étude expérimentale de la couche limite au-dessus d'un relief modéré proche d'une chaîne de montagne

✍ Scribed by G. Dubosclard; B. Benech; J. Noilhan; A. Druilhet

• Publisher: Springer
• Year: 1983
• Tongue: English
• Weight: 757 KB
• Volume: 25
• Category: Article
• ISSN: 0006-8314
• DOI: 10.1007/bf00123969

✦ Synopsis

&oppler sodar derived values of the temperature structure parameter C;, the vertical velocity variance w", and the rate of dissipation of turbulent energy E, were measured during unstable conditions above the Lannemezan heterogeneous site. The vertical profiles of these turbulent parameters, normalized by the classical convective scales are compared with those obtained using the same acoustic sounder above an homogeneous site during convective conditions.

The typical decrease of C$. as Z-'I3 is partially verified on the heterogeneous site: for the lower levels, C$ exhibits an increase with Z whereas for the intermediate levels C$ decreases as Z?".

For the upper levels, C$ increases with Z due to a signal-to-noise ratio lower than 1.

The vertical profiles ofW'2 above the two sites are rather similar. However, near the base of the convective inversion Zi, the values measured on the heterogeneous site are more scattered. The same scattering is also observed with the E values; moreover, for the lower levels (Z < 0.172,) the increase of E as Z decreases is more important at the homogeneous site than at the heterogeneous one.

It is suggested that these particular features observed at lower levels above the heterogeneous site are mainly related to a complex local boundary layer induced by the near environment of the sodar (vegetation and relief).