MYD13A3 v006

MODIS/Aqua Vegetation Indices Monthly L3 Global 1 km SIN Grid


PI: Kamel Didan

Description

The Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Vegetation Indices (MYD13A3) Version 6 data are provided monthly at 1 kilometer (km) spatial resolution as a gridded Level 3 product in the sinusoidal projection. In generating this monthly product, the algorithm ingests all the MYD13A2 products that overlap the month and employs a weighted temporal average.

The MODIS Normalized Difference Vegetation Index (NDVI) complements NOAA's Advanced Very High Resolution Radiometer (AVHRR) NDVI products and provides continuity for time series historical applications. MODIS also includes an Enhanced Vegetation Index (EVI) that minimizes canopy background variations and maintains sensitivity over dense vegetation conditions. The EVI uses the blue band to remove residual atmosphere contamination caused by smoke and sub-pixel thin clouds. The MODIS NDVI and EVI products are computed from surface reflectances corrected for molecular scattering, ozone absorption, and aerosols.

Vegetation indices are used for global monitoring of vegetation conditions and are used in products displaying land cover and land cover changes. These data may be used as input for modeling global biogeochemical and hydrologic processes as well as global and regional climate. Additional applications include characterizing land surface biophysical properties and processes, such as primary production and land cover conversion.

Provided along with the vegetation layers and the two quality assurance (QA) layers are reflectance bands 1 (red), 2 (near-infrared), 3 (blue), and 7 (mid-infrared), as well as three observation layers.

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Characteristics

Improvements/Changes from Previous Versions

  • The 16-day composite VI is generated using the two 8-day composite surface reflectance granules (MYD09A1) in the 16-day period.
  • This surface reflectance input is based on the minimum blue compositing approach used to generate the 8-day surface reflectance product.
  • The product format is consistent with the Version 5 product generated using the Level 2 gridded daily surface reflectance product.
  • A frequently updated long-term global Climate Modeling Grid (CMG) Average Vegetation Index product database is used to fill the gaps in the CMG product suite.

Product Maturity

Validation at stage 3 has been achieved for MYD13 vegetation products. Further details regarding product validation for the MYD13A3 data product is available from the MODIS land team validation site.

Collection and Granule

Collection

Characteristic Description
CollectionAqua MODIS
DOI10.5067/MODIS/MYD13A3.006
File Size~8 MB
Temporal ResolutionMonthly
Temporal Extent2002-07-01 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) Layers11
Columns/Rows1200 x 1200
Pixel Size1000 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
1 km monthly NDVI 1 km monthly NDVI NDVI 16-bit signed integer -3000 N/A -2000 to 10000 0.0001
1 km monthly EVI 1 km monthly EVI EVI 16-bit signed integer -3000 N/A -2000 to 10000 0.0001
1 km monthly VI Quality VI quality indicators Bit Field 16-bit unsigned integer 65535 N/A 0 to 65534 N/A
1 km monthly red reflectance Surface Reflectance Band 1 N/A 16-bit signed integer -1000 N/A 0 to 10000 0.0001
1 km monthly NIR reflectance Surface Reflectance Band 2 N/A 16-bit signed integer -1000 N/A 0 to 10000 0.0001
1 km monthly blue reflectance Surface Reflectance Band 3 N/A 16-bit signed integer -1000 N/A 0 to 10000 0.0001
1 km monthly MIR reflectance Surface Reflectance Band 7 N/A 16-bit signed integer -1000 N/A 0 to 10000 0.0001
1 km monthly view zenith angle View zenith angle of VI Pixel Degree 16-bit signed integer -10000 N/A 0 to 18000 0.01
1 km monthly sun zenith angle Sun zenith angle of VI pixel Degree 16-bit signed integer -10000 N/A 0 to 18000 0.01
1 km monthly relative azimuth angle Relative azimuth angle of VI pixel Degree 16-bit signed integer -4000 N/A -18000 to 18000 0.01
1 km monthly pixel reliability Quality reliability of VI pixel Rank 8-bit signed integer -1 N/A 0 to 3 N/A

Product Quality

The "1 km monthly VI Quality" layer is stored in an efficient bit-encoded manner. The unpack_sds_bits executable from the LDOPE Tools is available to the user community to help parse and interpret the quality layer.

In addition to data access and transformation processes, AppEEARS also has the capability to unpack and interpret the quality layers.

The QA bit flags for the "1 km monthly pixel reliability" layer are provided in Table 4 on page 15 and the "1 km monthly VI Quality" layer in Table 5 on page 16 of the User Guide.

In areas where no valid VI is retrieved, VI Quality bits 11-13 are correctly assigned to indicate the land/water type. The other bits are set to 1 which can create a false notion of the parameter description; however, since no valid VI is retrieved these values can be ignored.

Known Issues

For complete information about the MYD13A3 known issues please refer to the MODIS Land Quality Assessment website.

Documentation

Using the Data

E-Learning

Getting Started with MODIS Version 6 Vegetation Indices Data Part 1: All About Accessing Data

Getting Started with MODIS Version 6 Vegetation Indices Data Part 2: Using the Data

Getting Started with MODIS Version 6 Vegetation Indices Data Part 3: Interpreting Quality Information

Tools

Citation

DOI: 10.5067/MODIS/MYD13A3.006

About the Image

Aqua MODIS NDVI data from the MYD13A3 product over part of Brazil, July 2018.

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