MOD16A2GF v061

MODIS/Terra Net Evapotranspiration Gap-Filled 8-Day L4 Global 500 m SIN Grid


PI: Steve Running

Description

The Terra Moderate Resolution Imaging Spectroradiometer (MODIS) MOD16A2GF Version 6.1 Evapotranspiration/Latent Heat Flux (ET/LE) product is a year-end gap-filled 8-day 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 MOD16A2GF will be generated at the end of each year when the entire yearly 8-day MOD15A2H is available. Hence, the gap-filled MOD16A2GF is the improved MOD16, 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 MOD16A2GF in near-real time because it will be generated only at the end of a given year.

Provided in the MOD16A2GF 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 MOD16A2GF granule.

The pixel values for the two Evapotranspiration layers (ET and PET) are the sum of all eight days within the composite period, and the pixel values for the two Latent Heat layers (LE and PLE) are the average of all eight days within the composite period. The last acquisition period of each year is a 5 or 6-day composite period, depending on the 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/MOD16A2GF.061
File Size~25 MB
Temporal ResolutionMulti-Day
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 Evapotranspiration kg/m²/8day 16-bit signed integer 32761 to 32767 N/A -32767 to 32700 0.1
LE_500m Average Latent Heat Flux J/m²/day 16-bit signed integer 32761 to 32767 N/A -32767 to 32700 10000
PET_500m Total Potential Evapotranspiration kg/m²/8day 16-bit signed integer 32761 to 32767 N/A -32767 to 32700 0.1
PLE_500m Average Potential Latent Heat Flux J/m²/day 16-bit signed integer 32761 to 32767 N/A -32767 to 32700 10000
ET_QC_500m Evapotranspiration Quality Control flags Bit Field 8-bit unsigned integer 255 N/A 0 to 254 N/A

Product Quality

The pixel level quality control layer (ET_QC_500m) is a copy of the quality control data layer of the corresponding input LAI/FPAR (MOD15A2H) granule of the same 8-day composite period and does not reflect the quality of the retrieved evapotranspiration. For the improved and reprocessed MOD16A2, namely MOD16A2GF, users may ignore the QC data layer because cloud-contaminated LAI/FPAR gaps have been temporally filled before calculating ET.

Additional information related to the cloud/aerosol screening and quality for input products is provided under Section 3.2.1 in the User Guide. Mappings for the ET QC layer and an explanation of how to interpret this information are provided under Section 6.2.1 in 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/MOD16A2GF.061

About the Image

Terra MODIS evapotranspiration (ET) data from the MOD16A2GF product over Maranhao, Brazil from December 26 - 31, 2020.

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