LI-COR LI-6400, Руководство пользователя, Страница: 584 / 846

Diagnostics and Utilities
/Sys/Utility Programs
21-12 Using the LI-6400
21
ÒENERGYBALÓ
This program is useful when measuring chamber boundary layer conductanc-
es with wet filter paper. The problem with making these measurement is that
the leaf temperature will be wrong. There is such a strong gradient between
leaf (wet filter paper) and air, that conduction errors will always cause the
measured leaf temperature to be too warm. This program will compute the
leaf temperature based on four inputs: pressure (kPa), vapor pressure (kPa),
transpiration rate (mmol mol
-2
s
-1
), and air temperature (C). It then prints out
a computed boundary layer conductance (mol m
-2
s
-1
) and computed leaf
temperature (C). For a one-sided value, divide the displayed boundary layer
conductance value by 2 (this assumes that the leaf area used in the transpira-
tion rate was a one-sided value).
For more information on how the LI-6400 uses boundary layer conductances,
see
Boundary Layer Variables on page 14-17.
The theoretical basis of this program is described in Energy Balance And
Boundary Layer on page 17-9. The listing for this program is shown below.
/*******************
Energy Balance Analysis
********************/
:FCT EBmain
{
0 :FLOAT p_kpa
0 :FLOAT tair
0 :FLOAT vap_kpa
0 :FLOAT trans_mmol
Enter: P_kPa vap_kPa Trans_mmol Tair
90.73 1.45 13.7 24.97
BLC = 2.75 Tleaf = 16.6
Enter: P_kPa vap_kPa Trans_mmol Tair
Figure 21-5. "ENERGYBAL" takes four inputs, and computes
boundary layer conductance and leaf temperature. It will
prompt repeatedly; press
enter
with no inputs to terminate it.