The predicting potential of two different sensitivity coefficients in seven reference evapotranspiration models

The estimation of evapotranspiration is essential in water resources management. Among a group of methods, the Penman–Monteith has been commonly applied to calculate reference evapotranspiration as this method has been also recommended by the Food and Agriculture Organization of the U.N. (FAO). Other methods widely used are: the FAO 24 Penman, the modified Blaney and Criddle, the FAO 24 Makkink, and the Hargreaves. Sensitivity analysis is required to gain a better understanding of the meteorological systems; particularly to indicate the physical meaning of each meteorological parameter used in the estimation of the reference evapotranspiration. Several dimensionless sensitivity coefficients have been proposed, based on the partial derivative of the dependent variable (reference evapotranspiration) to the independent variables (meteorological variables). In this paper, a new sensitivity coefficient is proposed to drive sensitivity analysis of the evapotranspiration methods. The new sensitivity coefficient uses the partial derivative and the standard deviation of each independent variable. The meteorological variables, whose influence has been examined, are all the necessary meteorological parameters for the calculation of reference evapotranspiration, such as temperature, solar radiation, wind speed and relative humidity for each method. Data from the automatic meteorological station of Aminteo in the Prefecture of Florina, Western Macedonia, were used. The sensitivity coefficients were calculated for each month, year and irrigation period. The comparison of the sensitivity coefficients is performed for the month of water peak demand (July), the irrigation period and the year for each evapotranspiration method. Results show that the influence of the variables to evapotranspiration is not the same for each period, and also the order that the variables influence evapotranspiration is changing. A comparison between the five evapotranspiration methods shows that solar radiation and temperature are the main parameters that affect evapotranspiration, while relative humidity and wind speed are not so important for the calculation of evapotranspiration.

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Spatial variation of climatology monthly crop reference evapotranspiration and sensitivity coefficients in Shiyang river basin of northwest China

Agricultural Water Management ◽

10.1016/j.agwat.2010.05.004 ◽

2010 ◽

Vol 97 (10) ◽

pp. 1506-1516 ◽

Cited By ~ 45

Author(s):

Xiaotao Zhang ◽

Shaozhong Kang ◽

Lu Zhang ◽

Junqi Liu

Keyword(s):

Spatial Variation ◽

River Basin ◽

Reference Evapotranspiration ◽

Northwest China ◽

Sensitivity Coefficients ◽

Shiyang River Basin

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Seasonal Prediction of Regional Reference Evapotranspiration Based on Climate Forecast System Version 2

Journal of Hydrometeorology ◽

10.1175/jhm-d-13-087.1 ◽

2014 ◽

Vol 15 (3) ◽

pp. 1166-1188 ◽

Cited By ~ 17

Author(s):

Di Tian ◽

Christopher J. Martinez ◽

Wendy D. Graham

Keyword(s):

El Niño ◽

Reference Evapotranspiration ◽

El Nino ◽

Maximum Temperature ◽

Climate Forecast ◽

Coarse Scale ◽

Forecast System ◽

Climate Forecast System ◽

Sensitivity Coefficients ◽

Spatial Disaggregation

AbstractReference evapotranspiration (ETo) is an important hydroclimatic variable for water planning and management. This research explored the potential of using the Climate Forecast System, version 2 (CFSv2), for seasonal predictions of ETo over the states of Alabama, Georgia, and Florida. The 12-km ETo forecasts were produced by downscaling coarse-scale ETo forecasts from the CFSv2 retrospective forecast archive and by downscaling CFSv2 maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tmean), solar radiation (Rs), and wind speed (Wind) individually and calculating ETo using those downscaled variables. All the ETo forecasts were calculated using the Penman–Monteith equation. Sensitivity coefficients were evaluated to quantify how and how much does each of the variables influence ETo. Two statistical downscaling methods were tested: 1) spatial disaggregation (SD) and 2) spatial disaggregation with quantile mapping bias correction (SDBC). The downscaled ETo from the coarse-scale ETo showed similar skill to those by first downscaling individual variables and then calculating ETo. The sensitivity coefficients showed Tmax and Rs had the greatest influence on ETo, followed by Tmin and Tmean, and Wind. The downscaled Tmax showed highest predictability, followed by Tmean, Tmin, Rs, and Wind. SDBC had slightly better performance than SD for both probabilistic and deterministic forecasts. The skill was locally and seasonally dependent. The CFSv2-based ETo forecasts showed higher predictability in cold seasons than in warm seasons. The CFSv2 model could better predict ETo in cold seasons during El Niño–Southern Oscillation (ENSO) events only when the forecast initial condition was in either the El Niño or La Niña phase of ENSO.

