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

Ndulue, Emeka; Onyekwelu, Ikenna; Ogbu, K. N.; Ogwo, V.

doi:10.2478/jwld-2019-0053

Cited by 15 publications

(4 citation statements)

References 48 publications

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“…Wei et al [41] compared the skills of several eddy covariance ET methods in arid regions and showed 'Shuttleworth-Wallace' as the best method. Ndulue et al [42] assessed the relative skills of 15 solar radiation ET models in a humid tropical region. They showed large variability in the performance of different methods in different locations.…”

Section: Introductionmentioning

confidence: 99%

Ranking of Empirical Evapotranspiration Models in Different Climate Zones of Pakistan

Hamed

Khan

Muhammad

et al. 2022

Land

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Accurate estimation of evapotranspiration (ET) is vital for water resource development, planning and management, particularly in the present global warming context. A large number of empirical ET models have been developed for estimating ET. The main limitations of this method are that it requires several meteorological variables and an extensive data span to comprehend the ET pattern accurately, which is not available in most developing countries. The efficiency of 30 empirical ET models has been evaluated in this study to rank them for Pakistan to facilitate the selection of suitable models according to data availability. Princeton Global Meteorological Forcing daily climate data with a 0.25° × 0.25° resolution for 1948–2016 were utilized. The ET estimated using Penman–Monteith (PM) was considered as the reference. Multi-criteria group decision making (MCGDM) was used to rank the models for Pakistan. The results showed the temperature-based Hamon as the best model for most of Pakistan, followed by Hargreaves–Samani and Penman models. Hamon also showed the best performance in terms of different statistical metrics used in the study with a mean bias (PBias) of −50.2%, mean error (ME) of −1.62 mm and correlation coefficient (R2) of 0.65. Ivan showed the best performance among the humidity-based models, Irmak-RS and Ritch among the radiation-based models and Penman among the mass transfer-based models. Northern Pakistan was the most heterogeneous region in the relative performance of different ET models.

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Section: Introductionmentioning

confidence: 99%

Ranking of Empirical Evapotranspiration Models in Different Climate Zones of Pakistan

Hamed

Khan

Muhammad

et al. 2022

Land

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“…The study was conducted at a meteorological station, OAU-Metstation located in the Teaching and (Ayoola et al, 2014;Ndulue et al, 2019;Soneye et al, 2019;Ajao et al, 2020). The site is about 7 km from the main campus of the university.…”

Section: Methodsmentioning

confidence: 99%

“…The Sun is the primary and major source of radiant energy to the earth's surface. The amount of radiant energy emitted by the Sun to the earth's surface depends on factors such as land use, nature and area of surfaces, vegetation and cloud cover, presence of aerosols and particulate matters etc., for its spatiotemporal distributions (Dewitte and Clerbaux 2017;Kondratyev 1969;Nage 2018;Ndulue et al 2019;Wang and Liang 2009). The spatial distribution and temporal variation of such radiant energy in different regions or across the continents can either be in the form of global or net radiation (Jiang et al 2019;Wild et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Analysis of global and net radiation fluxes in relation to surface albedo at DACCIWA site in Ile-Ife, southwest Nigeria

