Sensitivity analysis of Evapotranspiration- A comparison of Northern and Southern climate of Italy

Understanding the sensitivity of reference evapotranspiration (ET₀) to meteorological variables is critical for improving urban water management and climate adaptation strategies. This study analyses the one-way and two-way sensitivity of ET₀ to maximum temperature (Tmax), wind speed (u₂), net solar radiation (Rn), and maximum relative humidity (RHmax) using the FAO-56 Penman-Monteith equation for multiple meteorological stations in Northern (Liguria and Lombardy) and Southern (Sicilia) regions of Italy. Although, local weather conditions, latitude and altitude of the area, urban setting and time of year alters the course of sensitivity but the relation of investigated input variables with ET₀ remains similar as observed in these results. Tmax, Rn and u2 positively affect the ET₀ while RHmax negatively impacts the ET₀, whereas vapour pressure deficit has a nonlinear behaviour. These findings underscore the need for region- and season-specific calibration of ET₀ models to support accurate urban drainage planning and water resource management.