CYCLONIC ACTIVITY OVER ROMANIA IN CONNECTION WITH THE AIR CIRCULATION TYPES

摘要

Generally, the severe weather phenomena are associated with cyclonic activity over Romania. The aim of this paper is to assess a correlation between the cyclone frequency into a representative area for Romania and the circulation types conform to "COST733 Catalogue". The selected domain was between 10° and 35° E longitude and 35° and 55° N latitude. The selected area is similar to Domain 10 from COST733 Catalogue. The Mediterranean cyclones, reaching this domain from the south-west can be accounted for. The cyclones of Icelandic origin with north-west to south-east trajectories sometimes are reactivated in Central Europe through cold air penetrating the upper troposphere and reach over Romanian territory. A peculiar category is that of cyclones moving along retrograde tracks. Using daily NCEP/NCAR reanalysis data for the sea level pressure, a subjective analysis of cyclone frequency has been performed for the cold period (the 1~(st) of November-the 31~(st) of March) between 1996-2002 years. All closed cyclonic nuclei with a pressure equal to or lower than 1,015 hPa in the sea-level pressure field were accounted for using LWT2 Cost 733 catalogue, the frequency of circulation types for the analyzed interval has been established. The anticyclonic circulation types seem to be the more frequent and, by the other hand, the graphical correlations show that the cyclonic activity in the domain is important especially during the periods with eastern or south-eastern dominant air circulation.