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Multi-Angle Implementation of Atmospheric Correction for MODIS: Algorithm MAIAC MODIS Science Team Meeting Alexei Lyapustin and Yujie Wang, GEST UMBC/NASA GSFC, mail code 614.4 January 26, 2010. 4a. Retrieve Snow sub-pixel Fraction and Snow Grain Size. QB:Is Snow Detected?. Queue of K days.
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Multi-Angle Implementation of Atmospheric Correction for MODIS:Algorithm MAIAC
MODIS Science Team Meeting
Alexei Lyapustin and Yujie Wang, GEST UMBC/NASA GSFC, mail code 614.4January 26, 2010
QB:Is Snow Detected?
Queue of K days
3. QB, LTP: Cloud Mask (Covariance-Based Algorithm)
2. LTP: Retrieve
Is B7 BRF known?
1. Grid L1B Data and Split in Tiles
Use MODIS Dark Target Algorithm
4. QB: Retrieve Spectral Regression Coefficients in Blue band B3 (bB).
7. QP: Retrieve BRF and albedo in reflective bands.
Backup: Lambertian retrieval
5. LTP: Retrieve B3 AOT using known surface BRF, B=7bB
6. LTP: Retrieve “Angstrom exponent”
Block-diagram of Processing
(Backup: Standard Algorithm)
Left – MODIS TERRA RGB, 2003 (5050km2), Right – MAIAC CM
Bright-Cold Cloud Test (@Pixel)
(BTij < BTG– 4) AND (r1ij >refcm.r1ij+0.05) PCLOUD
Generic Retrieval of SRC
Second run after initialization
Prescribed vs Retrieved SRC
(Example for Goddard Space Flight Center, 2000, DOY 84-93)
Water Cloud model
=0.8, High % of Coarse mode
=0.2, Low % of Coarse mode
=0, Fine mode
Aerosol Retrieval Algorithm
classification: Fine – Coarse - Cloud
Resolving thin clouds using Cloud Model
DOY 233-248 DOY 249-270, 2000
Hilker, T. et al. (2009). An assessment of photosynthetic light use efficiency from space: Modeling the atmospheric and directional impacts on PRI reflectance. RSE, doi:10.1016/j.rse.2009.07.012.
Photochemical Reflectance Index (PRI):
The “ocean fluorescence” band 531 nm is sensitive to
down-regulation of plant photosynthesis changing by several tenths of 1%, while reference band is stable. The ground measurements showed a good correlation of PRI with light use efficiency ().
Ground PRI (AMSPEC) vs MODIS PRI generated with 6S and MAIAC
(Vancouver Island, BC, Canada, March-October 2006)
6S, all angles
6S, backscattering angles
Problem of Brighter Surfaces
Wang, Y., A. Lyapustin, J. L. Privette, J. T. Morisette, B. Holben, Atmospheric Correction at AERONET Locations:
A New Science and Validation Data Set, . IEEE Trans. Geosci. Remote Sens., in press.
ASRVN Lambert Reflectance
Slope of regression decreases by up to ~15% in red and 35% in green
from consistent comparison of ASRVN-based BRF and RL (Wang, Lyapustin, Privette, Vermote, Schaaf, Wolfe, R. Cook et al.)
Observed biases over vegetated sites are similar to results of ASRVN-based comparison of BRF and RL which indicates that they are mostly due to Lambertian assumption.