Long term variability of the northerly winds over the Eastern Mediterranean as seen from historical wind observations

Abstract

The summer circulation over the eastern Mediterranean is characterized by a persistent northerly regime whose interannual variability is modulated both by mid and tropical latitudes. In this paper, we use historical wind observations taken aboard ships to assemble the first purely instrumental index quantifying this wind system since 1880. This has allowed evaluating the multidecadal and interannual variability of the northerlies in the eastern Mediterranean over the longest time period so far. Our results indicate that the first half of the 20th century was characterized by more frequent and persistent northerly winds in the eastern Mediterranean than the second half. We have also found that the well-known teleconnection between the eastern Mediterranean summertime winds and the Indian Summer Monsoon, with enhanced northerlies concurrent with a stronger monsoon, has not been steady along the 20th century. It is shown that the Indian summer monsoon modulation of convection over the western Indian Ocean plays a crucial role in the strength of this connection.