 |
| Titel |
Analysis of the diurnal development of a lake-valley circulation in the Alps based on airborne and surface measurements |
| VerfasserIn |
L. Laiti, D. Zardi, M. de Franceschi, G. Rampanelli, L. Giovannini |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 18 ; Nr. 14, no. 18 (2014-09-17), S.9771-9786 |
| Datensatznummer |
250119040
|
| Publikation (Nr.) |
 copernicus.org/acp-14-9771-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
This study investigates the thermal structures of the atmospheric
boundary layer (ABL) and the near-surface wind field associated with a
lake-valley circulation in the south-eastern Italian Alps – the so-called
Ora del Garda. Two flights of an equipped motorglider allowed for the exploration
of the diurnal evolution of this circulation, from the onset, on Lake Garda's
shoreline, throughout its development along the Sarca Valley and Lakes Valley (Valle dei Laghi), to
the outflow into the Adige Valley. At the same time, surface observations,
both from a targeted field campaign and from routinely operated weather
stations, supported the analysis of the development of the Ora del Garda at
the valley floor.
In particular, in the valleys typical ABL vertical structures, characterized
by rather shallow convective mixed layers (~ 500 m) and (deeper)
weakly stable layers above, up to the lateral crest height, are identified in
the late morning. In contrast, close to the lake the ABL is stably stratified
down to very low heights, as a consequence of the intense advection of colder
air associated with the Ora del Garda flow (up to 6 m s–1). The
combined analysis of surface and airborne observations (remapped over 3-D
high-resolution grids) suggests that the lake-breeze front propagating
up-valley from the shoreline in the late morning penetrates slightly later at
the eastern end of the valley inlet (delay: ~ 1 h), probably due to
the asymmetric radiative forcing caused by the N–S valley orientation. On
the other hand, in the early afternoon the Ora del Garda overflows through an
elevated gap, producing an anomalous, strong cross-valley wind
(5 m s–1) at the Adige Valley floor north of Trento, which overwhelms
the local up-valley wind. This feature is associated with a strong deepening
of the local mixed layer (from 400 to 1300 m). The potential temperature 3-D
field suggests that the intense turbulent mixing may be attributed to the
development of a downslope wind across the gap, followed by a hydraulic jump
downstream. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|