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Figure S1. Spatial pattern of the day at which the land surface freezes. DOY is day of the year.
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Fig S2. Spatial patterns of mean GDD requirement for vegetation green-up onset over the period
1982-2009. The GDD requirement is an integration of daily mean temperature above 5℃ from
the day of land surface froze in previous year to the day of green-up onset. Three satellitederived NDVI datasets (AVHRR (lift three panels), MODIS (middle three panels) and SPOT
(right three panels)) and four interpolation methods (Hants, Spline, Polyfit and Timesat) for each
dataset were used to extract the vegetation green-up onset.
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Fig S3. Spatial patterns of mean GDD requirement for vegetation green-up onset over the period
1982-2009. The GDD requirement is an integration of daily mean temperature above 0℃ from
the yearly average day of land surface froze in previous year to the day of green-up onset. Three
satellite-derived NDVI datasets (AVHRR (lift three panels), MODIS (middle three panels) and
SPOT (right three panels)) and four interpolation methods (Hants, Spline, Polyfit and Timesat)
for each dataset were used to extract the vegetation green-up onset.
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Fig S4. Spatial pattern of previous winter chilling accumulation. Chilling is expressed in chilling
days (CD), and a chilling day was accumulated when daily mean air temperature was below 0oC
from the day of land surface froze in previous year to the day of green-up onset.
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Fig S5 Spatial distribution of mean green-up onset date over the period of 1982-2009. Three
satellite-derived NDVI datasets (AVHRR (lift three panels), MODIS (middle three panels) and
SPOT (right three panels)) and four interpolation methods (Hants, Spline, Polyfit and Timesat)
for each dataset were used to extract the vegetation green-up onset.
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Figure S6. Spatial pattern of GDD requirement using 0℃ as temperature threshold calculated by
averaging the yearly GDD requirements per pixel over the period 1982-2009. The GDD
requirement for each year is an integration of daily mean temperature above 0℃ from the day
when land surface froze in the previous autumn to the day of mean vegetation green-up onset.
Three satellite-derived NDVI datasets (AVHRR (lift three panels), MODIS (middle three panels)
and SPOT (right three panels)) and four interpolation methods (Hants, Spline, Polyfit and
Timesat) for each dataset were used to extract the vegetation green-up onset.
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Fig S7. Spatial pattern of previous winter season precipitation. The previous winter season was
defined as the current month with the day of green-up onset plus the two previous months.
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