MODIS Estimate of Canopy Water Content Susan L. Ustin University of California Davis July 14, 2004.

MODIS Estimate of

Canopy Water Content

Susan L. UstinUniversity of California Davis

July 14, 2004

(Ustin et al., 1999)AVIRIS Composite 980 nm Water Absoroption

Cw/LAI Estimation from MODIS

0

0.1

0.2

0.3

0.4

0.5

0.6

400 900 1400 1900 2400

W ave le ngth (nm )

Ref

lect

ance

cw=0.001 cw=0.002 cw=0.003 cw=0.01

cw=0.015 cw=0.02 cw=0.03

cw=0.001

cw=0.03

Band4R858.5nm

Band5R1240nm

MODIS Water Index (SRWI):

1240

858SRWI

R

R

(Pablo Zarco-Tejada et al., 2001 IEEE; Rem. Sens. Env. 2003)

y = 0.04x - 0.0208R2 = 0.7238

0.00

0.01

0.02

0.03

0.04

0 0.5 1 1.5 2

Leaf (fw-dw)/dw

Est

ima

ted

Cw

(cm

)y = 0.0173x - 0.0095

R2 = 0.7772

0.00

0.01

0.02

0.03

0.04

0 0.5 1 1.5 2 2.5

Leaf (fw-dw)/dw

Est

ima

ted

Cw

(cm

)

y = 1.3355x - 0.0124R2 = 0.7183

0.00

0.01

0.02

0.03

0.04

0 0.01 0.02 0.03 0.04 0.05

Leaf [(fw-dw)/dw]*LHSAV

Est

ima

ted

Cw

(cm

)

y = 1.1134x - 0.0088R2 = 0.8644

0.000

0.005

0.010

0.015

0.020

0 0.01 0.02 0.03

Tim e Averaged [(fw-dw)/dw]*LHSAV

Est

ima

ted

Cw

(cm

)

Comparison between Field Measured Water Content VS. MODIS Prediction

Water Content estimation from MOD09A1: seasonal variation

Cw=0.03

Cw=0.02

Cw=0.01

Cw=0

(Zarco-Tejada et al., 2003 Rem. Sens. Env.)

Canopy water content in Southern California VegetationMeasured by MODIS Satellite

Seasonal Drought and Wildfire Potential

+

_

H2O

Canopy Water Content

• Estimates of LAI

• Estimates of Plant Water Stress

• Estimates of Wildfire Fuel Moisture Content

Roberts et al., Ecosystems 2004

LAI Estimated by NDVI VS EWT

Wind River Ameriflux Site

Wisconsin Tall Tower Flux Site

S.N. Burrows et al.Ecosystems 2002

MODIS Data 2000-2001

0

2

4

6

8

10

12

14

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57

Week Number

LA

IModel1

MODIS

Model2

Estimate of LAI from MODIS Water Content vs. MOD09A1

San Francisco

Los Angeles

1-980 CR AVIRIS Image

Estimating Water StressFrom Water Content

1-CR Ratio (899-1060 nm) vs. Time

0.00

0.01

0.02

0.03

0.04

0.05

0.06

8/25/99 8/30/99 9/4/99 9/9/99 9/14/99 9/19/99 9/24/99 9/29/99

Date of Year 1999

1-98

0 C

ontin

uum

Rem

oval

l

Changes in Canopy Water Content after Irrigation Cutoff

+ Water

- Water

Within Field Water Content vs.Days Since Last Irrigation

y = -469.4x + 54.649

R2 = 0.3251

0

2

4

6

8

10

12

14

16

18

0.08 0.085 0.09 0.095 0.1 0.105 0.11 0.115 0.12

1-980 Value

Days

Sin

ce L

ast I

rriga

tion

y = -409.06x + 51.855

R2 = 0.8128

0

2

4

6

8

10

12

14

16

18

0.08 0.085 0.09 0.095 0.1 0.105 0.11 0.115 0.12 0.125

1-980 CR

Days

Sin

ce L

ast I

rriga

tion

Pima Fields Only Acala Fields Only

Estimating Fuel Moisture Content

■ Dry Matter in Fresh Samples

y = 0.8308x + 0.0009

R2 = 0.342

0.00

0.01

0.01

0.02

0.02

0.03

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016

Inv-PROSPECT Dry matter (g/cm2)

Mea

sure

d D

ry m

atte

r fr

om f

resh

sam

ples

(g

/cm

2 )

Stephane Jacquemoud et al, 1996

P-value<0.0001

Estimates of Fuel Moisture Content■ dry matter estimated seasonally

■ water content from Water Index

0

50

100

150

200

250

300

96 112

128

144

160

176

192

208

224

240

256

272

Day of the year

FM

C

0

0.5

1

1.5

Fu

nct

ion

of

Da

y

Cistus

Grassland

Func-cistus

Func-grass

Emilio Chuvieco et al., in press