VJ121C1 v002

VIIRS/JPSS1 Land Surface Temperature/Emissivity Daily L3 Global 0.05 Deg CMG


PI: Glynn Hulley, Simon Hook

Description

The NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Temperature and Emissivity (LST&E) Climate Modeling Grid Version 2 product (VJ121C) is compiled daily from daytime Level 2 Gridded (L2G) intermediate products. The L2G process maps the daily VJ121 swath granules onto a sinusoidal MODIS grid and stores all observations overlapping a gridded cell for a given day. The VJ121C1 algorithm sorts through all these observations for each cell and estimates the final LST value as an average from all cloud-free observations that have good LST accuracies. The 0.05 degree (5,600 m) dataset is derived through resampling the native 750 meter VIIRS resolution in the input product.

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 VJ121C1 product contains 25 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 VJ121C1 granule.

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Characteristics

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

Collection

Characteristic Description
CollectionNOAA-20 VIIRS
DOI10.5067/VIIRS/VJ121C1.002
File Size~2.05 MB
Temporal ResolutionDaily
Temporal Extent2018-01-01 to Present
Spatial ExtentGlobal
Coordinate SystemGeographic Latitude and Longitude
DatumN/A
File FormatHDF-EOS5
Geographic DimensionsGlobal

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers25
Columns/Rows7200 x 3600
Pixel Size5600 m

Layers / Variables

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Offset
Count_Day Count of Daytime Input Values N/A 16-bit unsigned integer 0 N/A 1 to 65535 N/A N/A
Count_Night Count of Nighttime Input Values N/A 16-bit unsigned integer 0 N/A 1 to 65535 N/A N/A
Day_View_Angle Average Daytime View Zenith Angle Degree 8-bit unsigned integer 255 N/A 0 to 130 N/A -65
Day_View_Time Average Daytime View Time Hours 8-bit unsigned integer 255 N/A 0 to 240 0.2 N/A
Emis_14_Day Average Daytime Band 14 Emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_14_Day_err Root-mean-square error Daytime Band 14 Emissivity N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 0
Emis_14_Night Average Nighttime Band 14 Emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_14_Night_err Root-mean-square error Nighttime Band 14 Emissivity N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 0
Emis_15_Day Average Daytime Band 15 Emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_15_Day_err Root-mean-square-error Daytime Band 15 Emissivity N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 0
Emis_15_Night Average Nighttime Band 15 Emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_15_Night_err Root-mean-square-error Nighttime Band 15 Emissivity N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 0
Emis_16_Day Average Daytime Band 16 Emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_16_Day_err Root-mean-square-error Daytime Band 16 Emissivity N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 0
Emis_16_Night Average Nighttime Band 16 Emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_16_Night_err Root-mean-square-error Nighttime Band 16 Emissivity N/A 16-bit unsigned integer 0 N/A 1 to 65535 0.0001 0
LST_Day Average Daytime Land Surface Temperature Kelvin 16-bit unsigned integer 0 N/A 7500 to 65535 0.02 0
LST_Day_err Root-mean-square-error Daytime Land Surface Temperature Kelvin 8-bit unsigned integer 0 N/A 1 to 255 0.04 0
LST_Night Average Nighttime Land Surface Temperature Kelvin 16-bit unsigned integer 0 N/A 7500 to 65535 0.02 0
LST_Night_err Root-mean-square-error Nighttime Land Surface Temperature Kelvin 8-bit unsigned integer 0 N/A 1 to 255 0.04 0
Night_View_Angle Average Nighttime View Zenith Angle Degree 8-bit unsigned integer 255 N/A 0 to 130 N/A -65
Night_View_Time Average Nighttime View Time Hours 8-bit unsigned integer 255 N/A 0 to 240 0.2 N/A
Percent_land_in_grid Percent of Land Detections in Grid Cell Percent 8-bit unsigned integer 255 N/A 0 to 100 N/A 0
QC_Day Quality Control for Daytime LST and Emissivity N/A 8-bit unsigned integer N/A N/A 0 to 255 N/A N/A
QC_Night Quality Control for Nighttime LST and Emissivity N/A 8-bit unsigned integer N/A N/A 0 to 255 N/A N/A

Product Quality

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.

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

A global Land Surface Temperature image from the VJ121C1 product on May 12, 2020.

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Documentation

User Guide
Algorithm Theoretical Basis Document (ATBD)

Using the Data

Access Data

Citation

DOI: 10.5067/VIIRS/VJ121C1.002