Surface fluxes estimation over agricultural areas. Comparison of methods and the effects of land surface inhomogeneity

The Bowen Ratio-Energy Balance (BREB) and the aerodynamic method were used to estimate turbulent fluxes of sensible and latent heat flux over an irrig ated agricultural area (IAA) and over two dry agricultural areas (DAA1 and DAA2). These turbulent fluxes were analysed and particular attention paid t o two specific areas. First, a quantitative analysis of sensible and latent heat fluxes obtained by the BREB method was carried out, taking into accou nt different soil type, vegetation and surface conditions. The results show ed that in IAA latent heat flux was higher than sensible heat flux, except in summer months, while in DAA1 and DAA2, sensible heat flux was higher exc ept in the months when the vegetation was at the stage of maximum developme nt. Second, sensible and latent heat fluxes estimates from the BREB method were compared with those obtained from the aerodynamic method. In this comp arison factors such as soil type, soil vegetation cover, homogeneity or inh omogeneity of terrain and mesoscale effects such as orography and wind patt erns were taken into account. The results show that in conditions of light wind, the two methods only concur if the condition of horizontal homogeniet y is fulfilled. The influence of inhomogeneity seems to decrease and agreem ent between methods improves, if the wind is stronger and the effects of me so and synoptic scales are predominant.