Trends and variability of precipitation within the Mediterranean region, based on Global Precipitation Climatology Project (GPCP) and ground based datasets

Abstract

This study presents and analyzes the trends and variability of precipitation totals within the Mediterranean region, for the period 1980 - 2009, by using Global Precipitation Climatology Project (GPCP) gridded datasets and ground based observations from the Hellenic National Meteorological Service (HNMS) and the World Climate Data and Monitoring Programme (WCDMP) of the World Meteorological Organization. Besides, the trends of sea surface temperature (SST) and sea surface pressure (SLP) from NCEP/NCAR Reanalysis are investigated in order to explain the observed trends in precipitation. On the other hand, the influence of atmospheric circulation, by means of North Atlantic Oscillation Index (NAOI), on the precipitation variability is presented. The results showed that an anti-correlation, (statistically significant at 95% confidence level), exists between precipitation (mm/day), rain days and NAOI, within the rain season of the year (October-March), against a positive correlation within the dry season (April-September). Concerning the temporal distribution of precipitation, decreasing trends appear throughout the Mediterranean, especially in the eastern parts and within the rain season of the year, while these trends are positive within the dry period, but statistically insignificant (95% confidence level). Increasing trends of SST for both rain and dry season, and decreasing trends of SLP appear.