PP Systems CIRAS-2 - Page 165

Addendum
CIRAS-2 Operator's Manual Version 2.04
- 163 -
For clarity in the following expansion let (el - ea) = D (vapor pressure deficit).
Then from (1) and (2):
NERBD
NE
RS u ***2
*1
and :
NERBERBD
NE
RSu ***2**2
*1
Therefore :
NERBERBDNERBD
NERBDNEENERBERBDNE
RSlRSu ***2**2****2
***2*****2**2**11
Now,
RSl
1
RSu
1
1
RS
Therefore:
NERBDNEENERBERBDNE
NERBERBDNERBD
RS
***2*****2**2**
***2**2****2
Which expands to:
NNERBNERBDE
NNEERBRBNEERBRBDERBDD
RS
****4***4*
******4*****4***2*
(3)
If we assume that there is equal transpiration on both surfaces (i.e. N = 0.5), then:
E
ERBD
eqRS
*
)(
(4)
The error in determination of RS from making the assumption of equal transpiration on both sides of the
leaf is (3) - (4).
After expansion and simplification this becomes:
D
NNE
RB
NN
1**25.0
25.01*
(5)