Flow dynamics in Athens area under moderate large-scale winds

The purpose of the present paper is to study the wind regime in Greater Athens Area (GAA) during a day when the sea breeze was opposing a moderately strong synoptic-scale flow. The approach adopted in the present study is to analyze data from a field campaign and from numerical model simulations. The field 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-following coordinate system, which enables studies of flow over complex terrain. The results from the simulations compare reasonably well with the field data. The analysis of the field data and the numerical simulation results reveals that, under the present conditions, the temporal and spatial variations of the wind field are not as pronounced as in days with weak synoptic background flow. A sea breeze circulation is developing over the sea and reaches the shoreline but is counterbalanced by the opposing synoptic flow and it does not penetrate deeply over the land. The characteristics of the sea breeze systems developing in GAA under weak large-scale ambient winds are presented in a companion paper.