Maritime aerosol optical thickness measured by handheld sun photometers

Kirk D. Knobelspiesse, Christophe Pietras, Giulietta S. Fargion, Menghua Wang, Robert Frouin, Mark A. Miller, Ajit Subramaniam, William M. Balch

Research output: Contribution to journalArticlepeer-review

87 Scopus citations


For several years, the NASA SIMBIOS Project has collected, processed, and archived optical aerosol data from shipboard sun photometers. The calibration, processing, quality control, and archival methodology for handheld sun photometers are described here, along with their deployment statistics. Data processing has been standardized for all instruments by using identical calibration methods, ancillary data, and processing software. Statistical analysis reveals a dataset influenced by its temporal and geographic distribution, while multimodal histograms for aerosol optical thickness (AOT) and Ångström exponent reveal varied aerosol populations. A K-means unsupervised classification technique is used to separate these populations. This separation is validated by showing individual classes are more likely to be log-normally (for AOTs) or normally (for Ångström exponents) distributed than the dataset as a whole. Properties for each class are presented, along with the characteristics of each class by regional oceanic basin. Results also compare favorably with maritime aerosols measured by land-based AERONET Cimels in island sites, while providing data coverage in previously sparsely sampled regions. Aerosol models employed by SeaWiFS (Sea-Viewing Wide Field-of-View Sensor) also compare favorably with these ground based measurements.

Original languageEnglish (US)
Pages (from-to)87-106
Number of pages20
JournalRemote Sensing of Environment
Issue number1-2
StatePublished - Oct 30 2004
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Soil Science
  • Geology
  • Computers in Earth Sciences


  • Aerosol optical thickness
  • Maritime aerosols
  • Sun photometer
  • Ångström exponent

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