7/24/02 MODIS Science Meeting Seasonal Variability Studies Across the Amazon Basin with MODIS...
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7/24/02 MODIS Science Meeting
Seasonal Variability Studies Across the Amazon Basin with
MODIS Vegetation Indices
Alfredo Huete1, Kamel Didan1, Piyachat Ratana1, Laerte Ferreira2, Yosio Shimabokuro3, Tomoaki Miura1
Gao Xiang1
MOD13
*Terrestrial Biophysics and Remote Sensing Lab University of Arizona
1University of Arizona, Tucson, Arizona USA 2Universidade Federal de Goiás – UFG [email protected]
3Instituto Nacional de Pesquisas Espaciais - INPE [email protected]
7/24/02 MODIS Science Meeting
Validation
• Validation concerns the outputs or the intended uses of the VI’s so as to help the user community understand the reliability, credibility, and limitations of the products.
MOD09 (SR)--->MOD13(VI)
Phenology (seasonality)
Change detection (Interannual)
Biophysical (growth models)
7/24/02 MODIS Science Meeting
MODIS Vegetation Indices
ARVIAtmosphere
Resistance
)Re(Re*)1(
LdNIR
dNIRL+ρ+ρ
ρ−ρ+
SAVI
Canopy BackgroundCorrection
Soil-adjusted Vegetation Index
NDVINormalized DifferenceVegetation Index
dNIR
dNIR
Re
Re
ρρ
ρρ
+
−
EVI
Enhanced Vegetation Index
)Re(
Re*21 blueCdCNIRL
dNIRGρρρ
ρρ
−++
−
)(
,
ReRe dbluedrb
rbNIR
rbNIR
ρ−ργ−ρ=ρρ+ρρ−ρ
7/24/02 MODIS Science Meeting
Year
1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001
NDVI
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Caatinga Cerrado Dense Forest
Long term, time series AVHRR-NDVI data
(Pathfinder 8km -yearly averaged)
• Accurate and stable time series data is needed for studies on interannual variation of vegetation in response to climate and for characterization of vegetation anomalies at continental and regional scales.
Pinatubu
Sensor degradation
El Niño
7/24/02 MODIS Science Meeting
MONTH
JAN FEB MAR ABR MAY JUN JUL AUG SEP OCT NOV DEC
NDVI
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Caatinga (-9.41, -41.13)Cerrado (-10.80,-44.1)Dense Forest (-2.78,-54.27)
*20 year averaged monthly AVHRR - NDVI in Brazil (Pathfinder 8 km)
Seasonality & Phenology Role
7/24/02 MODIS Science Meeting
Objectives˚ Evaluate the initial two years of MODIS Vegetation
Index (VI) time series data over the Amazon Basin and surrounding regions of Brazil,
˚ Examine the usefulness of MODIS data in characterizing seasonality along a climate-based ecological transect from the Brazilian cerrado to the seasonal tropical rainforests,
˚ Examine the usefulness of MODIS data in discriminating land use/conversion patterns and in characterizing the resulting changes in seasonality.
7/24/02 MODIS Science Meeting
QuickTime™ and aGIF decompressor
are needed to see this picture.
MODIS EVI
Seasonality (2000-2002)
7/24/02 MODIS Science Meeting
7/24/02 MODIS Science Meeting
0
0 .0 5
0 . 1
0 .1 5
0 . 2
0 .2 5
0 . 3
0 0 .2 0 . 4 0 .6 0 .8 1
E V I
Percent (%)
1 k m E V I
5 0 0 m E V I
2 5 0 m E V I
0
0 .1
0 .2
0 .3
0 .4
0 .5
0 .6
0 0 .2 0 .4 0 .6 0 .8 1
N D V I
Percent (%)
1 k m N D V I
5 0 0 m N D V I
2 5 0 m N D V I
EVI
NDVI
Histograms of VI’s at 250 m, 500 m, and 1 km resolutions
South America (August 12 to August 27, 2000)
7/24/02 MODIS Science Meeting
QuickTime™ and aGIF decompressor
are needed to see this picture.
