TRMM-based rainfall variability over the Central Mediterranean and its relationships with atmospheric and oceanic climatic modes

The seasonal rainfall variability over the Central Mediterranean area was studied in this research using the Tropical Rainfall Measurement Mission (TRMM) monthly product for the 20-years period 1998-2017, with emphasis given on the fresh water flux over the marine areas. The relationships with the principal atmospheric and oceanic climatic modes were also explored. Significant positive trends were detected over the Ionian Sea during the autumn and mild negative trends over the Northern Italy - Dinaric Alps, enhancing over the Northern Ligurian Sea. These tendencies were found to be regulated by the North Atlantic Oscillation (NAO), the Scandinavian (SCAND) pattern, and particularly by the Mediterranean evaporation under the influence of the increasing Mediterranean Sea Surface Temperature (SST) and the East Atlantic - West Russia (EAWR) pattern. On the contrary, significant negative trends were detected in the winter and spring rainfall over the Ionian and the Tyrrhenian Seas, and positive trends over the Southern Alps and the Adriatic Sea - Balkans area. These stresses were modulated by the combined effects of the SCAND, EAWR, and NAO during the winter, and also associated with the Mediterranean evaporation and SST during the spring under the influence of NAO and the East Atlantic pattern. During the summer mild negative trends were detected over the Tyrrhenian Sea and coherent rainfall variations with the increasing Mediterranean SST over the Ionian Sea. These tendencies seem to be associated with the prevalence of negative anomalies in the summer NAO.