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Sensitivity of FAO Penman–Monteith reference evapotranspiration (ETo) to climatic variables under different climate types in Nigeria

Journal of Water and Climate Change ◽

10.2166/wcc.2020.200 ◽

2020 ◽

Cited By ~ 2

Author(s):

Ndulue Emeka ◽

Onyekwelu Ikenna ◽

Michael Okechukwu ◽

Anyadike Chinenye ◽

Echiegu Emmanuel

Keyword(s):

Climate Change ◽

Tropical Rainforest ◽

Reference Evapotranspiration ◽

Climatic Variables ◽

Maximum Temperature ◽

Sustainable Water Management ◽

Sensitivity Coefficients ◽

Port Harcourt ◽

Specific Objective ◽

The Impact

Abstract Understanding the impact of changes in climatic variables on reference evapotranspiration (ETo) is important for predicting possible implications of climate change on the overall hydrology of an area. This study aimed to determine the effects of changes in ETo with respect to changes in climatic variables. In addition, the specific objective was to determine the sensitivity coefficients of ETo in seven different locations in Nigeria with distinct agroecology, namely Maiduguri (Sahel savannah), Sokoto (Sudan savannah), Kaduna (Guinea savannah), Jos (Montane), Enugu (Derived Savannah), Ibadan (tropical rainforest), and Port Harcourt (coastal). The results showed that ETo is most sensitive to changes in maximum temperature (Tmax) in Maiduguri, Sokoto, Kaduna, and Jos. In Enugu and Ibadan, ETo is most sensitive to changes in solar radiation (Rs), while in Port Harcourt, ETo is most sensitive to relative humidity (RH). Overall, based on the average annual sensitivity coefficients (SCs) of the study area, the SC is ranked in the order: RH > Rs > Tmax > U2 > Tmin. Also, the results showed positive SCs of ETo to Rs, Tmax, U2, Tmin, and negative SC for RH. This study can serve as a baseline for sustainable water management in the context of climate change and adapted to areas with a similar climate.

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Annual Evapotranspiration and Crop Coefficients of Ligustrum japonica Growing in Three Container Sizes

HortScience ◽

10.21273/hortsci.33.3.512c ◽

1998 ◽

Vol 33 (3) ◽

pp. 512c-512

Author(s):

R.C. Beeson

Keyword(s):

Reference Evapotranspiration ◽

Actual Evapotranspiration ◽

Rooted Cuttings ◽

Supplemental Irrigation ◽

Mean Size ◽

Crop Coefficients ◽

Marketable Size

The objective of this study was to determine crop coefficients (KC) for Ligustrum japonica growing in three container sizes using the Penman equation to calculate reference evapotranspiration (ETR). Rooted cuttings were transplanted into 3-liter containers and upcanned as needed into 10- and 23-L containers. Production was scheduled such that a series of plants in each container size were about 2 months from commercial marketable size every 4 months. Beginning 1 Jan. 1995 until 31 Dec. 1996, three uniform plants of each size were suspended in weighing lysimeters and surrounded by similar size plants filling an area 3.7 by 4.9 m. Plants within each area were overhead irrigated at 2000 h as needed, based on a 30% moisture allowed deficit. Plants were exchanged every 4 months such that the annual mean size was that of a marketable plant. Actual evapotranspiration (ETA) was calculated from half-hour measurements of each plant's weight and adjusted for rainfall. From these and daily calculated ETR, KC were determined for each size of container. KCs ranged from 1.06 to 1.50 when ETA was converted to mm/day based on allocated bed space. Comparisons of volumes of supplemental irrigation to ETA and effects of assumptions required in converting ETA to mm/day will be discussed.

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