Extended Abstract (1.2M)15A.2
Case studies from a field campaign to measure canopy air flows over complex terrain
Rosey Grant, Institute for Atmospheric Science, Leeds, West Yorkshire, United Kingdom; and A. N. Ross, I. M. Brooks, B. A. Gardiner, K. H. Jones, and S. D. Mobbs
Dynamic interactions between forest canopies and the boundary layer
are important in understanding and parameterising the boundary
conditions in the atmosphere. These interactions also play a key role in
transporting gases between the forest and the boundary layer.
It is widely recognised that such canopy flows are
further complicated by the presence of complex terrain. Recent
theoretical and computational work has begun to look specifically at
canopy flow processes over complex terrain and it has been shown that
the presence of complex terrain within a forested area can change the
balance between terms in the momentum equation within and above the
forest canopy. On smaller hills in particular, this can lead to flow
into the forest over the upwind slope and flow out of the forest as
well as enhanced separation over the lee slope. This difference in
flow can also lead to an increase in the pressure drag over a forested
hill and can have important implications for scalar transport between
the forest canopy and the boundary layer above. However, there are
currently very few field measurements to validate the latest model
developments.
This work presents data from an intensive measurement
campaign undertaken on a forested hillside on the Scottish island of
Arran beginning in November 2006. Detailed profiles of the mean flow
and turbulence were
measured from three tall masts erected at selected points across the
ridge. In addition, a large network of automated weather stations was
used to reveal spatial variation in the pressure field and to identify
other significant features of the flow over a forested hill. A brief
introduction to the project will be presented before discussing
several case studies from the field campaign. Where possible
comparisons will be made with results obtained from the latest
theoretical models. The key differences from flow over flat forest
canopies will be highlighted.
Session 15A, BOUNDARY LAYER FLOWS ALONG SLOPING SURFACES—IV
Thursday, 12 June 2008, 3:30 PM-5:00 PM, Aula Magna Vänster
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