Improved Deep Blue Aerosol Data Records from SNPP/NOAA-20 VIIRS and Beyond

Deep Blue aerosol algorithms have provided validated, near-global aerosol data records from various satellite sensors spanning from historic Advanced Very High Resolution Radiometer (AVHRR) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) to more recent Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS). With mid-visible (550 nm) aerosol optical depth (AOD) being the centerpiece of the data sets, it also provides spectral AOD, Ångström exponent, fine-mode AOD fraction, and aerosol type products (depending on land/water surfaces and sensors used). The data record from SNPP VIIRS (previously Version 1.1) started from March 2012 and has been available on NASA Earthdata (https://earthdata.nasa.gov/) since late 2018. The algorithms used for the data set were based on the heritage Deep Blue algorithm for MODIS over land surfaces (with improvements for better retrieving nonspherical mineral dust) and the Satellite Ocean Aerosol Retrieval (SOAR) algorithm, which had originally been applied to SeaWiFS, over water surfaces.

The VIIRS algorithm suite has since been refined in many aspects and is poised for a major version change (Version 2). We will address changes made to the Version 2 algorithms, which significantly improve some of the known issues in the previous versions. Firstly, the algorithm now accounts for the effects of surface elevation (or pressure) physically rather than empirically as in the previous versions. Secondly, new surface database is introduced to better describe surface reflectance relationships between visible and 2.2 μm bands in each geographic grid. Lastly, new fine-mode dominant aerosol optical models are added to existing nonspherical dust models, together replacing the original Deep Blue optical models. For consistent retrievals between SNPP and NOAA-20 VIIRS, and also continuity with MODIS, cross-calibration gain factors derived using vicarious calibration at Dome C site are applied to NOAA-20 VIIRS. Another topic to be addressed is new aerosol layer height (ALH) and single scattering albedo (SSA) products from the synergistic use of VIIRS and the Ozone Mapping Profiler Suite Nadir Mapper (OMPS-NM), which will be added to the standard Deep Blue aerosol product suite in the later versions.