scholarly journals Spatiotemporal Variations of Reference Crop Evapotranspiration in Northern Xinjiang, China

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Jian Wang ◽  
Xin Lv ◽  
Jiang-li Wang ◽  
Hai-rong Lin
Keyword(s):  
Irrigation System ◽  
Global Climate ◽  
Meteorological Data ◽  
Kendall Test ◽  
Crop Evapotranspiration ◽  
Spatiotemporal Variations ◽  
Reference Crop Evapotranspiration ◽  
Factors Affecting ◽  
Northern Xinjiang ◽  
Reference Crop

To set up a reasonable crop irrigation system in the context of global climate change in Northern Xinjiang, China, reference crop evapotranspiration (ET0) was analyzed by means of spatiotemporal variations. The ET0values from 1962 to 2010 were calculated by Penman-Monteith formula, based on meteorological data of 22 meteorological observation stations in the study area. The spatiotemporal variations of ET0were analyzed by Mann-Kendall test, Morlet wavelet analysis, and ArcGIS spatial analysis. The results showed that regional average ET0had a decreasing trend and there was an abrupt change around 1983. The trend of regional average ET0had a primary period about 28 years, in which there were five alternating stages (high-low-high-low-high). From the standpoint of spatial scale, ET0gradually increased from the northeast and southwest toward the middle; the southeast and west had slightly greater variation, with significant regional differences. From April to October, the ET0distribution significantly influenced the distribution characteristic of annual ET0. Among them sunshine hours and wind speed were two of principal climate factors affecting ET0.

Study on Regional Analysis of Reference Crop Evapotranspiration Based on SPSS

2015 ◽  
Vol 733 ◽  
pp. 415-418
Author(s):  
Li Ying Cao ◽  
He Long Yu ◽  
Gui Fen Chen ◽  
Peng Sun
Keyword(s):  
Regression Analysis ◽  
Linear Regression ◽  
Linear Correlation ◽  
Meteorological Data ◽  
Linear Regression Analysis ◽  
Regional Analysis ◽  
Crop Evapotranspiration ◽  
Reference Crop Evapotranspiration ◽  
Reference Crop ◽  
Monteith Equation

Based on the meteorological data collected from 3 stations in recent 10 years in Fushun region, the reference crop evapotranspiration was calculated with the Penman-Monteith equation recommended by FAO in 1990. The evapotranspiration of the region was analyzed using linear regression analysis based on software of SPSS. The results showed that the linear correlation was evident between the evapotranspiration data of stations, but it is not significant for the linear correlation between the stations, neither between the stations. The result will be helpful to analysis of the space distributions of the reference crop evapotranspiration in the region.

scholarly journals (202) Microclimate and Reference Crop Evapotranspiration in High Tunnels and Open Field during Summer Lettuce Production

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1054D-1055
Author(s):  
Xin Zhao ◽  
Edward E. Carey
Keyword(s):  
Open Field ◽  
Meteorological Data ◽  
Daily Basis ◽  
Crop Evapotranspiration ◽  
Reference Crop Evapotranspiration ◽  
Horticultural Crops ◽  
High Tunnels ◽  
Use Efficiency ◽  
Leaf Lettuce ◽  
Reference Crop

High tunnels, unheated greenhouses, have been shown to be a profitable season-extending production tool for many horticultural crops. Production of cool-season vegetables during hot summer months can be achieved using shaded high tunnels. Microclimate in high tunnels and open field was monitored during summer trials of leaf lettuce, in which unshaded tunnels and shaded tunnels (39% PAK white shadecloth) were used, respectively, in 2002 and 2003. Wind speed was consistently lower in high tunnels. Compared to open field, daily air temperature was about 0.7 °C higher in unshaded high tunnels, and 0.5 °C lower in shaded high tunnels. Relative humidity was slightly lower in unshaded tunnels, but tended to increase in shaded tunnels, in comparison to the open field. When using shadecloth, soil temperature was lowered by 1∼3 °C and the leaf surface temperature was significantly reduced by 1.5∼2.5 °C. In shaded high tunnels, PAR light dropped by at least 50% relative to the outside, where the maximum PAR light intensity reached 1800 μmol·m-2·s-1. Overall, shaded high tunnels resulted in higher quality lettuce, with less bolting and bitterness. Reference crop evapotranspiration (ET0) was estimated from meteorological data on a daily basis using the FAO-56 method. ET0 was lowest in shaded high tunnels, and highest in the open field. Relatively lower ET0 in high tunnels indicated a likely lower water requirement and therefore improved water use efficiency compared with the open field.

