Reference Evapotranspiration (ETo) Methods Implemented as ArcMap Models with Remote-Sensed and Ground-Based Inputs, Examined along with MODIS ET, for Peloponnese, Greece

The present study develops ArcMap models to implement the following three methods: FAO-56 Penman–Monteith (FAO PM), Hargreaves–Samani (HS) and Hansen, with the former used as a reference. Moreover, three models implementing statistical indices (RMSD, MB, NMB) are also created. The purpose is threefold, as follows: to investigate the variability in the daily mean reference evapotranspiration (ETo) for the Decembers and Augusts during 2016–2019, over Peloponnese, Greece. Furthermore, to investigate the agreement between the methods’ ETo estimates, and examine the former along with MODIS ET (daily) averaged products. The study area is a complex Mediterranean area. Meteorological data from sixty-two stations under the National Observatory of Athens (NOA), and MODIS Terra LST products, have been employed. FAO PM is found sensitive to wind speed and depicts interactions among climate parameters (T, evaporative demand and water availability) in the frame of climate change. The years 2016–2019 are four of the warmest since the preindustrial era. Hargreaves–Samani’s estimations for the Decembers of 2016–2019 were almost identical to MODIS ET, despite their different physical meaning. However, for the Augusts there are considerable discrepancies between the methods’ and MODIS’s estimates, attributed to the higher evaporative demand in the summertime. The GIS models are accurate, reliable, time-saving, and adjustable to any study area.

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Performance of different methods for reference evapotranspiration estimation in Jaíba, Brazil

Revista Brasileira de Engenharia Agrícola e Ambiental ◽

10.1590/1807-1929/agriambi.v22n2p83-89 ◽

2018 ◽

Vol 22 (2) ◽

pp. 83-89 ◽

Cited By ~ 1

Author(s):

Gustavo H. da Silva ◽

Santos H. B. Dias ◽

Lucas B. Ferreira ◽

Jannaylton É. O. Santos ◽

Fernando F. da Cunha

Keyword(s):

Wind Speed ◽

Solar Radiation ◽

Standard Method ◽

Reference Evapotranspiration ◽

Meteorological Data ◽

Air Humidity ◽

Method Performance ◽

Relative Air Humidity ◽

Evapotranspiration Estimation ◽

Missing Variables

ABSTRACT FAO Penman-Monteith (FO-PM) is considered the standard method for the estimation of reference evapotranspiration (ET0) but requires various meteorological data, which are often not available. The objective of this work was to evaluate the performance of the FAO-PM method with limited meteorological data and other methods as alternatives to estimate ET0 in Jaíba-MG. The study used daily meteorological data from 2007 to 2016 of the National Institute of Meteorology’s station. Daily ET0 values were randomized, and 70% of these were used to determine the calibration parameters of the ET0 for the equations of each method under study. The remaining data were used to test the calibration against the standard method. Performance evaluation was based on Willmott’s index of agreement, confidence coefficient and root-mean-square error. When one meteorological variable was missing, either solar radiation, relative air humidity or wind speed, or in the simultaneous absence of wind speed and relative air humidity, the FAO-PM method showed the best performances and, therefore, was recommended for Jaíba. The FAO-PM method with two missing variables, one of them being solar radiation, showed intermediate performance. Methods that used only air temperature data are not recommended for the region.

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Simulation of future climate scenarios and the impact on the water availability in southern Brazil

Acta Scientiarum Technology ◽

10.4025/actascitechnol.v43i1.56026 ◽

2021 ◽

Vol 43 ◽

pp. e56026

Author(s):

Gabriela Leite Neves ◽

Jorim Sousa das Virgens Filho ◽

Maysa de Lima Leite ◽

Frederico Fabio Mauad

Keyword(s):

