Terra MODIS evapotranspiration (ET) data from the MOD16A3GF product over the Caspian Sea, 2003.View full-size image
The MOD16A3GF Version 6 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 Moderate Resolution Imaging Spectroradiometer (MODIS) remotely sensed data products such as vegetation property dynamics, albedo, and land cover.
The 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.
|File Size||4.8 MB|
|Temporal Extent||2000-02-18 to Present|
|Geographic Dimensions||1200 km x 1200 km|
|Number of Science Dataset (SDS) Layers||5|
|Columns/Rows||2400 x 2400|
|Pixel Size||500 m|
|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.
|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|
|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|
|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 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.