Microwave emissivity of land surfaces:
experiments and models
M. Brogioni, G.Macelloni, S.Paloscia, P.Pampaloni,
S.Pettinato, E.Santi
IFAC-CNR – Florence, Italy
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Introduction
‰ Experimental investigations conducted by the Microwave Remote
Sensing Group made it possible to realize a wide archive of microwave
emissivity of the following surface types:
¾ bare soil with different levels of moisture and types of
roughness
surface
¾ soil covered with wheat, corn, alfalfa, sunflower, natural grass at
various level of biomass
¾ deciduous and coniferous forests with different woody volumes
¾ soil covered with snow in different conditions (dry and wet) and depth.
¾ Ice sheet in Antarctica
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Experimental equipments
Dome-C
Antarctica
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Ground measurements
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Experimental results:
sensitivity to land features
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Emissivity spectra of land surfaces
1
Emissivity spectra of forests (poplar)
0,95
0,9
0,85
TnH
0,8
0,75
0,7
WHEAT
CORN
0,65
ALFALFA
SUNFL
0,6
BS (wet)
BS (dry)
SNOW (wet)
0,55
SNOW (dry)
FOREST
0,5
1
10
FREQUENCY
100
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
1.00
Emissivity of agricultural surfaces
0.90
Ka band
X band
L-band
TnH
0.80
0.70
0.60
Smooth bare
Soil moisture
0.50
0
1.00
10
20
30
40
SMCg (%)
0.90
X band
L-band
TnH
0.80
0.70
1 Km
0.60
Rough slightly
vegetated
0.50
2nd Workshop on Remote Sensing and Modeling of Surface0 Properties
10
20
9-11 June 2009, Météo France , Toulouse, France
SMCg (%)
30
40
Sensitivity to Plant Water Content of crops
emissivity
Broad
leaf
L
X
Small
leaf
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Ka
NDVI from SPOT4
Sensitivity to vegetation
(AMSR-E)
NDVI from AMSR-E
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Sensitivity to snow cover: dry snow accumulation
Snow Depth (cm)
0
15
30
45
60
75
100
150
200
250
Brightness Temperature (K)
270
250
230
210
TbV meas 10GHz
190
TbV DMRT 10GHz
TbV meas 37GHz
170
TbV DMRT 37GHz
150
0
50
Snow Water Equivalent (mm)
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Sensitivity to snow
wetness
280
V
TB (37 GHz)
260
Tb [K]
H
240
220
200
1
2
3
4
W%
5
Liquid water content
Melt-refreezing cycles
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
6
7
Sensitivity to snow cover
(AMSR-E)
100
90
80
70
FI
60
50
40
30
20
10
0
0
50
100
150
Snow Depth (cm)
12/2006
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Antarctica: Temporal variability L-band
Ground based
2 week Time stability
Mean = 192.32 K
Dev. st. = 0.18 K
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Antarctica: Spatial variability – AMSR-E
(Tb 37 GHz V - Yearly average)
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Antarctica: Temporal
variability AMSR-E
220
215
AMSR-E
205
-20
C
50 cm
200
-30
195
Tsnow R etrieved [°C ]
Brightness Temperature [K]
210
X
190
185
Ku
180
175
170
Ka
165
160
Jan-05 Apr-05
Jul-05
Oct-05 Jan-06 Apr-06
Jul-06
-40
-50
-60
-70
-80
Oct-06 Jan-07
-80
Date
-70
-20
-25
-50
-40
-30
-20
-30
-20
-20
Snow temp.
100 cm
-30
-35
Tsnow Retrieved [°C]
Snow Temperature [°C]
-30
-60
Tsnow Measured [°C]
-40
-45
-50
-55
-60
-65
-40
-50
-60
-70
-70
-80
-75
-80
Jan-05 Apr-05
-80
Jul-05
Oct-05 Jan-06 Apr-06
Date
Jul-06
Oct-06 Jan-07
-70
-60
-50
-40
Tsnow Measured [°C]
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Electromagnetc modelling
Surface scattering: soil
Volume scattering:
vegetation
snow
crops
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
forests
Sensitivity to forest biomass
Forest - Radiative
Transfer ( L-Band)
1.00
Total
e
v
eh
0.9
Crown
Emissivity
0.8
0.7
ev
Trunk
0.6
0.96
0.94
0.92
Data
0.90
Soil
0.5
0.98
Emissivity
1.0
eh
Disc. Model
0.88
Cont. Model
0.4
0
10
20
30
40
50
Incidence Angle (degs)
60
70
0.86
0
200
400
600
Woody Volume (m 3/ha)
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
800
Model sensitivity to soil roughness
V
V
H
H
ε = 7 – j2
θ = 55°
ε = 20 –j 5
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
θ = 55°
Model sensitivity to snow parameters
Snow depth
Grain size
Snow density
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France
Conclusions
‰ Microwave emissivity of land surfaces in the frequency
range 1- 40 GHz strongly depends on
™ Frequency, polarization and incidence agle of the
observing sensor
™ Cover type and physical conditions
¾ Bare soil: moisture, surface roughness
¾ Vegetation: crop/forest type, biomass
¾ Snow: depth, density (water equivalent), wetness, grain
dimension
2nd Workshop on Remote Sensing and Modeling of Surface Properties
9-11 June 2009, Météo France , Toulouse, France