NASA Gross and Net Primary Production

User GuidePI - Maosheng Zhao (SSAI/NASA GSFC)
Product ATBDCo-Is: Arthur Endsley (University of Montana), John Kimball (University of Montana), Sadashiva Devadiga (NASA GSFC)


The Gross and Net Primary Production (GPP/NPP) data products are designed to provide an accurate regular measure of the growth of the terrestrial vegetation. Primary Production is determined by first computing a daily GPP and net photosynthesis (PsnNet) values which are then composited over an 8-day interval of observations. At the end of each year, all daily GPP and PsnNet are summarized, and live wood respiration is subtracted to get annual total GPP and NPP.

The algorithm for the VIIRS GPP and NPP is based on the radiation use efficiency concept and the Q10 theory of plant respiration to changes in temperature. The data products may be used as inputs to data models for calculating terrestrial energy, carbon, water cycle processes, and biogeochemistry of vegetation. Modification of parameters in the Biome Property Look-Up Table (BPLUT) has been made to agree with GPP derived from measurements at eddy flux towers and synthesized NPP.

The issue of the cloud-contaminated remotely sensed inputs of 8-day VIIRS FPAR/LAI to the GPP and NPP products has been addressed. For the operational forward processing of 8-day GPP and PsnNet, the 5-year rolling climatology FPAR/LAI are being used as backup to replace the cloud-contaminated values in the input for 8-day GPP and PsnNet data products. More importantly, in each early year, year-end gap-filled 8-day GPP and PsnNet and annual GPP and NPP of the previous year will be created which use the year-end gap-filled VIIRS FPAR/LAI of the previous year as inputs to the algorithm to clean the cloud-contaminated data more thoroughly. We suggest users the use the VIIRS gap-filled GPP, PsnNet and NPP products for their studies if they do not require data for the present year. The gap-filled products are designated with “GF” in the HDF file names. The gap-filled product is post-processed data products created at the end of the year when the full 8-day VIIRS FPAR/LAI for an entire year are available. In addition, for annual GPP and NPP, there are only the gap-filled products.

LAI viirs/modis comparison

Global VIIRS Gross and Net Primary Production (GPP/NPP, VNP17/VJ117) continue the global MODIS GPP/NPP data product in a consistent manner to provide 8-day and annual 500m GPP/NPP for terrestrial ecosystems.

The products are provided in standard Hierarchical Data Format–Earth Observing System (HDF-EOS5) format. Currently, this collection is available from January 19, 2012 and forward.  Products from the VIIRS sensor aboard JPSS-1 (J1) will be also be available starting in mid-2023.

 

Product Details and DAAC links

Product Name SNPP JPSS-1
Gross Primary Productivity 8-Day L4 Global 500m SIN Grid VNP17A2 VJ117A2
Net Primary Production Gap-Filled 8-Day L4 Global 500m SIN Grid VNP17A2GF VJ117A2GF
Net Primary Production Gap-Filled Yearly L4 Global 500m SIN Grid VNP17A3GF VJ117A3GF