LST, April 15 - April 23, 2019 over the Western USA from VNP21A2.View full-size image
The NASA Suomi National Polar-Orbiting Partnership (Suomi NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Temperature and Emissivity (LST&E) 8-day product (VNP21A2) combines the daily VNP21A1D and VNP21A1N products over an 8-day compositing period into a single product.
The VNP21A2 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 VNP21A1D and VNP21A1N daily acquisitions from the 8-day period. Unlike the VNP21A1 datasets where the daytime and nighttime acquisitions are separate products, the VNP21A2 contains both daytime and nighttime acquisitions as separate science dataset (SDS) layers within a single Hierarchical Data Format (HDF) file.
The VNP21A2 product is developed synergistically with the Moderate Resolution Imaging Spectroradiometer (MODIS) LST&E Version 6 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). VIIRS LST&E products are available 2 months after acquisition due to latency of data inputs.
The VNP21A2 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 VNP21A2 granule.
|Collection||Suomi NPP VIIRS|
|File Size||~2.05 MB|
|Temporal Extent||2012-01-18 to Present|
|Geographic Dimensions||1200 km x 1200 km|
|Number of Science Dataset (SDS) Layers||11|
|Columns/Rows||1200 x 1200|
|Pixel Size||1000 m|
|SDS Name||Description||Units||Data Type||Fill Value||No Data Value||Valid Range||Scale Factor||Additional Offset|
|LST_Day_1KM||Day Land Surface Temperature||Kelvin||16-bit unsigned integer||0||N/A||7500 to 65535||0.02||N/A|
|QC_Day||Day Quality control for LST and emissivity||N/A||8-bit unsigned integer||0||N/A||1 to 255||N/A||N/A|
|View_Angle_Day||Day View zenith angle of LST||Degree||8-bit unsigned integer||255||N/A||0 to 130||N/A||-65|
|View_Time_Day||Day Time of LST observation||Hours||8-bit unsigned integer||255||N/A||0 to 240||0.1||N/A|
|LST_Night_1KM||Night 1 km Land Surface Temperature||Kelvin||16-bit unsigned integer||0||N/A||7500 to 65535||0.02||N/A|
|QC_Night||Night Quality control for LST and emissivity||N/A||8-bit unsigned integer||0||N/A||1 to 255||N/A||N/A|
|View_Angle_Night||Night View zenith angle of LST||Degree||8-bit unsigned integer||255||N/A||0 to 130||N/A||-65|
|View_Time_Night||Night Time of LST observation||Hours||8-bit unsigned integer||255||N/A||0 to 240||0.1||N/A|
|Emis_14||M14 emissivity||N/A||8-bit unsigned integer||0||N/A||1 to 255||0.002||0.49|
|Emis_15||M15 emissivity||N/A||8-bit unsigned integer||0||N/A||1 to 255||0.002||0.49|
|Emis_16||M16 emissivity||N/A||8-bit unsigned integer||0||N/A||1 to 255||0.002||0.49|
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 9 on page 25 of the User Guide.
For additional information on product quality, refer to the VIIRS Land Product Quality website.
For complete information about known issues please refer to the MODIS/VIIRS Land Quality Assessment website.