MYD21A2 v061

MODIS/Aqua Land Surface Temperature/3-Band Emissivity 8-Day L3 Global 1 km SIN Grid


PI: Glynn C. Hulley

Description

A suite of Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature and Emissivity (LST&E) products are available in Collection 6.1. The MYD21 Land Surface Temperature (LST) algorithm differs from the algorithm of the MYD11 LST products, in that the MYD21 algorithm is based on the ASTER Temperature/Emissivity Separation (TES) technique, whereas the MYD11 uses the split-window technique. The MYD21 TES algorithm uses a physics-based algorithm to dynamically retrieve both the LST and spectral emissivity simultaneously from the MODIS thermal infrared bands 29, 31, and 32. The TES algorithm is combined with an improved Water Vapor Scaling (WVS) atmospheric correction scheme to stabilize the retrieval during very warm and humid conditions.

The MYD21A2 dataset is an 8-day composite LST product that uses an algorithm based on a simple averaging method. The algorithm calculates the average from all the cloud free MYD21A1D and MYD21A1N daily acquisitions from the 8-day period. Unlike the MOD21A1 data sets where the daytime and nighttime acquisitions are separate products, the MYD21A2 contains both daytime and nighttime acquisitions as separate Science Dataset (SDS) layers within a single Hierarchical Data Format (HDF) file. The LST, Quality Control (QC), view zenith angle, and viewing time have separate day and night SDS layers, while the values for the MODIS emissivity bands 29, 31, and 32 are the average of both the nighttime and daytime acquisitions. MYD21A2 products are available two months after acquisition due to latency of data inputs. Additional details regarding the method used to create this Level 3 (L3) product are available in the Algorithm Theoretical Basis Document (ATBD).

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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 utilizes GEOS data replacing MERRA2.
  • Three new CMG products are available in the MxD21 suite (MxD21C1/C2/C3).

Product Maturity

Validation at stage 1 has been achieved for the MODIS Land Surface Temperature and Emissivity data products. Further details regarding MODIS land product validation for the MYD21 data products are available from the MODIS Land Team Validation site.

Collection and Granule

Collection

Characteristic Description
CollectionAqua MODIS
DOI10.5067/MODIS/MYD21A2.061
File Size~5.3 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) Layers11
Columns/Rows1200 x 1200
Pixel Size1000 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Additional Offset
LST_Day_1KM Land surface temperature Kelvin 16-bit unsigned integer 0 N/A 7500 to 65535 0.02 N/A
QC_Day Quality Control (QC) N/A 8-bit unsigned integer 0 N/A 0 to 255 N/A N/A
View_Angle_Day MODIS view zenith angle Degree 8-bit unsigned integer 255 N/A 0 to 130 N/A -65
View_Time_Day Time of MODIS observation Hours 8-bit unsigned integer 255 N/A 0 to 240 0.1 N/A
LST_Night_1KM Night Land Surface Temperature Kelvin 16-bit unsigned integer 0 N/A 7500 to 65535 0.02 N/A
QC_Night Night Quality Control (QC) N/A 8-bit unsigned integer 0 N/A 1 to 255 N/A N/A
View_Angle_Night Night view zenith angle Degree 8-bit unsigned integer 255 N/A 1 to 130 N/A -65
View_Time_Night Time of Observation for night Hours 8-bit unsigned integer 255 N/A 0 to 240 0.1 N/A
Emis_29 Average Day/Night Band 29 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_31 Average Day/Night Band 31 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_32 Average Day/Night Band 32 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49

Product Quality

The QC 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.

The final quality bit for the output product reflects the lowest quality values from all observations that went into the final average. The bit definition index for the QC layer is available in Table 12 of the User Guide.

Known Issues

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

Documentation

User Guide
Algorithm Theoretical Basis Document (ATBD)
File Specification

Using the Data

Access Data

Citation

DOI: 10.5067/MODIS/MYD21A2.061

About the Image

Aqua MODIS land surface temperature (LST) data from the MYD21A2 product over India on India from October 23 - 30, 2020.

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