VJ121 v002

VIIRS/JPSS1 Land Surface Temperature and Emissivity 6-Min L2 Swath 750 m

PI: Glynn Hulley, Simon Hook


The NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Temperature and Emissivity (LST&E) Version 2 swath product (VJ121) is produced daily in 6-minute temporal increments of satellite acquisition. The VJ121 product uses a physics-based algorithm to dynamically retrieve both the LST and emissivity simultaneously for VIIRS thermal infrared bands M14 (8.55 µm), M15 (10.76 µm), and M16 (12 µm) at a spatial resolution of 750 meters.

The VJ121 product is developed developed synergistically with the Moderate Resolution Imaging Spectroradiometer (MODIS) LST&E Version 6.1 product (MOD21) using the same input atmospheric products and algorithmic approach based on the ASTER Temperature Emissivity Separation (TES) technique. 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 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. VIIRS LST&E products are available two months after acquisition due to latency of data inputs. Additional details regarding the method used to create this Level 2 (L2) product are available in the Algorithm Theoretical Basis Document (ATBD).

Provided in the VJ121 product are layers for LST, quality control, emissivity for bands M14, M15, and M16, LST&E errors, view angle, ASTER Global Emissivity Dataset (GED), Precipitable Water Vapor (PWV), ocean-land mask, latitude, and longitude. A low-resolution browse image for LST is also available for each VJ121 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~80 MB
Temporal Resolution< Daily
Temporal Extent2018-01-01 to Present
Spatial ExtentGlobal
Coordinate SystemNone (Swath)
File FormatnetCDF-4
Geographic Dimensions3060 km x 3060 km


Characteristic Description
Number of Science Dataset (SDS) Layers15
Columns/Rows3200 x 3232
Pixel Size750 m

Layers / Variables

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Offset
Emis_14 M14 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_14_err M14 emissivity error N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 N/A
Emis_15 M15 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_15_err M15 emissivity error N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 N/A
Emis_16 M16 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_16_err M16 emissivity error N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 N/A
Emis_ASTER ASTER GED Emissivity (minimum of 5 band values) N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
LST Land Surface Temperature Kelvin 16-bit unsigned integer 0 N/A 7500 to 65535 0.02 N/A
LST_err Land Surface Temperature error Kelvin 8-bit unsigned integer 0 N/A 1 to 255 0.04 N/A
PWV Precipitable Water Vapor cm 16-bit unsigned integer N/A N/A 0 to 65535 0.001 N/A
QC Quality control for LST and emissivity N/A 16-bit unsigned integer N/A N/A 0 to 65535 N/A N/A
View_angle VIIRS view angle for current pixel Degree 8-bit unsigned integer 255 N/A 0 to 180 0.5 N/A
oceanpix Ocean-land mask N/A 8-bit unsigned integer N/A N/A 0 to 2 N/A N/A
latitude Pixel Latitude Degree 32-bit floating point -999 N/A -90 to 90 N/A N/A
longitude Pixel Longitude Degree 32-bit floating point -999 N/A -180 to 180 N/A N/A

Ocean-land mask Values

Value Description
0 Land
1 Water
2 Inland water

Product Quality

The bit flags for the QC layer are defined in Table 5 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

Land Surface Temperature from the VJ121 product over Chad, Africa on April 7, 2019.

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User Guide
Algorithm Theoretical Basis Document (ATBD)
File Specification

Using the Data

Access Data


DOI: 10.5067/VIIRS/VJ121.002