Thermodynamic configurations associated with heavy rainfall in Eastern Romania

摘要

Worldwide, meteorological events associated with severe weather affect life, property and infrastructure. Lately, heavy rainfalls led to loss of life and produced damage in various areas of Romania. The main aim of the article is to investigate the dynamic and thermodynamic, both synoptic and mesoscale, configurations associated with severe weather in eastern Romania. Using the empirical orthogonal functions (EOF) analysis, simultaneously applied to daily average geopotential field at different pressure levels (300, 500 and 850 hPa), a number of severe weather events were clustered into classes. At European scale, the analysis showed the existence of three eigenvectors which describe up to 73% of the data. Using the projections of these vectors on 62 days with severe weather, eight classes of synoptic configurations resulted. For each class, the main dynamic characteristics were highlighted. Repeating the EOF analysis on the same geopotential fields, but using reanalysis data at 6h interval, it was revealed that each class has a limited number of eigenvectors which can be used to explain the dynamic similarity between different baroclinic evolutions. The mesoscale feature analysis was performed using Doppler weather radar data. The increase from south to north of the thermodynamic instability and dynamic organizational factors is highlighted for all the classes. The occurrence of certain classes takes place in different times of the convective season, while the most persistent classes are positioned in the middle of the convective season. An important finding is that by projecting the first three eigenvectors on the numerical weather prediction models outputs, one can infer the most likely dynamic behaviour to expect in a synoptic time interval. The climatological evolution of the projection on the data of each class, for the 1980-2014 interval, shows a change in the baroclinic dynamic configuration associated with heavy rainfall.