composite parameter (Q –
2εσTa4 –
λgtwDa) |
a |
J
m-2 s-1
|
composite parameter (8εσTa3 +
cpagbh +
λgtws) |
b |
J
m-2 s-1
K-1
|
ratio of adaxial to abaxial boundary layer resistance in abscence of
hairs |
β |
- |
heat capacity of air |
cpa
|
J
mol-1 K-1
|
difference between leaf and air temperature |
δ |
K |
water vapor mole fraction deficit of the air |
Da
|
mol mol-1
|
final value of δ
|
δf
|
K |
depth of hair (trichome) layer |
dh
|
m |
binary diffusivity for heat in air |
Dha
|
m2 s-1
|
initial value of δ
|
δi
|
L |
leaf size (characteristic dimension) |
dl
|
m |
leaf dry mass |
DM |
g |
leaf to air water vapor mole fraction difference |
Δw
|
mol
mol-1
|
leaf thermal emissivity |
ε |
- |
boundary layer conductance to heat |
gbh
|
mol
m-2 s-1
|
leaf surface conductance to water vapor |
gsw
|
mol m-2 s-1
|
leaf total conductance to water vapor |
gtw
|
mol
m-2 s-1
|
leaf heat capacity |
k |
J m-2
K-1
|
latent heat of vaporization |
λ |
J
mol-1
|
leaf area |
LA |
m2
|
absorbed radiation |
Q |
J m-2
s-1
|
gas constant |
R |
Pa m3
mol-1 K-1
|
resistance added by hairs at one leaf surface |
rh
|
m2 s
mol-1
|
derivative of ws with respect to temperature |
s |
mol mol-1
K-1
|
Stefan-Boltzmann constant |
σ |
J m-2
s-1 K-4
|
leaf temperature |
T |
K |
air temperature |
Ta
|
K |
wind speed |
vw
|
m
s-1
|
ambient water vapor mole fraction |
wa
|
mol
mol-1
|
leaf fresh mass |
WM |
g |
saturated value of water vapor mole fraction |
ws
|
mol mol-1
|
water use efficiency |
WUE |
mmol mol-1
|
time constant for leaf cooling |
τ |
s |