Satellite Applications for Detecting Vegetation Phenology - Satellite-based Applications on Climate Change - page 259

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2001 2002 2003 2004

Year

2005 2006 2007

Fig. 17.1 Smoothed data by Fourier series. Original MODIS data are shown in blue points and
simulated data in black solid line . The red star marks are local maximum and local minimum

Fig. 17.2 Onset date detection. The solid line is fitted logistic model and the dashed line is the
curvature of the NDVI time series. The green point indicates the greenup onset ( left figure ) and the
dormancy onset ( right figure )

identify the single growth or senescence period are independent of the data set
temporal resolution and no empirical parameters settings. Based on the single
growth or senescence period, the logistic model provided by Zhang et al. ( 2003 )
(Eq. 17.4 ) is used to identify phenological metrics, by determining the curvature of
the fitted logistic models. The first point with largest curvature in increasing period
corresponds to the greenup onset, and the second point with largest curvature in
decreasing period corresponds to the dormancy onset (Fig. 17.2 ).

c

yðtÞ¼

þ e aþbt þ d

(17.4)

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