Relationships between Q-factor and seawater optical properties in a coastal region

Zibordi, Giuseppe, Jean-François Berthon

Limnol. Oceanogr., 46(5), 2001, 1130-1140 | DOI: 10.4319/lo.2001.46.5.1130

ABSTRACT: The Q-factor—the ratio between upwelling irradiance and upwelling radiance—describes the bidirectional structure of seawater apparent optical properties as a function of geometry and of marine and atmospheric optical characteristics. A 3-yr time series of Qn(λ) measurements—the Q-factor determined by nadir radiance—from the North Adriatic Sea coastal waters, has been analyzed. Scatter plots of Qn(λ) versus sun zenith, - 53 Bytes0, for different intervals of the diffuse attenuation coefficient Kd(λ) have shown a consistent exponential trend. In addition, leastsquares regressions of Qn(λ) versus Qn(490) have exhibited determination coefficients R2 that vary from 0.77 to 0.94 in the spectral range between 412 and 555 nm and R2 = 0.50 at 665 nm. To account for these findings, an empirical model for Qn(λ) as a function of - 53 Bytes0 and Kd0) at the reference wavelength λ0 = 490 nm is proposed for North Adriatic coastal waters.

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