Statistical Relationships between Large-Scale Oscillation Phenomena and Mesoscale Atmospheric Conditions over Central/Eastern Europe and Their Representation in CMIP5 General Circulation Models

Atmospheric oscillation phenomena or teleconnection systems are large-scale circulation patterns, which can be interpreted as regions with significant negative correlation between each other. The target area of the study is the Carpathian Basin located in Central/Eastern Europe where meso-scale atmospheric processes are especially dominated by large-scale atmospheric circulations during the winter months (December, January and February). That is why other months are excluded from the current analysis. First, we aim to assess the spatio-temporal changes of the action centers – which are the most intense areas of the teleconnection systems – from the early decades of the 20th century to the Millennium applying statistical methods such as empirical orthogonal functions (EOF). Then, the statistical relationships between identified oscillation phenomena over the northern mid-latitudes and atmospheric variables over the Carpathian Basin are explored in details. These evaluations are based on the time series of geopotential height at 500 hPa from the European Centre for Medium-Range Weather Forecasts’ (ECMWF) ERA-20C reanalysis datasets. After that, similar analyses are carried out on the historical simulations of general circulation models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Finally, the results of the GCM simulations are compared to the ERA-20C dataset. We aim to evaluate the abilities of the GCMs to reproduce oscillation phenomena. Differences between the GCM simulations and reanalysis dataset are assessed by computing metrics (e.g. root-mean-square error, RMSE). Our ultimate goal is to prepare improved climate predictions for the Carpathian Basin for the 21st century using the best-performing models.