PRESSURE COVARIABILITY OVER THE ATLANTIC, EUROPE AND N AFRICA - APPLICATION - CENTERS OF ACTION FOR TEMPERATURE, WINTER PRECIPITATION AND SUMMER WINDS IN ATHENS, GREECE

This paper deals with the surface pressure covariability over the Alta ntic/European sector of the Northern Hemisphere. using monthly grid po int data for 100 year period 1890 1989. Factor analysis is applied to 90 grid point time series for January, February. July, and August. The initial 90 pressure variables can be reduced to 7-8 factors in winter and 10 in summer. A winter teleconnection was identified. known as th e seesaw phenomenon, between the Icelandic low and the Azores subtropi cal anticyclone. In order to define the centers of action for temperat ure, winter precipitation and summer northern wind frequency (etesian days) in Athens and in the Aegean sea, the variability of the factor s cores and of these weather elements is compared. It is shown that the center of action for temperature in Athens is found to be in north and northwest Europe (centered over southern Scandinavia). For winter pre cipitation, the center of action is located in the west and southwest Mediterranean and northwest Africa. Finally, for the etesian winds fre quency variability, this center of action is found over the northern A driatic and northern former Yugoslavia, while there is no evidence of influence by the southwest Asia thermal low.