scholarly journals Estimating reference crop evapotranspiration with elevation based on an improved HS model

2018 ◽  
Vol 50 (1) ◽  
pp. 187-199 ◽  
Author(s):  
Pengcheng Tang ◽  
Bing Xu ◽  
Zhanyi Gao ◽  
Heping Li ◽  
Xiaoyu Gao ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Meteorological Data ◽  
High Elevation ◽  
Crop Evapotranspiration ◽  
Low Oxygen ◽  
Reference Crop Evapotranspiration ◽  
Improved Model ◽  
Short Time ◽  
Reference Crop ◽  
Different Time Scales

Abstract Estimation of ET0 in high-elevation (above sea level, ASL) areas of Tibet presents unique challenges: scarcity of monitoring stations, short-time coverage of meteorological data, low-oxygen and low-pressure environment, and strong solar radiation. In this study, altitude factors and modified temperature constants are utilized to improve the Hargreaves (HS) model based on 30-year daily meteorological data from 20 typical sites in Tibet. The improved model, Hargreaves-Elevation (HS-E) improved model, could provide better results at different time scales. Negative ET0 values were unavoidable in the HS model when applied to high-elevation areas. However, the HS-E model solved this problem and improved the accuracy of estimated ET0. In particular, the HS-E model performs better when the time scale becomes larger. Therefore, the HS-E model is highly recommended to estimate ET0 in high-elevation areas where the meteorological data are scarce, for example, in Tibet above 2,000 m.

scholarly journals Estimating actual, potential, reference crop and pan evaporation using standard meteorological data: a pragmatic synthesis

2013 ◽  
Vol 17 (4) ◽  
pp. 1331-1363 ◽  
Author(s):  
T. A. McMahon ◽  
M. C. Peel ◽  
L. Lowe ◽  
R. Srikanthan ◽  
T. R. McVicar
Keyword(s):  
Meteorological Data ◽  
Pan Evaporation ◽  
Potential Evaporation ◽  
Crop Evapotranspiration ◽  
Deep Lakes ◽  
Reference Crop Evapotranspiration ◽  
Class A ◽  
Actual Evaporation ◽  
Reference Crop ◽  
Class A Pan

Abstract. This guide to estimating daily and monthly actual, potential, reference crop and pan evaporation covers topics that are of interest to researchers, consulting hydrologists and practicing engineers. Topics include estimating actual evaporation from deep lakes and from farm dams and for catchment water balance studies, estimating potential evaporation as input to rainfall-runoff models, and reference crop evapotranspiration for small irrigation areas, and for irrigation within large irrigation districts. Inspiration for this guide arose in response to the authors' experiences in reviewing research papers and consulting reports where estimation of the actual evaporation component in catchment and water balance studies was often inadequately handled. Practical guides using consistent terminology that cover both theory and practice are not readily available. Here we provide such a guide, which is divided into three parts. The first part provides background theory and an outline of the conceptual models of potential evaporation of Penman, Penman–Monteith and Priestley–Taylor, as well as discussions of reference crop evapotranspiration and Class-A pan evaporation. The last two sub-sections in this first part include techniques to estimate actual evaporation from (i) open-surface water and (ii) landscapes and catchments (Morton and the advection-aridity models). The second part addresses topics confronting a practicing hydrologist, e.g. estimating actual evaporation for deep lakes, shallow lakes and farm dams, lakes covered with vegetation, catchments, irrigation areas and bare soil. The third part addresses six related issues: (i) automatic (hard wired) calculation of evaporation estimates in commercial weather stations, (ii) evaporation estimates without wind data, (iii) at-site meteorological data, (iv) dealing with evaporation in a climate change environment, (v) 24 h versus day-light hour estimation of meteorological variables, and (vi) uncertainty in evaporation estimates. This paper is supported by a Supplement that includes 21 sections enhancing the material in the text, worked examples of many procedures discussed in the paper, a program listing (Fortran 90) of Morton's WREVAP evaporation models along with tables of monthly Class-A pan coefficients for 68 locations across Australia and other information.