Climate Change ◽

Water Balance ◽

Water Availability ◽

Meteorological Data ◽

Future Climate ◽

Climate Scenarios ◽

Southern Brazil ◽

Climate Data ◽

Intergovernmental Panel ◽

The Impact

Water is an essential natural resource that is being impacted by climate change. Thus, knowledge of future water availability conditions around the globe becomes necessary. Based on that, this study aimed to simulate future climate scenarios and evaluate the impact on water balance in southern Brazil. Daily data of rainfall and air temperature (maximum and minimum) were used. The meteorological data were collected in 28 locations over 30 years (1980-2009). For the data simulation, we used the climate data stochastic generator PGECLIMA_R. It was considered two scenarios of the fifth report of the Intergovernmental Panel on Climate Change (IPCC) and a scenario with the historical data trend. The water balance estimates were performed for the current data and the simulated data, through the methodology of Thornthwaite and Mather (1955). The moisture indexes were spatialized by the kriging method. These indexes were chosen as the parameters to represent the water conditions in different situations. The region assessed presented a high variability in water availability among locations; however, it did not present high water deficiency values, even with climate change. Overall, it was observed a reduction of moisture index in most sites and in all scenarios assessed, especially in the northern region when compared to the other regions. The second scenario of the IPCC (the worst situation) promoting higher reductions and dry conditions for the 2099 year. The impacts of climate change on water availability, identified in this study, can affect the general society, therefore, they must be considered in the planning and management of water resources, especially in the regional context

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Soil moisture in forage cactus plantations with improvement practices for their resilience

Revista Brasileira de Engenharia Agrícola e Ambiental ◽

10.1590/1807-1929/agriambi.v21n7p481-487 ◽

2017 ◽

Vol 21 (7) ◽

pp. 481-487 ◽

Cited By ~ 3

Author(s):

Ailton A. de Carvalho ◽

Thieres G. F. da Silva ◽

Luciana S. B. de Souza ◽

Magna S. B. de Moura ◽

Gherman G. L. de Araujo ◽

...

Keyword(s):

Soil Moisture ◽

Water Content ◽

Water Availability ◽

Reference Evapotranspiration ◽

Meteorological Data ◽

Block Design ◽

Soil Density ◽

Vertical Variation ◽

Rainfall Events ◽

Randomized Block Design

ABSTRACT The present study evaluated soil moisture (θ) in forage cactus plantations under resilience practices such as irrigation, mulching and intercropping with sorghum. The experiment was arranged in a randomized block design with five water availability conditions (0, 8.75, 17.5, 26.25 and 35% of the reference evapotranspiration), and three planting systems: forage cactus exclusive system (PE), forage cactus with mulch (PC) and intercropping between forage cactus and sorghum (PS). Water content was measured until a depth of 0.60 m. Meteorological data were recorded between June 2012 and June 2013. Water content was not affected by different resilience practices and the variation coefficient was low to medium (4.0 to 22.1%). The temporal variation of soil moisture was more affected by the changes in rainfall, while the physical properties (soil density, porosity and grain size) were decisive in the vertical variation. It was concluded that periods with rainfall events favor the alternation of practices to improve forage cactus resilience (irrigation, mulch and intercropping).

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Spatial and temporal variation of reference evapotranspiration under climate change: a case study in the Sanjiang Plain, Northeast China

Hydrology Research ◽

10.2166/nh.2017.039 ◽

2017 ◽

Vol 49 (1) ◽

pp. 251-265 ◽

Cited By ~ 4

Author(s):

Xinyi Song ◽

Kui Zhu ◽

Fan Lu ◽

Weihua Xiao

Keyword(s):

