Impacts of Climatic Change on Reference Crop Evapotranspiration across Different Climatic Zones of Ningxia at Multi-Time Scales from 1957 to 2018

The impact of global climate change on agroecosystems is growing, affecting reference crop evapotranspiration (ET0) and subsequent agricultural water management. In this study, the climate factors temporal trends, the spatiotemporal variation, and the climate driving factors of ET0 at different time scales were evaluated across the Northern Yellow River Irrigation Area (NYR), Central Arid Zone (CAZ), and Southern Mountain Area (SMA) of Ningxia based on 20 climatic stations’ daily data from 1957 to 2018. The results showed that the Tmean (daily mean air temperature), Tmax (daily maximum air temperature), and Tmin (daily minimum air temperature) all had increased significantly over the past 62 years, whilst RH (relative humidity), U2 (wind speed at 2 m height), and SD (sunshine duration) had significantly decreasing trends across all climatic zones. At monthly scale, the ET0 was mainly concentrated from April to September. And at annual and seasonal scales, the overall increasing trends were more pronounced in NX, NYR, and SMA, while CAZ was the opposite. For the spatial distribution, ET0 presented a trend of rising first and then falling at all time scales. The abrupt change point for climatic factors and ET0 series was obtained at approximately 1990 across all climatic zones, and the ET0 had a long period of 25a and a short period of 10a at annual scale, while it was 15a and 5a at seasonal scale. RH and Tmax were the most sensitive climatic factors at the annual and seasonal scales, while the largest contribution rates were Tmax and SD. This study not only is important for the understanding of ET0 changes but also provides the preliminary and elementary reference for agriculture water management in Ningxia.

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Performance of Modified Temperature-Based Reference Crop Evapotranspiration Models Across Different Agro-Climatic Zones in Karnataka State, India

10.5194/egusphere-egu2020-1101 ◽

2020 ◽

Author(s):

Niranjan Siddalingamurthy ◽

Lakshman Nandagiri

Keyword(s):

Effective Temperature ◽

Alternative Methods ◽

Model Parameters ◽

Crop Evapotranspiration ◽

Local Calibration ◽

Climatic Zones ◽

Reference Crop Evapotranspiration ◽

Mean Temperature ◽

Karnataka State ◽

Reference Crop

Reference crop evapotranspiration (ET0) forms an essential forcing variable in hydrological, agricultural, irrigation and climate models. Among several available methods for ET0 estimation using regularly recorded climate data, the Food and Agriculture Organization (FAO) Penman-Monteith (PM) equation is popular among researchers due to its accuracy across different environments. However, routine use of the FAO-PM equation is hampered in data-scarce situations because of the requirement of input data pertaining to a large number of climate variables. Therefore, simpler alternative methods for ET0 estimation such as the Blaney-Criddle (BC) and Hargreaves (HG) have been proposed by previous researchers. However, for routine use of these empirical equations, local calibration of the model parameters may be desirable. Also, a few previous attempts have been made to replace the daily mean temperature with an effective temperature calculated as a weighted average of daily maximum and minimum temperatures.&#160; Therefore, the present study was taken up to evaluate the effect of two aspects on the accuracies of the BC and HG models 1) replacing mean temperature with effective temperature defined using different parameterizations 2) local calibration of parameters. For this purpose, climate records for the historical period 2006-2016 of 67 stations located across ten agro-climatic zones of Karnataka State, India were used and the analysis was carried out using a monthly time step. Since measured ET0 data was unavailable, calibration was performed using PM ET0 estimates and performance was evaluated using various statistical measures. Overall results showed that the BC equation with mean temperature yielded better results than the ones with effective temperature with calibrated parameters. However, the HG method showed an improvement with the use of effective temperature. Information on the spatial distribution of calibrated parameters was derived which will prove useful to practitioners who wish to derive ET0 estimates with only temperature inputs.

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A New Method to Estimate Reference Crop Evapotranspiration from Geostationary Satellite Imagery: Practical Considerations

Water ◽

10.3390/w11020382 ◽

2019 ◽

Vol 11 (2) ◽

pp. 382 ◽

Cited By ~ 4

Author(s):

Henk de Bruin ◽

Isabel Trigo

Keyword(s):

