Collection 2.0 - VIIRS/SNPP Dark Target Aerosol L2 6-Min Swath 6 km (NRT)

Last update: Nov. 20, 2023

Data Set Short Name:
AERDT_L2_VIIRS_SNPP_NRT

Data Set Long Name:
VIIRS/SNPP Dark Target Aerosol L2 6-Min Swath 6 km (NRT)

Platform:
Suomi National Polar-Orbiting Partnership (S-NPP)

Instrument:
Visible-Infrared Imaging-Radiometer Suite (VIIRS)

Product Description:

The Suomi National Polar-orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS) NASA standard Level-2 (L2) dark target (DT) aerosol product provides satellite-derived measurements of Aerosol Optical Thickness (AOT) and their properties over land and ocean, and spectral AOT and their size parameters over oceans every 6 minutes, globally. The VIIRS incarnation of the DT aerosol product is based on the same DT algorithm that was developed and used to derive products from the Terra and Aqua missions' Moderate Imaging Spectroradiometer (MODIS) instruments. Two separate and distinct DT algorithms exist. One helps retrieve aerosol information over ocean (dark in visible and longer wavelengths), while the second aids retrievals over vegetated/dark-soiled land (dark in the visible wavelengths).

This orbit-level product (Short-name: AERDT_L2_VIIRS_SNPP_NRT) has an at-nadir resolution of 6 km x 6 km, and progressively increases away from nadir given the sensor's scanning geometry and Earth's curvature. Viewed differently, this product's resolution accommodates 8 x 8 native VIIRS moderate-resolution (M-band) pixels that nominally have ~750 m horizontal pixel size. Hence, the Level-2 Dark Target Aerosol Optical Thickness data product incorporates 64 (750 m) pixels over a 6-minute acquisition. Version 2.0 constitutes the latest collection of the L2 Dark Target Aerosol product and contains improvements over its previous collection (v1.1).


Level-2 Dark Target Aerosol: SNPP VIIRS v2.0 improvements over v1.1
  • The SNPP VIIRS v2.0 products use a higher-resolution cloud mask, which is derived from the 375m image-band red-wavelength to allow for closer, near-cloud retrievals with less cloud contamination. This improved mask is especially visible over ocean, where many high AOD values are revised downward.
  • The SNPP VIIRS v2.0 products use NASA's Global Modeling and Assimilation Office (GMAO) inputs as their source of ancillary meteorological data over the previous NOAA's Global Data Assimilation System (GDAS) source.
  • The SNPP VIIRS v2.0 products use updated VIIRS Level-1B reflectances that have improved calibration over its previous version.
  • The SNPP VIIRS v2.0 products now report the mean and standard deviation reflectances over land for all seven wavelength bands compared to only over ocean that the v1.1 products reported.

The L2 netCDF product contains the following 37 Science Data Set (SDS) layers:

  • Aerosol_Cldmask_Land_Ocean
  • Aerosol_Cloud_Fraction_Land
  • Aerosol_Cloud_Fraction_Ocean
  • Aerosol_Type_Land
  • Angstrom_Exponent_1_Ocean
  • Angstrom_Exponent_2_Ocean
  • Asymmetry_Factor_Average_Ocean
  • Average_Cloud_Pixel_Distance_Land_Ocean
  • Backscattering_Ratio_Average_Ocean
  • Cloud_Pixel_Distance_Land_Ocean
  • Corrected_Optical_Depth_Land
  • Effective_Optical_Depth_Average_Ocean
  • Effective_Radius_Ocean
  • Error_Flag_Land_And_Ocean
  • Fitting_Error_Land
  • Image_Optical_Depth_Land_And_Ocean
  • Land_Ocean_Quality_Flag
  • Land_Sea_Flag
  • Least_Squares_Error_Ocean
  • Mass_Concentration_Land
  • Mass_Concentration_Ocean
  • Mean_Reflectance_Land
  • Mean_Reflectance_Ocean
  • Number_Pixels_Used_Land
  • Number_Pixels_Used_Ocean
  • Optical_Depth_By_Models_Ocean
  • Optical_Depth_Land_And_Ocean
  • Optical_Depth_Large_Average_Ocean
  • Optical_Depth_Ratio_Small_Land
  • Optical_Depth_Ratio_Small_Ocean_0p55micron
  • Optical_Depth_Small_Average_Ocean
  • PSML003_Ocean
  • STD_Reflectance_Land
  • STD_Reflectance_Ocean
  • Surface_Reflectance_Land
  • Topographic_Altitude_Land
  • Wind_Speed_Ncep_Ocean

Consult the Dark Target Aerosol Product User Guide for additional information regarding these SDS parameters.

Production Frequency:
~120 files per day

Spatial Coverage:
Global (daytime only)

Spatial Resolution:
6 km at nadir

File Size:
Variable, but typically 7-12 MB

Related Links:

Citation:
We kindly request that you cite the use of this data set in a publication using the following references:

Sawyer, V., R.C. Levy, S. Mattoo, G. Cureton, Y. Shi, and L.A. Remer (2020), Continuing the MODIS Dark Target Aerosol Time Series with VIIRS. Remote Sens. 2020, 12, 308; https://doi.org/10.3390/rs12020308

Levy, R.C., L. A. Munchak, S. Mattoo, F. Patadia, L. A. Remer, and R. E. Holz (2015), Towards a long-term global aerosol optical depth record: applying a consistent aerosol retrieval algorithm to MODIS and VIIRS-observed reflectance, Atmos. Meas. Tech., 8, 4083–4110.

Dataset Originator/Creator:
Dark Target aerosol team, Climate and Radiation Laboratory, NASA Goddard Space Flight Center

Dataset DOI:
TBD