Geoscience Reference
In-Depth Information
reciprocal
of stomatal resistance for each leaf. For example,
()
st
r
, the mean stomatal
resistance
per unit leaf area
of the
N
leaves in a (small) height range
δ
z
around the
level
z
is given by:
−
1
⎡
⎤
N
A
∑
(21.20)
()
r
=
⎢
i
⎥
st
z
i
r
⎣
⎦
i
=
1
ST
Energy budget of a dry leaf
On a per leaf area basis, the sensible heat and latent heat flux exchanges with the
surface of a leaf shown in Figure 21.5 are given by:
(
TT
R
−
)
(21.21)
l
Hc
=
r
s
z
ap
H
and:
r
c
eTe
(())
ap
Rr
−
(21.22)
l
E
l
=
sat
s
g
+
VST
Assuming the energy stored in the leaf is negligible, the surface energy budget is
given by:
(21.23)
l
EHR
l
+=
l
l
n
where
R
n
l
is the energy falling as net radiation per unit area of leaf.
If the equivalent linear rate of change in saturated vapor pressure between
T
s
and
T
,
Δ
, is defined by:
eTeT
TT
()
−
()
(21.24)
Δ=
sat
s
sat
−
s
then rearranging Equation (21.23), and substituting first Equations (21.21) and
then Equation (21.24) gives:
eTeT
ER c
(()
−
( )
(21.25)
l
l
l
=−
r
sat
s
sat
n
a p
Δ
H
which equation can be written as:
