VIIRS/NPP+JPSS Combined Aerosol Products from MAIAC Daily L3 Global at 0.05Deg CMG V002

The VCD19A2CMG Version 2 data product is a combined NASA/NOAA Suomi National Polar-orbiting Partnership (Suomi NPP) and NOAA-20 Visible Infrared Imaging Radiometer Suite (VIIRS) Land Aerosol Optical Depth (AOD) and Water Vapor Level 3 product produced daily in a 0.05 degree (5,600 meters at the equator) Climate Modeling Grid (CMG). The VCD9A2CMG product is corrected for atmospheric gases and aerosols using a Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm that is based on a time series analysis and a combination of pixel- and image-based processing.

The VCD19A2CMG AOD data product contains the variables for blue band AOD at 0.47 µm, green band AOD at 0.55 µm, AOD uncertainty, average cloud fraction, available AOD, satellite overpass times, line and sample number, offset, and number of AOD records.

Known Issues

* MAIAC Lookup Tables (LUTs) are built assuming pseudo-spherical correction in single scattering which has a reduced accuracy for high sun/view zenith angles. A reduced MAIAC performance is expected at solar zenith angles > 78°.
* MAIAC may be missing bright salt pans in several world deserts. In such cases, it may generate a persistent high Aerosol Optical Depth (AOD) resulting in missing surface retrievals.
* Because of inherent uncertainties of gridding on the coastline, the area of 1-3 pixels from the coastline may contain frequent artifacts in cloud mask (usually over-detection), AOD (higher values) and surface BRF. Users should exercise caution near the coastline as represented by the AOD QA bit 1010 (See Table 5.4 of the User Guide bits 8-11, 1010 -- AOD within +-2 km from the coastline is replaced by nearby AOD).
* Atmospheric Correction (AC) over detected snow: as MAIAC does not retrieve AOD over snow, it assumes a low climatology AOD=0.05 globally and 0.02 at high elevations (H>4.2 km). Over north-central China, which is often heavily polluted and low AOD assumption can lead to a significant bias, we use AOD averaged over mesoscale area of 150 km using reliable AOD retrievals over snow-free pixels. Such approach does improve quality of AC as compared to low-AOD assumption as judged by the reduced boundaries and color artifacts, but it does not account for the aerosol variability inside 150 km area.
* Ice Mask is currently unreliable.