MOD16A3GF v061

MODIS/Terra Net Evapotranspiration Gap-Filled Yearly L4 Global 500 m SIN Grid


PI: Steve Running

Description

The Terra Moderate Resolution Imaging Spectroradiometer (MODIS) MOD16A3GF Version 6.1 Evapotranspiration/Latent Heat Flux (ET/LE) product is a year-end gap-filled yearly composite dataset produced at 500 meter (m) pixel resolution. The algorithm used for the MOD16 data product collection is based on the logic of the Penman-Monteith equation, which includes inputs of daily meteorological reanalysis data along with MODIS remotely sensed data products such as vegetation property dynamics, albedo, and land cover.

The MODIS MOD16A3GF will be generated at the end of each year when the entire yearly 8-day MOD15A2H is available. Hence, the gap-filled MOD16A3GF is the improved MOD16, which has cleaned the poor-quality inputs from yearly 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 MOD16A3GF in near-real time because it will be generated only at the end of a given year.

Provided in the MOD16A3GF product are layers for composited ET, LE, Potential ET (PET), and Potential LE (PLE) along with a quality control layer. Two low resolution browse images, ET and LE, are also available for each MOD16A3GF granule.

The pixel values for the two Evapotranspiration layers (ET and PET) are the sum for all days within the defined year, and the pixel values for the two Latent Heat layers (LE and PLE) are the average of all days within the defined year.

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Characteristics

Improvements/Changes from Previous Versions

  • The Version 6.1 Level-1B (L1B) products have been improved by undergoing various calibration changes that include: changes to the response-versus-scan angle (RVS) approach that affects reflectance bands for Aqua and Terra MODIS, corrections to adjust for the optical crosstalk in Terra MODIS infrared (IR) bands, and corrections to the Terra MODIS forward look-up table (LUT) update for the period 2012 - 2017.
  • A polarization correction has been applied to the L1B Reflective Solar Bands (RSB).
  • The product uses Climatology LAI/FPAR as back up to the operational LAI/FPAR.

Product Maturity

Validation at stage 3 has been achieved for the MODIS Evapotranspiration data products. Further details regarding MODIS land product validation for the MOD16 data products are available from the MODIS Land Team Validation site.

Collection and Granule

Collection

Characteristic Description
CollectionTerra MODIS
DOI10.5067/MODIS/MOD16A3GF.061
File Size4.8 MB
Temporal ResolutionYearly
Temporal Extent2001-01-01 to Present
Spatial ExtentGlobal
Coordinate SystemSinusoidal
DatumN/A
File FormatHDF-EOS
Geographic Dimensions1200 km x 1200 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers5
Columns/Rows2400 x 2400
Pixel Size500 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
ET_500m Total of Evapotranspiration kg/m²/year 16-bit unsigned integer 65529 to 65535 N/A 0 to 65500 0.1
LE_500m Average of Latent Heat Flux J/m²/day 16-bit signed integer 32761 to 32767 N/A 0 to 32700 10000
PET_500m Total Potential Evapotranspiration kg/m²/year 16-bit unsigned integer 65529 to 65535 N/A 0 to 65500 0.1
PLE_500m Average of Potential Latent Heat Flux J/m²/day 16-bit signed integer 32761 to 32767 N/A 0 to 32700 10000
ET_QC_500m Evapotranspiration Quality Assessment Percent 8-bit unsigned integer 249 to 255 N/A 0 to 100 N/A

The header file of MOD16A3GF lists only one fill value per layer, but there are a total of seven fill values to describe non-vegetated pixels.

ET_500m and PET_500m Fill Value Classes

Value Description
65529 Land cover assigned as "unclassified" or not able to determine
65530 Land cover assigned as urban/built-up
65531 Land cover assigned as "permanent" wetlands/inundated marshland
65532 Land cover assigned as perennial snow, ice
65533 Land cover assigned as barren, sparse vegetation (rock, tundra, desert)
65534 Land cover assigned as perennial salt or water bodies
65535 Fill

LE_500m and PLE_500m Fill Value Classes

Value Description
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 vegetation (rock, tundra, desert)
32766 Land cover assigned as perennial salt or water bodies
32767 Fill

ET_QC_500m Fill Value Classes

Value Description
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
255 Fill

Product Quality

Quality for MOD16A3GF is expressed as a percentage in the ET_QC_500m science dataset layer. More information on how this value is derived can be found in Section 6.2.2 of the User Guide.

Additional information on the Collection 5.5 improved 1 km MOD16 product by the Numerical Terradynamic Simulation Group (NTSC) at the University of Montana and a comparison with the MOD16GF products are provided in MOD16GF_vs_NTSG.pdf.

Known Issues

Operational and uncertainty issues are provided under Section 3 in the User Guide.

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

Documentation

Using the Data

Access Data

Citation

DOI: 10.5067/MODIS/MOD16A3GF.061

About the Image

Terra MODIS evapotranspiration (ET) data from the MOD16A3GF product over the Caspian Sea, 2020.

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