An Extended Fourier Approach to Improve the Retrieved Leaf Area Index (LAI) in a Time Series from an Alpine Wetland
Author
Quan, Xingwen; He, Binbin; Wang, Yong; Tang, Zhi; Li, Xing
Abstract
An extended Fourier approach was presented to improve the retrieved leaf area
index (LAIr) of herbaceous vegetation in a time series from an alpine wetland. The retrieval
was performed from the Aqua MODIS 8-day composite surface reflectance product
(MYD09Q1) from day of year (DOY) 97 to 297 using a look-up table (LUT) based inversion
of a two-layer canopy reflectance model (ACRM). To reduce the uncertainty (the ACRM
inversion is ill-posed), we used NDVI and NIR images to reduce the influence of the soil
background and the priori information to constrain the range of sensitive ACRM parameters
determined using the Sobol’s method. Even so the uncertainty caused the LAIr versus time
curve to oscillate. To further reduce the uncertainty, a Fourier model was fitted using the
periodically LAIr results, obtaining LAIF. We note that the level of precision of the LAIF
potentially may increase through removing singular points or decrease if the LAIr data were
too noisy. To further improve the precision level of the LAIr, the Fourier model was
extended by considering the LAIr uncertainty. The LAIr, the LAI simulated using the Fourier
model, and the LAI simulated using the extended Fourier approach (LAIeF) were validated
through comparisons with the field measured LAI. The R2
values were 0.68, 0.67 and 0.72,
the residual sums of squares (RSS) were 3.47, 3.42 and 3.15, and the root-mean-square
errors (RMSE) were 0.31, 0.30 and 0.29, respectively, on DOY 177 (early July 2011). In late
August (DOY 233), the R2
values were 0.73, 0.77 and 0.79, the RSS values were 38.96,
29.25 and 27.48, and the RMSE values were 0.94, 0.81 and 0.78, respectively. The results
OPEN ACCESS
Remote Sens. 2014, 6 1172
demonstrate that the extended Fourier approach has the potential to increase the level of
precision of estimates of the time varying LAI.
Date
2015
Citation:
APA:
Quan, Xingwen, & He, Binbin, & Wang, Yong, & Tang, Zhi, & Li, Xing. (January 2015).
An Extended Fourier Approach to Improve the Retrieved Leaf Area Index (LAI) in a Time Series from an Alpine Wetland.
,
(),
-
. Retrieved from
http://hdl.handle.net/10342/8209
MLA:
Quan, Xingwen, and He, Binbin, and Wang, Yong, and Tang, Zhi, and Li, Xing.
"An Extended Fourier Approach to Improve the Retrieved Leaf Area Index (LAI) in a Time Series from an Alpine Wetland". .
. (),
January 2015.
September 21, 2023.
http://hdl.handle.net/10342/8209.
Chicago:
Quan, Xingwen and He, Binbin and Wang, Yong and Tang, Zhi and Li, Xing,
"An Extended Fourier Approach to Improve the Retrieved Leaf Area Index (LAI) in a Time Series from an Alpine Wetland," , no.
(January 2015),
http://hdl.handle.net/10342/8209 (accessed
September 21, 2023).
AMA:
Quan, Xingwen, He, Binbin, Wang, Yong, Tang, Zhi, Li, Xing.
An Extended Fourier Approach to Improve the Retrieved Leaf Area Index (LAI) in a Time Series from an Alpine Wetland. .
January 2015;
():
.
http://hdl.handle.net/10342/8209. Accessed
September 21, 2023.
Collections