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Overview of PROSPECT and SAIL Model 2nd IR/Microwave emissivity group meeting NOAA/NESDIS/STAR 2008.08.01 Bo Qian bqian@umd.edu

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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).

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transmitted + emitted absorbed 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 and biochemical leaf composition

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Description of the PROSPECT model N identical layers IsIs Elementary layer: n : refractive index K : global absorption coefficient Surface effects Hemispheric fluxes Global absorption: Specific absorption coefficients Content in absorbing material reflectance ( ) ( ) transmittance (A.Olioso, S.Jacquemoud,F.Baret, Adaptation of the leaf optical property model PROSPECT to thermal infrared, 2006)

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N leaf structure parameter C ab chlorophyll a+b concentration ( g.cm 2 ) C bp brown pigment concentration ( g.cm 2 ) C w equivalent water thickness (cm) C m dry matter content (g.cm 2 ) PROSPECT INPUTS PROSPECT OUTPUTS R( ) T ( ) – leaf reflectance – leaf transmittance

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Comparison of two different version 1998 version3.01 1995 version 2.01 Cw=0 Cw=0.002

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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, C ab = 50 g.cm 2, C dm = 0.005 g.cm 2 0.02 0.0

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Energy balance Kirchhoff’s Law The emissivity of a body equals its absorptivity at thermal equilibrium So, absorptivity = emissivity ??? One question ?

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Sensitivity of the Leaf Structure Parameter N N=1~1.5 Albino maize leaf and monocotyledons with compact mesophyll N=1.5~2.5 Dicotyledons by a spongy parenchyma with air cavities on the abaxial face N>2.5 Senescent leaves with a disorganized internal structure

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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

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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

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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 parameters of Cw=0.02 and N=3 should be non-reasonable. Relatively, the Cw=0.0 and N=3 will be a better choice.

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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

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Scattering by Arbitrarily Inclined Leaves-SAIL Model

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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.

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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

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bi-directional reflectance directional-hemispherical reflectance soil surface plant canopy SAIL model (Verhoef 1984-1985) sun absorption of directional incoming radiation

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SAIL Model parameters LAI mean leaf angle (θ l ) leaf reflectance (ρ l ) leaf transmittance (τ l ) soil reflectance (ρ s ) geometry of observation Sun position spectral reflectances absorption of solar radiation Inputs Outputs

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W.VERHOEF, (1984),Remote sensing of Environment,16:15-141 Bidirectional reflectance profiles in the green(550nm) SAIL Model Suits Model H=1.000 V=1.571

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W.VERHOEF, (1984),Remote sensing of Environment,16:15-141 Bidirectional reflectance profiles in the near infrared SAIL Model Suits Model H=1.000 V=1.571

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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

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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

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