Land Surface Temperature from the VJ121A2 product over the western United States during April 15 - April 23, 2019.
View full-size imageThe 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.
More details can be found in this VIIRS Land V2 Changes document.
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.
| Characteristic | Description |
|---|---|
| Collection | NOAA-20 VIIRS |
| DOI | 10.5067/VIIRS/VJ121A2.002 |
| File Size | ~2.05 MB |
| Temporal Resolution | Multi-Day |
| Temporal Extent | 2018-01-01 to Present |
| Spatial Extent | Global |
| Coordinate System | Sinusoidal |
| Datum | N/A |
| File Format | HDF-EOS5 |
| Geographic Dimensions | 1200 km x 1200 km |
| Characteristic | Description |
|---|---|
| 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 | Offset |
|---|---|---|---|---|---|---|---|---|
| Emis_14 | Average Band 14 emissivity | N/A | 8-bit unsigned integer | 0 | N/A | 1 to 255 | 0.002 | 0.49 |
| Emis_15 | Average Band 15 emissivity | N/A | 8-bit unsigned integer | 0 | N/A | 1 to 255 | 0.002 | 0.49 |
| Emis_16 | Average Band 16 emissivity | N/A | 8-bit unsigned integer | 0 | N/A | 1 to 255 | 0.002 | 0.49 |
| LST_Day_1KM | 8-day daytime 1km grid Land-surface Temperature | Kelvin | 16-bit unsigned integer | 0 | N/A | 7500 to 65535 | 0.02 | N/A |
| LST_Night_1KM | 8-day nighttime 1km grid Land-surface Temperature | Kelvin | 16-bit unsigned integer | 0 | N/A | 7500 to 65535 | 0.02 | N/A |
| QC_Day | Quality control for daytime LST and emissivity | N/A | 8-bit unsigned integer | 0 | N/A | 1 to 255 | N/A | N/A |
| QC_Night | Quality control for nighttime LST and emissivity | N/A | 8-bit unsigned integer | 0 | N/A | 1 to 255 | N/A | N/A |
| View_Angle_Day | Average view zenith angle of daytime Land-surface Temperature | Degree | 8-bit unsigned integer | 255 | N/A | 0 to 130 | N/A | -65 |
| View_Angle_Night | Average view zenith angle of nighttime Land-surface Temperature | Degree | 8-bit unsigned integer | 255 | N/A | 0 to 130 | N/A | -65 |
| View_Time_Day | Average time of daytime Land-surface Temperature observation | Hours | 8-bit unsigned integer | 255 | N/A | 0 to 240 | 0.1 | N/A |
| View_Time_Night | Average time of nighttime Land-surface Temperature observation | Hours | 8-bit unsigned integer | 255 | N/A | 0 to 240 | 0.1 | N/A |
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 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.
For complete information about known issues please refer to the MODIS/VIIRS Land Quality Assessment website and the User Guide.