scholarly journals Analysis of seven indirect methods for evaluation of reference evapotranspiration under climate conditions of Serbia

2018 ◽  
Vol 63 (1) ◽  
pp. 67-81
Author(s):  
Dzenita Idrizovic ◽  
Gordana Matovic ◽  
Enika Gregoric ◽  
Ruzica Stricevic
Keyword(s):  
Reference Evapotranspiration ◽  
Vegetation Period ◽  
Weather Data ◽  
Special Importance ◽  
Climate Conditions ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Using Data ◽  
Novi Sad ◽  
Taylor Methods

In order to calculate water deficit of agricultural crops, it is necessary to have an insight into the evapotranspiration process. As for evaluation of reference evapotranspiration, the Penman-Monteith (FAO56-PM) method, suggested by The International Commission on Irrigation and Drainage (ICID) and Food and Agriculture Organization of the United Nations (FAO), requires several climate parameters, which are often unavailable. Thus, in this paper, the methods for computing ETo, which use limited weather data, were tested and then compared to FAO56-PM. The selected methods were those most often used as the replacement for FAO56-PM: Hargreaves, adjusted Hargreaves, Copais, Turc, Priestley-Taylor, Makkink and Hamon. ETo was calculated at the daily and average monthly levels, for the 2010-2013 period, using data from the following meteorological stations: Nis, Belgrade, Novi Sad, Loznica, Valjevo, Zlatibor, Cuprija and Kikinda. Special importance was given to the vegetation period during the dry season due to the application of irrigation. The comparison of methods was based on statistical analysis, using parameters: MXE, MAE, RMSD, ARMSD, WRMSD, b and R2. The highest rate of matching FAO-PM at the average monthly level, as well as during the 2012 growing season, was shown by Copais, Turc and Priestley-Taylor methods, thus these methods may be recommended as the replacement for FAOPM under climate conditions of Serbia. In case only temperature data are available, the results of this research justify the use of the adjusted Hargreaves equation to calculate ETo for the vegetation period.

scholarly journals Investigating Time-Scale Effects on Reference Evapotranspiration from Epan Data in North China

2010 ◽  
Vol 49 (5) ◽  
pp. 867-878 ◽  
Author(s):  
Yi Li ◽  
Robert Horton ◽  
Tusheng Ren ◽  
Chunyan Chen
Keyword(s):  
Time Scales ◽  
North China ◽  
Reference Evapotranspiration ◽  
Scale Effects ◽  
Estimation Method ◽  
Soil Heat Flux ◽  
Weather Data ◽  
Prediction Errors ◽  
Food And Agriculture ◽  
Food And Agriculture Organization

Abstract Reference evapotranspiration (ETo) and pan evaporation (Epan) are key parameters in hydrological and meteorological studies. The authors’ objectives were to evaluate the ratio of ETo to Epan (kp) at daily and monthly scales and to predict average ETo in the following years using calibrated kp and observed Epan at the two time scales. Using 50 yr of data obtained at six typical sites in north China, daily and monthly ETo were calculated using the Food and Agriculture Organization estimation method (FAO-56) Penman–Monteith equation, and kp values were determined at the two time scales. Values of kp varied from 0.457 to 0.589 daily and from 0.392 to 0.528 monthly for the six sites. Both daily and monthly kp could be fitted as multilinear functions of longitude, latitude, elevation, and relative humidity. Relatively accurate predictions of daily mean ETo for the subsequent years following the calibration years at all six sites were obtained when the year number L used for calibrating daily mean kp was sufficient (>38). In cases when large deviations occurred between average kp for the L calibration years and the actual kp of the following (L + 1)th year, relatively large prediction errors resulted. For the monthly scale, soil heat flux G fluctuated periodically. When variations of G were included, the calculated monthly ETo values were smaller than the monthly ETo cumulated from daily ETo. Thus, monthly kp values were smaller than daily kp values. Predictions of monthly ETo in 2001 for the six sites were relatively accurate with relative errors ranging from −11.9% to 12.1%. In conclusion, this method is simple and accurate with a small demand for weather data.

scholarly journals Minimum weather data requirements for estimating reference evapotranspiration

2011 ◽  
Vol 9 (2) ◽  
pp. 335-345 ◽  
Author(s):  
Slavisa Trajkovic ◽  
Vladimir Stojnic ◽  
Milan Gocic
Keyword(s):  
Reference Evapotranspiration ◽  
Data Availability ◽  
Weather Data ◽  
Data Sets ◽  
Southeast Europe ◽  
Humid Climate ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Data Requirements ◽  
Maximum Air Temperature

The International Commission for Irrigation and Drainage (ICID) and Food and Agriculture Organization of the United Nations (FAO) have proposed using the Penman-Monteith method as the standard method for estimating reference evapotranspiration (ET0), and for evaluating other methods. The FAO-56 Penman-Monteith (FAO-56 PM) method requires the numerous weather data that are not available in the most of the stations. The objectives of this study were: first, to estimate errors that can arise if some weather data are not available and have to be estimated; second, to compare the FAO-56 PM ET0 values computed under various levels of data availability; and third, to determine minimum weather data requirements for estimating ET0 without decreasing the acceptable accuracy. For this study, full weather data sets were collected from six humid weather stations from Serbia (Southeast Europe).The main conclusion is that the minimum and maximum air temperature and "local default" value of wind speed are the minimum data requirements necessary to apply the FAO-56 PM method in humid climate.

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

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.

