Air temperature trends related to changes in atmospheric circulation in the wider area of Greece

Abstract

Surface air temperature trends in the wider region of Greece during the period 1951–2007, related to atmospheric circulation, are examined in this work. A network of 31 meteorological stations in the Hellenic area and the Asia Minor coasts and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis datasets were used for this purpose. The NCEP/NCAR reanalysis datasets were created by assimilating climate observations from different sources including ships, satellites, ground stations, radiosonde observations and radar. The general purpose of conducting the reanalyses was to produce multiyear global state-of-the-art gridded representations of atmospheric states, generated by a constant model and a constant data assimilation system.

The findings of the analysis show that the mean annual surface air temperature in the wider region of Greece exhibits a pronounced cooling trend from the beginning of the 1950s up to the mid-1970s. It then remained at low levels until the beginning of the 1990s, and then increased up to 2000, when a turning-point is clear although the temperature remained at high levels. The well-known atmospheric circulation indices of the wider region of Europe, namely the North Atlantic Oscillation Index (NAOI), the Mediterranean Oscillation Index (MOI) and the North Sea Caspian Pattern Index (NCPI), were used to investigate the relationship between surface air temperature and atmospheric circulation in this region of the Eastern Mediterranean. The surface air temperature is not correlated to the NAOI, while it is statistically significantly (95% confidence level (CL)) correlated to the MOI, but only during wintertime. On the contrary, good correlations, which are statistically significant (95% CL), appear between the NCPI and the surface air temperature during all seasons, but particularly in winter.