scholarly journals Statistical analysis of modified Hargreaves equation for precise estimation of reference evapotranspiration

2021 ◽  
Vol 73 (1) ◽  
pp. 1-12
Author(s):  
Rimsha Habeeb ◽  
Xiang Zhang ◽  
Ijaz Hussain ◽  
Muhammad Zaffar Hashmi ◽  
Elsayed Elsherbini Elashkar ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Reference Evapotranspiration ◽  
Precise Estimation ◽  
Hargreaves Equation

Characteristics of Reference Evapotranspiration of Wetland Based on Penman-Monteith and Hargreaves Methods

2012 ◽  
Vol 610-613 ◽  
pp. 3013-3016
Author(s):  
Xiang Hu Li ◽  
Qi Zhang ◽  
Yun Liang Li
Keyword(s):  
Correlation Coefficient ◽  
Direct Measurement ◽  
Water Depth ◽  
Water Loss ◽  
Strong Correlation ◽  
Reference Evapotranspiration ◽  
Relative Importance ◽  
Monthly Means ◽  
Different Types ◽  
Hargreaves Equation

Evapotranspiration (ET) constitutes the dominant water loss from many different types of wetlands. The relative importance of ET is apparent in its influence over water depth, temperature and salinity. However, direct measurement of ET, especially for wetland, is difficult, costly, and rarely available. In this study, the Penman-Monteith model was selected to estimate the reference evapotranspiration for short and tall canopies, moreover, Hargreaves equation was also used to simulate the ETref and test the precision of Penman-Monteith method. The results show that the reference evapotranspiration are maximal between June and August and minimal in winter, and ETrs is larger than ETos in the whole simulation periods. H ET0 and ETos have the same variation trend, but the former was smaller than the latter during May to September. Finally, there is a strong correlation between ETos and ETrs, with the correlation coefficient are 0.98 and 0.99 at daily and monthly means scale.

Variations and Sensitivity Analysis of Reference Evapotranspiration During 2010-2019 in the Zhangye Farmland Oasis, Northwest China

2021 ◽  
Author(s):  
Miao Fang
Keyword(s):  
Sensitivity Analysis ◽  
Reference Evapotranspiration ◽  
Sunshine Duration ◽  
Northwest China ◽  
Meteorological Factor ◽  
Maximum Temperature ◽  
Regression Equations ◽  
Significance Level ◽  
Hargreaves Equation ◽  
Increasing Trends

Abstract Reference evapotranspiration (ET0) is an important parameter for agricultural water management in the arid Zhangye farmland oasis. However, the ET0 variations in this oasis over the last decade and meteorological forcings of these variations are unknown. This study investigated the ET0 variations during 2010-2019 in this oasis using the FAO-56 Penman-Monteith (PM) and Hargreaves equations. Results showed that the ET0 features daily and monthly variations with peak values in mid-July and an annual cycle. Although the estimated ET0 series based on the two equations have high correlations in the time domain, the Hargreaves equation always underestimates the ET0 compared to the PM equation. The yearly ET0 showed statistically significant increasing trends (90% significance level) during 2010-2019, while statistically significant increasing trends in monthly ET0 are found only in March and November. Increasing trends reflected in monthly and yearly ET0 are mainly attributed to the increasing maximum temperature and sunshine duration and decreasing relative humidity. Sensitivity analysis demonstrated that the meteorological factor to which the ET0 is most sensitive varies with time scale and equation. Moreover, regression equations used to correct the underestimation associated with the Hargreaves equation for estimating ET0 in the Zhangye farmland oasis also were constructed.

scholarly journals Generating reference evapotranspiration surfaces from the Hargreaves equation at watershed scale

2011 ◽  
Vol 15 (8) ◽  
pp. 2495-2508 ◽  
Author(s):  
C. Aguilar ◽  
M. J. Polo
Keyword(s):  
Spatial Distribution ◽  
Reference Evapotranspiration ◽  
Local Scale ◽  
Weather Station ◽  
Watershed Scale ◽  
Daily Scale ◽  
Dry Seasons ◽  
Weather Stations ◽  
Hargreaves Equation ◽  
The Difference

