The Visible Infrared Imaging Radiometer Suite (VIIRS) and Cross-track Infrared Sounder (CrIS) Fusion product provides continuity to the Earth Observing System (EOS) Terra and Aqua missions’ Earth science data products. This Level-2 (L2) swath product leverages the VIIRS and CrIS instruments’ assets to create narrowband radiances based on the Aqua Moderate Resolution Imaging Spectroradiometer’s (MODIS) spectral response functions. This innovative fusion-based product between an imager and a sounder instrument is necessitated by the VIIRS instrument’s lack of Infrared (IR) bands that are responsive to atmospheric absorption. Using both VIIRS and CrIS inputs, this product helps derive MODIS-equivalent fusion-based radiances for VIIRS in the following absorption regions (the analogue MODIS bands in parenthesis):

• CO₂ : Around 4.3 µm (bands 23 – 25) and around 15 µm (bands 33 – 36)
• O₃ : Near 9 µm (band 30)
• H₂O: Near 6.7 µm (bands 27 and 28)
• 11 µm and 12 µm window (bands 31 and 32)

This L2 NOAA-20 VIIRS+CrIS Fusion Product relates to Version-2.0 (v2.0) collection, which has undergone some improvements over its previous version. In the v2.0 Fusion product, the quality check of the input VIIRS data is performed for individual scanlines instead of checking the entire input granule as was done in the previous version of this product. Such a process has helped salvage and use granules with continuous blocks of good data with good calibration. The v2.0 product also includes a couple of improvements to the VIIRS-CrIS collocation. The first relates to how VIIRS scan-sync-loss-events are addressed while the other correctly characterizes VIIRS pixels that should have been identified as falling within a CrIS Field-of-View. A final improvement in the v2.0 product attempts to correct an artifact detected over warm, dry surfaces in the water vapor channels that are derived using the MODIS Band-27 and -28 response functions that manifest signs of surface features that should not exist for these channels. Check the User Guide for further details on these improvements.

The L2 NOAA-20 VIIRS+CrIS Fusion product has a horizontal pixel size of 750 m, which is the native VIIRS moderate-resolution (M) band pixel-size. It contains the following Science Data Sets (SDS) that define its primary geophysical data:

1. Difference of measured minus fusion-reconstructed VIIRS M15 brightness temperature
2. Difference of measured minus fusion-reconstructed VIIRS M16 brightness temperature
3. MODIS-equivalent band 23 earth view fusion radiance
4. MODIS band 23 equivalent brightness temperature lookup table (Aqua)
5. MODIS-equivalent band 24 earth view fusion radiance
6. MODIS band 24 equivalent brightness temperature lookup table (Aqua)
7. MODIS-equivalent band 25 earth view fusion radiance
8. MODIS band 25 equivalent brightness temperature lookup table (Aqua)
9. MODIS-equivalent band 27 earth view fusion radiance
10. MODIS band 27 equivalent brightness temperature lookup table (Aqua)
11. MODIS-equivalent band 28 earth view fusion radiance
12. MODIS band 28 equivalent brightness temperature lookup table (Aqua)
13. MODIS-equivalent band 30 earth view fusion radiance
14. MODIS band 30 equivalent brightness temperature lookup table (Aqua)
15. MODIS-equivalent band 31 earth view fusion radiance
16. MODIS band 31 equivalent brightness temperature lookup table (Aqua)
17. MODIS-equivalent band 32 earth view fusion radiance
18. MODIS band 32 equivalent brightness temperature lookup table (Aqua)
19. MODIS-equivalent band 33 earth view fusion radiance
20. MODIS band 33 equivalent brightness temperature lookup table (Aqua)
21. MODIS-equivalent band 34 earth view fusion radiance
22. MODIS band 34 equivalent brightness temperature lookup table (Aqua)
23. MODIS-equivalent band 35 earth view fusion radiance
24. MODIS band 35 equivalent brightness temperature lookup table (Aqua)
25. MODIS-equivalent band 36 earth view fusion radiance
26. MODIS band 36 equivalent brightness temperature lookup table (Aqua)

Consult the VIIRS+CrIS Fusion product user guide for additional information regarding this product’s algorithm, file format, global and data-field attributes, quality control flags, etc.