chiefly
leverthe-
on could
plicated
empirical
iblished.
ion, two
and used
r placed
on, with
infrared
3 phy-
wumidity
(t and
ally
>, plant
physical
> order
degrees
zrees
«pressed
cempera-
(d bri-
/s negli-
ribed to
The brightness temperature of corn
Some of the data collected from June 12th to July 22th are repre-
sented in fig. 1. During this period in order to study the effect of water
deficit on MW emission the test site was intentionally mantained in drought
conditions till June 19th. After this date the field was normally .watered.
In this figure the values of Tb at 10 and 36 GHz measured at 12.00 a.m. of
each day (V polarization and angle of incidence equal to 40 degrees) are com-
pared with the infrared temperature of crop. Plant height, irrigation and rain-
falls are also represented. Both MW temperatures are strongly correlated with
the physical temperature of the crop, this latter was measured both with the
infrared radiometer and with termoresistences placed on leaves. Regression
lines between these parameters were drown with a correlation coefficients as
good as .9
The ratio of MW temperature to the crop temperature measured with
an infrared radiometer may roughly represent the emissivity of crop.
Only very small but well defined variations of e have been found
during the all period of observation, its mean value, measured at 12.00, is
.94 at 10 GHz and .96 at 36 GHz. The lowest value of e is on June 20th after
the watering (.92 at 10 GHz and .94 at 36 GHz).
o
X
o
3
318 - 3008
12.00
m Plent Height - 280
sos À VS SS ep
240
300
220
285 208 2
180 =
3
290 160 $
x
. 140
285 20
120 T
280 188
eg
18
275 60 p
48
270
20
2
265 2 TE
June July
20 es 38 5 19 15 20 25
15
N Irrigation
19
Fig. 1- Brightness and Infrared temperatures measured at 12.00 during the ob-
servation period (Tb1=36GHz, Tb2=10GHz, Tig =Infrared).
The dashed line is plant height.
The arrows indicate rainfalls in mm and the gray areas irrigations.
281
ascif ; s : pre E E E E EE E ER
MERC Em ES SER GE ON SEE MEM M RB EE :
