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Wave‐induced light field fluctuations in measured irradiance depth profiles: A wavelet analysis
Author(s) -
Wei Jianwei,
Lewis Marlon R.,
Dommelen Ronnie,
Zappa Christopher J.,
Twardowski Michael S.
Publication year - 2014
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2013jc009572
Subject(s) - irradiance , downwelling , amplitude , environmental science , atmospheric sciences , noise (video) , light field , optics , geology , remote sensing , physics , upwelling , oceanography , artificial intelligence , computer science , image (mathematics)
Rapid variations in the intensities of light are commonly observed in profiles of downwelling plane irradiance in the ocean. These fluctuations are often treated as noise and filtered out. Here an effort is made to extract the pertinent statistics to quantify the light field fluctuations from vertical profiles of irradiance measured under clear skies. The irradiance data are collected in oceanic and coastal waters using a traditional free‐fall downwelling plane irradiance sensor. The irradiance profiles are transformed into time‐frequency domain with a wavelet technique. Two signatures including the dominant frequency (<3.5 Hz) and the coefficient of variation of irradiance fluctuations along the water column are identified from the variance spectrum. Both the dominant frequency and the amplitude decrease as the inverse square root of depth, consistent with simple models of wave focusing and data from other studies. Mechanisms contributing to the observed variations and the observational uncertainties are discussed.