THERMAL EXCHANGES AT AIR WATER INTERFACES AND REPRODUCTION OF TEMPERATURE VERTICAL PROFILES IN WATER COLUMNS

For a 3-D eutrophication-diffusion macromodel of the central part of the Venice Lagoon, air-water heat fluxes are computed interpolating, through Fourier series expansion, meteoclimatic variables averaged over a thirty years survey. Also reproduced with the same interpolation methods, is the daily fluctuation of incident light as well as the annual variation of the photoperiod. With an iterative procedure temperature values, to be assigned at each grid's point and corresponding to each hour of a reference year, are computed also accounting for the thermal inertia of water columns of varying depths. By statistical examination of temperature vertical profiles, depth varying diffusivities are also estimated, which enables, without assumption of an instantaneous mixing, the reproduction of heat diffusion from the surface to the bottom water cells. Procedures. preliminarly refined and verified for a one-dimensional vertical system input, are next implemented on a three-dimensional submodel of reduced size provided of ''open boundaries'': this last submodel, under a continuous input of energy and of matter is seen to attain a steady states as well as to be capable of simulating regime conditions. A further validation is performed. on a submodel of 43 x 47 x 20 cells. encompassing a limited portion of the macromodel and presenting the actual lagoon bathymetry. Macromodel's seasonalisation so achieved, enables for a more correct simulation of the periodical behaviour of light and of temperature, forcing functions governing the eutrophication phenomena.