A Study of Divergence and Convergence of the Wind Field over Europe and the Mediterranean
In this work, the divergence and convergence of the wind field over Europe, the Mediterranean and North Africa is studied for the 60-year period 1950–2009. Mean monthly values (s−1) are utilized at 273 grid points, spaced by 2.5° × 2.5°, at 10 atmospheric pressure levels from 1,000 hPa up to 100 hPa. It is found that on a seasonal basis considerable differences appear among the various European regions both near the surface of the Earth and in the upper atmosphere. During winter, near the surface, high values of convergence appear in the cyclogenesis areas and along the tracks of depressions. Specifically: in the Mediterranean, with maximum values in the Gulf of Genoa, the Black Sea and from the North Sea up to the Baltic Sea. On the contrary, over the rest of the areas divergence prevails. This situation is reversed above approximately 600 hPa with positive values (divergence) over the Mediterranean and the Seas of northern Europe and negative (convergence) over central Europe. During summer, over the seas, where air is cooler than over land, positive values are observed (divergence). This difference is more intense over lower latitudes. Similarly to winter, in the upper atmosphere, the convergence-divergence field becomes smoother changing signs at about 600 hPa.
KeywordsSubtropical Anticyclone Height Rise High Pressure Level Atmosphere Stratum Heat Capacity Difference
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