The NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Temperature and Emissivity (LST&E) 8-day product (VJ121A2) combines the daily VJ121A1D and VJ121A1N products over an 8-day compositing period into a single product.

The VJ121A2 dataset is an 8-day composite LST&E product at 1 kilometer resolution that uses an algorithm based on a simple-averaging method. The algorithm calculates the average from all the cloud-free VJ121A1D and VJ121A1N daily acquisitions from the 8-day period. Unlike the VJ121A1 datasets where the daytime and nighttime acquisitions are separate products, the VJ121A2 contains both daytime and nighttime acquisitions as separate science dataset (SDS) layers within a single Hierarchical Data Format (HDF) file.

The VJ121A2 product is developed synergistically with the Moderate Resolution Imaging Spectroradiometer (MODIS) LST&E Version 6.1 product (MOD21A2) 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 VJ121A2 product contains 11 Science Datasets (SDS): LST, quality control, view zenith angle, and time of observation for both day and night observations along with emissivity for bands M14, M15, and M16. Low-resolution browse images for day and night LST are also available for each VJ121A2 granule.

Known Issues

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

Improvements/Changes from Previous Version

• 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.