Local simulations of land-sea breeze cycles in Athens based on large-scale operational analyses

Two different episodes of land-sea breeze evolution in the Athens area are numerically investigated using a non-hydrostatic mesoscale model, with E-ε turbulence closure, in the framework of the APSIS project. The initialization and the time evolving boundary conditions are derived from the ECMWF operational analyses. The simulated surface winds have been compared with available surface measurements. On these two situations, the use of operational analyses imposed on the boundary of a local model provides more realistic simulations than those based only on local soundings. The results obtained are closer to more sophisticated nested simulations except in a relaxation zone near the boundaries. The urbulence predicted by the E-ε turbulence model is very weak in early morning and increases to values representative of moderately convective conditions during the day in correspondence with the observed poor dispersion of pollutants.