Overview of PROSPECT and SAIL Model 2nd IR/Microwave emissivity group meeting NOAA/NESDIS/STAR Bo Qian

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 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

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)

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

Comparison of two different version 1998 version 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, , , , 0.02 cm -1 ) N = 1.5, C ab = 50  g.cm  2, C dm = g.cm 

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

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

Cw=0, N=1.0,1.5,2.0,2.5, Visible light Region

Cw=0.02, N=1.0,1.5,2.0,2.5, ,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 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.

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 ) sun absorption of directional incoming radiation

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

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

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