Land Surface Temperature from the VJ121 product over Chad, Africa on April 7, 2019.
View full-size imageThe 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.
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/VJ121.002 |
| File Size | ~80 MB |
| Temporal Resolution | < Daily |
| Temporal Extent | 2018-01-01 to Present |
| Spatial Extent | Global |
| Coordinate System | None (Swath) |
| Datum | N/A |
| File Format | netCDF-4 |
| Geographic Dimensions | 3060 km x 3060 km |
| Characteristic | Description |
|---|---|
| Number of Science Dataset (SDS) Layers | 15 |
| Columns/Rows | 3200 x 3232 |
| Pixel Size | 750 m |
| 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 |
| Value | Description |
|---|---|
| 0 | Land |
| 1 | Water |
| 2 | Inland water |
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.
For complete information about known issues please refer to the MODIS/VIIRS Land Quality Assessment website and the User Guide.