# Presentation: 064592

## MODIS Anisotropy and Albedo Product

- Crystal Schaaf
- Alan Strahler, Jicheng Liu,  Ziti Jiao, Yanmin Shuai, Miguel Roman,  Qingling Zhang, Zhuosen Wang
**Boston University**
- and many collaborators...

## MODIS Anisotropy and Albedo

**Anisotropy: The reflective character of a surface.**
**Albedo: The proportion of solar radiation that is reflected by a surface.**

## MODIS Anisotropy and Albedo

- Inputs
- Cloud-free, atmospherically-corrected, spectral surface reflectances from Aqua and Terra (MOD09/MYD09 BRFs) are used to sample the surface anisotropy over a 16 day period
- Output
- High quality full inversions provide well-sampled, best-fit anisotropy models of global land surfaces
- Ross Thick Li Sparse Reciprocal semi-empirical model captures volumetric and geometric-optical scattering
- Lower quality back-up algorithm performs  magnitude inversions by coupling available reflectances with an *a priori* BRDF database

## Semi-Empirical BRDF Model

**Semi-Empirical BRDF Model**

**Isotropic**

**Geometric**

**Volumetric**

- α*λ** *(θi, Φi; θr, Φr) = *f*iso + *f*geo*k*geo + *f*vol*k*vol

*k**vol**,** **k*geo  are kernels of view and illumination geometry
*f*iso, *f*geo, *f*vol are spectrally dependent weights

## MODIS Anisotropy and Albedo 

- Output
- BRDF Model parameters
- RossThickLiSparseR model parameters
- Use parameters directly in simple polynomial to estimate albedo or reflectance quantities
- Albedo quantities
- Bihemispherical reflectance under isotropic illumination (BHRiso)
- White-sky albedo (wholly diffuse)
- Directional-hemispherical reflectance (DHR) at local solar noon
- Black-sky al bedo (direct)
- Nadir BRDF-Adjusted Reflectance (NBAR)
- View angle corrected surface reflectances

**NBAR May 2004**

**adjoining swaths**

## MODIS Anisotropy and Albedo Product 

- Output
- Spectral (Collections 004 and 005)
- 7 shortwave bands and three broad bands
- Spatial
- 500m in sinusoidal 10deg2 tiles (005)
- 1km in sinusoidal 10deg2 tiles (004, 005)
- 0.05deg in global lat/lon  (004, 005)
- 30arcsec in global lat/lon (005)
- Temporal
- Every 16 days (004)
- Every 8 days based on the last 16 days (005)

## MODIS Anisotropy and Albedo

**ARM SGP EF-15 2003**

**1km**

**500m**

## Tile Product Quality

- MCD43 only (Terra +Aqua)
- Validated Stage-1
- Inland waters now produced (to capture snow and ice)
- MCD43A2/B2 now contain the quality flags
- byte mandatory QA (full/magnitude inversions or fill)
- byte snow/snow-free (majority situation over 16 day period)
- 16 bit packed information
- platform
- land/water mask
- szn of local solar noon
- 32 bit spectral inversion information

## MODIS Anisotropy and Albedo

**White sky albedo April 2004**

## CMG Product Quality

- MCD43C – 0.05degree CMG
- MCD43C1 now Parameters, C3 Albedo, C4 NBAR
- in keeping with MCD43A/MCD43B
- MCD43C2 contains a snow-free quality version of parameters
- MCD43C1-C4 still contain replicated quality flags
- byte quality flags (in data fields 31-34)
- QA, szn of lsn,% inputs,  % snow
- MCD43D – 1km CMG – not archived at EDC
- serves as input for gap filled anisotropy and albedo products
- joint effort between MODIS land and atmospheres teams
- MCD43D31 - MCD43D34
- byte quality flags
- QA, szn of lsn, % inputs, % snow

## Gap-filled Snow-free Products

**0.0****	****	****	****	****	****        0.8+****	**

**Global gap-filled white-sky albedo 1-16 Jan 2002 snow-free (top), snow-covered (below), 0.86****μm**
**(Moody et al., 2005**

## MODIS Anisotropy and Albedo

- Format changes make bridging reprocessing collections difficult – we don’t recommend it.
- Increased spatial resolution serves regional users
- But also serves as an improved subgrid characterization for global scale users.
- Increased temporal resolution provides more opportunities for high quality retrievals that will capture land surface dynamics
- NBAR serve as the primary input to the MODIS land cover and phenology products
- Research efforts
- Further improvement of  backup algorithm
- Utilization of the BRDF shape information for structural characterization
- Implementation of more frequent anisotropy and albedo measures to serve the Direct Broadcast and eventually NPP/NPOESS communities