The Visible Infrared Imaging Radiometer Suite (VIIRS) NASA standard Level 2 (L2) Deep Blue Aerosol Products from the Joint Polar Satellite System (JPSS) series NOAA-20 instrument provide satellite-derived measurements of Aerosol Optical Thickness (AOT) and their properties over land and ocean in 6-minute data granules with daily, global coverage. The Deep Blue algorithm draws its heritage from previous applications to retrieve AOT from Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) over both land and ocean, and Moderate Resolution Imaging Spectroradiometer (MODIS) measurements over land. This L2 description pertains to the VIIRS Deep Blue Aerosol version 2.1 (v2.1) product, whose record starts on January 5, 2018 (2018-005).

This orbit-level product (Short-name: AERDB_L2_VIIRS_NOAA20) has an at-nadir resolution of 6 km x 6 km and progressively increases away from nadir given the sensor’s scanning geometry and Earth’s curvature. Viewed differently, this product’s resolution accommodates 8 x 8 native VIIRS moderate-resolution (M-band) pixels that nominally have a horizontal pixel size of ~750 m. The L2 Deep Blue AOT data products, at 550 nm reference wavelength, are derived from VIIRS bands using two primary AOT retrieval algorithms: the Deep Blue algorithm over land, and the Satellite Ocean Aerosol Retrieval (SOAR) Algorithm over ocean. Although this product is called Deep Blue based on retrievals for the land algorithm, the data include over-water retrievals as well.

The L2 netCDF product, acquired every 6 minutes, contains 56 Science Data Set (SDS) layers that include the following:

1. Aerosol_Optical_Thickness_550_Expected_Uncertainty_Land
2. Aerosol_Optical_Thickness_550_Expected_Uncertainty_Ocean
3. Aerosol_Optical_Thickness_550_Land
4. Aerosol_Optical_Thickness_550_Land_Best_Estimate
5. Aerosol_Optical_Thickness_550_Land_Ocean
6. Aerosol_Optical_Thickness_550_Land_Ocean_Best_Estimate
7. Aerosol_Optical_Thickness_550_Ocean
8. Aerosol_Optical_Thickness_550_Ocean_Best_Estimate
9. Aerosol_Optical_Thickness_550_STDV_Land
10. Aerosol_Optical_Thickness_550_STDV_Ocean
11. Aerosol_Optical_Thickness_QA_Flag_Land
12. Aerosol_Optical_Thickness_QA_Flag_Ocean
13. Aerosol_Type_Land
14. Aerosol_Type_Land_Ocean
15. Aerosol_Type_Ocean
16. Algorithm_Flag_Land
17. Algorithm_Flag_Ocean
18. Angstrom_Exponent_Land
19. Angstrom_Exponent_Land_Best_Estimate
20. Angstrom_Exponent_Land_Ocean
21. Angstrom_Exponent_Land_Ocean_Best_Estimate
22. Angstrom_Exponent_Ocean
23. Angstrom_Exponent_Ocean_Best_Estimate
24. Cell_Average_Elevation_Land
25. Cell_Average_Elevation_Ocean
26. Fine_Mode_Fraction_550_Ocean
27. Fine_Mode_Fraction_550_Ocean_Best_Estimate
28. Idx_Atrack
29. Idx_Xtrack
30. Land_Bands
31. Latitude
32. Longitude
33. NDVI
34. Number_Of_Pixels_Used_Land
35. Number_Of_Pixels_Used_Ocean
36. Number_Valid_Pixels
37. Ocean_Bands
38. Ocean_Sum_Squares
39. Precipitable_Water
40. Reflectance_Bands
41. Relative_Azimuth_Angle
42. Scan_Start_Time
43. Scattering_Angle
44. Solar_Zenith_Angle
45. Spectral_Aerosol_Optical_Thickness_Land
46. Spectral_Aerosol_Optical_Thickness_Ocean
47. Spectral_Single_Scattering_Albedo_Land
48. Spectral_Surface_Reflectance
49. Spectral_TOA_Reflectance_Land
50. Spectral_TOA_Reflectance_Ocean
51. Surface_Pressure
52. Total_Column_Ozone
53. Unsuitable_Pixel_Fraction_Land_Ocean
54. Viewing_Zenith_Angle
55. Wind_Direction
56. Wind_Speed

Differences Between the v2.1 and v2.0 VIIRS Deep Blue Aerosol Collections

Significant changes in the v2.1 VIIRS Deep Blue Aerosol Product relative to the v2.0 collection include the following:

• VIIRS-derived Deep Blue Aerosol Products are now available from the NOAA-21, NOAA-20, and Suomi National Polar-orbiting Partnership (SNPP) platforms.
• Dome C (a calibration site in eastern Antarctica) cross-calibration between SNPP and NOAA-21 has been incorporated to ensure radiometric consistency.
• AOT spatial distribution has been improved over North Africa (particularly between the Sahara and Sahel regions) and South Asia (around the Thar Desert and Indus River Basin).
• Aerosol optical models (i.e., single-scattering albedo) have been adjusted over North America, the Sahel, Southern Africa, and India to further optimize retrieval performance.
• More rigorous Sun-glint screening has been implemented for over-water retrievals, reducing contamination at the expense of some spatial coverage.
• Cloud filters have been revised to better retain heavy dust plumes and to better remove thin clouds and sea fog over water.

Consult the VIIRS Deep Blue Aerosol Product User Guide for additional information regarding the global attributes, data field attributes, quality flags, software for handling and using these data products, and other relevant information.