overview of prospect and sail model 2nd ir/microwave emissivity group meeting noaa/nesdis/star...
TRANSCRIPT
Overview of PROSPECT and SAIL Model
2nd IR/Microwave emissivity group meeting
NOAA/NESDIS/STAR
2008.08.01
Introduction of PROSPECT
PROSPECT is a radiative transfer model that represents the optical properties of plant leaves from 400 nm to 2500 nm.
The key parameters in the model are leaf structure parameter (N), chlorophyll a+b (Cab) and the equivalent water thickness (Cw) .
transmitted + emitted
absorb
ed
PROSPECT- Leaf Optical Properties Spectra MODEL
reflected + emitted
S.Jacquemoud and F.Baret, REMOTE SENS. ENVIRON.34:75-91(1990)
depend on anatomical leaf structure andbiochemical leaf composition
i
iiCkK
Description of the PROSPECT model
Nidenticallayers
Is
Elementary layer:n: refractive indexK: global absorption coefficient
Surface effects
Hemispheric fluxes
Global absorption:
Specificabsorptioncoefficients
Content inabsorbingmaterial
reflectance
()
() transmittance
(A.Olioso, S.Jacquemoud ,F.Baret , Adaptation of the leaf optical property
model PROSPECT to thermal infrared, 2006)
N leaf structure parameterCab chlorophyll a+b concentration (g.cm2)Cbp brown pigment concentration (g.cm2) Cw equivalent water thickness (cm)Cm dry matter content (g.cm2)
PROSPECT INPUTS
PROSPECT OUTPUTS
R()T()
– leaf reflectance – leaf transmittance
Comparison of two different version1998 version3.01
1995 version 2.01
Cw=0 Cw=0.002
PROSPECT V3.01 outputs under Cw from 0.0 to 0.02 cm-1
(0.0,0.0002, 0.0011, 0.0065, 0.0155, 0.02 cm-1)
0.0
0.02
N = 1.5, Cab = 50 g.cm2, Cdm = 0.005 g.cm2
0.02
0.0
Energy balance
Kirchhoff’s Law
The emissivity of a body equals its absorptivity at thermal equilibrium
1 ATR
So, absorptivity = emissivity ???
One question ?
Sensitivity of the Leaf Structure Parameter N
N=1~1.5 Albino maize leaf and monocotyledons with compact
mesophyllN=1.5~2.5 Dicotyledons by a spongy parenchyma with air
cavities on the abaxial faceN>2.5 Senescent leaves with a disorganized internal
structure
Cw=0, N=1.0,1.5,2.0,2.5,3.0
3.0
2.5
2.0
1.5
1.0
Visible light Region
Cw=0.02, N=1.0,1.5,2.0,2.5,3.0
3.0
2.5
2.0
1.5
1.0
400,690,1450,1950,2500
reasonable
Non-reasonable
In fact, N=3 ,represents senescent leaves with disorganized structure, the Cw should be small even it is zero. So the combination given parametersof Cw=0.02 and N=3 should be non-reasonable. Relatively, the Cw=0.0 and N=3 will be a better choice.
Questions:
The key point is how to determine the value of the combination inputs parameters.
What is the relationships between inputs parameters realistically?
(N, Cab, Cw,Cm,Cbp)
Need in-situ data and satellites data validation
Scattering by Arbitrarily Inclined Leaves-SAIL Model
Introduction
The scattering and extinction coefficients of SAIL model are derived for the case of arbitrary leaf inclination angle and a random leaf azimuth distribution.
SAIL Model includes the G.H.Suits uniform model.
Canopy Layer Morphology Characteristics
The idealized morphology of a canopy layer assumed for the SAIL Model is given as following:
The layer is horizontal and infinitely extended The only canopy components are small and flat
leaves The layer is homogenous
bi-directional reflectance
directional-hemispherical reflectance
soil surface
plant canopy
SAIL model (Verhoef 1984-1985)
sun
absorption of directionalincoming radiation
SAIL Model parameters
LAI mean leaf angle (θl) leaf reflectance (ρl) leaf transmittance (τl) soil reflectance (ρs) geometry of observation Sun position
spectral reflectances absorption of solar
radiation
Inputs
Outputs
W.VERHOEF, (1984),Remote sensing of Environment,16:15-141
Bidirectional reflectance profiles in the green(550nm)
SAIL Model Suits ModelH=1.000
V=1.571
W.VERHOEF, (1984),Remote sensing of Environment,16:15-141
Bidirectional reflectance profiles in the near infrared
SAIL Model Suits ModelH=1.000
V=1.571
Conclusions
The SAIL Model is an improved version of Suits’s canopy reflectance model
The extinction and scattering coefficients in the Suits’s Model are calculated on the basis of a given LAI and leaf inclination distribution
The calculation of canopy reflectance is the same both models, the uniform Suits model is included as a special case
Next to do
As a very important aspect is try to understand how to exactly determine the inputs parameters for these two models
Understand the optical parameters calculation and details theory in the model