VNP21A1D v001

VIIRS/NPP Land Surface Temperature and Emissivity Daily L3 Global 1 km SIN Grid Day


PI: Glynn Hulley

Description

The NASA Suomi National Polar-Orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Temperature and Emissivity (LST&E) Day Version 1 product (VNP21A1D) is compiled daily from daytime Level 2 Gridded (L2G) intermediate products.

The L2G process maps the daily VNP21 swath granules onto a sinusoidal MODIS grid and stores all observations overlapping a gridded cell for a given day. The VNP21A1 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 daytime average is weighted by the observation coverage for that cell. Only observations having observation coverage more than a certain threshold (15%) are considered for this averaging. The 1 kilometer dataset is derived through resampling the native 750 meter VIIRS resolution in the input product.

The VNP21A1D product is developed synergistically with the Moderate Resolution Imaging Spectroradiometer (MODIS) LST&E Version 6 product (MOD21A1D) 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 VNP21A1D product contains seven Science Datasets (SDS): LST, quality control, emissivity for bands M14, M15, and M16, view zenith angle, and time of observation. A low-resolution browse image for LST is also available for each VNP21A1D granule.

Characteristics

Collection and Granule

Collection

Characteristic Description
CollectionS-NPP VIIRS
DOI10.5067/VIIRS/VNP21A1D.001
File Size~170 KB
Temporal ResolutionDaily
Temporal Extent2012-01-17 to Present
Spatial ExtentGlobal
Coordinate SystemSinusoidal
DatumN/A
File FormatHDF-EOS5
Geographic Dimensions1200 km x 1200 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers7
Columns/Rows1200 x 1200
Pixel Size1000 m

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor Additional Offset
LST_1KM Daily 1 km Land Surface Temperature Kelvin 16-bit unsigned integer 0 N/A 7500 to 65535 0.02 N/A
QC Daily Quality control for LST and emissivity N/A 16-bit unsigned integer 0 N/A 0 to 65535 N/A N/A
Emis_14 Daily M14 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_15 Daily M15 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
Emis_16 Daily M16 emissivity N/A 8-bit unsigned integer 0 N/A 1 to 255 0.002 0.49
View_Angle View zenith angle of LST Degree 8-bit unsigned integer 255 N/A 0 to 130 N/A -65
View_Time Time of LST observation Hours 8-bit unsigned integer 255 N/A 0 to 240 0.1 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 7 on pages 22-23 of the User Guide.

For additional information on product quality, refer to the VIIRS Land Product Quality website.

Known Issues

No known issues.

Documentation

Using the Data

Tools

Citation

DOI: 10.5067/VIIRS/VNP21A1D.001

About the Image