CLIMATOLOGY OF THE BRUNT-VÄISÄLÄ FREQUENCY OVER MILAN, ITALY

Abstract

In this paper we investigate the spatial and temporal variability of N over the city of Milan, using the historical record of soundings in the period 1991–2007, using 00GMT and 12GMT soundings and performing evaluations at intervals 300–700 m, 800–1800 m, 1500–2500 m, 2500–3500 m, 3000–4000 m, 4000–5000 m and 7000–8000 m. The values obtained reveal that the Brunt-Vaisala frequency is subject to a moderate change with height over the entire observation period, and once the height is fixed shows only weak seasonal changes. At the height interval 800–1800 m, the maximal values of N are observed between December and January, whereas from April to September smaller values of N represent a flat plateau. These variations generally decrease with increasing height. They are still recognizable in the interval 2500–3500 m, and fully diminish at 7000–8000 m.

Keywords

• brunt-vaisala frequency
• free atmosphere
• static stability