Ajao

Abiye²,

Agboola³

2023

Theor Appl Climatol

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Measurements of global solar and net radiation fluxes were made above a grass-covered surface at DACCIWA site in a tropical location, Ile-Ife, southwest Nigeria for a period of three years (2017 -2019). The radiation data sets were obtained from a four-component net radiometer (model NR01). Observations were made for cases of clear sky and cloudy conditions during the measurement period. The results showed considerable fluctuations of both radiation fluxes occurring during the period of measurements at the location. For clear sky conditions, the magnitudes of global and net radiation fluxes were higher than those observed for cloudy conditions due to attenuation by clouds and aerosols. For the period of observation, the highest radiation flux values occurred in 2018 while the lowest were observed in 2017. The daily surface albedo (𝛼) values ranged from 0.16 to 0.22 at the site. Empirical relationships obtained for global solar and net radiation are 𝑅 𝑁 = 0.754 𝑅 𝐺 -17.4 Wm -2 and 𝑅 𝑁 = 0.657 𝑅 𝐺 -32.7 Wm -2 for wet and dry seasons respectively. Based on the empirical relationships, daily net and global solar radiation can be obtained when measurements like these are not available. Linear relationships between 𝑅 𝑁 and 𝑅 𝐺 show that for all days (cloudy and clear sky conditions), average 𝑅 𝑁 is about 65 % of 𝑅 𝐺 , and about 50 % of 𝑅 𝐺 for clear sky conditions at the location.

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“…Solar radiation (R s ) is shown to be an important parameter for ET o calculation [52][53][54]. In this study, the accuracy of the R s estimate was checked through the R s and R so ratio curve.…”

Section: Correction Of Solar Radiation Datamentioning

confidence: 98%

Assessment of Empirical Methods for Estimating Reference Evapotranspiration in Different Climatic Zones of Bosnia and Herzegovina

Srdić,

Srđević,

Stričević

et al. 2023

Water

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The study evaluated nine empirical methods for estimating reference evapotranspiration (ETo) in Bosnia and Herzegovina (BiH) across different climatic zones. The methods compared were the Hargreaves–Samani method (HS), the modified Hargreaves–Samani method (HM), the calibrated Hargreaves–Samani method (HC), the Priestley–Taylor method (PT), the Copais method (COP), the Makkink method (MAK), the Penman–Monteith method based on air temperature and overall average windspeed (PMT2), the Penman–Monteith method based on air temperature and regional average windspeed (PMT1.3), and the Penman–Monteith method based on air temperature and site-specific windspeed (PMTlok). These methods were tested against the “Food Agricultural Organization-Penman Monteith approach” (FAO-PM). The evaluation was performed using data from 20 meteorological stations in BiH, considering a common irrigation season (April–October) for two periods (2000–2005 and 2018–2022). The stations represented three climatic zones: semi-arid (SA), dry sub-humid (DSH), and moist sub-humid (MSH). The performance and ranking of the ETo methods were analyzed using the TOPSIS method. The trend of ETo during the common irrigation season for the period from 2018 to 2022 was determined using the Mann–Kendall test. The results of the study indicated that the HC method showed the best performance across all three climatic zones. The average root mean square error (RMSE) was 0.67 mm day−1, 0.49 mm day−1, and 0.50 mm day−1 for the SA, DSH, and MSH zones, respectively. As an alternative to the HC method, the PT method is recommended for its favorable results in both periods and in all zones. On the other hand, the HS method exhibited the highest average overestimation, particularly in the MSH zone, where ETo values were 18% higher compared with those of the FAO-PM method. The COP method also showed high overestimation and was not recommended for use. Regarding the MAK method, it resulted in underestimation during the period from 2000 to 2005, ranging from 17% in the DSH zone to 11% in the MSH zone. However, its performance improved during the period from 2018 to 2022, for which it ranked second place in the MSH zone. Among the PMT methods, the PMTlok, which utilized local average windspeed, yielded the best results. Despite performing well in the neighboring country of Serbia, the HM method showed poor overall performance in BiH. The findings of this study can serve as a foundation for further research in BiH to enhance irrigation practices in response to climate changes.

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

Cited by 15 publications

References 48 publications

Ranking of Empirical Evapotranspiration Models in Different Climate Zones of Pakistan

Ranking of Empirical Evapotranspiration Models in Different Climate Zones of Pakistan

Analysis of global and net radiation fluxes in relation to surface albedo at DACCIWA site in Ile-Ife, southwest Nigeria

Assessment of Empirical Methods for Estimating Reference Evapotranspiration in Different Climatic Zones of Bosnia and Herzegovina

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