Geostationary Satellite ◽

Total Solar Radiation ◽

Crop Evapotranspiration ◽

Reference Crop Evapotranspiration ◽

Main Driver ◽

Scarce Water ◽

Meteorological Observations ◽

The Impact ◽

Reference Crop ◽

Stressed Surface

Reference crop evapotranspiration (ETo) plays a role in irrigation advisory being of crucial importance for water managers dealing with scarce water resources. Following the ETo definition, it can be shown that total solar radiation is the main driver, allowing ETo estimates from satellite observations. As such, the EUMETSAT LSA-SAF operationally provides ETo primarily derived from the European geostationary satellite MSG. ETo estimations following the original FAO report require several meteorological observations gathered over actual well-watered grass. Here we will consider the impact of two effects on ETo using the LSA-SAF and FAO methodologies: (i) local advection, related to the impact of advection of surrounding warm dry air onto the reference non-water stressed surface; and (ii) the so-called surface aridity error, which occurs when calculating ETo according to FAO, but with input data not collected over well-watered grass. The LSA-SAF ETo is not sensitive to any of these effects. However, it is shown that local advection may increase evapotranspiration over a limited field by up to 30%, while ignoring aridity effects leads to a great overestimation. The practical application of satellite estimates of ETo provided by the LSA-SAF are discussed here, and, furthermore, water managers are encouraged to consider its advantages and ways for improvement.

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Reference crop evapotranspiration derived from geo-stationary satellite imagery – a case study for the Fogera flood plain, NW-Ethiopia and the Jordan Valley, Jordan

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-7-4925-2010 ◽

2010 ◽

Vol 7 (4) ◽

pp. 4925-4956 ◽

Cited By ~ 2

Author(s):

H. A. R. de Bruin ◽

I. F. Trigo ◽

M. A. Jitan ◽

N. Temesgen Enku ◽

C. van der Tol ◽

...

Keyword(s):

Solar Radiation ◽

Satellite Imagery ◽

Air Temperature ◽

Land Surface ◽

Crop Evapotranspiration ◽

Jordan Valley ◽

Data Set ◽

Reference Crop Evapotranspiration ◽

First Results ◽

Reference Crop

Abstract. First results are shown of a project aiming to estimate daily values of reference crop evapotranspiration ET0 from geo-stationary satellite imagery. In particular, for Woreta, a site in the Ethiopian highland at an elevation of about 1800 m, we tested a radiation-temperature based approximate formula proposed by Makkink (MAK) adopting ET0 evaluated with the version of the Penman-Monteith equation described in the FAO Irrigation and Drainage paper 56 as the most accurate estimate. More precisely we used the latter with measured daily solar radiation as input (denoted by PMFAO-Rs). Our data set for Woreta concerns a period where the surface was fully covered with short green non-stressed vegetation. Our project was carried out in the context of the Satellite Application Facility on Land Surface Analysis (LANDSAF) facility. Among others, the scope of LANDSAF is to increase benefit from the EUMETSAT Satellite Meteosat Second Generation (MSG). In this study we applied daily values of downward solar radiation at the surface obtained from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) radiometer. In addition, air temperature at 2 m was obtained from 3-hourly forecasts provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Both MAK and PMFAO-Rs contain the psychrometric "constant", which is proportional to air pressure, which, in turn, decreases with elevation. In order to test elevation effects we tested MAK and its LANDSAF input data for 2 sites in the Jordan Valley located about 250 m b.s.l. Except for a small underestimation of air temperature at the Ethiopian site at 1800 m, the first results of our LANDSAF-ET0 project are promising. If our approach to derive ET0 proves successfully, then the LANDSAF will be able to initiate nearly real time free distribution of ET0 for the full MSG disk.

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Climate change effects on reference crop evapotranspiration across different climatic zones of China during 1956–2015

Journal of Hydrology ◽

10.1016/j.jhydrol.2016.09.060 ◽

2016 ◽

Vol 542 ◽

pp. 923-937 ◽

Cited By ~ 57

Author(s):

Junliang Fan ◽

Lifeng Wu ◽

Fucang Zhang ◽

Youzhen Xiang ◽

Jing Zheng

Keyword(s):

Climate Change ◽

Crop Evapotranspiration ◽

Climatic Zones ◽

Reference Crop Evapotranspiration ◽

Climate Change Effects ◽

Reference Crop

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Sensitivity of Reference Crop Evapotranspiration in Shaanxi Province

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.700.374 ◽

2014 ◽

Vol 700 ◽

pp. 374-385

Author(s):

Yue Song ◽

Xiao Ling Su

Keyword(s):

Wind Speed ◽

Relative Humidity ◽

Shaanxi Province ◽

Shanxi Province ◽

Crop Evapotranspiration ◽

Reference Crop Evapotranspiration ◽

Daily Sunshine ◽

The Impact ◽

Reference Crop ◽

Sunshine Hour

Reference crop evapotranspiration (ET0) is a key to estimate crop water requirements, and also an important component of irrigation schedule and water resources planning, sensitivity analysis are crucial in assessing the impact of climate changes inET0estimations. In this study, based on the daily meteorological data of 18 meteorological stations in Shanxi Province from 1961 to 2000, the dailyET0values were calculated using Penman-Monteith equation recommended by FAO-56. The trends of climate variables were detected by using Mann-Kendall test. Sensitivity coefficients were employed to predict responses ofET0to five climatic variables, combined with annual of meteorological factors quantitative analysis ofET0changes. The results show that statistically significant decreasing trends are observed in wind and daily sunshine hours in Guanzhong and southern Shaanxi. Relative humidity has a significant decreasing trend in northern Shaanxi. In general,ET0value is on the decline; relative humidity is the most sensitive variable, followed by solar radiation, daily sunshine hour, wind speed and mean temperature. The change ofET0is primarily attributed to the significantly decreasing in wind speed and sunshine hour.