scholarly journals Performance evaluation of solar radiation equations for estimating reference evapotranspiration (ETo) in a humid tropical environment

2019 ◽  
Vol 42 (1) ◽  
pp. 124-135
Author(s):  
Emeka Ndulue ◽  
Ikenna Onyekwelu ◽  
Kingsley Nnaemeka Ogbu ◽  
Vintus Ogwo
Keyword(s):  
Solar Radiation ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Accurate Estimate ◽  
Tropical Environment ◽  
Crop Evapotranspiration ◽  
Reference Crop Evapotranspiration ◽  
Field Crops ◽  
Essential Input ◽  
Reference Crop

Abstract Solar radiation (Rs) is an essential input for estimating reference crop evapotranspiration, ETo. An accurate estimate of ETo is the first step involved in determining water demand of field crops. The objective of this study was to assess the accuracy of fifteen empirical solar radiations (Rs) models and determine its effects on ETo estimates for three sites in humid tropical environment (Abakaliki, Nsukka, and Awka). Meteorological data from the archives of NASA (from 1983 to 2005) was used to derive empirical constants (calibration) for the different models at each location while data from 2006 to 2015 was used for validation. The results showed an overall improvement when comparing measured Rs with Rs determined using original constants and Rs using the new constants. After calibration, the Swartman–Ogunlade (R2 = 0.97) and Chen 2 models (RMSE = 0.665 MJ∙m−2∙day−1) performed best while Chen 1 (R2 = 0.66) and Bristow–Campbell models (RMSE = 1.58 MJ∙m−2∙day−1) performed least in estimating Rs in Abakaliki. At the Nsukka station, Swartman–Ogunlade (R2 = 0.96) and Adeala models (RMSE = 0.785 MJ∙m−2∙day−1) performed best while Hargreaves–Samani (R2 = 0.64) and Chen 1 models (RMSE = 1.96 MJ∙m−2∙day−1) performed least in estimating Rs. Chen 2 (R2 = 0.98) and Swartman–Ogunlade models (RMSE = 0.43 MJ∙m−2∙day−1) performed best while Hargreaves–Samani (R2 = 0.68) and Chen 1 models (RMSE = 1.64 MJ∙m−2∙day−1) performed least in estimating Rs in Awka. For estimating ETo, Adeala (R2 =0.98) and Swartman–Ogunlade models (RMSE = 0.064 MJ∙m−2∙day−1) performed best at the Awka station and Swartman–Ogunlade (R2 = 0.98) and Chen 2 models (RMSE = 0.43 MJ∙m−2∙day−1) performed best at Abakaliki while Angstrom–Prescott–Page (R2 = 0.96) and El-Sebaii models (RMSE = 0.0908 mm∙day−1) performed best at the Nsukka station.

scholarly journals ESTUDO DA DISTRIBUIÇÃO DA EVAPOTRANSPIRAÇÃO DE REFERÊNCIA VISANDO O DIMENSIONAMENTO DE SISTEMAS DE IRRIGAÇÃO.

Irriga ◽  
2002 ◽  
Vol 7 (1) ◽  
pp. 10-17
Author(s):  
João Carlos Cury Saad ◽  
Guilherme Augusto Biscaro ◽  
Osmar Delmanto Júnior ◽  
José Antonio Frizzone
Keyword(s):  
System Design ◽  
Irrigation System ◽  
Systems Design ◽  
Mean Value ◽  
Crop Evapotranspiration ◽  
Peak Period ◽  
Reference Crop Evapotranspiration ◽  
Kolmogorov Smirnov ◽  
Reference Crop ◽  
Irrigation System Design