Sensitivity Analysis ◽

Wind Speed ◽

Reference Evapotranspiration ◽

Sunshine Duration ◽

Meteorological Data ◽

Negative Influence ◽

Sanjiang Plain ◽

Spatial And Temporal Variation ◽

The Sanjiang Plain ◽

Mountainous Regions

Abstract It is essential to understand the changing patterns in reference evapotranspiration (ET0) and its relation to climate variables. In this study, meteorological data obtained from the Sanjiang Plain (SJP) between 1959 and 2013 are used to calculate ET0 via the Penman–Monteith method. This study analyses the spatial and temporal changes of ET0 and determines which meteorological variables have an impact on this. The Mann–Kendall test, moving t-test, sensitivity analysis and simulated results have been used to conduct these analyses. The results demonstrate the following. (1) Spatially, there is an increasing trend in the annual ET0 values in agricultural areas. However, significant decreasing trends (P < 0.05) can be found in mountainous regions. (2) Temporally, two abrupt changes can be detected in the early 1980s and the late 1990s for the entire SJP, leading to large inter-annual differences. (3) Sensitivity analysis shows that relative humidity (RH) is the most sensitive climate variable and has a negative influence on ET0, followed by temperature, sunshine duration and wind speed, all of which exert positive impacts. (4) The simulated result shows that ET0 is most sensitive to RH. However, significant reductions in wind speed can exert large influences on the ET0 values.

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Complexity of Forces Driving Trend of Reference Evapotranspiration and Signals of Climate Change

Atmosphere ◽

10.3390/atmos11101081 ◽

2020 ◽

Vol 11 (10) ◽

pp. 1081 ◽

Cited By ~ 3

Author(s):

Mohammad Valipour ◽

Sayed M. Bateni ◽

Mohammad Ali Gholami Sefidkouhi ◽

Mahmoud Raeini-Sarjaz ◽

Vijay P. Singh

Keyword(s):

Climate Change ◽

Wind Speed ◽

Hydrological Cycle ◽

Reference Evapotranspiration ◽

Interactive Effects ◽

Meteorological Variables ◽

Data Series ◽

Serial Correlations ◽

Study Sites ◽

The Impact

Understanding the trends of reference evapotranspiration (ETo) and its influential meteorological variables due to climate change is required for studying the hydrological cycle, vegetation restoration, and regional agricultural production. Although several studies have evaluated these trends, they suffer from a number of drawbacks: (1) they used data series of less than 50 years; (2) they evaluated the individual impact of a few climatic variables on ETo, and thus could not represent the interactive effects of all forces driving trends of ETo; (3) they mostly studied trends of ETo and meteorological variables in similar climate regions; (4) they often did not eliminate the impact of serial correlations on the trends of ETo and meteorological variables; and finally (5) they did not study the extremum values of meteorological variables and ETo. This study overcame the abovementioned shortcomings by (1) analyzing the 50-year (1961–2010) annual trends of ETo and 12 meteorological variables from 18 study sites in contrasting climate types in Iran, (2) removing the effect of serial correlations on the trends analysis via the trend-free pre-whitening approach, (3) determining the most important meteorological variables that control the variations of ETo, and (4) evaluating the coincidence of annual extremum values of meteorological variables and ETo. The results showed that ETo and several meteorological variables (namely wind speed, vapor pressure deficit, cloudy days, minimum relative humidity, and mean, maximum and minimum air temperature) had significant trends at the confidence level of 95% in more than 50% of the study sites. These significant trends were indicative of climate change in many regions of Iran. It was also found that the wind speed (WS) had the most significant influence on the trend of ETo in most of the study sites, especially in the years with extremum values of ETo. In 83.3% of the study sites (i.e., all arid, Mediterranean and humid regions and 66.7% of semiarid regions), both ETo and WS reached their extremum values in the same year. The significant changes in ETo due to WS and other meteorological variables have made it necessary to optimize cropping patterns in Iran.