Abstract. In this study, Hargreaves' formulation is considered to be appropriate for the water and energy balance at a daily scale due to its simplicity of application once the distributed values of temperature are available at cell scale. However, the coefficient of the Hargreaves equation must be previously calibrated. The interplay of different factors at different temporal scales became evident in the calibration process at the local scale of weather stations. The best fits against daily estimates by ASCE-PM were achieved when differentiating between the wet and the dry season. For the spatial distribution of Hargreaves coefficient at watershed scale, a regionalization in the area around each weather station was proposed in terms of areas of influence. The best results at watershed scale were obtained after a spatial correction for alpine areas, when the average of the difference cell by cell between ASCE-PM and Hargreaves's distributed daily estimates were 0.02 and 0.15 mm day−1 for the wet and the dry seasons, respectively. In all the cases, the best interpolation results were obtained using C-I (calculate and interpolate) procedures.

scholarly journals SENSITIVITY ANALYSIS AND REGIONALIZATION OF REFERENCE EVAPOTRANSPIRATION FOR THE AMAZON REGION.

2017 ◽  
Vol 7 (5) ◽  
pp. 258 ◽  
Author(s):  
Helder J Farias Silva ◽  
Weber Andrande Gonçalves ◽  
Bergson Guedes Bezerra
Keyword(s):  
Sensitivity Analysis ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Seasonal Pattern ◽  
Sensitivity Coefficient ◽  
Climate Variables ◽  
Data Set ◽  
Precise Estimation ◽  
Influential Variable ◽  
Homogeneous Regions

Sensitivity Analysis (SA) is important to understand the relative importance of climate variables in the reference evapotranspiration (ETo) computation. In this study, a sensitivity coefficient was used to predict ETo responses to disturbances of five climatic variables in the Amazonian Hydrographic Region - AHR (Brazilian Amazon). The ETo was estimated using the standardized equation of Penman-Monteith-FAO (PM-FAO). A 15-year meteorological data set of 38 surface meteorological stations were used in the study. An additional analysis was also presented to determine homogeneous regions of ETo by means of Cluster Analysis. The results showed that seven homogeneous sub-regions are sufficient to divide the AHR into different ETo patterns which were separated considering the intensity and the seasonal pattern of ETo. By the SA, the variables that contribute most to the computation of ETo using the PM-FAO method were the balance of radiation (Rn) and wind speed (u2). These results demonstrate that, in general, it should be emphasized to precise measures of insolation, since the precise estimation of Rn is directly associated with the measurement of this variable as well as of u2, which proved to be the second most influential variable in the ETo computation.

Statistical analysis of classification

1966 ◽  
Vol 24 ◽  
pp. 188-189
Author(s):  
T. J. Deeming
Keyword(s):  
Multivariate Analysis ◽  
Statistical Analysis ◽  
Classification Scheme ◽  
Analytical Procedure ◽  
Narrow Band ◽  
Scientific Research ◽  
Maximum Amount ◽  
Amount Of Information

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.

Quantitative parallel EELS spectrum imaging developed as a new tool in AEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1202-1203
Author(s):  
Gianluigi Botton ◽  
Gilles L'espérance
Keyword(s):  
Statistical Analysis ◽  
Spatial Resolution ◽  
Personal Computer ◽  
Systematic Study ◽  
Present Author ◽  
Chemical Elements ◽  
Detection Limits ◽  
Research Groups ◽  
Quantitative Performance ◽  
Spectrum Imaging

As interest for parallel EELS spectrum imaging grows in laboratories equipped with commercial spectrometers, different approaches were used in recent years by a few research groups in the development of the technique of spectrum imaging as reported in the literature. Either by controlling, with a personal computer both the microsope and the spectrometer or using more powerful workstations interfaced to conventional multichannel analysers with commercially available programs to control the microscope and the spectrometer, spectrum images can now be obtained. Work on the limits of the technique, in terms of the quantitative performance was reported, however, by the present author where a systematic study of artifacts detection limits, statistical errors as a function of desired spatial resolution and range of chemical elements to be studied in a map was carried out The aim of the present paper is to show an application of quantitative parallel EELS spectrum imaging where statistical analysis is performed at each pixel and interpretation is carried out using criteria established from the statistical analysis and variations in composition are analyzed with the help of information retreived from t/γ maps so that artifacts are avoided.

Sign in / Sign up

Export Citation Format

Share Document