The MOD16A2GF Version 6 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 Moderate Resolution Imaging Spectroradiometer (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.
Validation at stage 1 has been achieved for MODIS Evapotranspiration products.
|File Size||1.7 MB|
|Temporal Extent||2000-01-01 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 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|
Users are asked to disregard the class assignments for Fill Values 32761 through 32767 irrespective of the assigned quality for these pixels. Class assignments may be incorrect and users are advised to exercise caution while using the product in their application. See known issue PM_MOD16_18074 for further information.
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.