VJ121A1N v002

VIIRS/JPSS1 Land Surface Temperature/Emissivity Daily L3 Global 1 km SIN Grid Night

PI: Glynn Hulley, Simon Hook


The NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Temperature and Emissivity (LST&E) Night Version 2 product (VJ121A1N) is compiled daily from nighttime Level 2 Gridded (L2G) intermediate products.

The L2G process maps the daily VJ121 swath granules onto a sinusoidal MODIS grid and stores all observations overlapping a gridded cell for a given night. The VJ121A1 algorithm sorts through all these observations for each cell and estimates the final LST value as an average from all cloud-free observations that have good LST accuracies. The nighttime average is weighted by the observation coverage for that cell. Only observations having observation coverage more than a certain threshold (15%) are considered for this averaging. The 1 kilometer dataset is derived through resampling the native 750 meter VIIRS resolution in the input product.

The VJ121A1N product is developed synergistically with the Moderate Resolution Imaging Spectroradiometer (MODIS) LST&E Version 6.1 product (MOD21A1N) using the same input atmospheric products and algorithmic approach. The overall objective for NASA VIIRS products is to ensure the algorithms and products are compatible with the MODIS Terra and Aqua algorithms to promote the continuity of the Earth Observation System (EOS) mission. Additional details regarding the method used to create this Level 3 (L3) product are available in the Algorithm Theoretical Basis Document (ATBD).

The VJ121A1N product contains seven Science Datasets (SDS): LST, quality control, emissivity for bands M14, M15, and M16, view zenith angle, and time of observation. A low-resolution browse image for LST is also available for each VJ121A1N granule.

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Improvements/Changes from Previous Versions

  • Improved calibration algorithm and coefficients for entire NOAA-20 mission.
  • Improved geolocation accuracy and applied updates to fix outliers around maneuver periods.
  • Corrected the aerosol quantity flag (low, average, high) mainly over brighter surfaces in the mid- to high-latitudes such as desert and tropical vegetation areas. This has an impact on the retrieval of other downstream data products such as VNP13 Vegetation Indices and VNP43 Bidirectional Reflectance Distribution Function (BRDF)/Albedo.
  • Improved cloud mask input product for corrections along coastlines and artifacts from use of coarse resolution climatology data.
  • Replaced the land/water mask input product with the eight-class land/water mask from the VNP03 geolocation product that better aligns with MODIS.
  • Replaced MERRA2 inputs with GEOS5.
  • Included inland water body pixels to allow for LST retrieval over these areas.
  • Introduced daily, 8-day, and monthly LST CMG products.

More details can be found in this VIIRS Land V2 Changes document.

Product Maturity

Validation at stage 1 has been achieved for the VIIRS Land Surface Temperature and Emissivity product suite. Visit VIIRS Land Product Quality Assessment Product Maturity for information on product maturity status.

Collection and Granule


Characteristic Description
CollectionNOAA-20 VIIRS
File Size~1 MB
Temporal ResolutionDaily
Temporal Extent2018-01-01 to Present
Spatial ExtentGlobal
Coordinate SystemSinusoidal
File FormatHDF-EOS5
Geographic Dimensions1200 km x 1200 km


Characteristic Description
Number of Science Dataset (SDS) Layers7
Columns/Rows1200 x 1200
Pixel Size1000 m

Layers / Variables

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Offset
Emis_14 Daily Band 14 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_15 Daily Band 15 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_16 Daily Band 16 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
LST_1KM Daily 1km Land-surface Temperature Kelvin 16-bit unsigned integer 0 N/A 7500 to 65535 0.02 N/A
QC Daily QC for LST and emissivity N/A 16-bit unsigned integer N/A N/A 0 to 65535 N/A N/A
View_Angle View zenith angle of LST Degree 8-bit unsigned integer 255 N/A 0 to 130 N/A -65
View_Time Time of LST observation Hours 8-bit unsigned integer 255 N/A 0 to 240 0.1 N/A

Product Quality

The final quality bit for the output product reflects the lowest quality values from all observations that went into the final average. The bit flags for the QC layer are defined in Table 7 on pages 22-23 of the User Guide.

The 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.

Quality assurance information should be considered when determining the usability of data for a particular science application. The ArcGIS MODIS-VIIRS Python Toolbox contains tools capable of decoding quality data layers while producing thematic quality raster files for each quality attribute.

For additional information on product quality, refer to the VIIRS Land Product Quality website.

Known Issues

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

About the image

Nighttime Land Surface Temperature from the VJ121A1N product over the western United States on June 18, 2018.

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User Guide
Algorithm Theoretical Basis Document (ATBD)
File Specification

Using the Data

Access Data


DOI: 10.5067/VIIRS/VJ121A1N.002