Relationships between Q-factor and seawater optical properties in a coastal region
Giuseppe Zibordi and Jean-François Berthon
Limnol. Oceanogr., 46(5), 2001, 1130–1140

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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(lambda.lc.gif - 58 Bytes) measurements—the Q-factor determined by nadir radiance—from the North Adriatic Sea coastal waters, has been analyzed. Scatter plots of Qn(lambda.lc.gif - 58 Bytes) versus sun zenith, theta.lc.gif - 53 Bytes0, for different intervals of the diffuse attenuation coefficient Kd(lambda.lc.gif - 58 Bytes) have shown a consistent exponential trend. In addition, leastsquares regressions of Qn(lambda.lc.gif - 58 Bytes) 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(lambda.lc.gif - 58 Bytes) as a function of theta.lc.gif - 53 Bytes0 and Kd(lambda.lc.gif - 58 Bytes0) at the reference wavelength lambda.lc.gif - 58 Bytes0 = 490 nm is proposed for North Adriatic coastal waters.