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Research Article

Turk J Agric For 34 (2010) 497-507 © TÜBİTAK doi:10.3906/tar-0909-398

Sensitivity analysis of the evaporation module of the E-DiGOR model

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2 M e h m e t A Y D I N 1 , * , S u z a n F i l i z K E Ç E C İ O Ğ L U Department of Soil Science, Faculty of Agriculture, Mustafa Kemal University, TR-31040, Hatay - TURKEY Technical Training College of Antakya, Mustafa Kemal University, TR-31040, Hatay - TURKEY 2

Received: 14.09.2009

Abstract: Sensitivity analysis of the soil-water-evaporation module of the E-DiGOR (Evaporation and Drainage investigations at Ground of Ordinary Rainfed-areas) model is presented. e model outputs were generated using measured climatic data and soil properties. e rst-order sensitivity formulas were derived to compute relative sensitivity coecients.

A change in the net solar radiation signicantly aected potential evaporation from bare soils estimated by the Penman-Monteith equation. e sensitivity coecients were positive, with a mean value of 0.82. e sensitivity of potential soil evaporation to soil heat ux was lower during the summer months and higher during the winter. e gradient of saturated vapour pressure–temperature curve increased or decreased the potential evaporation rates because of the occurrence of the gradient variable in both the numerator and denominator of the equation. Increases in the vapour pressure decit increased the evaporation and its eect was more pronounced in the winter. In the case of aerodynamic resistance, the coecients were constantly negative, and became more negative in the winter, which means a negative correlation between the input and output.

In Aydın’s equation, the dependent variable (actual soil evaporation) was initially very sensitive to a change in the water potential of a wet soil. e sensitivity decreased progressively during the drying period. e coecients related to the absolute values of soil water potential were constantly negative, with a mean value of –0.19. e sensitivity of actual soil evaporation to air-dry water potential remained low in the wet soil and was higher in the drier soil. e sensitivity coecient to measure the impact of potential evaporation on actual evaporation did not change during the study. According to Aydın and Uygur’s equation, potential soil evaporation greatly aected the output (soil water potential) in the wet soils. In Kelvin’s equation, increases in air temperature increased the absolute value of water potential at air- dryness. e sensitivity coecients, owing to relative humidity, showed a great deal of uctuation.

Key words: E-DiGOR model, sensitivity analysis, soil evaporation

E-DiGOR modelindeki buharlaşma modülünün duyarlılık analizi

Özet: Bu çalışmada E-DiGOR (Evaporation and Drainage investigations at Ground of Ordinary Rainfed-areas) modelinin toprak -suyunun- buharlaşması modülü için bir duyarlılık analizi sunulmaktadır. Model çıktıları, gözlemlenen iklim verileri ve toprak özellikleri kullanılarak üretilmiştir. Göreceli duyarlılık katsayılarını hesaplamak için birinci-derece duyarlılık formülleri türetilmiştir.

  • *

    E-mail: maydin@mku.edu.tr

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