On the Formation Mechanism of Low-Level Jet over Bucharest’s Airports

摘要

The presence in the lower atmosphere of the Low-Level Jets (LLJs) affects the safety of aircrafts at landing or take-off. In this work, the physical mechanisms of LLJ formation are studied. For this purpose, three cases of observed LLJs associated to three main types previous determined for Bucharest area, were selected. A synoptic and mesoscale analysis for all cases was made and a thermal wind computation for 6 hours before and 6 hours after the appearance of the low-level jet was performed, using the hourly ALARO model data. The analysis has shown that the mechanisms found act either alone or in combination. Thus, for type I, the baroclinicity induced by the development of a Mediterranean cyclone is the mechanism that leads to the low-level jet formation; for type II- the Blackadar mechanism is responsible and for type III- the combination of Blackadar mechanism and the orography determine the formation of LLJs.