Environmental Engineering Reference
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350
Dormancy
Onset
300
250
200
Growing
Length
150
100
Greenup
Onset
50 31 32 33 34 35 36 37 38 39 40
Latitude
41 42 43 44 45 46 47 48 49 50
Fig. 17.3 The variation of MODIS-derived phenology in DBF along latitudes over the Eastern US
17.3.3 MODIS-Derived Vegetation Phenology
The newer generation of sensor MODIS was launched in December 1999.
Improved geometry, radiometry, and overall data quality of MODIS, combined
with its free-of-charge data policy, provide readily available high-quality data for
phenology studies. MODIS onboard NASA's Terra and Aqua satellites collect daily
reflectance data at spatial resolution of 250 m, 500 m, and 1 km globally. One of the
standard MODIS land products is the Land Cover Dynamics product (MOD12Q2),
distributed from the Land Processes Distributed Active Archive Center, which
includes several phenology metrics at 1-km spatial resolution (Zhang et al. 2003 ).
The MODIS-derived phenology can be used in the similar research areas of
AVHRR-derived phenology, such as trends of vegetation dynamics, response to
climate change, land cover change, and disaster monitoring (Ahl et al. 2006 ; Kang
et al. 2003 ; Kim and Wang 2005 ; Peckham et al. 2008 ; Zhang et al. 2004 ).
Besides these research areas, the higher spatial and temporal resolution has
enabled MODIS-derived vegetation phenology to develop a stronger understanding
of how environmental conditions affect phenological patterns among regional and
broad scales. Li et al. ( 2010a ) have quantified the effects of latitude, elevation, and
ecoregions on MODIS-derived vegetation phenology in Deciduous Broadleaf
Forest (DBF) over continental USA during 2000-2008. Figure 17.3 shows an
obvious phenological pattern dependent on latitude. The rate of change for greenup
onset and dormancy onset is about 2 days per degree latitude. They also have
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