The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on board the Suomi National Polar‐orbiting Partnership (S‐NPP) spacecraft was launched in October 2011. The instrument has 22 spectral channels with band centers from 412 nm to 12,050 nm. The VIIRS aerosol data products are derived primarily from the radiometric channels covering the visible through the short‐wave infrared spectral regions (412 nm to 2250 nm). The major components of the VIIRS aerosol retrieval process are data screening, land inversion, ocean inversion, suspended matter typing, and aggregation. The primary data product produced is the aerosol optical thickness (AOT) environmental data record. A higher resolution AOT intermediate product is also produced. These AOT products and their corresponding retrieval algorithms are described in detail, including theoretical basis, retrieval limitations, and data quality flagging. Preliminary evaluation of the data products has been undertaken by the VIIRS aerosol calibration/validation team using Aerosol Robotic Network ground‐based observations to show that the performance of AOT retrievals meets the requirements specified in the Joint Polar Satellite System Level 1 requirements.

The Visible Infrared Imaging Radiometer Suite (VIIRS) is the next-generation polar-orbiting operational environmental sensor with a capability for global aerosol observations. The VIIRS aerosol Environmental Data Record (EDR) is expected to continue the decade-long successful multispectral aerosol retrieval from the NASA's Earth Observing System Moderate Resolution Imaging Spectroradiometer (MODIS) for scientific research and applications. Since the launch of the Suomi National Polar-orbiting Partnership (S-NPP), the VIIRS aerosol calibration/validation team has been continuously monitoring, evaluating, and improving the performance of VIIRS aerosol retrievals. In this study, the VIIRS aerosol optical thickness (AOT) at 550 nm EDR at current Provisional maturity level is evaluated by comparing it with MODIS retrievals and measurements from the Aerosol Robotic Network (AERONET) and the Maritime Aerosol Network (MAN). The VIIRS global mean AOT at 550 nm differs from that of MODIS by approximately À0.01 over ocean and 0.03 over land (0.00 and À0.01 for the collocated retrievals) but shows larger regional biases. Global validation with AERONET and with MAN measurements shows biases of 0.01 over ocean and À0.01 over land, with about 64% and 71% of retrievals falling within the expected uncertainty range established by MODIS over ocean (±(0.03 + 0.05AOT)) and over land (±(0.05 + 0.15AOT)), respectively. The VIIRS retrievals over land exhibit slight overestimation over vegetated surfaces and underestimation over soil-dominated surfaces. These results show that the VIIRS AOT at 550 nm product provides a solid global data set for quantitative scientific investigations and environmental monitoring.

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[1] Information on radiative fluxes that reach the ground is needed in numerous areas of climate research. On a global scale, such information is obtainable only from satellites. Top of the atmosphere satellite observations during clear and cloudy sky conditions have been found useful for inferring, among others, information on aerosol optical depth (AOD) and cloud optical depth (COD). These are important elements for estimating surface radiative fluxes. Satellite retrievals of AOD are based on the assumption that the aerosols are of a specific type. In certain climatic regions, dust aerosols and those from biomass burning are injected into the atmosphere simultaneously and are distributed distinctly in the vertical. In this study, it is demonstrated that in such scenarios inaccurate assumption on the vertical distribution of the aerosols can lead to errors in AOD estimates from satellites and, subsequently, in the inferred shortwave (SW) radiative fluxes that reach the surface. The magnitude of such errors can be as high as 80 W m −2 . The frequency of these mixed situations has not as yet been documented, and it is possible that on global scale the impact is small. Using available records of observed SW radiative fluxes, their reduction ("dimming") at numerous locations has been reported. Some relate this reduction to aerosol effects. The findings of this study have implications for the ability to assess such "dimming" from satellites in areas where the vertical structure of aerosol distribution needs to be accounted for.