ESTUDO DA DISTRIBUIÇÃO DA EVAPOTRANSPIRAÇÃO DE REFERÊNCIA VISANDO O DIMENSIONAMENTO DE SISTEMAS DE IRRIGAÇÃO.   João Carlos Cury.SaadGuilherme Augusto BiscaroOsmar Delmanto Jr.Dept° de. Eng. Rural,  FCA/UNESP, CP. 237, CEP 18603-970 - Botucatu, SP.José Antonio FrizzoneDepto. Eng. Rural, ESALQ/USP, CP. 09, CEP 13419-900 - Piracicaba, SP.Q   1 RESUMO   Visando caracterizar a distribuição de freqüência da evapotranspiração de referência na região de Piracicaba, SP, e avaliar as práticas usuais de estimativa da necessidade de água para fins de dimensionamento de sistemas de irrigação, foram utilizados 30 anos de dados de evapotranspiração do mês de setembro, que foi dividido em períodos de 5, 10, 15 e 30 dias. As distribuições Beta e Normal foram aplicadas aos dados e ambas mostraram-se  aptas para representá-los.  Para valores de probabilidade de ocorrência iguais ou superiores a 60%, verificou-se o aumento do valor da evapotranspiração de referência com a diminuição do período. Adotando como parâmetros o período de máxima exigência hídrica de 2 a 3 semanas e a evapotranspiração de referência ao nível de 75% de probabilidade, verificou-se que o uso do valor médio mensal da evapotranspiração no dimensionamento de sistemas de irrigação conduz ao subdimensionamento, enquanto a adoção do máximo valor diário da evapotranspiração acarreta o superdimensionamento.   UNITERMOS: Evapotranspiração de referência, distribuição de freqüência, dimensionamento de sistemas de irrigação.   SAAD, J. C. C., FRIZZONE, J. A., BISCARO, G. A., DELMANTO JR., O. STUDY OF THE REFERENCE CROP EVAPOTRANSPIRATION DISTRIBUTION  RELATED TO IRRIGATION SYSTEM DESIGN.   2 ABSTRACT  This paper has studied 30 year reference crop evapotranspiration data distribution  aiming to improve  irrigation system design. Evapotranspiration was analyzed using 5,10, 15 and 30 day -  time periods over  the month of September, for the region of Piracicaba city, São Paulo state.  Normal and  Beta distribution have been applied to data and through Kolmogorov-Smirnov test their adequacy to represent  reference crop evapotranspiration data has been  verified. An increase of reference crop evapotranspiration value has been obtained for occurrence probability values equal or higher than 60 % when the period of time has been shortened. Considering 2 to 3 weeks the water requirement peak period and 75% probability the reference crop evapotranspiration , it could be observed that using monthly mean value of evapotranspiration to get irrigation system design leads to its underestimation whereas maximum daily value of evapotranspiration leads to its overestimation.   KEYWORDS: frequency distribution, reference crop evapotranspiration, irrigation systems design. 

scholarly journals An assessment of the water requirements of a mountain pasture sward in the Polish Western Carpathians

2011 ◽  
Vol 15 (1) ◽  
pp. 193-208 ◽  
Author(s):  
Antoni Kuźniar ◽  
Stanisław Twardy ◽  
Agnieszka Kowalczyk ◽  
Marek Kostuch
Keyword(s):  
Surface Resistance ◽  
Meteorological Data ◽  
Crop Coefficient ◽  
Western Carpathians ◽  
Crop Evapotranspiration ◽  
Water Requirements ◽  
Reference Crop Evapotranspiration ◽  
Mountain Pasture ◽  
Weather Stations ◽  
Reference Crop

An assessment of the water requirements of a mountain pasture sward in the Polish Western Carpathians The water requirements of the pasture sward using the Penman-Monteith method (FAO-56), which is seldom applied in Poland, was assessed. The reference crop evapotranspiration ETo from a hypothetical grass crop with an assumed crop height of 0.12 m, a fixed surface resistance of 70 s·m-1 and an albedo of 0.23, was used. These assumptions are similar under conditions of ruminant grazing. ETo was computed by using meteorological data from 43 weather stations. The crop evapotranspiration ETc is the product of ETo, and single crop coefficient Kc. The differences between precipitation and ETo and ETc (climatic water balances) were determined for mountain pastures. The results were summarised form of a table and maps of isohyets and isolines elaborated by applying the Geographic Information System techniques (Arc View 9) with the data interpolated by the geostatic method (Kriging).

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