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Effect of local calibration on the performance of the Hargreaves reference crop evapotranspiration equation

Journal of Water and Climate Change ◽

10.2166/wcc.2021.360 ◽

2021 ◽

Author(s):

S. Niranjan ◽

Lakshman Nandagiri

Keyword(s):

Air Temperature ◽

Daily Temperature ◽

Historical Period ◽

Model Parameters ◽

Crop Evapotranspiration ◽

Local Calibration ◽

Time Step ◽

Reference Crop Evapotranspiration ◽

Statistical Performance Evaluation ◽

Reference Crop

Abstract Obtaining accurate estimates of reference crop evapotranspiration (ET0) using limited climatic inputs is essential in data-short situations where the preferred FAO-56 Penman–Monteith (PM) equation cannot be implemented. Among several available for ET0 estimation, the empirical temperature-based Hargreaves–Samani (HG) equation remains a popular alternative. However, accurate HG estimates can be obtained by local calibration and replacing the mean daily temperature with the effective daily temperature. Therefore, the present study was taken up to evaluate the effects of site-specific calibration of model parameters and the use of effective air temperature on the accuracy of ET0 estimates by the HG model. For this purpose, climate records for the historical period 2006–2016 of 67 stations located across 10 agro-climatic zones of Karnataka State, India, were used and the analysis was carried out using a monthly time step. Calibration and statistical performance evaluation was performed using FAO-56 PM ET0 estimates as a reference. Overall results showed significant improvement in HG estimates across all zones with the use of locally calibrated parameters, whereas the use of effective air temperature did not lead to any significant gain in prediction accuracies. The derived information on the spatial distribution of calibrated parameters will help obtain accurate ET0 estimates with only air temperature inputs.

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Reference crop evapotranspiration derived from geo-stationary satellite imagery: a case study for the Fogera flood plain, NW-Ethiopia and the Jordan Valley, Jordan

Hydrology and Earth System Sciences ◽

10.5194/hess-14-2219-2010 ◽

2010 ◽

Vol 14 (11) ◽

pp. 2219-2228 ◽

Cited By ~ 36

Author(s):

H. A. R. de Bruin ◽

I. F. Trigo ◽

M. A. Jitan ◽

N. Temesgen Enku ◽

C. van der Tol ◽

...

Keyword(s):

Solar Radiation ◽

Satellite Imagery ◽

Air Temperature ◽

Land Surface ◽

Crop Evapotranspiration ◽

Jordan Valley ◽

Data Set ◽

Reference Crop Evapotranspiration ◽

First Results ◽

Reference Crop

Abstract. First results are shown of a project aiming to estimate daily values of reference crop evapotranspiration ET0 from geo-stationary satellite imagery. In particular, for Woreta, a site in the Ethiopian highland at an elevation of about 1800 m, we tested a radiation-temperature based approximate formula proposed by Makkink (MAK), adopting ET0 evaluated with the version of the Penman-Monteith equation described in the FAO Irrigation and Drainage paper 56 as the most accurate estimate. More precisely we used the latter with measured daily solar radiation as input (denoted by PMFAO-Rs). Our data set for Woreta concerns a period where the surface was fully covered with short green non-stressed vegetation. Our project was carried out in the context of the Satellite Application Facility on Land Surface Analysis (LANDSAF) facility. Among others, the scope of LANDSAF is to increase benefit from the EUMETSAT Satellite Meteosat Second Generation (MSG). In this study we applied daily values of downward solar radiation at the surface obtained from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) radiometer. In addition, air temperature at 2 m was obtained from 3-hourly forecasts provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Both MAK and PMFAO-Rs contain the psychrometric "constant", which is proportional to air pressure, which, in turn, decreases with elevation. In order to test elevation effects we tested MAK and its LANDSAF input data for 2 sites in the Jordan Valley located about 250 m b.s.l. Except for a small underestimation of air temperature at the Ethiopian site at 1800 m, the first results of our LANDSAF-ET0 project are promising. If our approach to derive ET0 proves successfully, then the LANDSAF will be able to initiate nearly real time free distribution of ET0 for the full MSG disk.

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