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
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
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 coecients.
A change in the net solar radiation signicantly aected potential evaporation from bare soils estimated by the Penman-Monteith equation. e sensitivity coecients 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 decit increased the evaporation and its eect was more pronounced in the winter. In the case of aerodynamic resistance, the coecients 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 coecients 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 coecient 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 aected 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 coecients, 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.