XAERDT_L2_VIIRS_SNPP - VIIRS/SNPP Dark Target Aerosol 6-Min L2 Swath 6 km

The Geostationary Earth Orbit (GEO)-Low-Earth Orbit (LEO) Dark Target Aerosol project under NASA's Making Earth System Data Records for Use in Research Environments (MEaSUREs) program, led by Robert Levy, uses a special version of the MODIS Dark Target (DT) aerosol retrieval algorithm to produce Aerosol Optical Depth (AOD) and other aerosol parameters derived independently from eight sensor/platform combinations, where four are in GEO and four are in LEO. The four GEO sensors include Advanced Baseline Imagers (ABI) on both GOES-16 (GOES-East) and GOES-17 (GOES-West), and Advanced Himawari Imager (AHI) on Himawari-8 and Himawari-9. The four LEO sensors include MODIS on both Terra and Aqua, and VIIRS on both Suomi-NPP and NOAA-20. Adding the LEO sensors reinforces a major goal of this project, which is to render a consistent science maturity level across DT aerosol products derived from both types and sources of orbital satellites.

Within this Level-2 (L2) product suite, the DT algorithm is applied over land and ocean separately, which produces AOD and other aerosol parameters over land only, over ocean only, and a combined subset. Users may assess each retrieved land or ocean aerosol value in these L2 products based on their quality flag (Land_Ocean_Quality_Flag) and confidence levels based on their error flag (Error_Flag_Land_And_Ocean). This project has made a concerted effort to ensure that products within both the GEO and LEO groups are structurally consistent in their data and metadata elements as much as possible.

The SNPP/VIIRS L2 Dark Target Aerosol product, in netCDF4 format, is provided at 6-km spatial resolution (at-nadir) and a 6-minute cadence that typically yields about 130 granules over the daylit hours of a 24-hour period. The SNPP/VIIRS L2 collection record spans from January 2019 through December 2022.

The L2 netCDF product contains the following 45 Science Data Set (SDS) layers that include eight geolocation and 37 geophysical SDSs:

Geolocation_Data

1. longitude
2. latitude
3. solar_zenith_angle
4. solar_azimuth_angle
5. sensor_zenith_angle
6. sensor_azimuth_angle
7. Scattering_Angle
8. Glint_Angle

Geophysical_Data

1. Aerosol_Cldmask_Land_Ocean
2. Aerosol_Cloud_Fraction_Land
3. Aerosol_Cloud_Fraction_Ocean
4. Aerosol_Type_Land
5. Angstrom_Exponent_1_Ocean
6. Angstrom_Exponent_2_Ocean
7. Asymmetry_Factor_Average_Ocean
8. Average_Cloud_Pixel_Distance_Land_Ocean
9. Backscattering_Ratio_Average_Ocean
10. Cloud_Pixel_Distance_Land_Ocean
11. Corrected_Optical_Depth_Land
12. Effective_Optical_Depth_Average_Ocean
13. Effective_Radius_Ocean
14. Error_Flag_Land_And_Ocean
15. Fitting_Error_Land
16. Image_Optical_Depth_Land_And_Ocean
17. Land_Ocean_Quality_Flag
18. Land_Sea_Flag
19. Least_Squares_Error_Ocean
20. Mass_Concentration_Land
21. Mass_Concentration_Ocean
22. Mean_Reflectance_Land
23. Mean_Reflectance_Ocean
24. Number_Pixels_Used_Land
25. Number_Pixels_Used_Ocean
26. Optical_Depth_By_Models_Ocean
27. Optical_Depth_Land_And_Ocean
28. Optical_Depth_Large_Average_Ocean
29. Optical_Depth_Ratio_Small_Land
30. Optical_Depth_Ratio_Small_Ocean_0p55micron
31. Optical_Depth_Small_Average_Ocean
32. PSML003_Ocean
33. STD_Reflectance_Land
34. STD_Reflectance_Ocean
35. Surface_Reflectance_Land
36. Topographic_Altitude_Land
37. Wind_Speed_GMAO_Ocean