Abstract : 1C.20
Clustering of the high resolution backward trajectories for Slovenia

Rahela ŽAbkar, JožE Rakovec
University of Ljubljana, Faculty of mathematics and Physics, Chair of Meteorology

High resolution backward air trajectories arriving at four measuring sites in Slovenia were calculated for months from April to September of years 2003-2006 with Flextra model (http://www.forst.uni-uenchen.de/EXT/LST/METEO/stohl/flextra.html). An improved K-means clustering methodology was used for classification of trajectories into groups with similar curvature, length and direction. To establish the influence of air mass origin on air masses main characteristics in Slovenia were studied precipitation, air temperature and relative humidity conditions in Slovenia (at trajectory endpoints) for groups of similar trajectories (clusters).

Trajectories were calculated on ALADIN meteorological fields with 10 km spatial and 1 hour temporal resolution. The length of trajectories is 96 hours in time and their endpoints are located 50 m above ground as well as 1500 m and 5500 m above mean sea level. Different analyses of trajectories, like number density, mean age, height, velocity and residential time of trajectories, reveal the most typical flow patterns and effects of alpine barrier on air mass traveling.