SPATIAL DISTRIBUTION OF PRECIPITATIONS ASSOCIATED TO CUT-OFF LOWS IN ROMANIA IN 2014

ABSTRACT

The paper analysis the precipitations associated to the cut-off lows and their regional distribution induced by the air circulation types and the position of cut-off lows in relation to the different regions of the country, in Romania in 2014.
Cut-off lows have been identified using geopotential, air temperature and circulation maps at 500 and 300 hPa levels within the region of latitude 40 to 50 °N and longitude 15 to 35 °E. To establish the atmospheric circulation type for each cut-off event, HYSPLIT model was used (Draxler and Rolph, 2012). Based on the daily precipitation data for the year 2014 from 150 meteorological stations from Romania, divided into historical and geographical regions, the total amount of precipitation for each cut-off low event was determined. It was also calculated the monthly and annual amount of precipitation for each weather station and the ratio between the monthly (and annual) amount of precipitation and those associated to the cut-off lows.
The most important findings are: 13 cases of cut-off lows were identified, the highest number in July (3 cases); in most of the cases the cut-off lows lasted for 2 days (5 cases), the longest case having 8 days; the most significant amounts of precipitation were recorded in May and April, and the highest value recorded exceeded 100 mm (125.7 mm in Banat region); masses of air reach in moisture advected from the south (S, SV, SE) and west (V, NV), recorded a high frequency; high percentages of precipitations induced by cut-off lows from the total rainfall of the year were recorded in the regions situated in the south, east, south-west and west part of Romania as a consequence of air circulation types generating cut-off lows existence.

Keywords: precipitations, cut off-low, air circulation, Romania.