500-year Winter Temperature and Precipitation Variability over the Mediterranean Area and its Connection to the Large-scale Atmospheric Circulation

Abstract

Spatio-temporal highly resolved estimates of past natural climate variability over the Mediterranean are important to assess recent significant climate trends. Principal component regression analysis has been performed to reconstruct monthly (AD 1659–1900) and seasonal (AD 1500–1658) temperature and precipitation fields over the land areas including Europe, North Africa and the Near East (Luterbacher 2001). The reconstructions are based on the combination of early instrumental station series (temperature, pressure and precipitation) and proxy reconstructions from Eurasian sites. The statistical relationships were derived over the 1901–1990 period and were applied to the available data prior to 1900 in order to derive the temperature and precipitation reconstructions back to AD 1500.We derived a winter mean Mediterranean precipitation and temperature time series from AD 1500–1995 through averaging 2159 gridpoints over the larger Mediterranean area (10°W-40°E; 30°N-47°N). Several cold relapses and warm intervals as well as dry and wet periods on the decadal timescale, on which shorter-period quasi-oscillatory behaviour was superimposed, could be shown.1891 was the coldest, 1772 the warmest, 1609 the driest and 1684 the wettest Mediterranean winter over the last few centuries. The corresponding connected sea level pressure (SLP) fields are analysed and compared with the long-term 20th century mean. The potential and the limitations of these reconstructions are presented.A negative highly significant correlation has been found between the winter North Atlantic Oscillation Index (NAOI) and winter Mediterranean precipitation, but only a weak connection between the NAOI and Mediterranean temperature.