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| Titel |
Roughness length estimation over a complex topography under different wind conditions |
| VerfasserIn |
Marco Falocchi, Stefano Barontini, Roberto Ranzi |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083228
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| Zusammenfassung |
| The choice of a representative value of the roughness length (z0) is a key aspect to
estimate the momentum flux in the lowest atmosphere layer by means of traditional
micrometeorological methods. In complex terrains however the orography and the
non–uniform land use around the measurement point affect both the winds regime, their
turbulent characteristics and therefore the estimate of the representative roughness length as
well. Aiming at better characterising this parameter in view of hydrological water–balance
applications in complex mountain environments, a micrometeorological station equipped
with eddy covariance devices was installed during summer 2012 at Cividate Camuno (Oglio
river basin, Central Italian Alps, 274ma.s.l.). The soil of the experimental site was a lawn
covered with 0.6m–grass for most of the field campaign duration, and with about 0.1m
during the last days.
The wind analyses detected an alternation between two main wind regimes: an Eastern
katabatic wind blowing daily since 8 pm until 5 am and a local South–Western wind, called
Óra, rising the valley from Lake Iseo in the afternoon. Secondary and less frequent drainage
conditions were also detected. The aerodynamic drag coefficients (CD) were calculated from
the 30 minutes–averaged turbulent momentum flux and for eight different equally spaced
wind direction classes. According to the von Kàrmàn logaritmic law for the vertical
wind speed profile and to the universal stability functions of the Monin–Obukhov
similarity theory, the z0 was then estimated. The obtained values show a sensitivity to
the wind directions, but they seems not to be strongly influenced by the landcover
variations. |
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