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Comparative Study of Evapotranspiration Variation and its Relationship with other Climatic Parameters in Asaba and Uyo

FUOYE Journal of Engineering and Technology ◽

10.46792/fuoyejet.v3i2.221 ◽

2018 ◽

Vol 3 (2) ◽

Author(s):

Okwunna M Umego ◽

Temitayo A Ewemoje ◽

Oluwaseun A Ilesanmi

Keyword(s):

Wind Speed ◽

Relative Humidity ◽

Solar Radiation ◽

Reference Evapotranspiration ◽

Meteorological Data ◽

Small Variation ◽

Climatic Variables ◽

Maximum Temperature ◽

Climatic Parameters ◽

Sunshine Hours

This study was carried out to assess the variations of Reference Evapotranspiration (ETO also denoted with RET) calculated using FAO-56 Penman Monteith model of two locations Asaba and Uyo and evaluate its relationships with the variations of other climatic parameters. Meteorological data of forty one years (1975-2015) and thirty five years (1981-2015) period for Asaba and Uyo, respectively gotten from Nigeria Meteorological Agency, Abuja were used. It was observed that the variations of Evapotranspiration (ET) in both locations were in line with two seasons (rainy and dry) normally experienced in Nigeria having its highest value in March (4.8 mm/day) for Asaba and for Uyo in February (4.5 mm/day); and its lowest value in August (3.1 mm/day) for Asaba and in July (2.9 mm/day) for Uyo. ET variation when compared with other climatic variables in both locations was observed to have the same trend with maximum temperature, solar radiation and sunshine hours. It also has the same variation with minimum temperature though with slight deviation. It was observed that ET variation is inversely proportional to the variation relative humidity. Wind speed displayed relatively small variation in its trend over the study period and is not in line with the variations of ET.Keywords— Evapotranspiration, Climatic Variables, FAO Penman-Monteith Model, Variations

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Trends in evaporative demand in Great Britain using high-resolution meteorological data

10.5194/hess-2015-520 ◽

2016 ◽

Cited By ~ 2

Author(s):

Emma L. Robinson ◽

Eleanor M. Blyth ◽

Douglas B. Clark ◽

Jon Finch ◽

Alison C. Rudd

Keyword(s):

Climate Change ◽

Great Britain ◽

Spatial Scales ◽

Meteorological Data ◽

Temporal Trends ◽

Natural Environments ◽

Climate Variables ◽

Climate Data ◽

Evaporative Demand ◽

Local Topography

Abstract. Observations of climate are often available on very different spatial scales from observations of the natural environments and resources that are affected by climate change. In order to help bridge the gap between these scales using modelling, a new dataset of daily meteorological variables was created at 1 km resolution over Great Britain for the years 1961–2012, by interpolating coarser resolution climate data and including the effect of local topography. These variables were used to calculate evaporative demand at the same spatial and temporal resolution, both excluding (PET) and including (PETI) the effect of water intercepted by the canopy. Temporal trends in evaporative demand were calculated, with PET found to increase in all regions and PETI found to increase in England. The trends were found to vary by season, with spring evaporative demand increasing by 14 % (11 % when the interception correction is included) in Great Britain over the dataset, while there is no statistically significant trend in other seasons. The trends in PET were attributed analytically to trends in the climate variables, with the spring trend in evaporative demand being driven by radiation trends, particularly by increasing solar radiation.

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Forcing the Penman-Montheith Formulation with Humidity, Radiation, and Wind Speed Taken from Reanalyses, for Hydrologic Modeling

Water ◽

10.3390/w11061214 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1214 ◽

Cited By ~ 3

Author(s):

Simon Ricard ◽

François Anctil

Keyword(s):

Wind Speed ◽

Water Availability ◽

Reference Evapotranspiration ◽

Low Flow ◽

Hydrologic Response ◽

Hydrologic Models ◽

Suggested Approach ◽

Hydrologic Processes ◽

Calibration And Validation ◽

Physically Based

The Penman-Monteith reference evapotranspiration (ET0) formulation was forced with humidity, radiation, and wind speed (HRW) fields simulated by four reanalyses in order to simulate hydrologic processes over six mid-sized nivo-pluvial watersheds in southern Quebec, Canada. The resulting simulated hydrologic response is comparable to an empirical ET0 formulation based exclusively on air temperature. However, Penman-Montheith provides a sounder representation of the existing relations between evapotranspiration fluctuations and climate drivers. Correcting HRW fields significantly improves the hydrologic bias over the pluvial period (June to November). The latter did not translate into an increase of the hydrologic performance according to the Kling-Gupta Efficiency (KGE) metric. The suggested approach allows for the implementation of physically-based ET0 formulations where HRW observations are insufficient for the calibration and validation of hydrologic models and a potential reinforcement of the confidence affecting the projection of low flow regimes and water availability.

