries and by observers from the UN Food and Agriculture Organization (FAO) and the European Economic Community. According to the press, the results of the second annual review, published on December 12, 1960, revealed that although climatic conditions had created unusually favorable preconditions for an expansion of the world wheat trade during 1960–61, the world surplus at the end of the season was expected to be larger than ever. The press reported that the cause of the wheat surplus problem was government intervention in production, pricing, and trading. Government measures introduced during and shortly after World War II to meet supply deficiencies in a war-disrupted world had been allowed to continue in effect, although the years since the war had seen growing surpluses. According to reports, there had been few changes in national policies affecting producer price supports in 1960; among 25 cases classified by the Council, supports had been reduced in only two instances, while in six instances they had been raised and in seventeen they had remained unchanged. In the four main wheat exporting countries—the United States, Canada, Argentina, and Australia—the end-of-season carry-overs as of July 31 were expected to reach an unprecedented total of 60.4 million metric tons, 37.3 million metric tons over the normal stock surplus. The ultimate solution of wheat surplus problems, concluded the press, depended on a growing adjustment of national wheat policies to international realities.

Attributing the Changes in Reference Evapotranspiration in Southwestern China Using a New Separation Method

2017 ◽  
Vol 18 (3) ◽  
pp. 777-798 ◽  
Author(s):  
Shanlei Sun ◽  
Haishan Chen ◽  
Ge Sun ◽  
Weimin Ju ◽  
Guojie Wang ◽  
...  
Keyword(s):  
Reference Evapotranspiration ◽  
Separation Method ◽  
Southwestern China ◽  
Complete Analysis ◽  
Physical Mechanisms ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Monthly Changes ◽  
Meteorological Observations ◽  
New Perspective

Abstract This study investigated monthly and annual reference evapotranspiration changes over southwestern China (SWC) from 1960 to 2012, using the Food and Agriculture Organization of the United Nations’ report 56 (FAO-56) Penman–Monteith equation and routine meteorological observations at 269 weather sites. During 1960–2012, the monthly and annual decreased at most sites. Moreover, the SWC regional average trend in annual was significantly negative (p &lt; 0.05); this trend was the same in most months. A new separation method using several numerical experiments was proposed to quantify each driving factor’s contribution to changes and exhibited higher accuracy based on several validation criteria, after which an attribution analysis was performed. Across SWC, the declining annual was mainly due to decreased net radiation (RN). Spatially, the annual changes at most sites in eastern SWC (excluding southeastern West Guangxi) were generally due to RN, whereas wind speed (WND) or vapor pressure deficit (VPD) was the determinant at other sites. Nevertheless, the determinants differed among 12 months. For the whole SWC, increased VPD in February and decreased WND in April, May, and October were the determinant of decreased ; however, decreased RN was the determinant in other months. Overall, the determinant of the monthly changes exhibited a complex spatial pattern. A complete analysis of changes and the related physical mechanisms in SWC is necessary to better understand hydroclimatological extremes (e.g., droughts) and to develop appropriate strategies to sustain regional development (e.g., water resources and agriculture). Importantly, this separation method provides new perspective for quantitative attribution analyses and thus may be implemented in various scientific fields (e.g., climatology and hydrology).

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