Analysis of Precipitation Climatology Trends over Greece Based on Gridded Observational and Reanalysis Databases

This study presents an analysis of 40-years (1981–2020) precipitation climatology of ERA5-Land and E-OBS gridded datasets over Greece. The analysis focused on trends in total annual, low, moderate, and extreme precipitation—as well as number of rainy days—corresponding to the climatically diverse geographical areas of Greece. Substantial differences were found in the results between the two datasets that could be attributed to the nature of data sources. In general, ERA5-Land revealed slightly negative trends in total precipitation amount, an increase in low and moderate precipitation intensity, and an overall positive trend in extreme precipitation intensity. E-OBS demonstrated a rather negative trend in total precipitation amount, a clear decline in Crete in low precipitation intensity, a positive trend in northern Greece, and a negative trend in Southern Greece and Crete for moderate intensity, while no clear trend was revealed for most parts of Greece for extreme precipitation intensity. Regarding the corresponding results for the number of rainy days (NRD), a significant reduction was evident for E-OBS data and a slight increase for ERA5-Land data for total precipitation amount. Analysis of low precipitation intensity indicated a slight increase for ERA5-Land and an overall reduction for E-OBS. The differences are less pronounced for moderate precipitation intensity, while for extreme precipitation intensity, differences were considered as rather localized. Finally, both datasets showed positive trends in northern or mountainous geographical areas while exhibiting controversial results mainly over southern and coastal zones.