RETRIEVING BRDF OF DESERT USING TIME SERIES OF MODIS IMAGERY Haixia Huang, Bo Zhong, Qinhuo Liu, and Lin Sun Presented by Bo Zhong [email protected] Institute of Remote Sensing Applications, Chinese Academy of Sciences IGRSS 2011, Vancouver , Canda
RETRIEVING BRDF OF DESERT USING TIME SERIES OF MODIS IMAGERY
Haixia Huang, Bo Zhong, Qinhuo Liu, and Lin Sun
Presented by Bo Zhong
Institute of Remote Sensing Applications, Chinese Academy of Sciences
IGRSS 2011, Vancouver , Canda
Background
BRDF is the key parameter for:
Quantitative remote sensing
Erath radiation budget
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Desert is one of the main landcover types
Strongly reflecting the solar radiation
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Methodology-flowchartMODIS imagery
Converting DN to TOA reflectance
Identifying the “clearest” of each
observations
Retrieving reflectance of “clearest”
observations
Fitting to Staylor-Suttles BRDF
model
Lookup Tables
BRDF of desert
Methodology- site choosing
Location of the experimental site(MODIS imagery color composite)
Cole view of the site(TM imagery color composite)
Methodology- site choosing
It is stable, so it can be seen as an invariant
object;
There are a lot of lakes within the calibration
site, which are seldom polluted, so the lowest
AOD of calibration site can be determined by
Dark Object (DO) method using Landsat TM
and ETM+ data.
AOD retrieval using DO method
40 60 80 1000
1
2
3
Aerosol
opti
cal
depth
Apparent radiance(w/m2/sr/mic)
Aerosol optical depth and radiance curve
Corresponding path radiance and aerosol optical depth
52.87
0.43
ETM+
imaging
date
Aerosol
optical
depth
TM
imaging
date
Aerosol
optical
depth
2000.03.03 0.1543 2006.09.20 0
2000.04.29 0 2006.10.31 0.0440
2001.10.16 0.0218 2007.05.18 0.1536
2001.11.17 0 2007.06.03 0
2002.01.04 0.0657 2009.06.17 0.4279
2002.03.18 0.2801 2009.08.11 0.05444
2002.05.28 0.3274 2009.08.27 0.0043
2002.09.17 0.1058 2009.09.28 0.0096
2002.11.04 0.3633 2010.02.03 0.07676
2002.11.13 0.0286 2010.06.04 0.254
2002.12.15 0.1195 2010.07.29 0.3552
2003.03.28 0.4273 2010.08.14 0
2010.08.23 0.2178
Original method
Time series of
MODIS imagery
Identifying clear
pixels
Reflectance of
clear pixels
BRDF fitting
Reflectance of
hazy pixels
AOD of hazy
pixels
LUT
MODIS surface
reflectance
Modifications for the original method
AOD determination for the “clearest” days;
Shrinking the use of the algorithm from globe to the
desert calibration site, which is stable;
Identifying the “clearest” observations for every 10
degrees in view zenith angles from 0-50 degree (0-10, 11-
20, 21-30, 31-40, and 41-50);
Using Staylor-Suttles BRDF model instead of Walthall BRDF.
Applications I: inter-calibration of AVHRR using retrieve BRDF
Spectral matching of AVHRR and MODIS
AVHRR data simulation using the new method
Inter-calibration
Validation
Applications II: global desert BRDF retrieval
Mapping of the desert
BRDF and AOD retrieval simultaneously using
the new method
Preliminary validation
The geolocations of the deserts
Desert
Name
Lat(°) Lon(°) Altitude
(m)
Duration
(yyyy.mm.d)
Taklimakan 39.0°N-40°N 84°E-85°E 1050 2009.10.1-
210.10.1
Rabal-
Khali
18.8°N-19.8°N 45.5°E-46.5°E 700 2009.10.1-
210.10.1
Lybia 24°N-25°N 12°E-13°E 740 2009.10.1-
210.10.1
Sahara 19.5°N-20.5°N 8°W-9°W 260 2009.10.1-
210.10.1
Conclusions
The new method is able to catch the BRDF
characterization of deserts
This method can be used for inter-calibration of
reflective bands of moderate satellite data like
AVHRR
This method is helpful for researches on earth
radiation budget