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 < 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).

scholarly journals Prediction of Biome-Specific Potential Evapotranspiration in Mongolia under a Scarcity of Weather Data

Water ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 2470
Author(s):  
Khulan Batsukh ◽  
Vitaly A. Zlotnik ◽  
Andrew Suyker ◽  
Paolo Nasta
Keyword(s):  
Potential Evapotranspiration ◽  
Aridity Index ◽  
Crop Coefficient ◽  
Weather Data ◽  
Gobi Desert ◽  
Area Index ◽  
Food And Agriculture ◽  
Food And Agriculture Organization ◽  
Practical Guidelines ◽  
Specific Potential

We propose practical guidelines to predict biome-specific potential evapotranspiration (ETp) from the knowledge of grass-reference evapotranspiration (ET0) and a crop coefficient (Kc) in Mongolia. A paucity of land-based weather data hampers use of the Penman–Monteith equation (FAO-56 PM) based on the Food and Agriculture Organization (FAO) guidelines to predict daily ET0. We found that the application of the Hargreaves equation provides ET0 estimates very similar to those from the FAO-56 PM approach. The Kc value is tabulated only for crops in the FAO-56 guidelines but is unavailable for steppe grasslands. Therefore, we proposed a new crop coefficient, Kc adj defined by (a) net solar radiation in the Gobi Desert (Kc adjD) or (b) leaf area index in the steppe region (Kc adjS) in Mongolia. The mean annual ETp obtained using our approach was compared to that obtained by FAO-56 guidelines for forages (not steppe) based on tabulated Kc values in 41 locations in Mongolia. We found the differences are acceptable (RMSE of 0.40 mm d−1) in northern Mongolia under high vegetation cover but rather high (RMSE of 1.69 and 2.65 mm d−1) in central and southern Mongolia. The FAO aridity index (AI) is empirically related to the ETp/ET0 ratio. Approximately 80% and 54% reduction of ET0 was reported in the Gobi Desert and in the steppe locations, respectively. Our proposed Kc adj can be further improved by considering local weather data and plant phenological characteristics.

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>

Evaluation of the FAO Penman–Montheith, Priestley–Taylor and Hargreaves models for estimating reference evapotranspiration in southern Malawi

2012 ◽  
Vol 44 (4) ◽  
pp. 706-722 ◽  
Author(s):  
Cosmo Ngongondo ◽  
Chong-Yu Xu ◽  
Lena M. Tallaksen ◽  
Berhanu Alemaw
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Vapour Pressure ◽  
Reference Evapotranspiration ◽  
Climate Variables ◽  
Limited Data ◽  
Full Data ◽  
Data Intensive ◽  
Food And Agriculture ◽  
Food And Agriculture Organization

This study evaluated the performance of the Food and Agriculture Organization (FAO) Penman–Monteith (PM) reference evapotranspiration (ET0) method for various limited data scenarios in southern Malawi. The study further evaluated the full data PM method against the radiation-based Priestley–Taylor (PT) and the temperature-based Hargreaves (HAG) methods, which are less data-intensive approaches commonly used to estimate ET0 in data-scarce situations. A comprehensive daily climate dataset observed at the Nchalo Sugar Estate in southern Malawi for the period 1971–2007 was the basis of the study. The results suggested that lack of data on wind speed and actual vapour pressure did not significantly affect the PM ET0 estimates. However, the estimation of radiation using various combinations of observed wind speed and relative humidity all resulted in significant deviations from the PM ET0. Further, the HAG and PT methods significantly underestimated the PM. However, the PM method computed with estimated climate variables instead of observed climate variables still outperformed both the PT and HAG methods if their original parameters and estimated radiation were used. Thus, new monthly parameters for the PT and the HAG methods are proposed for more accurate daily ET0 estimates.

scholarly journals Comparison of methods for estimation of reference evapotranspiration in North-Central Plateau zone of Odisha

2018 ◽  
Author(s):  
Rajashree Khatua ◽  
S. Pasupalak
Keyword(s):  
Water Management ◽  
Reference Evapotranspiration ◽  
Vital Role ◽  
Estimation Methods ◽  
Weather Data ◽  
Comparison Of Methods ◽  
Central Plateau ◽  
North Central ◽  
The North ◽  
Taylor Methods

Estimation of Evapotranspiration is vital role for proper water management and efficient farming activities. A decision support system (DSS_ET) was developed which supports 22 ET0 estimation methods with varied options for calculation of various intermediate parameters. The objective of the study is to estimate ET0 in the North central Plateau zone of Odisha, using weather data of the respective locality and screening of methods to estimate ET0 close to FAO-56 Penman Monteith method. The FAO-24 Penman(c=1) and Turc methods yielded the highest (5.605 mm/day) and the lowest mean ET0 (4.201 mm/day) respectively. For this zone, the highest ET0 values was found to be 10.32 mm/d for FAO-24 Penman(c=1) method followed by Businger-van Bavel (9.73 mm/d) and FAO-PPP-17-Penman (9.68 mm/d) in the month of May, whereas, lowest ET0 value was found in the month of December (2.54 mm/d) for the Priestly-Taylor method followed by 1982 Kimberly-Penman method (3.07 mm/d). Among all the methods, Penman-Monteith and Priestley-Taylor methods were ranked first and tenth respectively. For this zone, correction factor for Penman-Monteith and 1982 Kimberly-Penman methods approaches to one. The FAO-24 Penman (c=1) and Businger-van Bavel methods give more diversion from FAO-56 Penman-Monteith method.

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.

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