Lower Tropospheric Structure and Synoptic Scale Circulation Patterns During Prolonged Temperature Inversions over Athens, Greece

Summary In this paper an attempt is made to detect prolonged (of more than 24 hours duration) temperature inversions in the planetary boundary layer over Athens, to study their main characteristics and to find out the synoptic situations with which the inversions are associated. Given the close relationship between the synoptic-scale atmospheric circulation and the occurrence, maintainance and decay of temperature inversions, a simultaneous three category classification of presented inversions and their respective synoptic situations is presented. The classification relies mainly on the similarities and differences in the formation and the maintenance of prolonged temperature inversions. To provide a record of the structure of the lower troposphere and the synoptic conditions favourable to the formation of inversions, mean ascents of temperature and dew-point temperature and mean wind profiles for the years 1980–1994 were calculated for each category into which a total of 297 cases fell. The main element of this structure which strongly affects the pollution of the lower troposphere is the prolonged temperature inversion. Also, for each category, mean 500 and 850 hPa heights and temperature charts, 500 hPa height anomaly charts, mean sea level (MSL) pressure charts and MSL pressure anomaly charts were drawn. Received March 11, 1997 Revised October 6, 1997