Geoscience Reference
In-Depth Information
1.0
0.8
0.6
0.4
z
max
/
h
c
=0.2
z
max
/
h
c
=0.5
z
max
/
h
c
=0.8
0.2
0.0
0.1
0.2
0.5
1.0
2.0
5.0
10.0
Plant area index (-)
0.2
z
max
/
h
c
=0.2
z
max
/
h
c
=0.5
z
max
/
h
c
=0.8
0.15
0.1
0.05
0.0
0.1
0.2
0.5
1.0
2.0
5.0
10.0
Plant area index (-)
Figure 3.19
Relationship between relative displacement height (
d/h
c
, top) and rough-
ness length (
z
0
/h
c
, bottom) and the plant area index (one-sided area of plant material
per unit ground area). Based on the model of Massman (
1997
), assuming a triangular
vertical distribution of plant material (maximum at
z
max
).
sink of momentum is provided by the vegetation elements that provide a signiicant form
drag and are located well above the soil surface. On the other hand, the main source of
heat is located at the soil surface, which is smoother and located below the vegetation
elements.
Determination of the Fluxes
For the case that we need to determine luxes from observations at one height, in com-
bination with surface values, the system of equations of Eq. (
3.29
) becomes:
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