Gross Primary Productivity 8-Day L4 Global 1km
MYD17A2
The MODerate-resolution Imaging Spectroradiometer
(MODIS) Gross Primary Productivity (GPP) product
(MYD17A2) is a cumulative composite of GPP values
based on the radiation use efficiency concept that may
be used as inputs to data models for calculating
terrestrial energy, carbon, water cycle processes, and
biogeochemistry of vegetation. MYD17A2 is an 8-day
composite at 1-kilometer spatial resolution provided as
a gridded level-4 product in the Sinusoidal projection.
Version-5 MODIS/Aqua GPP products are Validated
Stage 3, meaning accuracy has been assessed, and the
uncertainties in the product well-established via
independent measurements made in a systematic and
statistically robust way that represents global
conditions. Although there may be later improved
versions, these data are ready for use in scientific
publications.
These images are examples of the GPP
and PSN values reported in the
MYD17A2 product with data acquired
June 10-17, 2005 in tile h08v05 over the
western US.
Values are low in the desert Southwest,
increasing towards the more vegetated
coastline.
Data Set Characteristics
Temporal Coverage
Area
File Size
Projection
Data Format
Dimensions
Resolution
Science Data Sets (SDS HDF Layers)
July 4, 2002 ~10 x 10 lat/long
~1 MB compressed
Sinusoidal
HDF-EOS
1200 x 1200 rows/columns
1 kilometer
3
Layers
Science Data Sets for MODIS/Aqua Gross Primary Productivity 8-Day L3 Global 1km SIN Grid
V005 (MYD17A2):
Science Data Sets (HDF UNITS BIT TYPE FILL
VALID
MULTIPLY BY
Layers) (3)
RANGE SCALE FACTOR
Gpp_1km: Gross Primary
Production
kg_C/m2 16-bit signed 32761–
integer
32767
0–30000
0.0001
PsnNet_1km: Net
Photosynthesis (GPP –
maintenance respiration)
kg_C/m2 16-bit signed 32761–
integer
32767
-30000–
30000
0.0001
0–254
na
PSN_QC_1km: QC for GPP/PSN Bit
8-bit
unsigned
integer
255
The QA information below is excerpted from the MOD17A2 file specifications.
Table 1: MYD17A2.005 GPP/PSN QA (8-bit)
Bit
Parameter Name
Bit
PSN_QC_1km
No.
Comb.
0
1
2
3–4
5–7
MODLAND_QC bits
Sensor
DeadDetector
CloudState (inherited from
Aggregate_QC bits {0,1} cloud state)
SCF_QC (five level confidence score)
0
Good quality
1
Other quality
0
Terra
1
Aqua
0
Detectors apparently fine for up to 50% of
channels 1,2
1
Dead detectors caused >50% adjacent
detector retrieval
00
0 Significant clouds NOT present (clear)
01
1 Significant clouds WERE present
10
2 Mixed cloud present on pixel
11
3 Cloud state not defined, assumed clear
000
0, Very best possible
001
1, Good, very usable, but not the best
(saturation in FPAR/LAI has occurred)
010
2, Substandard due to geometry problems –
use with caution
011
3, Substandard due to other than geometry
problems – use with caution
100
4, Couldn't retrieve pixel (NOT PRODUCED AT
ALL – non-terrestrial biome)
111
7, Fill Value
MYD17A2 Fill Values
Table 1: For Gpp_1km and PsnNet_1km
Value
Description
32767 Fillvalue
32766 land cover assigned as perennial salt or inland fresh water
32765 land cover assigned as barren, sparse vegetation (rock, tundra, desert.)
32764 land cover assigned as perennial snow, ice
32763 land cover assigned as "permanent" wetlands/inundated marshlands
32762 land cover assigned as urban/built-up
32761 land cover assigned as "unclassified" or not able to determine