The Adriatic bora: special case studies

Abstract

Two cases of the most severe bora episodes along the Adriatic coast of Croatia are investigated. In the first case of 29 January 1994 the absolute maximum gust of 48.5 m s^-1 was recorded in Split. The second case is related to the longer-lasting bora of 13-17 March 1962, when it was possible to investigate the vertical atmospheric by means of downstream sounding in Split and two upstream sounding in Zagreb and Beograd.

Although in both cases the bora onset is caused by a frontal passage, the maximal local speeds occur afterwards and coincide with a pronounced short period pressure perturbation.

 Both cases were characterized by the temporal occurrence of the well marked superadiabatic layers in the low troposphere.

 The vertical structure in the March case shows the temperature inversion in Split data that is strongest during the maximum bora speed, and an unstable layer below inversion, in agreement with the turbulent “dead” region defined in the internal hydraulic theory.