Sensitivity analysis of Penman evaporation method

In this paper the influence of key meteorological variables in Penman evaporation method was explored. Monthly data over a 16-years period (1993-2008)were used from Thissio-Athens meteorological station. The climatic parameters of surface air temperature, relative humidity, wind speed and sunshine duration were varied in Penman method and the obtained results were compared. Moreover, the investigationof sunshine duration during winter months was thoroughly examined. An open source software (Hydrognomon) was used for this exploration. The analysis showed that: (a) the influence of the meteorological parameters to evaporation is almost linear, (b) the temperature has the greater influence to annual evaporation while the relative humidity, wind speed and sunshine duration follow, and (c) the relationship between sunshine duration and evaporation in a monthly scale is not constant. During the winter months the increase of sunshine duration leads to decrease of evaporation. The performed analysis could be used to quantify the impact of climatic change on evaporation, to determine the accuracy of predicted evaporation against that obtained from the meteorological instruments, and to investigate the alternative values of several meteorological variables in the case of limited data sets.