Evapotranspiration on Terrestrial Eastern Asia Estimated by Satellite Remote Sensing

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Evapotranspiration on Terrestrial Eastern Asia
Estimated by Satellite Remote Sensing
JWH02/04P/D-002 1400-027 Poster IUGG 2003, July
4, Sapporo

• Kenlo Nishida
• Institute of Agricultural and Forest Engineering,
  University of Tsukuba
• kenlo_at_sakura.cc.tsukuba.ac.jp

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MOD16 Evapotranspiration Project

• MOD16 is a project for operational estimation of
  terrestrial evapotranspiration (ET) by a
  satellite sensor (Aqua/MODIS)
• MOD16 algorithm is applicable not only for
  Aqua/MODIS but also for Terra/MODIS, ADEOS2/GLI,
  and NOAA/AVHRR etc.
• Currently, the algorithm has been established.
  (Nishida et al., 2003)
• Tests have been done mainly on North America.
• In this study, we test MOD16 logic with
  NOAA/AVHRR data for Eastern Asia.

• Nishida, K., Nemani, R. R., Running, S. W.,
  Glassy, J. M. (2003) An operational remote
  sensing algorithm of land surface evaporation.
  Journal of Geophysical Research D, in press
• Nishida, K., Nemani, R. R., Running, S. W.,
  Glassy, J. M. (2003) Development of an
  evapotranspiration index from Aqua/MODIS for
  monitoring surface moisture status. IEEE
  Transactions of Geoscience and Remote Sensing,
  41(2), 493-501.

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MOD16 ET Logic (1) Conceptual Frame
Actual landscape mixture of
forest, farm, grassland, road, etc.
Simplification (Two-source model)
ETbare
ET fveg ET veg (1 - fveg) ET soil
ETveg
Qveg
Qbare EF fveg ------- EFveg (1 - fveg)
------ EFbare Q
Q
Available Energy
Fraction of bare soil 1.0 - fveg
Net radiation (radiation absorbed on the land)
Ground heat transfer
Fraction of vegetation fveg
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MOD16 ET Logic (2) Estimating EFveg
Assuming complementary relationship (ET PETPM
2PETPT PETPMPenmans PET PETPTPriestley-Tay
lors PET), we can get
Derivative of saturated vapor pressure curve
(change with T)
Constant. 1.26
a ? EFveg
------------------------------------ ? ? (
1 rc / 2 ra)
Psychrometric constant (slightly change with T)
Aerodynamic resistance
Canopy resistance
1 / rc f1(T) f2(VPD) f3(PAR) f4(?) / rcMIN
Temperature
Solar radiation
Soil water
Humidity
Change of VI
1 / rc f1(T) f3(PAR) / rcMIN
Implementation
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MOD16 ET Logic (3) Estimating EFbare
satellite image
Ts
Tbare max
Warm Edge
Wind speed
Tbare
Window
Tbare max Tbare EFbare -------------------
--- Tbare max Tbare min
TvegTbare min
Air temperature
VI
VImax
VImin
VI
VI-Ts diagram (Nemani Running, 1989 1993)
Qbare0 ET Tbare
------------------------------------ Ta
4esTa3 (1- CG) ? Cp/ra bare
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MOD16 ET Logic (4) Data Stream
Satellite data
VI albedo
Channel reflectance
Thermal IR
Ts
Tbare max Tbare Ta
VI Ts
VI-Ts diagram
EFbare
fveg
VI
OrbitTa
Rd PAR
Radiative transfer model
Qbare Qbare0 Qveg
Rd Taalbedo
EF
Radiation budget
Qbare Tbare max Ta
U50m ra
Energy budget
Ta PAR
rc
Conductance model
Ta ra rc
Penman-Monteith Complementary relation
EFveg
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Test in USA
Nishida et al., 2003, JGR
Comparison of estimated EF by AVHRR and observed
EF at AmeriFlux sites
--------------------------------------------------
--------------------------------------------------
---------------------------------- site
(symbol) type data size R 2
bias standard error ---------------------------
--------------------------------------------------
--------------------------------------------------
------- Harvard Forest DBF 28
0.75 -0.05 0.13 Walker
Branch DBF 29 0.88
0.01 0.13 Willow Creek DBF
8 0.80 -0.14 0.18
WLEF Tower DBF 17 0.89
-0.18 0.20 Blodgett ENF
11 0.30 -0.12 0.21
Duke Forest ENF 13 0.70
0.04 0.19 Howland ENF
20 0.84 -0.02 0.10
Metolius ENF 15 0.20
-0.12 0.23 Bondville
Crop 37 0.81 -0.07
0.19 Ponca Crop 6
0.36 -0.10 0.31 Little Washita
Grass 20 0.86 0.04
0.14 Shidler Grass 10
0.91 -0.03 0.12 Ski Oaks
Shrub 16 0.29 -0.07
0.17 all sites --- 230
0.74 -0.05 0.17
-------------------------------------------------
--------------------------------------------------
-----------------------------------
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Test in Eastern Asia

• Data
• NOAA/AVHRR 1km-10day composite, 1999, by Iwate
  University(Yokoyama, Lei, and Purevdorj, 2002)
• Land Cover Dataset, Asian Association on Remote
  Sensing (AARS)0.5minute grid

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1999/02
1999/01
EFv
EF
EF
EFv
EFb
fv
EFb
fv
1999/03
1999/04
EFv
EF
EFv
EF
fv
EFb
fv
EFb
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1999/06
1999/05
EF
EFv
EF
EFv
EFb
fv
EFb
fv
1999/08
1999/07
EF
EFv
EFv
EF
fv
fv
EFb
EFb
12
1999/10
1999/09
EFv
EF
EFv
EF
fv
EFb
EFb
fv
1999/11
1999/12
EFv
EF
EFv
EF
fv
EFb
EFb
fv
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Validation at Takayama Flux Site
Courtesy for field data Dr. Saigusa, AIST
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Validation at EGAT Tower
Courtesy for field data Dr. Toda, Hokkaido Univ.
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Evaluation of Water Budget
(vertical only)
Gain precipitationGPCC, global, monthly, 1deg
Loss evapotranspirationEF (Rn-G)
Rn NCEP reanalysis G Moran, 1989 G0.58
exp(-2.13NDVI)
Gain Loss Budget
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1999/01 1999/02 1999/03
1999/04
1999/05 1999/06 1999/07
1999/08
1999/09 1999/10 1999/11
1999/12
mm/month
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Conclusion

• MOD16 logic was tested in Eastern Asia, 1999,
  with NOAA/AVHRR composite.
• Validation with ground observation data from two
  sites showed consistent accuracy with North
  America.
• In combination of radiation and precipitation
  data, MOD16 EF product provides vertical water
  budget, which has implication on water resource
  monitoring.

Acknowledgements Dr. Liping Lei in Basic
Engineering Co., Ltd. allowed me to use AVHRR
composite dataset. Mr. W. Takeuchi in the
University of Tokyo arranged the AVHRR datasets.
Dr. N. Saigusa in AIST provided me with energy
flux data taken in Takayama flux site. Drs. M.
Toda and N. Ohte carried out the energy flux
observation in EGAT Tower site with a support
from GAME(GEWEX Asian Monsoon Experiment)-Tropics.
The MOD16 algorithm development was supported by
JSPS Fellowship for Study Abroad as well as NASA
and Numerical Terradinamic Simulation Group
(NTSG) of University of Montana.