
News
Reprocessed all MOD15A2GFS and MOD15A2PHN products
for years 2000 through 2005 to address the following issues...
MOD15A2GFS (GapFilled, smoothed LAIfPAR):
 Summary:
 Scaled weights can be outside range of 16 bit integer. This causes
incorrect QC categories to be assigned, which can lead to misclassified
high quality and low quality data.
 Details:
 After adjustment for second iteration TIMESAT run, small LAI values get
smaller weight and high LAI values get higher weight due to upfold
weighting scheme. The weight is multiplied by 10000 and saved in short
integer (16bit) format. The highest possible weight is 4, which is out
of valid range of 16bit integer after scaling by 10000. Also, pixels
with weights smaller than 0.249 are not classified due to a bug in the
program. The pixels falling into these two situations are marked with
original LAI values in QC layer. Therefore, both high and low quality
data have a chance to slip into MODIS_LAI_FPAR_QC layer with original LAI
values. Four SDS layers are affected: COMPOSED_LAI, COMPOSED_FPAR,
MODIS_LAI_FPAR_QC, COMPOSED_LAI_FPAR_QC.
 Solution:

1.Use a weight of 1000 instead of 10000. This avoids the highest weight
out of valid range of 16bits integer after scaling.
2.Added trap to handle pixels with an adjusted weight between 0.01 to 0.249.
MOD15A2PHE (Phenology derived from GapFilled, smoothed
LAIfPAR):
 Summary:
 Improve temporal resolution of phenology dates from 8 days to 1 day.
 Details:
 In previous version, the greenup (browndown) date is marked at the
fitted point, which is closest to the time for which the left (right)
edge has increased (decreased) to 10% of the seasonal amplitude measured
from the left (right) minimum level. Therefore, the temporal resolution
of the phenology dates is 8day.
 Solution:
 In current version, the greenup (browndown) date is calculate as a
fractional time of an 8day period by a linear interpolation from
neighbor fitted points before and after 10% of the seasonal amplitude.
The interpolation parameters are calculated from the LAI value at 10%
of the seasonal amplitude and the LAI values from the neighbor fitted
points before and after it.

