The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008
Date
DOY
Site
BR(field)
BR(Est)
25-Jul
206
Crop
0.324
0.451
28-Jul
209
Crop
0.945
0.725
5-Aug
217
Crop
0.711
0.510
8-Aug
220
Crop
0.738
0.691
9-Aug
221
Crop
0.466
0.554
25-Jul
206
Grass
0.552
0.561
28-Jul
209
Grass
0.672
0.582
5-Aug
217
Grass
0.666
0.676
8-Aug
220
Grass
0.739
0.682
9-Aug
221
Grass
0.534
0.406
Table III. comparison of Bowen ratio in TOngyu, 2003
Results in Table III show that BR estimated tend to be less
variable than field data, partly caused by the spatial average.
The H/LE patterns are good consistent with field
data(coefficient of correlation, r=0.762), although absolute error
in daily ET is about 20% that means error in a single day could
reach 2mm/day at most. But for a longer term, such error will
decline rapidly.
4.5 Sensible heat maps
Figure III shows results for output sensible heat components,
briefly decomposed using fractional vegetation cover, fc. The
gross main structure of the sensible heat flux on canopy is
explained by the fc derived from MODIS LAI products, but
such simplified assumption of thermodynamic temperature
decomposed would be improper in refined resolution.
SitiSible Ileal Flux in Ttmfcy u.Sep-10-2003
it? it mam m is mti
UTR tut are. i2».e m are
Sensible Heat Mux uf $<Hl,Tu«i&yu.Sep-10-2003
u? it MfWK taut m art mi<
117 R 120 E 121 are
‘iis*bk‘ Ileal Mux uf Plant Ciuop),Toog)«LScp-10-20®3
it?« n«ar»i taut i?t*m mn
¡i? r ttaarK i2qe i2i are
Figure 3: (left)(center)(right),tongyu,09/10/2003
5. CONCLUSION
A new method to estimate surface fluxes using two-time surface
temperature measurement is presented. It is a combination of
PBL and SVAT: The surface energy balance equations serve as
a lower boundary constraint for a simple model of planetary
boundary evolution, and the sensible heat flux happened on the
surface layer could be related to variation of surface
temperature. The primary strength of the methods is that it
requires no more precious and spatialized air temperature as
model input.
The model has been validated using limited field data from
Tongyu site of CEOP experiment, 2003. Comparisons between
modeled and measured fluxes and air temperature show
relatively small RMSE. And Bowen ratio shows an accepted
correlation coefficient(r=0.76) in clear-sky cases. Because of
the limited verification data and dates, the model results are
preliminary and need further testing.
The model can be improved in the follow aspect: A temporal
scaling component would be introduced to fill the gaps
contaminated by cloud; the spatial patterns of Bowen ratio
should be compared with refined resolution image such as
ASTER or ETM to analyze the influence of linear
decomposition of Trad to soil temperature and canopy
temperature using LAI.
ACKNOWLEDGMENT
Thanks to CEOP for providing fluxes and meteorological data
of Tongyu station, 2002-2003.
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