<p>The study deals with probabilities of transitions from arid to humid environment and vice versa in<br>Europe. Aridity index, defined as a ratio of potential evapotranspiration and precipitation and<br>representing the ratio between energy availability and water availability, is used to characterize humid<br>(wet) and arid (dry) regions and allows us to study transitions between individual periods (wet-wet,<br>wet-dry, dry-dry, dry-wet). Three gridded datasets &#8211; CRU (UEA, 2020), E-OBS (ECAD, 2020) and ERA5<br>(ECMWF, 2020) &#8211; are used for this purpose. The aim of the study is to compare the three datasets as<br>to transitions between wet and dry conditions, which are determined according to the aridity index,<br>and evaluate the variability in Europe over 1950&#8211;2019. The changes in the aridity index since 1950 are<br>found to be most pronounced in Northern and Central Europe.</p><p><br>references:<br>ECAD, 2020: E-OBS gridded dataset, available from<br><https://www.ecad.eu/download/ensembles/download.php>.<br>UEA, 2020: University of East Anglia &#8211; Climatic Research Unit, available from<br><https://lr1.uea.ac.uk/cru/data>.<br>ECMWF, 2020: European Centre for Medium-Range Weather Forecasts &#8211; ERA5, available from<br><https://www.ecmwf.int/en/forecasts/datasets/reanalysis-datasets/era5>.</p>