Anatomy of the sea-breeze circulation in Athens area under weak large-scale ambient winds

The city of Athens is located near an irregular coastline and is surrounded by moderately high mountains. The complex structure of the sea breezes developing in Greater Athens Area (GAA) during a day with weak large-scale ambient winds is examined using consolidated field data and results from numerical model simulations. The data used in the analysis are from the MEDditerranean CAmpaign of PHOtochemical Tracers-TRAnsport and Chemical Evolution (MEDCAPHOT-TRACE) which took place in the GAA during the period 20 August-20 September 1994. The numerical simulations were performed using a three-dimensional, higher-order turbulence closure model. All model equations are transformed to a terrain-influenced coordinate system, which enables studies of flow over complex terrain. A full diurnal cycle has been simulated for the typical sea-breeze day of 15 September 1994. Major characteristics of the sea-breeze circulation including surface wind pattern, inland penetration of the sea-breeze front and vertical extension and intensity as well as diurnal variation of the vertical eddy thermal diffusivity are identified and discussed. Model predictions show a good agreement with the comprehensive data set. (C) 1998 Elsevier Science Ltd. All rights reserved.