Validation of the NPP/VIIRS Operational Aerosol Products Through Multi-Sensor Intercomparisons

The Suomi National Polar-orbiting Partnership (NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) instrument began collecting data shortly after its launch in October 2011 and its aerosol products have been available at a beta maturity state beginning in May 2012. The NPP/VIIRS operational aerosol products include aerosol optical depth (AOD) at 11 wavelengths, aerosol size parameter (Angström Exponent, AE) and type-related information (Suspended Matter). VIIRS aerosol retrieval is performed at moderate resolution pixel level (~0.75 to 1.6 km from nadir to edge), and aggregates to ~6 to 12.8 km resolution for the Environment Data Record products. To use this newly released data in numerical weather prediction and to build it into long-term aerosol climate record requires a thorough characterization of the aerosol products, particularly in comparison to the preceding established well-characterized aerosol products. This talk highlights the multi-sensor intercomparison approach that is currently used for the calibration/validation (Cal/Val) of the VIIRS aerosol products. The aerosol products are compared with multiple ground (Aerosol Robotic Network, AERONET) and spaceborne (MODIS, MISR, CALIPSO, etc.) sensors, and similarities and discrepancies are discussed. The Cal/Val results from a period of May 02-Jun 02, 2012 indicated that VIIRS achieves comparable performance to MODIS in terms of observing spatial and temporal variability of global aerosols. In comparison to MODIS and AERONET, the VIIRS AOD retrieval algorithm performs better over ocean than over land, while significant AOD overestimations are still observed over land and some AOD underestimations are found over dust outflow areas over ocean. In addition, VIIRS tends to have relatively higher small mode fraction and AE over ocean. More detailed data analyses are currently underway to further improve the algorithms. The most updated results from the ongoing extended evaluation will be reported in the talk. It is expected that through intensive Cal/Val activities and algorithm refinements, the NPP/VIIRS aerosol products will prove a valuable asset to the data user community in meeting the operational and research needs of air quality, weather forecasting, and climate impact studies.