Studia Universitatis Babeş-Bolyai: Geographia (Jun 2014)
VALIDATION OF SEVERAL ATMOSPHERIC STABILITY INDICES FOR THE STORMS GENERATING TORRENTIAL RAIN SHOWERS IN THE NORTH-WEST OF ROMANIA
Abstract
Validation of Several Atmospheric Stability Indices for the Storms Generating Torrential Rain Showers in the North-West of Romania. The present study deals with the atmospheric instability types that lead to torrential rain formation in the North-Western part of Romania and with the role that certain stability indices play in establishing the atmospheric instability potential. 35 years of warm season rainfall data from 14 meteorological stations in the North-West of Romania have been analysed in this respect. The Hellman criterion was employed in order to establish the torrential character of the rainfall events, having made use of 271 of such rainfall events in the analysed period (1975-2009). Considering that the synoptic context of the torrential rain occurrence differs according to the instability type existing at the moment of their apparition, the analysis of the stability indices has taken this feature into consideration as well. Hence, three types of instability have been identified (convective lifting, frontal lifting and that produced due to the “cut off” nuclei) their analysis underlining the highest frequency of torrential rains caused by the convective lifting (49.1%), followed by the frontal type (27.7%) and the ‘cut off” type (23.2%), their highest percentage being registered in the summer. The values of 5 stability indices have been taken into account (KI, VT, CT, TTI and LI), determined on the basis of the aerologic survey at 00 GMT time, undertaken in Cluj-Napoca, plus two more modified indices (KMOD and TTMOD). Having analysed them, it was possible to identify the most useful ones for determining the convective storms conditions generating torrential rains in the North-West region of Romania.
