MOD17A3 v055

MODIS/Terra Net Primary Production Yearly L4 Global 1 km SIN Grid

Description

The Moderate Resolution Imaging Spectroradiometer (MODIS) Net Primary Productivity (NPP) product (MOD17A3) defines the rate at which all plants in an ecosystem produce net useful chemical energy. In other words, NPP is equal to the difference between the rate at which plants in an ecosystem produce useful chemical energy or Gross Primary Productivity (GPP), and the rate at which they expend some of that energy for respiration.

Version 5.5 of the NPP product is produced by the Numerical Terradynamic Simulation Group (NTSG) at the University of Montana (UMT). It corrects the problem with cloud-contaminated MODIS Leaf Area Index (LAI)/Fraction of Photosynthetically Active Radiation (FPAR) inputs to the MOD17 algorithm. The original, uncorrected datasets constitute the Version 4 NPP products. For further details regarding the differences between the NTSG and NASA versions of this product, please consult the document referenced in the following news release: Terra MODIS GPP/NPP Products from NTSG/University of Montana.

Version 5.5 Terra MODIS NPP products are validated to stage 3. This means that its accuracy was assessed and uncertainties in the product were well established via independent measurements made in a systematic and statistically robust way that represents global conditions. These data are deemed ready for use in science applications.

The following data citation is recommended when using MOD17A3 data: Running, S., Mu, Q., Zhao, M. (2011). MOD17A3 MODIS/Terra Net Primary Production Yearly L4 Global 1km SIN Grid V055 [Data set]. NASA EOSDIS Land Processes DAAC.

Characteristics

Collection and Granule

Collection

Characteristic Description
CollectionTerra MODIS
DOI
File Size~7 MB
Temporal ResolutionYearly
Temporal Extent2000-01-01 to 2014-12-31
Spatial ExtentGlobal
Coordinate SystemSinusoidal
DatumN/A
File FormatHDF-EOS
Geographic Dimensions1200 km x 1200 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers3
Columns/Rows1200 x 1200
Pixel Size1000 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Additional Offset
Gpp_1km Gridded 1 km Annual Gross Primary Productivity kg C/m² 16-bit unsigned integer 65529 to 65535 N/A 0 to 65500 0.0001 N/A
Npp_1km Gridded 1 km Annual Net Primary Productivity kg C/m² 16-bit unsigned integer 65529 to 65535 N/A 0 to 65500 0.0001 N/A
Gpp_Npp_QC_1km Quality Control Percent 8-bit unsigned integer 250 to 255 N/A 0 to 100 N/A N/A

GPP and NPP Fill Values

Value Description
65529 Unclassified pixel
65530 Urban/built-up cover type
65531 Permanent wetlands/inundated marshland type
65532 Perennial snow or ice cover type
65533 Barren, sparsely vegetated (rock, tundra, desert) cover type
65534 Perennial salt or inland fresh water body cover type
65535 Fill value assigned to pixels not falling into other categories

Interpreting the Gpp_Npp_QC_1km SDS

The improved, yearly MODIS GPP/NPP product does not use QA bit-fields but a meaningful percent value. This number refers to the percentage of filled MOD15 LAI caused by cloud-contamination during a growing season (defined when daily minimum air temperatures are above -8 Celsius) in a year. Therefore, the valid annual QA values range from 0 to 100; a high value refers to a high frequency of cloud-contamination. For example, QA is high for tropical rainforests but low in arid areas. The QC fill values' descriptions correspond to the different non-vegetated land cover types identified in table above.

Quality Control Fill Values

Value Description
250 Urban/built-up cover type
251 Permanent wetlands/inundated marshland type
252 Perennial snow or ice cover type
253 Barren, sparsely vegetated (rock, tundra, desert) cover type
254 Perennial salt or inland fresh water body cover type
255 Fill value assigned to pixels not falling into other categories

Product Quality

Information on accuracy can be found on the MODIS Land Validation Web Site.

Known Issues

For complete information about the MOD17A3 known issues please refer to the MODIS Land Quality Assessment website.

Documentation

Using the Data

Tools

Citation

DOI:

About the Image