The MOD17A3HGF Version 6 product provides information about annual Net Primary Production (NPP) at 500 meter (m) pixel resolution. Annual NPP is derived from the sum of all 8-day Net Photosynthesis (PSN) products (MOD17A2H) from the given year. The PSN value is the difference of the Gross Primary Productivity (GPP) and the Maintenance Respiration (MR).
The MOD17A3HGF will be generated at the end of each year when the entire yearly 8-day MOD15A2H is available. Hence, the gap-filled MOD17A3HGF is the improved MOD17, which has cleaned the poor-quality inputs from 8-day Leaf Area Index and Fraction of Photosynthetically Active Radiation (LAI/FPAR) based on the Quality Control (QC) label for every pixel. If any LAI/FPAR pixel did not meet the quality screening criteria, its value is determined through linear interpolation. However, users cannot get MOD17A3HGF in near-real time because it will be generated only at the end of a given year.
|File Size||~0.79 MB|
|Temporal Extent||2000-02-18 to Present|
|Geographic Dimensions||1200 km x 1200 km|
|Number of Science Dataset (SDS) Layers||2|
|Columns/Rows||2400 x 2400|
|Pixel Size||500 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor|
|Npp_500m||Net Primary Productivity||kgC/m²/year||16-bit signed integer||32761 to 32767||N/A||-30000 to 32700||0.0001|
|Npp_QC_500m||Quality Control Bits||Percent||8-bit unsigned integer||249 to 255||N/A||0 to 100||N/A|
|32761||Land cover assigned as "unclassified" or not able to determine|
|32762||Land cover assigned as urban/built-up|
|32763||Land cover assigned as "permanent" wetlands/inundated marshland|
|32764||Land cover assigned as perennial snow, ice|
|32765||Land cover assigned as barren, sparse veg (rock, tundra, desert)|
|32766||Land cover assigned as perennial salt or inland fresh water|
|249||Land cover assigned as "unclassified" or not able to determine|
|250||Land cover assigned as urban/built-up|
|251||Land cover assigned as "permanent" wetlands / inundated marshland|
|252||Land cover assigned as perennial snow, ice|
|253||Land cover assigned as barren, sparse vegetation (rock, tundra, desert)|
|254||Land cover assigned as perennial salt or water bodies|
Quality for MOD17A3HGF is expressed as a percentage in the Npp_QC_500m science dataset layer. More information on how this value is derived can be found in Section 4.2 of the User Guide.
Additional information on the Collection 5.5 improved 1 km MOD17 product by the Numerical Terradynamic Simulation Group (NTSC) at the University of Montana and a comparison with the MOD17HGF products are provided in MOD17HGF_vs_NTSG.pdf.