Remote Sensing Phenology


Deriving Phenological Metrics from NDVI

Plotting time-series NDVI data produces a temporal curve that summarizes the various stages that green vegetation undergoes during a complete growing season. Such curves can be analyzed to extract key phenological variables, or metrics, about a particular season, such as the start of the growing season (SOS), peak of the season (POS), and end of the season (EOS). These characteristics may not necessarily correspond directly to conventional, ground-based phenological events, but do provide indications of ecosystem dynamics.

A complete list of the phenological metrics we extract from smoothed, time-series NDVI data is shown in Table 2. Calculated for each year or growing season, these metrics are the basis for diverse research and monitoring applications, including climate change studies.

To download metrics, click on the Get Data tab above. For information regarding how metrics are derived, see below.

Table 2. Remote sensing phenology data sets for the conterminous U.S.
RSP Data Set Acronym Phenological Interpretation Description
Start of Season - Time

Start of Season – Time click to enlarge
SOST Beginning of measurable photosynthesis in the vegetation canopy Day of year identified as having a consistent upward trend in time series NDVI
Start of Season - NDVI

Start of Season – Time click to enlarge
SOSN Level of photosynthetic activity at the beginning of measurable photosynthesis NDVI value (or baseline) identified at the day of year identified as a consistent upward trend in time series NDVI
End of Season - Time

Start of Season – Time click to enlarge
EOST End of measurable photosynthesis in the vegetation canopy Day of year identified at the end of a consistent downward trend in time series NDVI
End of Season - NDVI

Start of Season – Time click to enlarge
EOSN Level of photosynthetic activity at the end of measurable photosynthesis NDVI value corresponding with the day of year identified at the end of a consistent downward trend in time series NDVI
Time of Maximum

Start of Season – Time click to enlarge
MAXT Time of maximum photosynthesis in the canopy Day of year corresponding to the maximum NDVI in an annual time series
Maximum NDVI

Start of Season – Time click to enlarge
MAXN Maximum level of photosynthetic activity in the canopy Maximum NDVI in an annual time series
Duration

Start of Season – Time click to enlarge
DUR Length of photosynthetic activity (the growing season) Number of days from the SOST and EOST
Amplitude

Amplitude click to enlarge
AMP Maximum increase in canopy photosynthetic activity above the baseline Difference between MAXN and SOSN
Time Integrated NDVI

Start of Season – Time click to enlarge
TIN Canopy photosynthetic activity across the entire growing season Daily (interpolated) integration of NDVI above the baseline for the entire duration of the growing season

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