Validation and calibration of various reference evapotranspiration alternative methods under the climate conditions of Bosnia and Herzegovina

In Bosnia and Herzegovina (BiH), the number of weather stations (WS) that are monitoring all climatic parameters required for FAO-56 Penman-Monteith (FAO-PM) equation is limited. In fact, it is of great need and importance to achieve the possibility of calculating reference evapotranspiration (ET0) for every WS in BiH (around 150), regardless of the number of climate parameters which they collect. Solving this problem is possible by using alternative equations that require less climatological data for reliable estimation of daily and monthly ET0. The main objective of this study was to validate and determine, compared to the FAO-PM method, a suitable and reliable alternative ET0 equations that are requiring less input data and have a simple calculation procedure, with a special focus on Thornthwaite and Turc as methods previously often used in BiH. To fulfill this objective, 12 alternative ET0 calculation methods and 21 locally adjusted versions of same equations were validated against FAO-PM ET0 method. Daily climatic data, recorded at sixteen WS, including mean maximum and minimum air temperature (°C), precipitation (mm), minimum and maximum relative humidity (%), wind speed (m s−1) and sunshine hours (h) for the period 1961–2015 (55 years) were collected and averaged over each month. Several types of statistical indicators: the determination coefficient (R2), mean bias error (MBE), the variance of the distribution of differences (sd2), the root mean square difference (RMSD) and the mean absolute error (MAE) were used to assess alternative ET0 equation performance. The results, confirmed by various statistical indicators, shows that the most suitable and reliable alternative equation for monthly ET0 calculation in BiH is the locally adjusted Trajkovic method. Adjusted Hargreaves-Samani method was the second best performing method. The two most frequently used ET0 calculation methods in BiH until now, Thornthwaite and Turc, were ranked low.publishedVersio

A reference evapotranspiration map for Bosnia and Herzegovina

There are three major challenges for climatic data availability for Reference Evapotranspiration (ET0) calculations in Bosnia and Herzegovina: limited data availability, discontinuity of data records, and low station density. The main objective of this study was to apply reliable methods to calculate and spatially distribute ET0, while considering the impact of the elevation. A 20 m spatial resolution map was created for mean ET0 values at monthly, vegetation period (April–September) and annual temporal resolution at municipality (143 municipalities), regional (4 regions) and national spatial resolutions. 108 weather stations for the period 1961–2016 (56 years) were utilized for spatial interpolation of ET0 using kriging with external drift method. The required elevation for ET0 estimation at each grid node was extracted from the digital elevation model of Bosnia and Herzegovina. ET0 was calculated using FAO-56 Penman-Monteith, and in cases where only minimum and maximum temperature data were available the Hargreaves-Samani equation adjusted with locally appropriate empirical radiation coefficient was used. A gradual decrease of mean ET0 values from the southern to central and northern to central part of the country is notable. For the all seasons (monthly, vegetation and annually), the southern region has greater ET0 than the other three regions (north, west and central-east), which are similar. The long-term mean annual ET0 for Bosnia and Herzegovina is 716 mm, approximately 78% (559 mm) of which occurs during in the vegetation period. Keywords: Reference evapotranspiration, Interpolation, Penman-Monteith, Limited data, Calibratio

Yield-scaled N₂O emissions.

<p>Different letters indicate significant differences across treatments at P < 0.05.</p

Soil physical properties 20 months after the establishment of contrasting tillage regimes (August 2015).

<p>Soil physical properties 20 months after the establishment of contrasting tillage regimes (August 2015).</p

Average crop yields corrected for 14% moisture in CT, RT and NT.

<p>Average crop yields corrected for 14% moisture in CT, RT and NT.</p

La Charente

20 décembre 19081908/12/20 (A37,N10812)-1908/12/20.Appartient à l’ensemble documentaire : PoitouCh

N₂O emission factors.

<p>Different letters indicate significant differences across treatments at P < 0.05.</p

Net income per hectare under different tillage systems based on the difference of crop net income and variable costs of production.

<p>Net income per hectare under different tillage systems based on the difference of crop net income and variable costs of production.</p

Average monthly temperatures and precipitation close to the sampling site.

<p>Average monthly temperatures and precipitation close to the sampling site.</p

Cumulative N₂O emissions.

<p>Cumulative N₂O emissions.</p