MYD16A2GF v006

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


PI: Steve Running

Description

The MYD16A2GF 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 improved algorithm 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 MYD16A2GF will be generated at the end of each year when the entire yearly 8-day MYD15A2H is available. Hence, the gap-filled MYD16A2GF is the improved MYD16, 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 MYD16A2GF in near-real time because it will be generated only at the end of a given year.

Provided in the MYD16A2GF 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 MYD16A2GF 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

  • Spatial resolution of Version 6 products has increased to nominal 500 m from nominal 1,000 m in Version 5.
  • Version 5 data products were previously distributed by the Numerical Terradynamic Simulation Group at the University of Montana. The Version 6 products are a continuation of this project.

Product Maturity

Validation at stage 1 has been achieved for MODIS Evapotranspiration products.

Collection and Granule

Collection

Characteristic Description
CollectionAqua MODIS
DOI10.5067/MODIS/MYD16A2GF.006
File Size1.7 MB
Temporal ResolutionMulti-Day
Temporal Extent2002-07-04 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

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.

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 (MYD15A2H) granule of the same 8-day composite period and does not reflect the quality of the retrieved evapotranspiration. For the improved and reprocessed MYD16A2, namely MYD16A2GF, 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.

Known Issues

Operational and uncertainty issues are provided on page 13 in the User Guide.

Please refer to the MODIS Land Quality Assessment website for complete information about MYD16A2GF known issues.

Documentation

Using the Data

Access Data

Citation

DOI: 10.5067/MODIS/MYD16A2GF.006

About the Image

Aqua MODIS evapotranspiration (ET) data from the MYD16A2GF product over Parana, Brazil from January 1 - 8, 2003.

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