Formation of reversed lee flow over the north-eastern Adriatic during bora

Abstract

In-situ measurements indicate the existence of reversed near-surface airflow over the north-eastern Adriatic during the bora wind. Here we examine its structure and evolution by means of a numerical simulation. The studied phenomenon developed during typical summer frontal bora that is associated with a cold air advection from the north-east. It is characterized by a sudden increase in wind speed and a brief duration. Within a sheltered area near the town of Malinska on the island of Krk, onshore flow occurred as the bottom branch of the lee rotor-like circulation that was associated with the hydraulic jump. While the closed circulation somewhat resembles the hypothesized hydraulic-jump rotor, there are significant differences, particularly in the strength of the turbulence associated with the rotor formation.