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Impacts of Climate Change on Water Availability and Reservoir Based Hydropower

Journal of Forest and Natural Resource Management ◽

10.3126/jfnrm.v1i1.22653 ◽

2019 ◽

Vol 1 (1) ◽

pp. 52-68 ◽

Cited By ~ 3

Author(s):

Suman Ghimire ◽

Nabin Dhungana ◽

Suraj Upadhaya

Keyword(s):

Climate Change ◽

Water Level ◽

Water Availability ◽

Meteorological Data ◽

Secondary Data ◽

Primary Data ◽

Reservoir Water ◽

Reservoir Water Level ◽

Monthly Data ◽

Impacts Of Climate Change

The impacts of climate change (CC) are observed in several sectors, and water resource is one of them. This study explored the impacts of CC on water availability and reservoir based hydropower. It determined the impacts of CC in the reservoir water level and major watershed characteristics and has explored the perception of people on CC impacts in the reservoir. The primary data were collected through questionnaire and field survey and secondary data were gathered from different literatures. The analysis of meteorological data generated from meteorological station. temperature and rainfall data, discharge of Kulekhani River, monthly data of reservoir level and annual energy generation revealed increasing pattern of temperature and decreasing seasonal and annual precipitation in the study area. Similarly, because of the increased sedimentation, the water level of the reservoir has been increasing though the precipitation has been observed declining. Consideration could be taken while designing such hydropowers to hold water year-round, resulting minimal power shortage. A clear institutional direction and strategies could make reservoir based hydropower climate resilient and enable sustainable generation of electricity.

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Evaluation of FAO-56 Procedures for Estimating Reference Evapotranspiration Using Missing Climatic Data for a Brazilian Tropical Savanna

Water ◽

10.3390/w13131763 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1763

Author(s):

Luiz Claudio Galvão do Valle Júnior ◽

George L. Vourlitis ◽

Leone Francisco Amorim Curado ◽

Rafael da Silva Palácios ◽

José de S. Nogueira ◽

...

Keyword(s):

Wind Speed ◽

Relative Humidity ◽

Water Resource Management ◽

Reference Evapotranspiration ◽

Meteorological Data ◽

Climatic Conditions ◽

Climatic Variables ◽

Climatic Data ◽

Wet Season ◽

Radiation Data

The Brazilian savanna (Cerrado) has been heavily impacted by agricultural activities over the last four to five decades, and reliable estimates of reference evapotranspiration (ETo) are needed for water resource management and irrigation agriculture. The Penman–Monteith (PM) is one of the most accepted models for ETo estimation, but it requires many inputs that are not commonly available. Therefore, assessing the FAO guidelines to compute ETo when meteorological data are missing could lead to a better understanding of which variables are critically important for reliable estimates of ETo and how climatic variables are related to water requirements and atmospheric demands. In this study, ETo was computed for a grass-dominated part of the Cerrado from April 2010 to August 2019. We tested 12 different scenarios considering radiation, relative humidity, and/or wind speed as missing climatic data using guidelines given by the FAO. Our results presented that wind speed and actual vapor pressure do not affect ETo estimates as much as the other climatic variables; therefore, in the Cerrado’s conditions, wind speed and relative humidity measurements are less required than temperature and radiation data. When radiation data were missing, the computed ETo was overestimated compared to the benchmark. FAO procedures to estimate the net radiation presented good results during the wet season; however, during the dry season, their results were overestimated because the method could not estimate negative Rn. Our results indicate that radiation data have the highest impact on ETo for our study area and presumably for regions with similar climatic conditions. In addition, those FAO procedures for estimating radiation are not suitable when radiation data are missing.

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