XAERDT_L2_AHI_H08 - AHI/Himawari-08 Dark Target Aerosol 10-Min L2 Full Disk 10 km

This Level-2 (L2) Dark Target Aerosol product derived from the Himawari-8 Advanced Himawari Imager (AHI) instrument has been partially reprocessed since its original release in March 2024 to address two issues. Since neither issue required reprocessing from the original Level-1B, this dataset is re-released under its original version number (v1.0), and it contains the following updates:

• Sensor and Solar Azimuth Angles' Fill-Value Modification: The fill-value for both the sensor azimuth angle and solar azimuth angle variables in the Level-2 (L2) product was modified. This modification includes two updates:
  • The FillValue was changed from -9999 to -19999.
  • Instances with actual missing information were replaced with the new FillValue. This change enables the plotting and/or analyzing of valid azimuth angles of -99.99 degrees, which otherwise runs the risk of being screened out by certain image processing systems.
• Quality Assurance Filtering Correction: The Quality Assurance (QA)-filtered Science Data Set (SDS) named Optical_Depth_Land_And_Ocean was corrected, to include only over-land retrievals (Corrected_Optical_Depth_Land) for which the QA flag value is greater than or equal to 2 (medium and high confidence), rather than QA greater than or equal to 1.
• Data Provenance Enhancement: Given the fact that this reprocessed collection retains the same version 1.0 number, an additional global metadata attribute called original_GranuleID was added. It provides the original file name (or LocalGranuleID) with its processing date and time to facilitate data provenance trails for users who may have acquired products from the earlier collection. The new file's name, its processing date and time are provided in the LocalGranuleID attribute.
• Correctly processed 191 datafiles: As part of the original release of the L2 GEO-LEO Dark Target Aerosol products in March 2024, 191 files (that include 15 files from ABI/G16, 4 files from ABI/G17, and 172 files from the Advanced Himawari Imager/H08) were not processed correctly that rendered them dysfunctional. All 191 files have been successfully reprocessed in this new release.

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 is led by Robert Levy. It uses a special version of the MODIS (Moderate Resolution Imaging Spectroradiometer) Dark Target (DT) aerosol retrieval algorithm to produce Aerosol Optical Depth (AOD), and other aerosol parameters derived independently from eight sensor/platform combinations. They include the following:

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 Himawari-8 platform served in the operational Himawari position (near 140.7°E) between October 2014 and 13 December 2022. Himawari-9 replaced Himawari-8 and is currently operational. The Himawari/AHI L2 Dark Target Aerosol product, in netCDF4 format, is provided at 10-km spatial resolution (at-nadir) and a 10-minute full-disk cadence that typically yields about 144 granules over the daylit hours of a 24-hour period. These GEO observations are regional but provide daytime time dependence. The Himawari-8/AHI collection record spans from January 2019 through 12 December 2022. The final 19 days of 2022 (13 - 31 December) are served by L2 products derived from the Himawari-9/AHI instrument.

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