| ABSTRACT | The East Asian trough (EAT) is the strongest stationary wave in the Northern Hemisphere mid-latitudes. In this study, we investigate how its strength affects the amplitude and location of the eastern Mediterranean trough that causes temperature variability over the eastern Mediterranean. We used daily ERA-Interim dataset whose time span is from 1979 to 2018 and whose horizontal resolution is 0.75 degrees. We employed two indices to reveal the strength of the connection between the East Asian and eastern Mediterranean troughs. For the EAT, a Trough Intensity Index (TII) is calculated by averaging the 500 hPa geopotential heights over the region between 30 -45oN and 125-145oE. For the eastern Mediterranean trough, an index (called Trough Displacement Index, TDI) to show zonal displacement of the trough is calculated by taking difference of 500 hPa geopotential heights between two points, 39°N-10°E and 39°N-50°E. We found statistically significant correlation (~0.5) between TII and TDI at the 13th pentad which represents the beginning of March. We applied EOF analysis to the 500 hPa geopotential heights over the East Asian region for the 13th pentad to separate the intensity mode of the EAT from the others. The principal component time series of EOF2, which is found to represent the intensity of the trough, have a strong negative signal for the year 2004. The observations show that the eastern Mediterranean region was anomalously warm in early March 2004. Our study indicates that a strong EAT displaces the eastern Mediterranean trough westward and increases its amplitude. The latter results in the advection of warm air of tropical region towards higher latitudes, which causes anomalous rises in temperatures over the eastern Mediterranean region, especially over the eastern Anatolia. Such an event in early March 2004 melted snowpack over the eastern Anatolian highlands, which produced unprecedented amounts of discharge in the snow-fed rivers of Euphrates and Tigris at this time of the year. |