FLOW DYNAMICS IN ATHENS AREA UNDER MODERATE LARGE-SCALE WINDS

The purpose of the present paper is to study the wind regime in Greate r Athens Area (GAA) during a day when the sea breeze was opposing a mo derately strong synoptic-scale Bow. The approach adopted in the presen t study is to analyze data from a field campaign and from numerical mo del simulations. The field data used in the analysis are from the MEDd iterranean CAmpaign of PHOtochemical Tracers-TRAnsport and Chemical Ev olution (MEDCAPHOT-TRACE) which took place in the GAA during the perio d 20 August-20 September 1994. The numerical simulations were performe d using a three-dimensional, higher-order turbulence closure model. Al l model equations are transformed to a terrain-following coordinate sy stem, which enables studies of Bow over complex terrain. The results f rom the simulations compare reasonably well with the field data. The a nalysis of the field data and the numerical simulation results reveals that, under the present conditions, the temporal and spatial variatio ns of the wind field are not as pronounced as in days with weak synopt ic background Bow. A sea breeze circulation is developing over the sea and reaches the shoreline but is counterbalanced by the opposing syno ptic flow and it does not penetrate deeply over the land. The characte ristics of the sea breeze systems developing in GAA under weak large-s cale ambient winds are presented in a companion paper. (C) 1998 Elsevi er Science Ltd. All right reserved.