A study on the total cloud cover variability over the Mediterranean region during the period 1979–2014 with the use of the ERA-Interim database

Abstract

The variability and the trends of total cloud cover over the Mediterranean region are studied for the period 1979–2014, using ERA-Interim monthly 1° × 1° grid point data. A data reduction process is applied, and the main modes of inter-annual variation are found for each of the four seasons. Statistically significant positive linear trends are found only for winter over northern Italy and the northwestern Balkans, while significant negative trends are found over large parts of the region for the rest of the seasons, especially for summer. The connection between cloud cover and the large-scale atmospheric oscillations is also examined, revealing statistically significant correlations between cloud cover and the indices of the North Atlantic Oscillation, the North Sea-Caspian Pattern, the Arctic Oscillation, the Southern Oscillation, and the Eastern Atlantic/Western Russia Pattern. These connections highlight the strong dependence of the Mediterranean climate on specific characteristics of the large-scale atmospheric circulation.