Long-term climatic trends for the Mediterranean region and their association with atmospheric circulation

The Mediterranean region is characterized by high vulnerability and changes in the atmospheric circulation and water cycle with significant socio-economic implications. Many regions in the Mediterranean basin face extreme climate events, while others do not exhibit the same sensitivity to climate change. In this study, the spatial and temporal variability of climatic parameters such as precipitation, temperature, and dew point are investigated. Furthermore, their sensitivity to changes in atmospheric circulation is also examined in terms of the response of the surface climatic conditions for different atmospheric circulation types. Long-term data are extracted from the ERA 5 reanalysis dataset over the period of 1961-2020 (70 years) at a spatial resolution of 0.25° × 0.25°. The analysis procedure includes the identification of trends in the time series using the non-parametric Mann-Kendall and Sen's methods. Regions with statistically significant trends are identified and discussed. Discrepancies are also examined between the trends identified from the ERA 5 reanalysis datasets and from E-OBS and in-situ climate records. The atmospheric circulation framework is based on the following a) Definition of the spatial and temporal scales, b) Standardization of the spatial and temporal time series and data reduction using Principal Components Analysis c) Classification and assignment of cases into atmospheric circulation regimes using the k-means algorithm and d) Atmospheric circulation regimes assembly of the daily regimes (weather types) catalog. Trends and high-impact areas of global warming are identified and therefore the association between atmospheric circulation and climate change is highlighted.