7/24/02 MODIS Science Meeting
Brasilia National Park
• Blue = ASD
•Yellow = DigitalImages
7/24/02 MODIS Science Meeting
MQUALS and MODIS(Global)
MQUALS Reflectances
0.0 0.1 0.2 0.3 0.4
MODIS Composite Reflectances0.0
0.1
0.2
0.3
0.4
JornadaWalnut GulchCerradoTapajos
Blue Red NIR
MQUALS VI
0.0 0.2 0.4 0.6 0.8 1.0
MODIS Composite VI
0.0
0.2
0.4
0.6
0.8
1.0
JornadaWalnut GulchCerradoTapajos
NDVI EVI
MO
DIS
7/24/02 MODIS Science Meeting 0.00 0.20 0.40 0.60 0.80 1.00
EVI
EVI Histogram of Brasilia Tile (Cerrado + conversions)
Dry
8/00
8/01
Wet
3/02
4/01
7/24/02 MODIS Science Meeting
7/24/02 MODIS Science Meeting
Cerrado physiognomies
0.0000
0.1000
0.2000
0.3000
0.4000
0.5000
0.6000
8/29/009/29/0010/29/0011/29/0012/29/00
1/29/012/28/013/29/014/29/015/29/016/29/017/29/018/29/019/29/0110/29/0111/29/0112/29/01
1/29/02
DOY
EVI
Cerrado grass1
Shrub cerrado1
Wood Cerrado2
Cerrado wood3
Gallery Forest1
Pasture1
Cerrado Physiognomies
7/24/02 MODIS Science Meeting
Cangaçu & Santana do Araguaia
• Red = ASD
•Yellow = DigitalImages
7/24/02 MODIS Science Meeting
MODIS VI Seasonal Profiles of Land Converted Areas
biomass: 147.16 to 205.29 t / haLAI: 5.61 to 7.06
biomass: ~1.3 t / haLAI: ~2.82
biomass: 6.85 to 134.94 t / haLAI: 4.11 to 6.27
Primary Forest (“High”) Pasture site
Regeneration site
MODIS 250m EVI
7/24/02 MODIS Science Meeting
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Cerrado
Forest
Converted Pastures
Land Conversion at Santana do Araguaia & Cangaçu (Forest - Cerrado
Transition)
7/24/02 MODIS Science Meeting
7/24/02 MODIS Science Meeting
Dry
11/00
11/01
Wet
7/01
4/02
0.00 0.20 0.40 0.60 0.80 1.00
EVI
EVI Histogram of Tapajos Tile (Seasonal Forest)
7/24/02 MODIS Science Meeting
7/24/02 MODIS Science Meeting
Forest (Tapajos) 3x3
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
Mar-00 Jun-00 Sep-00 Dec-00 Apr-01 Jul-01 Oct-01 Jan-02
EVI
7/24/02 MODIS Science Meeting
Litterfall Seasonal Dynamics (Tapajos)
(Woods Hall/ LBA/ <ftp://ftp.as.harvard.edu/pub/tapajos/>)
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Pasture sites near Tapajos
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
23-Jun-00 1-Oct-00 9-Jan-01 19-Apr-01 28-Jul-01 5-Nov-01 13-Feb-02 24-May-02
Vegetation Index
7/24/02 MODIS Science Meeting
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
Mar-00 Jun-00 Sep-00 Jan-01 Apr-01 Jul-01 Oct-01 Feb-02
NDVI
Tapajos Forest BNP-allANP-Forest ANP-Cerrado
Forest
Cerrado
open
closed
7/24/02 MODIS Science Meeting
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
Mar-00 Jun-00 Sep-00 Jan-01 Apr-01 Jul-01 Oct-01 Feb-02
EVI
Tapajos Forest BNP-allANP-Forest ANP-Cerrado
Forest
Cerrado
open
closed
7/24/02 MODIS Science Meeting
VI Ratio (Tapajos/ BNP)
0.5
1
1.5
2
2.5
3
3.5
6-Feb-00
16-May-00
24-Aug-00
2-Dec-00
12-Mar-01
20-Jun-01
28-Sep-01
6-Jan-02
16-Apr-02
25-Jul-02
Forest- Cerrado Ratio
NDVI
EVI
August Dry Peak
7/24/02 MODIS Science Meeting
Conclusions (Brazil)
• We found MODIS to be useful in characterizing the spatial and temporal dynamics of the Amazon Basin,
• Multitemporal profiles of the MODIS data revealed well-defined seasonal patterns in the cerrado region with decreasing dry-wet seasonal patterns in the transitional areas near Santana do Araguaia,
• Seasonality was observed to a small and uncertain extent at the Tapajos National Forest site, however, it was unclear whether this was associated with seasonal changes in forest leaf area or temporal changes in understory vegetation,
• We further found MODIS VI seasonal patterns to significantly vary in land converted areas.
7/24/02 MODIS Science Meeting
7/24/02 MODIS Science Meeting
Algorithm summary
Composite result
7/24/02 MODIS Science Meeting
7/24/02 MODIS Science Meeting
7/24/02 MODIS Science Meeting
Clouds, cloud shadow, and BRDF induce the largest uncertainties.
7/24/02 MODIS Science Meeting
Snow Problem in VI’sNDVI EVI
Snow effects: • Blue > Red > NIR• NDVI gives false negative signal• EVI gives false positive signal
7/24/02 MODIS Science Meeting
SAVI0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
EVI
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Cereal Crop / GrasslandBroadleaf ForestNeedleleaf ForestBroadleaf Forest
EVI & SAVI Relationships for Snow
EV
I
RT-Model
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.1 0.2 0.3 0.4 0.5 0.6
SAVI
Sevilleta
Jornada
Walnut Gulch
Konza
Harvard Forest
Cascades
MODIS Data (2000-2001)
7/24/02 MODIS Science Meeting
EVI0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
NDVI
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Cereal Crop / GrasslandBroadleaf CropNeedleleaf ForestBroadleaf Forest
North America Sites
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
EVI
NDVIYuma Sands
Sevilleta
Jornada
Walnut Gulch
Konza
Harvard Forest
Cascades
NDVI & EVI Relationships
RT-Model MODIS Data (2000-2001)
7/24/02 MODIS Science Meeting
Biophysical Validation
7/24/02 MODIS Science Meeting
Mongu NDVI and Fpar (2000-2002)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 60 120 180 240 300 360 420 480 540 600 660 720 780
Cumulative Days
Trac Fpar
MODIS NDVI
Trac SZA 10° to 30°
Trac SZA 30º to 50º
Trac SZA 50º to 75º
Huemmrich and Privette
7/24/02 MODIS Science Meeting
Conclusions• VI products are provisionally validated from
radiometric, seasonal, interannual and biophysical perspectives,
• product accuracy has been assessed by a number of independent measurements, at a number of locations or times representative of conditions portrayed by the product.
• Residual cloud, cloud shadow, BRDF, topography, and snow induce the largest uncertainties in the VI’s,• Assessment of feasibility of using snow product and BRDF products.
• VI product accuracy varies with QA.